Retrospective Theses and Dissertations Iowa State University Capstones, Theses andDissertations

1982

Nitrogen and phosphorus fertilization ofSparganium eurycarpum and Typha glauca stands,Eagle Lake, IowaRobert Kyle NeelyIowa State University

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Universi Microrilms

Intemationêil 300 N. Zeeb Road Ann Arbor, Ml 48106

8224239

Neely, Robert Kyle

NTTROGEN AND PHOSPHORUS FERTILIZATION OF SPARGANIUM EURYCARPUM AND TYPHA GLAUCA STANDS, EAGLE LAKE, IOWA

lov/a State University Ph.D. 1982

University Microfilms

Intsrnâtionâl m N. Zeeb Road. Ann Arbor. MI 48106

Nitrogen and phosphorus fertilization of Sparganium eurycarpum

and Typha glauca stands. Eagle Lake, Iowa

•by

Robert Kyle Neely

A Dissertation Submitted to the

Graduate Faculty in Partial Fulfillment of the

Requirements for the Degree of

DOCTOR OF PHILOSOPHY

Major: Botany

Approved:

In Chag^e of Major Work

For the Major Departme^

ror the Gradfete College

Iowa State University Ames, Iowa

1982

Signature was redacted for privacy.

Signature was redacted for privacy.

Signature was redacted for privacy.

ii

TABLE OF CONTENTS

Page

GENERAL INTRODUCTION 1

Explanation of Thesis Format 2

SECTION I. NITROGEN AND PHOSPHORUS CONCENTRATIONS IN SURFACE AND INTERSTITIAL WATER OF A PRAIRIE MARSH 6

ABSTRACT 7

INTRODUCTION 9

METHODS 11

Study Site 11

Experimental Design 12

Collection and Analysis of Samples 14

Statistical Procedures 16

RESULTS 18

Seasonal Patterns 18

Surface water 18

Nitrogen 18

Phosphorus 20

Interstitial water 23

1979 23

1980 26

Nitrogen 26

Phosphorus 28

Short-Term Patterns 30

Surface water 30

iii

15-cm interstitial water 30

DISCUSSION 33

LITERATURE CITED 38

SECTION II. NUTRIENT LIMITATION OF SPARGANIUM EURYCARPUM AND TYPHA GLAUCA IN A PRAIRIE MARSH 43

ABSTRACT 44

INTRODUCTION 45

METHODS 48

Study Site 48

Construction and Fertilization of Enclosures 49

Collection and Analysis of Samples 49

Sediment and interstitial H^O 49

Vegetation 51

Statistical Analyses 52

RESULTS 54

Interstitial H^O 54

Sediment 56

Above-ground Vegetative Response 58

Nitrogen content 58

Shoot density 60

Biomass and production 60

Below-ground Vegetative Response 66

Nitrogen content 66

Biomass 67

DISCUSSION 69

iv

Nutrient Availability 69

Production 70

LITERATURE CITED 74

SECTION III. NITROGEN, PHOSPHORUS, AND THE DECOMPOSITION OF TYPHA GLAUCA AND SPARGANIDM EURYCARPDM IN A PRAIRIE MARSH 80

ABSTRACT 81

INTRODUCTION 83

METHODS 87

Study Site 87

Fertilization Experiments 87

Shoot tissues 88

Root-rhizome tissues 89

Shoot Decomposition and Initial Nutrient Content 89

Statistical Analyses 90

RESULTS 92

Shoot Decomposition 92

Dry weight 92

Nitrogen content 94

Phosphorus content 97

Root-rhizome Decomposition 99

Dry weight 99

Nitrogen content 100

DISCUSSION 102

Dry Weight 102

Shoot litter 102

V

Eoot-rhizome litter 105

Nutrient Content 106

Shoot litter 106

Below-ground litter 110

CONCLUSIONS 112

LITERATURE CITED 115

ST3MMARY 120

LITERATURE CITED 123

ACKNOWLEDGEMENTS 125

vi

LIST OF FIGURES

Page

Figure 1. The location of Eagle Lake marsh, Iowa 3

Figure 2. The location of fertilized and unfertilized

sampling plots at Eagle Lake marsh 4

Figure 3. The internal arrangement of Eagle Lake sampling

plots 5

Figure I-l. The location of fertilized and unfertilized

sampling plots at Eagle Lake marsh 13

Figure 1-2. Interstitial water sampling well 15

Figure 1-3. The average concentration of NH^-N, NO^-N, and

organic nitrogen in Eagle Lake fertilized and

unfertilized surface water during 1979 and 1980 19

Figure 1-4. The average concentration of PO^-P, total

dissolved phosphorus (TDP), and particulate

phosphorus (PP) in Eagle Lake fertilized and

unfertilized surface water in 1979 and 1980 21

Figure 1-5. The average concentration of NH^-N, NO^-N, and

organic nitrogen in Eagle Lake fertilized and

unfertilized interstitial water at 15-cm and

45-cm depths 27

Figure 1-6. The average concentration of PO.-P and total 4 •

phosphorus (TP) in Eagle Lake fertilized and

unfertilized interstitial waters at 15-cm and

45-cm depths 29

vii

Figure 1-7. The average concentration of NO^-N, and

PO^-P in surface water (n=6) and in 15-cm inter­

stitial water (n=2) on successive days after

fertilization in July and October

Figure II-l. Location of Sparganium and Typha control and

fertilized enclosures at each of 3 sites in

Eagle Lake marsh. The actual arrangement of

plots at each site is not indicated

Figure II-2. Average NH^-N, NO^-N, and PO^-P concentrations

in interstitial water and sediments of control

and fertilized plots during 1979 and 1980

Figure II-3. Average percentage nitrogen in Sparganium and

Typha shoot and root-rhizome tissues from con­

trol and fertilized plots during 1979 and 1980

Figure II-4. Average Sparganium and Typha shoot density in

control and fertilized plots in 1979 and 1980

Figure II-5. Average Sparganium and Typha total above-ground

biomass in control and fertilized plots during

1979 and 1980

Figure II-6. Summary of the 1980 effects of fertilization on

Sparganium and Typha stands on NH^-N, NO^-N, and

PO^-P concentrations in interstitial waters;

NH,-N and PO,-P concentrations in sediments; 4 4

percentage nitrogen in shoots and roots-rhizomes

maximum shoot density; net primary production

viii

(NPP); and autumn below-ground biomass. Signif­

icance at the 0.10 confidence level is desig­

nated by an asterisk. Summer averages are used

for all nutrient concentrations 72

Figure III-l. Sources of carbon, nitrogen, and phosphorus

for microbial decomposers 84

Figure III-2- The average percentage of original dry weight

remaining in submerged Typha and Spar gam'um

shoot and root-rhizome litterbags 93

Figure III-3. The average concentration of nitrogen in

submerged Typha and Sparganium shoot and root-

rhizome litterbags 95

Figure III-4. The average percentage of original nitrogen

remaining in submerged Typha and Sparganium

shoot and root-rhizome litterbags 96

Figure III-5. The average concentration of phosphorus and

the percentage of original phosphorus re­

maining in submerged Typha and Sparganium

shoot litterbags 98

Figure 4. The movement and effect of nitrogen and phos­

phorus fertilizer in Eagle Lake marsh. After

application, the fertilizer moved through the

litter layer into the interstitial water column.

As a result, nitrogen and phosphorus concentra­

tions in both compartments were elevated. Emer-

ix

gent plant uptake and accumulation of nitrogen

from interstitial waters in 1979 and 1980 stimu­

lated an increase in shoot density in 1980, an

increase in net primary production (NPP) in

1980, and eventually an increase in the rate

of decomposition. Percentages denote the 1980

post-fertilization changes in nitrogen and phos­

phorus concentration of interstitial water and

live tissues; the change in the absolute quan­

tity of nitrogen and phosphorus in litter; the

change in shoot density; the change in NPP;

and the change in the rate of decomposition

X

LIST OF TABLES

Page

Table I-l. 1979 15-cm interstitial concentrations (mg/1) in

Typha glauca and Sparganium eurycarpum experi­

mental plots 24

Table 1-2. 1979 45-cm interstitial concentrations (mg/1) in

Typha glauca and Sparganium eurycarpum experi­

mental plots 25

Table II-l. 1979 15-cm interstitial concentrations (ppm) in

Typha glauca and Sparganium eurycarpum experi­

mental plots 57

Table II-2. 1979 and 1980 average net annual above-ground

2 production (g/m ), average maximum above-ground

2 biomass (g/m ), average autumn below-ground bio-

2 mass (g/m ), and below-ground: above-ground bio­

mass ratios for Typha glauca and Spar gam'urn

eurycarpxmi in control and fertilized plots 64

Table II-3. Typha and Sparganium above-ground biomass or

annual production values in inland freshwater

marshes 65

Table III-l. The amount of precipitation (cm) at Eagle Lake

between fall, 1978 and spring, 1979 104

Table III-2. Approximate C:N and C:P ratios (assuming C as 45%

of dry weight - Prentki et al., 1978) of unferti­

lized, fertilized, and swine enriched litter 108

xi

Table III-3- Percentage remaining of original dry-weight,

nitrogen, and phosphorus quantities in Typha

glauca and Sparganium eurycarpum litter after

505 days 113

1

GENERAL INTRODUCTION

Through the combination of unique biological, chemical and

physical properties, wetland ecosystems can act as sinks for inor­

ganic nitrogen and phosphorus. In a review of 17 studies, van der Valk

et al. (1978) reported that all wetland types function as nitrogen and

phosphorus traps on at least a seasonal basis. Anaerobic interstitial

water and anaerobic water at the sediment-water interface accelerate

the loss of NOg-N by denitrification (Brezonik and Lee 1968; Chen et al.

1972; Patrick and Tusneem 1972; Keeney et al. 1971; Bartlett et al.

1979; Reddy et al. 1980); and anaerobic conditions also inhibit the

mineralization of nitrogen and phosphorus from decomposing vegetation

(Chamie and Richardson 1978; Heal et al. 1978). Aerobic surface

waters cause the precipitation of PO^-P with iron (Stumm and Morgan

1970). Live plants remove inorganic nitrogen and phosphorus from

interstitial waters (Valiela and Teal 1974). And, microbes associated

with decomposing emergent macrophyte litter remove inorganic nitro­

gen and phosphorus from surface waters (De La Cruz and Gabriel 1974;

Klopatek 1975; Brinson 1977; Davis and Harris 1978; Davis and

van der Valk 1978a, 1978b; and others). Thus, considerable interest

and research has been focused on the use of wetlands for wastewater

renovation (See Spangler et al. 1976; Til ton et al. 1976; Tourbier

and Pierson 1976; Good et al. 1978; Greeson et al. 1978).

Although data exist regarding the effectiveness of a marsh as

a nutrient sink, few studies have assessed the effect of high loadings

2

on abiotic and biotic marsh components. If natural wetlands are to

be utilized as wastewater renovation sites, the short- and long-term

effects of nutrient enrichment on the ecosystem must be known. This

study is such an assessment. This dissertation describes and quanti­

fies the change in interstitial and surface water chemistry, emergent

plant decomposition, and emergent vegetation dynamics during two

years of nitrogen and phosphorus enrichment of a prairie marsh.

Eagle Lake, Iowa (Figure 1).

Explanation of Thesis Format

This dissertation is divided into three sections, each of which

is written in a format suitable for publication in a technical journal.

References cited in the general introduction may be found at the end of

the dissertation. References cited within a section may be found at

the end of that section.

The three sections of this dissertation discuss interstitial and

surface water chemistry, emergent vegetation dynamics, and emergent

plant decomposition, respectively. Each section is a subdivision

of a single research project. The experimental design of this project

was based on a series of fertilized watertight enclosures and unfer­

tilized open plots within Eagle Lake marsh (Figure 2). All data in

this thesis were obtained from these structures. The internal

arrangement of each enclosure and open plot is presented in Figure 3.

Refer to the individual sections for a detailed description of the

sampling procedures used within enclosures and open plots.

3

IOWA

EagI* Laic*

Ames 42

I-80

Des Moines

.Council Bluffs

80 km

Figure 1, The location of Eagle Lake marsh, Iowa

4

1/4 mi.

• CONTROL • FERTILIZED

Figure 2. The location of fertilized and unfertilized sampling plots at Eagle Lake marsh

5

3m 2m •f Im -|

M

Root/Shoot (Root Production)

Shoot Litter Bags

Walkway

Turnover Plots (Shoot Production)

J.

Root litter Bags

J "5. E 0 Ui

o U)

o o X (A

0

S

Figure 3. The internal arrangement of Eagle Lake sampling plots

6

SECTION I. NITROGEN AND PHOSPHORUS CONCENTRATIONS IN SURFACE

AND INTERSTITIAL WATER OF A PRAIRIE MARSH

7

ABSTRACT

In 1979 and 1980, nitrogen and phosphorus concentrations in surface

and interstitial water at 15-cm and 45-cm depths were examined in

fertilized and unfertilized sample plots at Eagle Lake marsh, Iowa.

In the unfertilized plots, the average concentration of NH^-N in

surface water was 0.71 mg/1 in 1979 and 0.25 mg/1 in 1980. The average

15-cm interstitial NH^-N concentration in these plots was 0.50 mg/1 in

1979 and 0.28 mg/1 in 1980. NO^-N concentrations in unfertilized plots

averaged 0.92 and 1.44 mg/1 in surface water during 1979 and 1980, re­

spectively, and averaged 0.32 and 0.20 mg/1 in 15-cm interstitial water

during 1979 and 1980, respectively. Concentrations of organic

nitrogen in surface water and 15-cm interstitial water of unfertilized

plots ranged between 6.6 and 8.7 mg/1. The average PO^-P concentra­

tion in unfertilized surface water was 0.34 mg/1 in 1979 and 0.47 mg/1

in 1980, and the average 15-cm interstitial PO^-P concentration in

unfertilized plots was 0.53 mg/1 in 1979 and 0.58 mg/1 in 1980.

Total dissolved phosphorus in unfertilized surface water averaged

0.56 and 0.54 mg/1 in 1979 and 1980, respectively. Particulate

phosphorus in these plots was usually less than 0.75 mg/1. Total

phosphorus in 15-cm interstitial water of the unfertilized plots

averaged 0.75 mg/1 in 1980. In general, nitrogen and phosphorus

concentrations in 45-cm interstitial water resembled concentrations

in 15-cm interstitial water.

On the basis of seasonal averages, fertilization in 1979 caused in­

8

creases of NH^-N (+144%), NO^-N (+291%), and PO^-P (+47%) in 15-cm

interstitial water. In 1980, fertilization caused increases in NH^-N

(+189%), PO^-P (+60%), and also the non-PO^-P fraction of total

phosphorus (+50%). Although NO^-N concentrations were not permanently

elevated in 1980, NO^-N concentrations in 15-cm interstitial water did

increase temporarily by 0.3-0.4 mg/1 in the first 24 hours after

fertilization. Concentrations of NH^-N, NOg-N, and PO^-P in 45-cm

interstitial water in fertilized plots during 1979 were increased by

250%, 7%, and 106%, respectively. Fertilization had no effect on

nitrogen and phosphorus concentrations in 45-cm interstitial water

in 1980.

Key words: interstitial water, nitrogen, phosphorus, nutrients,

marsh, wetland, submerged sediments, wastewater renovation.

9

INTRODUCTION

The chemical transformations within and movement of minerals

between sediments, interstitial water, and overlying surface water

have been studied in lake ecosystems (Mortimer 1941; Keeney et al.

1970; Konrad et al. 1977; Brunskill et al. 1971; Lerman and

Brunskill 1971; Graetz et al. 1973; Syers et al. 1973; Serruya et al.

1974; Viner 1975, 1977; Holdren et al. 1977; and others) and in

marine ecosystems (Bischoff et al. 1970; Bray et al. 1973;

Sholkovitz 1973; Li and Gregory 1974; Martens et al. 1978). Inter­

stitial water chemistry of wetlands dominated by emergent macrophytes,

however, is less well-understood. Our current understanding of wet­

land interstitial water chemistry comes mostly from a few studies

of coastal marshes (Valiela and Teal 1974; Correll et al. 1975) and

from the more extensive literature on flooded rice soils (Singlachar

and Samaniego 1973; Sevant and De Datta 1979, 1980; Alva et al.

1980). Because of high levels of plant biomass productivity, litter

accumulation, and the penetration of rhizomes and fibrous root

systems to depths of at least 30 cm, the subsurface characteristics

of an emergent plant dominated wetland differ fundamentally from

subsurface characteristics of open water systems. First, nutrients

are assimilated from wetland interstitial water by growing plants.

Second, large deposits of organic matter at the sediment-water

interface may reduce movement of dissolved nutrients between surface

10

and interstitial water. Third, while a lake sediment is an anaerobic

(reducing) zone, wetland sediments are essentially anaerobic environ­

ments permeated by extensive oxidized microzones around living below-

ground macrophyte tissues; hence, oxidative processes such as

nitrification (Irzumi et al. 1980) and phosphate immobilization by

precipitation with iron (Alva et al. 1980) can occur in this otherwise

anoxic environment.

The purposes of this investigation were (1) to characterize

seasonal patterns of nitrogen and phosphorus concentrations in

interstitial water at two depths, (2) to examine the change in

concentration and form of interstitial nitrogen and phosphorus after

surface water fertilization, and (3) to assess the rate of nitrogen

and phosphorus depletion in surface water and nitrogen and phosphorus

increase in interstitial water during 28-day intervals after fertiliza­

tion.

11

METHODS

Study Site

Eagle Lake, Hancock County, Iowa is a hardwater marsh of the North

American prairie pothole region (Davis and van der Valk 1978a).

Eagle Lake has a surface area of 365 ha and drains approximately

2,653 ha. Water depth can be regulated by a dam at the northern

edge of the marsh and rarely exceeds 1 m. A semipermanent zone of

open water is found in the center of the marsh; thus, the marsh is

classified as a Type I? wetland.

Over 76% of the Eagle Lake drainage basin is used for agricul­

tural purposes; 66% is used in row-crop cultivation of corn and

soybeans. Runoff and drainage from cultivated fields carry large

amounts of nitrogen and phosphorus into the marsh. In 1979, 9.1 kg

NH^-N/ha, 210 kg NO^-N/ha, and 3.5 kg PO^-P/ha entered the: marsh

in precipitation and agricultural runoff (Davis et al. 1981). Of

these amounts, 86% of the entering NO^-N and 78% of NH^-N was

removed from the water as it passed through the marsh. Conversely,

PO^-P was not removed appreciably by the marsh.

More than 40 species of aquatic plants occur in Eagle Lake.

But, in years of high water levels such as 1979 and 1980, the

marsh is dominated by Typha glauca and Sparganium eurycarpum.

Currier (1979), Davis and van der Valk (1978a, 1978b, 1978c), and

van der Valk and Davis (1978a, 1978b, 1979, 1980) have described

the production, decomposition, seed bank dynamics, and nutrient

12

fluctuations of the major plant species in Eagle Lake.

Average annual precipitation for the Eagle Lake area is

approximately 802 mm. Precipitation during 1979 and 1980 was 957

and 710 mm, respectively. Average daily temperatures ranged from a

winter 1979 temperature of -8.1 C to 23 C in the summer of 1980.

Experimental Design

In the early spring of 1979, two 6- x 6-m watertight enclosures

were constructed in each of three areas of Eagle Lake; northern,

western, and southern (Figure I-l). In each area, one enclosure was

erected in a monodominant stand of Typha, and the second was erected

in a monodominant stand of Sparganium. Each enclosure consisted of

a 1.9 cm marine plywood frame braced with 5 x 10 cm wooden supports.

To restrict fertilizer leakage, the 1.9 cm side panels were driven

approximately 10-cm into the substrate and all seams were sealed. Dye

tests confirmed that there was no exchange of water between the enclo­

sures and the marsh. Each enclosure was fertilized with a solution

of NH^NOg and a suspension of (NH^)gHPO^ at 28-day intervals

throughout the 1979 and 1980 growing seasons. Applications were

calculated to bring available nitrogen and phosphorus concentrations

within the water column in each enclosure to 5 mg PO^-P/1, 25 mg

NH -N/1, and 20 mg NO -N/1. Control plots were established near each

enclosure by staking a 6- x 6-m area of open marsh. These plots were

not fertilized.

13

1/4 mi.

• CONTROL •FERTILIZED

Figure I-l. The location of fertilized and unfertilized sampling plots at Eagle Lake marsh

14

Collection and Analysis of Samples

Single, 300 ml surface water samples and 121 ml interstitital

water samples at 15-cm and 45-cm depths were collected biweekly from

treatment and control plots during the 1979 and 1980 growing seasons.

The interstitial samples were obtained from permanently situated,

suction-operated sampling wells. The wells were constructed of PVC

pipe fitted with a plexiglass plate which lay flush with the sediment-

water interface, with a filtered water intake at the sampling depth,

with two tygon tubes for suction and air intake, and with a plexi­

glass seal inside the pipe to prevent water movement up the entire

length of the pipe (Figure 1-2). Each well was tested for leakage

before it was used.

During a warm summer month (July) and a cool autumn month

(October), surface and interstitial water sampling was intensified;

triplicate surface samples and iS-cm deep interstitital samples were

collected from selected enclosures throughout the entire 28-day inter­

val between fertilizations. Samples were taken 1, 3, 5, 8, 11, 13,

21, and 28 days after fertilization in July. And, samples were

collected 1, 3, 5, 10, 15, 21, and 27 days after fertilization in

October. This intensified sampling provided a more accurate estimate

of nutrient change and variation within the fertilized enclosures

over shorter time inteirvals.

All water samples were preserved immediately in the field by adding

1 ml concentrated H^SO^/l of sample and placing the sample on ice.

In the lab, all samples were stored at 5 C until analyzed. Surface

15

>ing

Suction Tube Air intake

PVC Pipe & Fittings Plexiglass Plate

15 or 45 cm

10 cm

Nylon Cloth Filter ' ~

Interstitial Water

Figure 1-2. Interstitial water sampling well

16

water samples were analyzed for PO^-P, total dissolved phosphorus (TDP,

as PO^-P), particulate phosphorus (PP, as PO^-P), NO^-N, and

organic nitrogen (as NH^-N). Biweekly interstitial samples were

analyzed for PO^-P, total phosphorus (TP, as PO^-P), NO^-N, and

organic nitrogen. Interstitial sançles collected in the short-term

studies were analyzed for NO^-N and PO^-P only. Phosphorus

analyses were conducted by using ascorbic acid reduction (Murphey and

Riley 1962). Phosphorus forms other than PO^-P were differentially

filtered (Gelman GA-6 membrane filter, 0.45 um, 47 mm) and digested

with 5% potassium persulfate prior to reduction (Lind 1979; A.P.H.A.

1975). NH^-N concentrations were determined by the phenate colori-

metric procedure (Stainton et al. 1974). NO^-N concentrations were

carried out by using the Technicon Auto-Analyzer II system cadmium

reduction procedure. Microkjeldahl procedures were used to determine

organic nitrogen concentrations (A.P.H.A. 1975).

Statistical Procedures

Data analysis was performed by using Statistical Analysis Systems

(SAS). Analyses of variance (ANOVA) were calculated using a factorial

model with 2 species and 2 treatments over all sampling dates. Each

MOVA was used to evaluate the significance of the following factors

or interactions in influencing nutrient concentrations: site, species,

treatment, species x treatment, site x species x treatment, time,

time X species, time x treatment, and time x species x treatment.

Nitrogen and phosphorus concentrations in wetland interstitial

17

water typically esdiibit high variability; thus, statistical

significance was established at the a = 0.1 critical level CSee

Richardson et al. 1976). Mean square values for site, species, treat­

ment and species x treatment were computed by using the site x species x

treatment interaction as an error term. Mean square values for the

remaining ANOVA terms were calculated with the standard error term,

but conservative degrees of freedom were used to evaluate the F values.

18

RESULTS

Seasonal Patterns

Surface water

Nitrogen Figure 1-3 depicts the change in mean concentra­

tions of NH^-N, NO^-N, and organic nitrogen during the 1979 and

1980 growing seasons. During both study years, NH^-N concentrations

within fertilized enclosures oscillated in an expected manner. The

oscillations were the result of repeated application of NH^-N and

the subsequent declines of the elevated NH^-N levels over 28-day

intervals. Concentration differences between fertilized and unfer­

tilized plots were significant in 1979 and 1980. The NH^-N seasonal

averages were as follows: 0.71 mg/1 in 1979 unfertilized plots,

0.25 mg/1 in 1980 unfertilized plots, 3.35 mg/1 in 1979 fertilized

enclosures and 1.53 mg/1 in 1980 unfertilized enclosures. During the

2-year study period, and particularly in 1979, highest NH^-N levels

were detected near the end of thé growing season.

Fluctuations in NO^-N concentrations did not resemble those for

NH^-N (Figure 1-3). Because NO^-N was removed rapidly after applica­

tion, no oscillation of concentrations was detected. On the basis

of the biweekly samples, NO^-N levels in surface water were not

influenced by fertilization. Seasonal averages were 0.92 and 1.44 mg/1

in unfertilized.plots in 1979 and 1980, respectively. Averages in

fertilized enclosures were 0.90 mg/1 in 1979 and 0.73 mg/1 in 1980.

1979 1980

J A S O

unfert i l ized fert i l ized

ë

Figure 1-3. The average concentration of NH^-N, NO^-N, and organic nitrogen in Eagle Lake ferti­

lized and unfertilized surface water during 1979 and 1980

20

Through each season, NO^-N levels were variable, but maximum concen­

trations generally occurred in the mid to latter part of each growing

season (Figure 1-3).

Organic nitrogen concentrations were not affected significantly

by fertilization in either study year (Figure 1-3), The average

1979 organic nitrogen concentration was 8.2 mg/1 in unfertilized

plots and 8.7 mg/1 in fertilized enclosures. The 1980 averages were

slightly lower, 6.6 mg/1 in unfertilized plots and 7.0 mg/1 in fer­

tilized enclosures. Consistent seasonal trends of organic nitrogen

concentration were not observed. In 1979, concentrations fluctuated

eradically, ranging from 4.5 to 14 mg/1 in treatments. In 1980, a

peak of 16.3 mg/1 in control plots and 18.9 mg/1 in fertilized plots

occurred in July.

Phosphorus The 1979 and 1980 changes in average PO^-P, total

dissolved phosphorus (TOP), and particulate phosphorus (PP) concentra­

tions in unfertilized and fertilized areas are illustrated in

Figure 1-4. In both years, PO^-P concentrations were significantly

higher in fertilized enclosures; averages were 0.34 mg/1 in 1979

unfertilized plots, 1.06 mg/1 in 1979 fertilized enclosures, 0.47

mg/1 in 1980 unfertilized plots, and 1,25 mg/1 in 1980 fertilized

enclosures. The slow disappearance of applied PO^-P after fertiliza­

tion in 1979 produced an oscillating concentration pattern similar to

that for NH^-N (Figure 1-3). In contrast to 1979, 1980 PO^-P

concentrations only occasionally showed any correlation with PO^—P

1979

m g 2.0

0.5—

1980

— V"

J ' J ' A ' S ' O

unfert i l ised fert i l ized

Figure 1-4. The average concentration of PO^-P, total dissolved phosphorus (TDP), and particulate

phosphorus (PP) in Eagle Lake fertilized and unfertilized surface water in 1979 and

1980

22

application. Maximum PO^-P concentrations occurred in autumn of both

years, 2.1 mg/1 in October, 1979 and 2.3 mg/1 in September, 1980.

Concentrations in unfertilized plots were relatively stable during

the summer, with levels consistently below 1 mg/1.

Because PO^-P represented a large portion of TDP, there was

little difference between the seasonal fluctuations of the phosphorus

fractions (Figure 1-4). In each year, TDP concentrations were signif­

icantly greater in fertilized enclosures. TDP values in unfertilized

plots averaged 0.56 and 0.54 mg/1 in 1979 and 1980, respectively.

The fertilized averages were almost 200% higher, 1.53 mg/1 in 1979

and 1.31 mg/1 in 1980. On the basis of seasonal averages, dissolved

phosphorus other than PO^-P amounted to only 39% in 1979 and 7% in

1980 of TDP in unfertilized plots. Similarly, the non-PO^-P fraction

of TDP in fertilized enclosures was 31% in 1979 and 5% in 1980. In

1979 only was the non-PO^-P fraction of TDP significantly higher in

fertilized enclosures.

Particulate phosphorus (PP) concentrations were not affected by

fertilizations in either study year (Figure 1-4). With the exception

of isolated peaks in July of each year, concentrations were stable

and usually less than 0.75 mg/1. Averaged over both treatments, mean

PP concentration was 0.27 mg/1 in 1978 and 0.13 mg/1 in 1980.

23

Interstitial Water

1979 In 1979, 15-cm and 45-cm interstitial water samples were

analyzed for NH^-N, NO^-N, and PO^-P only. Because of extensive

muskrat damage to sampling wells in 1979, numerous wells were removed

from the field, repaired and replaced; thus, we were unable to gather

data on several dates. On other dates we were able to gather informa­

tion from 1 site only. Because of numerous gaps in the 1979 data,

no statistical analyses were performed. The data, however, are

summarized in Table I-l and 1-2.

Tables I-l and 1-2 indicate tremendous variability among sampling

dates, but on the basis of seasonal averages some trends are sug­

gested. 15-cm NH^-N and PO^-P mean concentrations in Typha and

Sparganium fertilized enclosures were substantially greater than

values from unfertilized plots. Sparganium NO^-N values at 15-cm

were evidently unaffected by fertilization. But, because of an

extraordinarily high June 3 NO^-N value in fertilized Typha plots,

the average Typha NO^-N concentration in fertilized plots -was 5 times

the unfertilized concentrations. Mean Typha concentrations at 15-cm

for all nutrients under both treatments were consistently higher

than Sparganium levels.

At 45-cm, NH^-N and PO^-P concentrations in fertilized enclosures of

both species were generally at least twice the unfertilized concentra­

tions (Table 1-2). NO^-N concentrations at 45 cm in unfertilized and

fertilized Typha plots were similar; however, the Sparganium fertilized

Table I-l, 1979 15-cm interstitial concentrations (rag/1) in Typha glauca and Sparganium eurycarpum experimental plots

Typha glauca

Control Fertilized

Date NH^-N NOg-N PO,-P 4

NH,-N 4

NOg-N PO,-P 4

June 3^ 0.80 0,00 0.70 1.80 7.00 1.53

June 30^ — — — —

Aug. 8 0.70 1.80 0.65 2.48 0.17 1.10

Aug. 25 = — — — —

Sept. 8 — — — —

Sept. 22* 0.32 0.01 0.99 1.87 2.20 0.53

Oct. 7 0.45 0.03 0.97 0.08 0.09 1.18

Mean 0.57 0.46 0.83 1.56 2.36 1.08

Sparganlum eurycarpum

Control Fertilized

m.-N 4

NOg-N PO4-P NH,-N 4

NOg-N PO4-P

1.51 0.15 0.40 1.86 0.07 1.00

0.40 0.55 0.30 1.58 0.18 0.82

0.00 0.01 0.06 0.13 0.04 0.51

— — 0.23 0.06 0.10 0.02 0.19

0.06 0.07 0.18 0.58 0.38 0.16

0.11 0.05 0.32 1.00 0.07 0.14

0.42 0.18 0.22 0.87 0.13 0.47

^ater sample collected immediately before fertilizer application.

Table 1-2. 1979 45-cm interstitial concentrations (mg/1) in Typha glauca and Sparganium eurycarpum experimental plots

Typha glauca Sparganium eurycarpum

Control Fertilized Control Fertilized

Date NH^-N NOg-N PO4-P NH^-N NOg-N PC, -P 4

NH^-N NOg-N PO4-P NH,-N 4

NOg-N PO4-P

June 30^ 0.33 0.39 0.41 2.18 0.16 1.19 0.35 0.08 0.24 3.58 0.16 0.93

Aug. 8 0.59 0.69 0.53 0.14 0.06 0.07 0.26 0.10 0.26 0.59 0.07 0.59

Aug. 25® 0.00 1.58 0.49 0.75 0.23 0.82 — — —

Sept. 8 0.05 0.03 0.09 0.08 0.01 0.32 — — —

Sept. 22* 0.26 0.13 0.37 1.04 0.91 0.58 0.37 0.01 0.31 0.05 0.01 0.19

Oct. 7 0.38 0.04 0.25 0.11 0.90 0.67 0.00 0.13 0.25 0.00 0.61 0.89

Mean 0.27 0.48 0.36 0.72 0.38 0.71 0.25 0.08 0.27 1.10 0.22 0.60

^ater sample collected immediately before fertilizer application.

26

concentrations were nearly 3 times the unfertilized values.

1980

Nitrogen The mean 1980 NO^-N, and organic

nitrogen concentrations in 15-cm and 45-cm deep interstitial water

from fertilized enclosures and unfertilized plots are illustrated in

Figure 1-5. From early June, 1980 through October, 1980, NH^-N

concentrations at 15-cm in fertilized enclosures declined from

1.73 to 0.13 mg/1; however, an isolated peak of 1.3 mg/1 did occur

in September. Concentrations in unfertilized plots declined from

0.44 mg/1 to below detection. At 15-cm, average NH^-N concentrations

were significantly higher in fertilized plots; concentrations averaged

0.81 mg/1 in fertilized enclosures and 0.28 mg/1 in unfertilized

areas. The NH^-N increase at 15-cm in Sparganium enclosures was 25

times the increase at 15-cm in Typha stands. This species x treatment

interaction was statistically significant.

NOg-N and organic nitrogen concentrations at 15-cm were highest

in fertilized enclosures; however, the differences were not signifi­

cant. The seasonal averages for NO^-N in unfertilized and fertilized

plots were 0.06 and 0.20 mg/1, respectively. Organic nitrogen con­

centrations averaged 8.56 mg/1 in unfertilized plots and 11.03 mg/1

in fertilized enclosures. NO^-N concentrations underwent an obvious

decline through the summer, and throughout August NO^-N concentrations

were below detection (Figure 1-5). Organic nitrogen concentrations

were also generally lower late in the year but were highly variable.

z X z

15-cm

? o E Z 0.5-

e D D)

-4

'-n

45-cm

ro

unfert i l ized fert i l ized

Figure 1-5. The average concentration of NH^-N, NO^-N, and organic nitrogen in Eagle Lake ferti­

lized and unfertilized interstitial water at 15-cm and 45-cm depths

28

NH^-N, NO^-N, and organic nitrogen concentrations at 45-cm

were not affected by fertilizer application in 1980. NH^-N concen­

trations averaged 0.29 mg/1 in unfertilized plots and 0.32 mg/1 in

fertilized enclosures. Seasonal averages of NO^-N were 0.10 mg/1 in

unfertilized plots and 0.06 mg/1 in fertilized enclosures. Organic

nitrogen averaged 7.1 mg/1 and 6.4 mg/1 in unfertilized and fertilized

plots, respectively. Concentrations of the three forms of nitrogen

tended to decline throughout the summer (Figure 1-5).

Phosphorus The change in interstitial PO^-P and TP

concentrations at 15-cm and 45-cm depths is presented in Figure 1-6.

The 15-cm PO^-P concentrations averaged 0.58 mg/1 in unfertilized

plots and 0.93 mg/1 in fertilized enclosures. This difference was

statistically significant. The 45-cm PO^-P concentrations were

0.48 and 0.42 mg/1 in unfertilized and fertilized plots, respectively.

The difference at 45-cm was not significant.

Total phosphorus concentrations at 15-cm were significantly

higher in fertilized plots; averages were 1.19 mg/1 in fertilized

enclosures and 0.75 mg/1 in unfertilized plots. 45-cm averages were

0.61 mg/1 in unfertilized plots and 0.64 mg/1 in fertilized enclosures.

The 45-cm difference was not significant. An ANOVA calculated on the

dissolved and particulate phosphorus, excluding PO^-P (TP - PO^-P),

also indicated a significant increase after fertilization in these

other phosphorus forms at 15-cm, but not at 45-cm. The PO^-P concen­

trations accounted for 77% of TP in 15-cm unfertilized and fertilized

15-cm 45-cm

\ D)

E

fert i l ized

j A S

unfert i l ized

Figure 1-6. The average concentration of PO^-P. and total phosphorus (TP) in Eagle Lake fertilized and

unfertilized interstitial waters at 15-cm and 45-cm depths

30

samples, 79% in 45-cm unfertilized sangles, and 66% in 45-cm ferti­

lized samples. At 15-cm, PO^-P and TP tended to decline through

the summer (Figure 1-6).

Short-Term Patterns

Surface water

Figure 1-7 gives the change in concentrations of NH^-N, NO^-N, and

PO^-P in surface water and 15-cm interstitial of the fertilized enclo­

sures water on successive days after fertilization in July and October,

1980. Elevation of PO^-P, NH^-N, and NO^-N surface water levels after

fertilization was transitory. After each application, NO^-N concentra­

tions declined quickly; 5-8 mg/l/day immediately after fertilization in

July. The rate of NH^-N removal was much slower, averaging 1.5 to 3.5

mg/l/day during the first two weeks after fertilization in July. PO^-P

disappeared at a rate of about 0.3 to 0.5 mg/l/day during the first

two weeks after fertilization in July. During the cooler autumn

months, removal rates were slower for each nutrient. The mean

surface water temperature was 23.8 C in July and approximately 7 C

in October.

15-cm interstitial water

After fertilization in July and October, 15-cm NO^-N concentra­

tions increased 0.3-0.4 mg/1 within 24 hours (Figure 1-7). The

NO^-N levels returned to normal 3 days after fertilization in July

and after approximately 5 days in October. Because the July NH^-N

31

Surface 15 cm

1.0 +

\ 0>

E CO 0.2

O 0.8

DAYS

JULY OCTOBER Figure 1-7. The average concentration of NH^-N, NO^-N, and PO^-P in

surface water (n=6) and in 15-cm interstitial water (n=2)

on successive days after fertilization in July and October.

Bars denote ± 1 standard deviation

32

concentrations at 15-cm were initially high before application, an

increase after fertilization did not occur. In October, however,

NH^-N concentrations rose approximately 0.5 mg/1 in a 24-hour period

after fertilization. This concentration then declined slowly over

the 27-day interval. There was no increase in PO^-P concentration

after fertilization in either month (Figure 1-7). But, as

demonstrated in Figure 1-6, 15-cm PO^-P concentrations were elevated

by fertilization throughout 1980.

33

DISCUSSION

It is clear that the- interstitial water down to 15-cm was responding

to fertilization of Eagle Lake surface waters. Kadlec (1976) found

that added nutrients did not accumulate in interstitial waters of a

Michigan peatland. But, in that study no effort was made to confine

the applied nutrients. Other studies have reported an increase in

NH,-N concentration of 10-cm interstitial water of an estuarine 4

Spartina alterniflora stand after application of urea (Valiela and

32 Teal 1974); an accumulation of P (acid-labile phosphorus, ortho-

phosphate, and total phosphorus) in approximately 3-cm interstitial

water of an estuarine Typha angustifolia stand (Correll et al. 1975);

an elevation of NH,-N concentration in 1- to 4-cm interstitial water

of a wetland rice soil after application of urea (Sevant and De Datta

1980) ; and an increase in NO^-N, NH^-N, and SKP in interstitial water

from cultivated, fertilized plots of the Holland Marsh, Ontario

(Nicholls and MacCrimmon 1974). At Eagle Lake, fertilization caused

significant increases in PO^-P and NH^-N concentrations at 15-cm

(Figures 1-5 and 1-6). Data collected one day after fertilization

also indicated that 15-cm NO^-N concentrations were elevated

temporarily.

The mechanisms accounting for the movement of these nutrients

into the sediment profile at Eagle Lake are not well understood.

Correll et al. (1975) presented evidence that phosphorus was transferred

into an estuarine sediment by downward moving microbial cells. In

34

that study, the movement of phosphorus was extremely slow, requiring

20 days for less than 5-cm penetration. Studies of wastewater

renovation and fertilizer application in soils have also suggested

very slow penetration of phosphorus into a soil profile (Hill 1972;

Kao and Blanchar 1973; Sawney and Hill 1975). Interstitial PO^-P

concentrations did not change during 28-day periods after fertiliza­

tion at Eagle Lake (Figure 1-7); but, over the entire 1980 summer

PO^-P levels were elevated significantly because of fertilization

(Figure 1-6). Thus, PO^-P penetration into interstitial water

obviously occurred to a depth of 15-cm; however, on a short-term

basis the downward penetration of PO^-P was evidently a gradual

process in balance with the removal or transformation of PO^-P already

in the interstitial water column.

In contrast to PO^-P, NO^-N 15-cm concentrations increased

approximately 0.3-0.4 mg/1 within a 24-hour period after fertilization

in July and October (Figure 1-7). Such rapid penetration probably

cannot be explained by downward moving microbes. Immediately after

fertilization, an extreme concentration gradient did exist between

interstitial and surface water NO^-N concentrations; usually less

than 1.0 mg/1 in interstitial water versus 20 mg/1 in surface water.

Thus, diffusion may in part account for the movement of NO^-N.

Over the 1980 summer, NH^-N concentrations were elevated in

15-cm interstitial water because of fertilization. In July, 1980

concentrations of NH^-N in 15-cm interstitial water, however, did

not increase after fertilization; thereby suggesting a gradual down­

35

ward penetration of NH^-N in a manner similar to that of PO^-P. On

the other hand, NH^-N penetration into the interstitial water in

October was rapid (nearly 0.4 mg/1 in a 24-hour period) and resembled

more closely the movement of NO^-N.

The separation of the aerobic surface water column from the

anaerobic interstitial water profile of lakes and ponds can lead

to accumulation of some nutrients in interstitial water. This is

particularly true of phosphate, e.g., in Lake Mendota phosphate

has been reported to reach a level in 0-6 cm water 5-20 times surface

water concentrations (Holdren et al. 1977). In the Eagle Lake

unfertilized plots, concentrations of NH^-N and PO^-P in 15-cm

interstitial water resembled NH,-N and P0,-P concentrations in surface 4 4

water. In both study years, PO^-P concentrations were highest in

the interstitial water, 56% higher in 1979 and 21% higher in 1980;

but, these differences are small compared to Holdren et al.'s data.

The concentration of NH^-N in Eagle Lake 15-cm interstitial water

was 12% greater in 1979, but 42% less in 1980 than surface water

concentrations. These smaller differences at Eagle Lake indicate

that a near steady state situation may exist for PO^-P and NH^-N

across the sediment-water interface. The concentrations of

and PO^-P in fertilized plots were also similar between surface

and interstitial waters, but as one might expect, surface NH^-N

and PO^-P concentrations were slightly higher. In marshes, oxygen

concentrations in shallow surface water can be reduced by decomposi­

tion of vegetation (Maystrenko et al. 1969; Jewell 1971); and

36

Planter (1970) and Pribil and Dykjova (1973) have observed that dis­

solved oxygen concentrations inside shallow emergent stands can be

less than concentrations in or near open water. Oxygen measure­

ments at Eagle Lake in November, 1980 revealed an average surface

water Og concentration of 1.1 mg/1, less than 10% of saturation.

Interstitial 0^ concentrations averaged less than 0.1 mg/1. Thus,

the distinction between an anaerobic interstitial water column and

an aerobic surface water column is probably less pronounced in a

shallow marsh than in an oligotrophic lake.

Although surface and interstitial waters of marshes may be

more similar than their counterparts in lakes, substantial buildup

of emergent litter at the sediment-water interface in a marsh may

potentially contribute to a separation of marsh surface and

interstitial waters. Because of microbial activity, nitrogen and

phosphorus can be immobilized in the fallen litter compartment

(Kaushik and Hynes 1968, 1971; Odum and De La Cruz 1967; Maystrenko

et al. 1969; Boyd 1970; Klopatek 1975; Mason and Bryant 1975;

Richardson et al. 1976; Davis and Harris 1978; Davis and van der Valk

1978a, 1978b, 1978c; and others) thereby minimi zing the amounts

of nitrogen and phosphorus available to move into the interstitial

water. At Eagle Lake, the increase in NH^-N concentration in 15-cm

interstitial water of lypha plots was significantly less than the

increase in interstitial waters of Sparganium plots. Although

PO^-P interstitial concentrations at 15-cm did not show a signif­

icant species-specific response to fertilization, the accumulation

37

of PO^—P in 15-cm interstitial water of Sparganium stands was 15%

greater than the accumulation in Typha stands. These differences

may be a function of the amount of litter deposited at the sediment-

water interface by the two plant species. Larger quantities of

Typha litter which take several years for complete decomposition

(Davis and van der Valk 1978a, 1978b) may reduce the interaction of

surface and interstitial water constituents in Typha stands.

Conversely, Sparganiiim litter, which decomposes rapidly, may have

only a slight effect on the movement of nutrients between surface

and interstitial waters. The buildup of litter at the sediment-

water interface may be as important in influencing interstitial

water chemical components as is the oxygen status of the surface

and interstitial waters. The role of litter in minimizing the down­

ward movement of nutrients is (1) as a physical barrier and (2) as

a substrate for microbes which remove nutrients from the surface

water.

38

LITERATURE CITED

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American Public Health Association, American Water Works, and Water Pollution Control Federation. 1975. Standard methods for the examination of water and wastewater. 14th ed. A.P.H.A., Washington, D.C. 1193 pp.

Bischoff, J. L., R. E. Greer, and A.O. Luistro. 1970. Composition of interstitial waters of marine sediments; Temperature of squeezing effect. Science 167:1245-1246.

Boyd, C. E. 1970. Losses of mineral nutrients during decomposition of Typha latifolia. Archiv fur Hydrobiologie 66:511-517.

Bray, J. T., 0. P. Bricker, and B. N. Troup. 1973. Phosphate in interstitial waters of anoxic sediments: Oxidation effects during sampling procedure. Science 180:1362-1364.

Brunskill, G. J., D. Povoledo, B. W. Graham and M. P. Stainton. 1971. Chemistry of surface sediments in sixteen lakes in the Experimental Lakes Area (ELA), northwestern Ontario. Journal of Fisheries Research Board of Canada 28:277-294.

Correll, D. L., M. A. Faust, and D. J. Severn. 1975. Phosphorus flux and cycling in estuaries. Pages 108-136 L. E. Cronin, ed. Estuarine Research. Vol. I. Academic Press, New York. 738 pp.

Currier, P. J. 1979. Floristic composition and primary production of the postdrawdown vegetation of Eagle Lake marsh, Hancock County, Iowa. M.S. Thesis. Iowa State University. 149 pp.

Davis, C. B. and A. G. van der Valk. 1978a. The decomposition of standing and fallen litter of Typha glauca and Scirpus fluviatilis. Canadian Journal of Botany 56:662-675.

Davis, C. B. and A. G. van der Valk. 1978b. Litter decomposition in prairie glacial marshes. Pages 99-113 R. E. Good, D. F. Whigham and R. L. Simpson, eds. Freshwater wetlands: Ecological processes and management potential. Academic Press, New York. 378 pp.

39

Davis, C. B. and A. G. van der Valk. 1978c. Minerai release from the litter of Bid ens cernua L., a mudflat annual at Eagle Lake, Iowa. Proceedings of the International Association for Theoretical and Applied Limnology, 20:452-457.

Davis, C. B., J. L. Baker, A. G. van der Valk, and C. E. Baker. 1981. Prairie pothole marshes as traps for nitrogen and phosphorus in agricultural runoff. Pages 153-163 B. Richardson, ed. Pro­ceedings of the Midwest Conference on Wetland Values and Management. Freshwater Society, 2500 Shadywood Road, Box 90, Navarre, Minnesota. 55372. 660 pp.

Davis, S. M. and L. A. Harris. 1978. Marsh plant production and phosphorus flux in Everglades Conservation Area 2. Pages 105-131 in M. A. Drew, ed. Environmental quality through wetland utiliza­tion. Coordinating Council on the Restoration of the Kissimmee River Valley and Taylor Creek-Nubbin Slough Basin, Tallahassee, Florida. 243 pp.

Graetz, D. A., D. R. Keeney, and R. B. Aspiras. 1973. Eh status of lake sediment-water systems in relation to nitrogen transforma­tions. Limnology and Oceanography 18:908-918.

Hill, D. E. 1972. Wastewater renovation in Connecticut soils. Journal of Environmental Quality 1:163-167.

Holdren, G. C., D. E. Armstrong, and R. F. Harris. 1977. Intersti­tial inorganic phosphorus concentrations in Lakes Mendota and Wingra. Water Research 11:1041-1047,

Irzumi, H., A. Hattori, and C. P. McRoy. 1980. Nitrate and nitrite in interstitial waters of eelgrass beds in relation to the rhizosphere. Journal of Experimental Marine Biology and Ecology 47:191-201.

Jewell, W. J. 1971. Aquatic weed decay: dissolved oxygen utiliza­tion and nitrogen and phosphorus regeneration. Journal-Water Pollution Control Federation 43:1457-1467.

Kadlec, R. H. 1976. Dissolved nutrients in a peatland near Houghton Lake, Michigan. Pages 27-50 D, L. Til ton, R. H. Kadlec, and C. J. Richardson, eds. Freshwater wetlands and sewage effluent disposal. The University of MicTiigan, Ann Arbor, Michigan. 343 pp.

Kao, C. W. and R. W. Blanchar. 1973. Distribution and chemistry of phosphorus in an Albaqualf soil after 82 years of phosphate fertilization. Journal of Environmental Quality 2:237-240.

40

Kaushik, N. K. and H. B. N. Hynes. 1968. Experimental study on the role of auttmn-shed leaves in aquatic environments. Journal of Ecology 56:229-243.

Kaushik, N. K. and H. B. N. Hynes. 1971. The fate of the dead leaves that fall into streams. Archiv fur Hydrobiologie 68:465-515.

Keeney, D. R., J. G. Konrad and G. Chesters. 1970. Nitrogen distri­bution in some Wisconsin lake sediments. Journal-Water Pollution Control Federation 42:411-417.

Klopatek, J. M. 1975. The role of emergents in mineral cycling in a freshwater marsh. Pages 357-393 F. Howell, J. B. Gentry, and M. H. Smith, eds. Symposium on mineral cycling in southeastern ecosystems. ERDA Symposium Series (CONF 740513). 898 pp.

Konrad, J. G., D. R. Keeney, G. Chesters, and K. L. Chen. 1970. Nitrogen and carbon distribution in sediment cores of selected Wisconsin lakes. Journal-Water Pollution Control Federation 42:2094-2101.

Lerman, A. and G. J. Brunskill. 1971. Migration of major constit­uents from lake sediments into lake water and its bearing on lake water composition. Limnology and Oceanography 16:880-890.

Li, Y. H. and S. Gregory. 1974. Diffusion of ions in sea water and deep sea sediments. Geochimica et Cosmochimica Acta 38:703-714.

Lind, 0. T. 1979. Handbook of common methods in limnology. 2nd ed. C. V. Mosby Co., St. Louis. 199 pp.

Martens, C. S., R. A. Berner, and J. K. Rosenfeld. 1978. Interstitial water chemistry of anoxic Long Island Sound sediments. 2. Nutrient regeneration and phosphate removal. Limnology and Oceanography 23:605-617.

Mason, C. F. and R. J. Bryant. 1975. Production, nutrient content and decomposition of Phragmites communis Trin. and Typha angustifolia L. Journal of Ecology 63:71-95.

Maystrenko, Yu, A. I. Denisova, V. M. Bognyuk and Zh. M. Arymaova. 1969. The role of higher aquatic plants in the accumulation of organic and biogenic substances in water bodies. Hydrobiological Journal 5:20-31.

Mortimer, C. H. 1941. The exchange of dissolved substances between mud and water in lakes. Journal of Ecology 30:147-199.

41

Murphey, J. and J. Riley. 1962. A modified single solution method for the determination of phosphate in natural waters. Analytica Chemica Acta 27:31-36.

Nicholls, K. H. and H. R. MacCrinmon. 1974. Nutrients in subsurface and runoff waters of the Holland Marsh, Ontario. Journal of Environmental Quality 3:31-35.

Odum, E. P. and A. A. De La Cruz. 1967. Particulate organic detritus in a Georgia salt marsh-estuarlne ecosystem. Pages 383-388 G. H, Lauff, ed. Estuaries. American Association for the Advance­ment of Science, University of Georgia, Athens. 757 pp.

Planter, M. 1970. Physico-chemical properties of the water of reed-belts in Nikola j skie, Taltowisko, and Sniardwy Lakes. Pol skie Archiwum Hydrobiologii 17:337-356.

Pribil, S. and D. Dykyjova. 1973. Variation in some physical and chemical properties of the water in the stand of Phragmites communis. Pages 71-78 S. Hejny, ed. Ecosystem study on wetland biome in Czechoslovakia. Czechoslovak Acadmy of Sciences. 262 pp.

Richardson, C. J., W. A. Wentz, J. P. M. Chamie, J. A. Kadlec, and D. L. Til ton. 1976. Plant growth, nutrient accumulation and decomposition in a central Michigan peatland used for effluent treatment. Pages 77-117 D. L. Til ton, R. H. Kadlec, and C. J. Richardson, eds. Freshwater wetlands and sewage effluent disposal. The University of Michigan, Ann Arbor, Michigan. 343 pp.

Sawney, B. L. and D. E. Hill, 1975. Phosphate sorption characteris­tics of soils treated with domestic waste water. Journal of Environmental Quality 4:342-346.

Serruya, C., M. Edelstein, U. Pollingher, and S. Serruya. 1974. Lake Kinneret sediments: Nutrient conqjosition of the pore water and mud water exchanges. Limnology and Oceanography 19:489-508.

Sevant, N. K. and S. K. De Datta. 1979. Nitrogen release patterns from deep placement sites of urea in a wetland rice soil. Soil Science Society of America Journal 43:131-134.

Sevant, N. K. and S. K. De Datta. 1980. Movement and distribution of ammonium-N following deep placement of urea in a wetland rice soil. Soil Science Society of America Journal 44:559-565.

Sholkovitz, E. 1973. Interstitial water chemistry of the Santa Barbara Basin sediments. Geochlmica et Cosmochlmica Acta 37:2043-2073.

42

Singlachar, M. A., and R. Samaniego. 1973. Effect of floodi^ and cropping on the changes in the inorganic phosphate fractions in some rice soils. Plant and Soil 39:351-359.

Stainton, M. P., M. J. Carpel, and F. A. J. Armstrong. 1974. The chemical analysis of freshwater. Fisheries Research Board of Canada Miscellaneous Special Publication 25. 125 pp.

Syers, J. K., R. F. Harris, and D. E. Armstrong. 1973. Phosphate chemistry in lake sediments. Journal of Environmental Quality 2:1-14.

Valiela, I., and J. M. Teal. 1974. Nutrient limitation in salt marsh vegetation. Pages 547-563 R. J. Reimold and W. H. Queen, eds. Ecology of Halophytes. Academic Press, New York and London. 605 pp.

van der Valk, A. G. and C. B. Davis. 1978a. Primary production in prairie glacial marshes. Pages 21-37 R. E. Good, D. F. Whigham, and R. L. Simpson, eds. Freshwater wetlands: Ecological processes and management potential- Academic Press, New York. 378 pp.

van der Valk, A. G., and C. B. Davis. 1978b. The role of the seed bank in the vegetation dynamics of prairie glacial marshes. Ecology 59:322-335.

van der Valk, A. G., and C. B. Davis. 1979. A reconstruction of recent vegetational history of a prairie glacial marsh. Eagle Lake, Iowa, from its seed bank. Aquatic Botany 5:19-51.

van der Valk, A. G. and C. B. Davis. 1980. The impact of a natural draw-down on the growth of four emergent species in a prairie glacial marsh. Aquatic Botany 9:301-322.

Viner, A. B. 1975. The sediments of Lake George (Uganda) III: Uptake of phosphate. Archiv fur Hydrobiologie 76:393-410.

Viner, A. B. 1977. The sediments of Lake George (Uganda) IV: Vertical distribution of chemical features in relation to. ecological history and nutrient recycling. Archiv fur Hydrobiologie 80:40-69.

43

SECTION II. NUTRIENT LIMITATION OF SPARGANIDM EURYCAEPUM

AND TYPHA GLAUCA IN A PRAIRIE MARSH

44

ABSTRACT

In 1979 and 1980, nitrogen and phosphorus fertilizer was applied

to stands of Typha glauca and Sparganiurn eurycarpum in a prairie marsh.

Eagle Lake, Iowa. Fertilizer additions resulted in significant in­

creases of NH^-N and PO^-P in interstitial waters, significant increases

in sediment and nonsignificant increases in sediment PO^-P.

Nitrogen concentrations in above-ground and below-ground plant structures

were significantly increased because of the fertilizer treatment. That

both species had been nutrient limited was indicated by significant 1980

increases in above-ground biomass and net annual above-ground production

in fertilized plots. Increases in shoot density and below-ground biomass

also occurred in fertilized plots in 1980, but were not statistically

significant.

Keywords: Typha glauca, Sparganium eurycarpum, cattail, bur-reed,

freshwater wetland, emergent production, interstitial water, nitrogen,

phosphorus, nutrient cycling.

45

INTRODUCTION

Marine and freshwater wetlands dominated by emergents have long

been recognized as productive ecosystems (Westlake 1963). The high

primary production of emergent communities generally is attributed to

the assumption that emergent macrophyte growth is not limited by defi­

ciencies of water, light, or nutrients. But, more recent data indicate

that nutrient availability can and does limit the potential production

of some emergents.

Most evidence of emergent nutrient limitation comes from studies

of coastal salt marshes and shore communities (Tyler 1967; Sullivan

and Daiber 1974; Valiela and Teal 1974; Valiela et al. 1975, 1976;

Gallagher 1975; Broome et al. 1975). An experimental approach, adding

known amounts of specific nutrients or sewage sludge fertilizer to

plant stands, has demonstrated that nitrogen often is limiting to

coastal species. Sullivan and Daiber (1974), Valiela and Teal (1974),

and Gallagher (1975) reported positive responses in above-ground stand­

ing crop of Spartina alterniflora to applications of urea or ammonium

nitrate. Similarly, the standing biomass of Juncus gerardi and

Plantago maritima increased after application of (Tyler 1967). In

greenhouse studies, Pigott (1969) demonstrated that soil nitrogen

levels influence the zonation and growth of Salicomia species and

Suaeda maritime. Because of an adequate supply in seawater, phosphorus

is rarely limiting in coastal marshes (Valiela and Teal 1974). Under

some circumstances, however, phosphorus may be limiting in coastal

systems (Tyler 1967; Broome et al. 1975).

46

There have been numerous studies of growth, nutrient assimilation,

and water purification by freshwater species and wetlands under enriched

conditions (Steward and Omes 1975; de Jong 1976; Ewel 1976; Seidel 1976;

Richardson et al. 1976; Spangler et al. 1976, 1977; Turner et al. 1976;

Whigham and Simpson 1976a, 1976b; Werblan 1979); however, not all of

these studies are useful for an assessment of nutrient limitation. And,

the useful studies are contradictory. Steward and Omes (1975) found

that stands of Cladium jamaicense in the Everglades were not limited by

nitrogen or phosphorus. Additionally, Whigham and Simpson (1976b) found

above-ground biomass values in a freshwater tidal marsh to be suppressed

by sewage application, particularly when the sewage was applied contin­

uously. In the latter study, however, the presence of chlorine in the

sewage effluent undoutedly had an inhibitory effect on the vegetation.

In contrast to these two studies, standing crops of Phrapinites

coTmmmis, Sagittaria falcata, Scirpus validus, and Spartina patens in

a Louisiana marsh increased after application of fisheries wastewater

(Turner et al. 1976). In Iowa, the above-ground biomass of Typha glauca

and Sparganium eurycarpum grown in artificial marshes enriched with raw

swine waste was substantially higher than biomass values for the same

species growing in nearby prairie marshes (Werblan 1979). Sichardson

et al. (1976) noted that the biomass of Carex species in the field was

unaffected by low concentrations of an added nutrient solution, but was

stimulated by higjier concentrations of the same solution. These studies

do not allow one to assess the role of any one nutrient, nor was it

their intent; but, in other studies, Cyperus esculentus and Scinjus

47

valldus, grown in the greenhouse on sediments of varying texture,

nitrogen concentration, and phosphorus concentration, were reported

to be limited by nitrogen on most sediments (Barko and Smart 1978,

1979). Cyperus esculentus was thought to be limited by phosphorus on

one sediment (Barko and Smart 1978). Boyd and Hess (1970) also found

that standing crops of Typha latifolla were positively correlated

with phosphorus in saturated sediments and surface waters.

The need for additional baseline data in freshwater systems is

obvious and has been stated (De la Cruz 1978; Kadlec 1979). The

purpose of this study was to examine the effects of nitrogen and

phosphorus enrichment on above- and below-groimd production of

natural stands of Typha glauca and Sparganium eurycarpum in a prairie

marsh.

48

METHODS

Study Site

Eagle Lake, Hancock Co., Iowa, is a 365-ha, Type IV (Stewart and

Kantrud 1971) prairie marsh dominated by Typha glauca, Sparganium

eurycarpum, and Carex atherodes. The marsh is owned and managed by

the Iowa Conservation Commission. Water depth can be controlled by a

dam across the northern edge of the marsh and rarely exceeds 1 m. The

production, decomposition, seed bank dynamics, and nutrient fluctua­

tions of plant species in Eagle Lake have been described by Currier

(1979), Davis and van der Valk (1978a, 1978b), and van der Valk and

Davis (1978a, 1978b, 1979, 1980).

The Eagle Lake drainage basin covers 2,563 ha. Approximately

1,959 ha are used for agricultural purposes, including over 1,700 ha

used exclusively in row-crop cultivation of com and soybeans. During

occurrences of high precipitation, surface runoff and tile drainage

from these fields can add large quantities of nutrients, particularly

nitrate, to the marsh. In 1979, 2.5 kg NH^-N/ha, 204 kg NO^-N/ha

and approximately 3.5 kg PO^-P/ha entered the marsh with surface runoff

and subsurface drainage. An additional 6.6 kg NH^-N/ha and 6.3 kg

NOg-N/ha were added to the marsh by precipitation (Davis et al. 1981).

During the study period, 1979 and 1980, annual precipitation was

957 mm and 710 mm, respectively. Average annual precipitation for

this area is 802 mm. Average daily temperatures during the study

ranged from a low 1979 winter temperature of -8 C to a high 1980

summer temperature of 23 C.

49

Construction and Fertilization of Enclosures

During May, 1979, 6 watertight enclosures (6 m x 6 m) for fertiliza­

tion were constructed in monodominant stands of Typha glauca (Typha) and

Sparganium eurycarpum (Sparganlum) at Eagle Lake marsh. Three enclosures

were built for each species and located in the northern, southern, and

western parts of the marsh (Figure II-l). A control plot was established

near each enclosure by staking a 6- x 6-m area of open marsh. Each enclo­

sure was constructed of 1.9 cm thick marine plywood with 6-cm x 10-cm wood

supports. To minimize fertilizer leakage, all sides were driven approxi­

mately 10 cm into the substrate and 5-cm x 10-cm boards were used as in­

terior and exterior seals. Dye tests revealed no leakage.

The area within each watertight enclosure was fertilized at 28-day

intervals. All fertilizer additions were calculated to restore available

nitrogen and phosphorus concentrations in the water column to approxi­

mately 25 mg NH^-N/1, 20 mg NG^-N/l, and 5 mg PO^-P/1. Nitrogen was added

as a solution of NH^NO^ and phosphorus as a suspension of (NH^) 2^^^^ '

Collection and Analysis of Samples

Sediment and interstitial H«0

One sediment sample and one 15-cm deep interstitial water sample

were collected biweekly from Typha and Sparganium enclosures and control

plots during the 1979 and 1980 growing seasons. During both years,

interstitial samples were collected from only the northern and western

sites. The interstitial water samples were collected from permanent

sanqpling wells and were preserved in the field by addition of 1 ml

50

1/4 mi.

• CONTROL • FERTILIZED

Figure II-l. Location of Sparganium and Typha control and fertilized enclosures at each of 3 sites in Eagle Lake marsh. The actual arrangement of plots at each site is not indicated

51

concentrated HgSO^/l sançle. Sediment and water samples were refrigerated

at 5 C until analyzed.

In the laboratory, NH^-N, NO^-N, and PO^-P analyses were performed

on all interstitial water samples. The phenate method (Stainton et al.

1974) was used for NH^-N determinations. PO^-P concentrations were

determined by using the ascorbic acid reduction procedure (Murphey and

Riley 1962). NO^-N analyses were carried out according to the Technicon

Auto-Analyzer II system cadmium reduction procedure. Sediment samples

from 1979 and 1980 were dried and analyzed for PO^-P after extraction

in a sodium bicarbonate solution (North Dakota Agricultural Experiment

Station Bulletin No. 499, 1973). NH^-N concentrations in wet 1980

sediment samples were determined by titration with 0.005 N HgSO^ after

distillation with MgO (A.O.A.C. 1960).

Vegetation

Throughout the study, vegetative and flowering shoot densities

were counted at biweekly intervals. Within each enclosure and control

2 plot, counts were made in 3 permanent 1-m quadrats. Flowering and

vegetative dry—shoot weights were obtained after each count by

collecting approximately 50 shoots in and near unfertilized plots and

10-15 shoots from fertilized enclosures. Shoots were dried for 1 week

at 60 C before being weighed. Shoot densities were used to calculate

standing biomass and net annual above-ground production (van der Valk

and Davis 1978a).

Combined root and rhizome biomass (root-rhizome) was estimated

52

by excavating 50- x 50-cm substrate samples in unfertilized and ferti­

lized plots to a depth of approximately 30 cm. Thirty samples were

collected before fertilization in May, 1979. In November, 1979 and

October, 1980, 15 samples were collected from each treatment. In the

laboratory, dead below-ground material was removed and discarded from

each sample, but no effort was made to separate roots and rhizomes.

All remaining live material was thorou^ly washed in distilled water,

dried at 60 C for 1 week, and weighed. Dried root-rhizome and shoot

material was subsampled and groiind in a Wiley mill with a #20 mesh.

Microkjeldahl procedures were used to determine total N in these

subsamples.

Statistical Analyses

The experimental design used in this study represents a 2 x 2

factorial model with 3 replicates carried through time; i.e., 2 species

and 2 treatments at each of 3 sites on each sample data. An analysis

of variance was used to determine the effects of site, species, treat­

ment, species x treatment, time, time x species, time x treatment,

and time x species x treatment on the following parameters in each

year: NH^-N, NO^-N, and PO^-P concentrations in interstitial water;

NH^-N and PO^-P sediment concentrations; shoot density; dry-shoot

weight; above-ground biomass; and percentage nitrogen in shoots and

roots. Net annual above-ground production and the final root-rhizome

biomass data were used in a second ANOVÂ generated as a 2 x 2 factorial;

but, because these measurements did not take place over time, time

53

effects were excluded from the ANOVA.

Because of the intrinsic variability characteristic of wetlands,

statistical significance was set at the a = 0.10 confidence level (see

Richardson et al. 1976). In both analyses, the site x species x

treatment interaction was used as an error term when computing site,

species, treatment, and species x treatment mean square values. Mean

square values for the remaining ANOVA terms were calculated by using

the standard error term, but the F values were evaluated by using con­

servative degrees of freedom. These modifications were incorporated

because measurements over time and multiple measurements in a single

treatment plot do not represent true replicates.

54

RESULTS

Interstitial H^O

The mean NO^-N, and PO^-P concentrations in interstitial

water from fertilized and control plots over the 1980 growing season

are presented in Figure II-2. At Eagle Lake, a general decline in

interstitial concentrations of these nutrients in fertilized and control

plots occurred during the 1980 growing season, but only the NH^-N

concentration change in time was significant. Fertilization of surface

waters significantly increased NH^-N and PO^-P interstitial concentra­

tions. On all dates, levels of these two nutrients were higher in

fertilized plots. In contrast, NO^-N concentrations were greater in

fertilized plots only during the early summer and fall months, and not

significantly so. Probably because of denitrification (Patrick and

Tusneem 1972), NO^-N levels in control and fertilized plots were below

the detection limit during the mid-summer months. Although differences

between all control and fertilized nutrient concentrations seem to

change with time, the effect of fertilization was statistically uniform

throughout the season.

An effect not shown in Figure II-2 was a significant species-

specific increase in interstitial NH^-N concentrations of fertilized

plots. The mean summer NH^-N concentration in Sparganium fertilized

plots was 25 times greater than the increase in Typha plots. For both

species, the amount of NH^-N moving into the interstitial water was small

relative to the concentration of the surface water. Despite restoration

of surface water NH^-N concentrations to 25 ppm every 4 weeks, inter-

INTERSTITIAL H^O 1.5

Z 1

41 : »•' I i 10

E 30 Q.

T I I r

JUNE JULY AUG. SEPT.

SEDIMENT .

' *

f 10

T

P* A. #

1 1 1 1

JUNE JULY AUG. SEPT.

Ln

C O N T R O L F E R T I L I Z E D 1 9 8 0 o 1979

Figure II-2. Average NH^-N, NO^-N, and PO^-P concentrations in interstitial water and sediments

of control and fertilized plots during 1979 and 1980

56

stitial concentrations never reached 2 ppm.

Because of continuous damage to sampling wells by muskrats, few

interstitial samples were collected in 1979. On several of the dates,

we could collect only 1 sample; thus, the 1979 interstitial data were

not statistically analyzed. The data that we could obtain are pre­

sented in Table II-l. Fertilization in 1979 did seem to increase

NH,-N and PO.-P interstitial concentrations. NO -N concentrations in 4 4 3

Sparganium plots were unaffected by fertilization, and the NO^-N

values from Typha plots show no trend.

Sediment

1979 and 1980 available sediment phosphorus and 1980 sediment

NH^-N concentrations are also illustrated in Figure II-2. Available

soil phosphorus concentrations in fertilized and control plots are

similar until near the end of the 1979 growing season. In late August,

phosphorus concentrations in fertilized plots rose quickly and remained

elevated through the 1980 season. In neither year were the increases

significant, but in 1979 the late increase produced a significant time

X treatment interaction. Because Eagle Lake surface waters contain

oxygen, an elevation of PO^-P levels in sediments of fertilized plots

is to be expected. PO^-P is removed from an aerated water column to

the soil compartment as an iron precipitate (Stumm and îlorgan 1970).

Mean 1980 sediment NH^-N response to nutrient enrichment was posi­

tive (Figure II-2) and statistically significant. This measurement

Table II-l, 1979 15-cra interstitial concentrations (ppm) in Typha glauca and Sparganium eurycarpum experimental plots

Date

June 3

Typha glauca

Control

NH,-N NO -N PO,-P 4 3 4

0.80 0.00 0.70

Fertilized

NH,-N NO.-N P0,-P 4 3 4

1.80 7.00 1.53

Sparganium eurycarpum

Control Fertilized

NH,-N N0_-N P0,-P 4 3 4

NH^-N NOg-N PO^-P

June 30 — — — — — — — 1.51 0.15 0.40 1.86 0.07 1.00

Aug. 8 0.70 1.80 0.65 2.48 0.17 1.10 0.40 0.55 0.30 1.58 0.18 0.82

Aug. 25 — - - — — — — 0.00 0.01 0.06 0.13 0.04 0.51

Sept . 8 — — — — — — — 0.23 0.06 0.10 0.02 0.19

Sept . 22 0.32 0.01 0.99 1.87 2.20 0.53 0.06 0.07 0.18 0.58 0.38 0.16

Oct, 7 0.45 0.03 0.97 0.08 0.09 1.18 0.11 0.05 0.32 1.00 0.07 0.14

Mean 0.57 0.46 0.83 1.56 2.36 1.08 0.42 0.18 0.22 0.87 0.13 0.47

58

represents the amount of NH^-N adsorbed to sediment particles. Thus,

an increase in interstitial NH,-N concentration should cause an increase

in adsorbed NH^-N. In mid-June and late September, concentrations in

fertilized plots were lower than in control plots, but the time x treat­

ment interaction was not signficant.

Above-ground Vegetative Response

Nitrogen content

1979 and 1980 nitrogen concentrations in Typha and Sparganium

live shoots of control and fertilized plots are given in Figure II-3.

The steady decline in nitrogen concentration over the growing season

is a pattern typical of many emergent species and various nutrients

(Boyd 1969, 1970; Boyd and Hess 1970; Boyd and Vickers 1971; Bayly and

O'Neill 1972; Mason and Bryant 1975; Prentki et al. 1978). Although

fertilization had no effect on this pattern, the treatment did cause

a significant increase in tissue nitrogen levels. Average summer

nitrogen concentrations of Sparganium in fertilized plots were 30% and

34% hi^er than in control plots in 1979 and 1980, respectively.

Increases in the nitrogen concentration of Typha were smaller, 7% in

1979 and 14% in 1980. The difference in the degree of response between

the two species was significant and may be due to the smaller concentra­

tions of NH^-N in interstitial water of fertilized Typha plots.

SHOOT •A,

1979

Z

1- -1980

JUNE JULY AUG. SEPT.

ROOT 2 -

1 %e • • • ••

1979

Z

1980

JUNE JULY AUG. SEPT,

ASPARGANIUM «TYPHA CONTROL FERTILIZED

Figure II-3. Average percentage nitrogen in Sparganlum and Typha shoot and root-rhizome tissues from control and fertilized plots during 1979 and 1980

60

Shoot density

2 The average number of shoots/m for each species, treatment, and

year are presented in Figure II-4. During 1979, Sparganitim mean

2 maximum shoot density was 110 shoots/m in unfertilized plots and 109

2 shoots/m in fertilized plots. In this same year, Typha shoots peaked

2 2 at 64 shoots/m and 77 shoots/m in unfertilized and fertilized plots,

respectively. The occurrence of higher Typha shoot densities in fer­

tilized plots during 1979 was probably not the result of fertilization.

Typha rhizomes begin forming new shoots in autumn, and these overwinter

until spring (Bernard and Bernard 1973); hence, 1979 shoot density may

have been fixed 6 months before the initiation of this study. The

2 1980 mean maximum shoot densities reached 94 shoots/m in unfertilized

2 and 113 shoots/m in fertilized Sparganium stands. Similarly, Typha

2 mean shoot densities peaked at 74 shoots/m in unfertilized plots and

2 96 shoots/m in fertilized plots. Differences between fertilized and

control plots were not significant in 1979 or 1980.

Biomass and production

The product of shoot weight and density provides an estimate of

above-ground biomass on each sampling date. Total biomass data for

1979 and 1980 are presented in Figure II-5. The pattern in 1979

illustrates no difference in biomass between treatments in early summer

and larger differences in mid- to late-summer. The time x treatment

interaction was significant. Maximum biomass estimates in control

2 2 plots were 816 g/m for Sparganium and 1,351 g/m for Typha. These

61

Z

JUNE ' JULY ' AUG. ' SEPT. '

SPARGANIUM TYPHA • •

CONTROL FERTILIZED

Figure II-4. Average Sparganium and Typha shoot density in control and fertilized plots in 1979 and 1980

62

«A «m < % O 2 1980

*A*

J U N E ' J U L Y ' A U G . ' S E P T

SPARGANIUM TYPHA A •

CONTROL FERTILIZED

Figure I1-5. Average Sparganium and Typha total above-ground biomass in control and fertilized plots during 1979 and 198.0

63

2 2 values compare with biomass estimates of 904 g/m and 1,781 g/m in

Sparganium and Typha fertilized plots, respectively (Table II-2).

There was no significant treatment effect in 1979.

In 1980, biomass values were significantly larger in fertilized

plots. Again, the effect of fertilization was most noticeable later

in the growing season and produced a significant time x treatment

2 interaction. The Sparganium maximum biomass estimates were 637 g/m

2 in control plots and 1,185 g/m in fertilized plots. Typha plots pro-

2 2 duced a maximum biomass of 1,726 g/m in control plots and 2,343 g/m

in fertilized plots (Table II-2).

Mean annual net above-ground primary production values are listed

in Table II-2. In both years, the Eagle Lake fertilized plots were

more productive. Typha production in fertilized plots exceeded pro-

2 2 duction in unfertilized plots by 532 g/m in 1979 and 405 g/m in

1980. Likewise, Sparganium production in fertilized plots surpassed

that in unfertilized plots by 129 g/m^ in 1979 and 524 g/m^ in 1980.

Because of high variation between plots, only the 1980 differences were

statistically significant, van der Valk and Davis estimated produc-

2 2 tion of Typha to be 2,297 g/m and Sparganium to be 1,066 g/m in

Eagle Lake (Table II-3) . Our control values are all within ± 1

standard deviation of their production figures (Table II-2). Mean

production of Typha in fertilized plots at Eagle Lake is similar to the

estimate of 2,630 g/m produced by Typha after enrichment with swine

waste (Werblan 1979). Sparganium values are lower than Werblan's

2 production estimate of 2,092 g/m . •

2 Table II-2. 1979 and 1980 average net annual above-ground production (g/m ), average maximum

above-ground biomass (g/m^), average autumn below-ground biomass (g/m^), and below-ground:above-ground biomass ratios for Typha glauca and Sparganium eurycarpum in control and fertilized plots

Typha glauca

Control Fertilized

Sparganlum eurycarpum

Control Fertilized

Annual Net Above-ground production

1979

1980

Above-ground Biomass

1979

1980

Below-ground Biomass

May, 1979

Nov., 1979

Oct., 1980

Root-Rhizome/Shoot

1979

1980

1,623 ± 704

2,173 ± 544

1,351 ± 692

1,726 ± 479

1,300 ± 676

1,679 ± 511

1,451 ± 409

1.55

0.84

2,155 + 646

2,578 ± 775

1,781 ± 781

2,343 ± 645

1,654 ± 516

1,779 ± 590

0.93

0.76

1,058 ± 135

924 ± 134

816 ± 254

637 ± 150

681 ± 252

1,123 ± 508

855 + 356

1.38

1.34

1,187 ± 309

1,448 ± 200

904 ± 135

1,185 ± 210

1,010 ± 434

1,046 ± 580

1.11 0.88

Table II-3. Typha and Sparganlum above-ground biomass or annual production values in inland freshwater marshes

Biomass or Site Production

Typha sp. 1,527 g/mf OK

1,360 g/mf MN

1,336 g/m^ TX

730 g/mf OK

416 g/m^ NE

378 g/mf SD

404 g/ra^ ND

Typha latifolia 686 g/m^ SC

530-1,132 g/mf SC

428-2,252 g/mf S.E. U.S

2,456 g/m^/yr WI

1,483 g/mf SC

Typha glauca 1,549 g/mf lA

2,106 g/mf lA®

2,297 g/m^/yr lA^

Sparganium eurycarpum 1,950 g/mf WI

770 g/mf lA

1,054 g/m^ lA^

1,066 g/m^/yr lA®

^Values from Eagle Lake.

Reference

Penfound 1956

Bray 1962

McNaughton 1966

McNaughton 1966

McNaughton 1966

McNaughton 1966

McNaughton 1966

Boyd 1970

Boyd 1971

Boyd and Hess 1970

Klopatek 1975

Polisini and Boyd 1972

Van Dyke 1972

van der Valk and Davis 1978a

van der Valk and Davis 1978a

Lindsley et al, 1976

Van Dyke 1972

van der Valk and Davis 1978a

van der Valk and Davis 1978a

66

Below-ground Vegetative Response

Nitrogen content

The change in percentage of nitrogen in root-rhizome tissues for

each study species and treatment during 1979 and 1980 is presented in

Figure II-2. Nitrogen concentrations in below-ground structures of

wetland species are usually replenished in the autumn months after a

summer decline (Bjork 1967; Klopatek 1975; Prentki et al. 1978). This

pattern occurred in both study years at Eagle Lake. Fertilization in

1979 produced little change in root-rhizome nitrogen concentration

until late in the growing season. By mid-September of 1979, root-rhizome

nitrogen levels in Sparganium fertilized plots surpassed those of un­

fertilized plots. Also, during the final sampling interval of 1979,

Typha underground tissues in fertilized plots exhibited a faster rate

of nitrogen increase than did roots-rhizomes in unfertilized plots

(Figure II-2). There was not a significant treatment effect in 1979.

At the onset of the 1980 growing season, root-rhizome nitrogen

concentrations of both species were higher in fertilized plots and

greater than maximum values in 1979. Early in the season, however,

these high concentrations declined more rapidly than did levels in

control plots. By the third sampling date, root-rhizome nitrogen

concentrations in fertilized plots had decreased to levels equal to

or lower than those of control plots. After this, nitrogen levels in

fertilized plots increased rapidly to concentrations again greater

than unfertilized plots. For the entire season, concentrations were

significantly greater in fertilized plots. The faster nitrogen

67

disappearance from 1980 roots-rrhizomes in fertilized enclosures was

probably due to the high 1980 shoot densities in the fertilized enclo­

sures and suggests the positive influence of winter root—rhizome

nutrient concentrations on shoot initiation and growth.

Biomass

Mean 1979 spring, 1979 autumn, and 1980 autumn below-ground biomass

estimates are recorded in Table II-2. Estimates of Typha autumn below-

2 ground biomass in prairie marshes have ranged from 1,431 g/m (Davis

2 and van der Valk, unpublished) to 1,450 g/m (Van Dyke 1972). Van Dyke

2 also estimated Sparganium below-ground biomass at 1,638 g/m . In

artificial, manure-enriched marshes, Werblan (1979) estimated Typha

2 and Sparganium below-ground biomass of these species to be 2,642 g/m

2 and 737 g/m , respectively. Estimates of autumn below-ground biomass

of Typha and Sparganium in 1979 and 1980 at Eagle Lake are within these

ranges.

On the basis of the autumn biomass estimates, fertilization in

1979 did not stimulate root-rhizome production of the species and may

have inhibited growth during the first summer (Table II-2). Control

2 biomass values exceeded those in fertilized plots by 25 g/m and

2 113 g/m for Typha and Sparganium, respectively. These differences

were not significant. Between autumn, 1979, and autumn, 1980,

below-ground biomass declined in control plots and increased in

fertilized plots (Table II-2). Because of this occurrence, 1980

root-rhizome biomass in fertilized plots surpassed that of control

68

2 plots by 328 g/m . The difference between Sparganium biomass estimates

2 from fertilized and control plots was 191 g/m . These differences were

not significant.

69

DISCUSSION

Nutrient Availability

Fertilization of surface waters in Eagle Lake increased concen­

trations of NH^-N, NOg-N, and PO^-P available to the plants (Figure

II-6). The accumulation of these nutrients in sediments and intersti­

tial waters, however, was small relative to quantities added to the

surface water. Past studies indicate the complexity of the process

whereby nutrients are made available to emergent vegetation after sur­

face enrichment. Valiela and Teal (1974) recorded increases in nitro­

gen and phosphorus parameters of sediment waters in a tidal salt marsh

after fertilization. On the other hand, sediment nutrient status of a

freshwater sawgrass stand did not change after nitrogen, phosphorus,

and potassium additions (Steward and Omes 1975); added nutrients did

not accumulate in the interstitial water of a Wisconsin peatland (Kadlec

1976); and, applications of a dilute nutrient solution did not raise

sediment nutrient levels at depths of 15, 30, or 105 cm (Richardson

et al. 1976). Such discrepancies between systems are probably the

result of differences between forms of nutrients added, sediment types,

and the quantities and combinations of other nutrients already present.

But, the most important factors responsible for removal of some nu­

trients before penetration into the sediment/interstitial water column

are evidently litter buildup and high organic content in sediments

(Kadlec 1976; Richardson et al. 1976; Whigham and Bayly 1978).

At Eagle Lake, NH^-N movement into the interstitial water was

correlated with some feature of the plants themselves. The increase

70

in NH^-N concentrations in interstitial waters of Typha fertilized

plots was much less than the response in Sparganium fertilized plots.

Because microbial populations on decomposing plant litter remove nitro­

gen from surface water, the movement of NH^-N into the interstitial

water may have been a function of the amounts of dead plant litter at

the sediment-water interface. Typha litter requires several years

before conçlete decomposition occurs (Davis and van der Valk 1978a,

1978b); thus, substantial litter buildup occurs. Sparganium tissue,

however, decomposes relatively rapidly, with little litter persisting

after one year. Large quantities of Typha litter and the associated

populations of microbes could reduce the amount of NH^-N available

to move into the interstitial water column.

Production

Eagle Lake receives high inputs of nitrogen and phosphorus from

precipitation and, more importantly, from field runoff and subsurface

drainage. Perhaps because of this loading, the production of Typha

and Sparganium in Eagle Lake is at the high end of the range of values

typical for these genera in inland freshwater marshes (Table II-3).

Our Typha production values (Table II-2) and those of van der Valk and

Davis (1978a, Table II-3) from Eagle Lake, exceed most other Typha

values in Table II-3. The only exceptions are Klopatek (1975) and

Boyd and Hess (1970). There are few Sparganium estimates from inland

freshwater marshes for comparison with Eagle Lake estimates. But,

2 Lindsley et al. (1976) reported a maximum biomass of 1,950 g/m for

71

SpargaiiTnm in Wisconsin. Although Sparganium maximum biomass at

Eagle Lake is substantially lower than this value, Sparganium at Eagle

Lake demonstrates considerable production, particularly when compared

with some of the Typha values (Table II-3).

Despite their already high production, Typha and Sparganium in

Eagle Lake are limited by nitrogen and/or phosphorus. Valiela et al.

(1976) presented data indicating that, when nutrients are limiting,

fertilization may not stimulate production until after the first year

of application. This was the case at Eagle Lake. The best indication

of nutrient limitation occurred in 1980, the second year of the study.

During that year, above-ground biomass, net annual production, and

percentage nitrogen in roots and shoots were significantly higher in

fertilized plots. Increases also occurred in below-ground biomass and

shoot density, but they were not significant (Figure II-6) . The one

year lag in vegetative response seems related to the timing of nutrient

accumulation and storage in roots and rhizomes (Valiela and Teal

1974). Our results suggest that shoot density, biomass, and production

increased in 1980 because of the storage of nitrogen, and possibly

phosphorus, in below-ground structures during the previous autumn and

winter. Thus, nutrient quantities stored in below-ground structures

after one season can probably influence the initiation and production

of shoots in the next season.

Although shoot initiation and growth may be related to the supply

of nutrients in overwintering below-ground tissues, the effect of

elevated root-rhizome nutrient level on root—rhizome production is

72

TYPHA ABOVE-GROUND

I DENSITY

SPARQANIUM ABOVE-GROUND

• -control

ENSITY

BE LOW-GROUND

SEDIMENT INTERSTITIAL HgQ,

BELOW-GROUND

NH^N PO|$-P NH4-N NO3-N PO4-P (ppm)

«N BIOMASS «N BIOMASS

Figure II-6. Summary of the 1980 effects of fertilization in

Sparganium and Typha stands on NO^-N, and

PO^-P concentrations in interstitial waters; NH^-N

and PO^-P concentrations in sediments; percentage

nitrogen in shoots and roots-rhizomes; mavimmn

shoot density; net primary production (NPP); and

autumn below—ground biomass. Significance at the

0.10 confidence level is designated by an asterisk.

Summer averages are used for all nutrient concen­

trations

73

unclear. Past studies of below-ground biomass and production have

produced various responses to enrichment. Valiela et al. (1976) have

demonstrated that, although Spartina altemiflora net annual below-

ground production is enhanced by fertilization, the effect is not equal

between roots and rhizomes, i.e., root biomass tended to decrease

with enrichment. Steward and Omes (1975) found that sawgrass

root-rhizome biomass decreased with increasing nutrient additions.

And, Broome et al. (1975) observed a significant increase in Spartina

alterniflora root and rhizome biomass after additions of nitrogen

fertilizer. In the first year at Eagle Lake, fertilization had no

effect on rootrrhizome biomass of either species. In the second year,

mean biomass estimates were greater in fertilized plots, but dif­

ferences were not statistically significant. Although it is debatable

whether fertilization stimulated production, fertilization did not have

a negative effect on root-rhizome biomass over the two-year span.

Barko and Smart (1979) presented evidence from their own work and

the literature indicating that emergent below-ground :above-ground

biomass ratios decline on fertile sites. Our Eagle Lake data support

this hypothesis (Table II-2). Most Sparganium and Typha ratios of

autumn rootrrhizome biomass to maximum shoot biomass were above 1 in

control areas and below 1 in fertilized plots. Barko and Smart (1979)

theorize that greater biomass allocation to below-ground tissues may

be a phenotypic modification in nutrient-poor habitats whereby root

absorptive area and/or storage capacity are increased.

74

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Bar ko, J. W., and R. Michael Smart. 1978. The growth and biomass distribution of two emergent freshwater plants, Cyperus exculentus and Scirpus validus, on different sediments. Aquatic Botany 5:109-117.

Barko, J. W., and R. Michael Smart. 1979. The nutritional ecology of Cyperus esculentus, an emergent aquatic plant, grown on different sediments. Aquatic Botany 6:13-28.

Bayly, I. L., and T. A. O'Neill. 1972. Seasonal ionic fluctuations in a Phragmites communis community. Canadian Journal of Botany 50:2103-2109.

Bernard, J. M., and F. A. Bernard. 1973. Winter biomass in Typha glauca Godr. and Sparganitmi eurycarpum Engelm. Bulletin of the Torrey Botanical Club 100:125-131.

Bjork, S. 1967. Ecologic investigations of Phragmites communis. Studies in theoretical and applied limnology. Folia Limnologica Scandinavica 14:1-148.

Boyd, C. E. 1969. Production, mineral nutrient absorption and biochemical assimilation by Justicia americana and Alternanthera philoxeroides. Archiv fur Hydrobiologie 66:139-160.

Boyd, C. E. 1970. Production, mineral accumulation and pigment concentrations in Typha latifolia and Scirpus americanus. Ecology 51:285-290.

Boyd, C. E. 1971. Further studies on productivity, nutrient and pigment relationships in Typha latifolia populations. Bulletin of the Torrey Botanical Club 98:144-150.

Boyd, C. E., and L. W. Hess. 1970. Factors influencing shoot production and mineral nutrient levels in Typha latifolia. Ecology 51:285-290.

Boyd, C. E., and D. H. Vickers. 1971. Relationship between production, nutrient accumulation and chlorophyll synthesis in an Eleocharis quadrangulata population. Canadian Journal of Botany 49:883-888.

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Bray, J. R. 1962. Estimates of energy budgets for a Typha (cattail) marsh. Science 136:1119-1120.

Broome, S. W., W. W. Woodhouse, and E. D. Seneca. 1975. The relation­ship of mineral nutrients to growth of Spartina altemiflora in North Carolina. II. The effects of N, P and Ee fertilizers. Soil Science Society of America Proceedings 39:301-307.

Currier, P. J. 1979. Floristic composition and primary production of the postdrawdown vegetation of Eagle Lake marsh, Hancock County, Iowa. M.S. thesis. Iowa State University. 149 pp.

Davis, C. B., and A. G. van der Valk. 1978a. The decomposition of standing and fallen litter of Typha glauca and Scirpus fluviatilis. Canadian Journal of Botany 56:662-675.

Davis, C. B., and A. G. van der Valk. 1978b. Litter decomposition in prairie glacial marshes. Pages 99-113 R. E. Good, D. F. Whigham, and R. L. Simpson, eds. Freshwater wetlands: Ecological processes and management potential. Academic Press, New York. 378 pp.

Davis, C. B., J. L. Baker, A. G. van der Valk, and C. E. Baker. 1981. Prairie pothole marshes as traps for nitrogen and phosphorus in agricultural runoff. Pages 153-163 B. Richardson, ed. Proceedings of the Midwest Conference on Wetland Values and Management. Freshwater Society, 2500 Shadywood Road,

Box 90, Navarre, Minnesota. 55372. 660 pp.

de Jong, J. 1976. The purification of wastewater with the aid of rush or reed ponds. Pages 133-149 J. Tourbier and R. W. Pierson, Jr., eds. Biological control of water pollution. University of Pennsylvania, Philadelphia, Pennsylvania. 340 pp.

De la Cruz, A. A. 1978. Primary production processes: Summary and recommendations. Pages 79-86 R. E. Good, D. F. Whigham, and R. L. Simpson, eds. Freshwater wetlands: Ecological processes and management potential. Academic Press, New York. 378 pp.

Ewel, K. C. 1976. Effects of sewage effluent on ecosystem dynamics in cypress domes. Pages 169-195 D. L. Tilton, R. H. Kadlec, and C. J. Richardson, eds. Freshwater wetlands and sewage effluent disposal. The University of Michigan, Ann Arbor, Michigan. 343 pp.

Gallagher, J. L. 1975. Effect of ammonium nitrate pulse on the growth and elemental composition of natural stands of Spartina altemiflora and Juncus roemerianus. American Journal of Botany 62:644—648.

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Polisini, J. M., and C. E. Boyd. 1972. Relationships between cell-wall fractions, nitrogen, and standing crop in aquatic macrophytes. Ecology 53:484-488.

Prentki, R. G., T. D. Gustafson, and H. S- Adams. 1978. Nutrient movements in lakeshore marshes. Pages 168-194 R. E. Good, D. F. Whigham, and R. L. Simpson, eds. Freshwater wetlands: Ecological processes and management potential. Academic Press, New York. 378 pp.

Richardson, C. J., W. A. Wentz, J. P. M. Chamie, J. A. Kadlec, and D. L. Tilton. 1976. Plant growth, nutrient accumulation and decomposition in a central Michigan peatland used for effluent treatment. Pages 77-117 D. L. Tilton, R. H. Kadlec, and C. J. Richardson, eds. Freshwater wetlands and sewage effluent disposal. The University of Michigan, Ann Arbor, Michigan. 343 pp.

Seidel, K. 1976. Macrophytes and water purification. Pages 109-121 in J. Tourbier and R. W. Pierson, Jr., eds. Biological control of water pollution. University of Pennsylvania, Philadelphia, Pennsylvania. 340 pp.

Spangler, F., W. E. Sloey, and C. W. Fetter. 1976. Experimental use of emergent vegetation for the biological treatment of municipal wastewater in Wisconsin. Pages 161-171 J. Tourbier and R. W. Pierson, Jr., eds. Biological control of water pollution. University of Pennsylvania, Philadelphia, Pennsylvania. 340 pp.

Spangler, F., C. W. Fetter, and W. E. Sloey. 1977. Phosphorus accu­mulation—discharge cycles in marshes. Water Resources Bulletin 13:1191-1201.

Stainton, M. P., M. J. Carpel, and F. A. J. Armstrong. 1974. The chemical analysis of freshwater. Fisheries Research Board of Canada Miscellaneous Special Publication 25. 125 pp.

Steward K. K., and W- H. Omes. 1975. Assessing a marsh environment for wastewater renovation. Journal-Water Pollution Control Federation 47:1880-1891.

Stewart, R. E., and H. A. Kantrud. 1971. Classification of natural ponds and lakes in the glaciated prairie region. U.S. Fish and Wildlife Service, Resource Publication 92. 57 pp.

Stumm, W., and J. J. Morgan. 1970. Aquatic Chemistry. Wiley-Inter-science. New York. 583 pp.

Sullivan, J. J., and F. C. Daiber. 1974. Response in production of cord grass, Spartina altemiflora, to inorganic nitrogen and phosphorus fertilizer. Chesapeake Science 15:121-123.

77

Kadlec, J. A. 1979. Nitrogen and phosphorus in inland freshwater wetlands. Pages 17-41 R. A. Bookhour, ed. Waterfowl and wetlands—An integrated review. La Cross Printing Co., La Crosse, Wisconsin. 152 pp.

Kadlec, R. H. 1976. Dissolved nutrients in a peatland near Houghton Lake, Michigan. Pages 27-50 D. L. Tilton, R. H. Kadlec, and C. J. Richardson, eds. Freshwater wetlands and sewage effluent disposal. The University of Michigan, Ann Arbor, Michigan. 343 pp.

Klopatek, J. M. 1975. The role of emergent macrophytes in mineral cycling in a freshwater marsh. Pages 367-393 i^ F. G. Howell, J. B. Gentry, and M. H. Smith, eds. Mineral cycling in south­eastern ecosystem. ERDA (Energy Res. Dev. Admin.) (Conf-740513). 898 pp.

Lindsley, D., T. Schuck, and F. Steams. 1976. Productivity and nutrient content of emergent macrophytes in two Wisconsin marshes. Pages 51-75 D. L. Tilton, R. H. Kadlec, and C. J. Richardson, eds. Freshwater wetlands and sewage effluent disposal. The University of Michigan, Ann Arbor, Michigan. 343 pp.

Mason, C. F., and R. J. Bryant. 1975. Production, nutrient content and decomposition of Phragmites communis Trin. and Typha angustifolia L. Journal of Ecology 63:71-95.

McNaughton, S. J. 1966. Ecotype function in the Typha community-type. Ecological Monographs 36:297-325.

Murphey, J., and J. Riley. 1962. A modified single solution method for the determination of phosphate in natural waters. Analytical Chemica Acta 27:31-36.

North Dakota Agricultural Experiment Station. 1975. Recommended chemical soil test procedures for the north central region. North Dakota Agricultural Experiment Station Bulletin 499. 23 pp.

Penfound, W. T. 1956. Production of vascular aquatic plants. Limnology and Oceanography 1:92-101.

Patrick, W. H., Jr., and Tusneem, M. E. 1972. Nitrogen loss from a flooded soil. Ecology 53:735-737.

Pigott, C. D. 1969. Influence of mineral nutrition on the zonation of flowering plants in coastal salt marshes. Pages 25-35 I. H. Rorison, ed. Ecological aspects of mineral nutrition in plants. Blackwell Scientific Publications, Oxford and Edinburgh. 484 pp.

78

Turner, R. E., J. J. Day, Jr., M. Meo, P. M. Payonk, T. B. Ford, and W. G. Smith. 1976. Aspects of land-treated waste application in Louisiana wetlands. Pages 77-117 D. L. Tilton, R. H. Kadlec, and C. J. Richardson, eds. Freshwater wetlands and sewage effluent disposal. The University of Michigan, Ann Arbor, Michigan. 343 pp.

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Valiela, I., and J. M. Teal. 1974. Nutrient limitation in salt marsh vegetation. Pages 547-563 R. J. Reimold and W. H. Queen, eds. Ecology of halophytes. Academic Press, New York. 605 pp.

Valiela, I., J. M. Teal,, and N. Y. Persson. 1976. Production and dynamics of experimentally enriched salt marsh vegetation: below-ground biomass. Limnology and Oceanography 21:245-252.

Valiela, I., J. M. Teal, and W. J- Sass. 1975. Production and dynamics of salt marsh vegetation and the effect of experimental treatment with sewage sludge. I. Biomass, production, and species composition. Journal of Applied Ecology 12:973-981.

van der Valk, A. G., and C. B. Davis. 1978a. Primary production in prairie glacial marshes. Pages 21-37 R. E. Good, D. F. Whigham, and R. L. Simpson, eds. Freshwater wetlands: Ecological processes and management potential. Academic Press, New York. 378 pp.

van der Valk, A. G., and C. B. Davis. 1978b. The role of the seed bank in the vegetation dynamics of prairie glacial marshes. Ecology 59:322-335.

van der Valk, A. G., and C. B. Davis. 1979. A reconstruction of recent vegetational history of a prairie glacial marsh. Eagle Lake, Iowa from its seed bank. Aquatic Botany 6:29-51.

van der Valk, A. G., and C. B. Davis. 1980. The impact of a natural drawdown on the growth of four emergent species in a prairie gla­cial marsh. Aquatic Botany 9:301-322.

Van Dyke, G. 1972. Aspects relating to emergent vegetation dynamics in a deep marsh, northcentral Iowa. Ph.D. thesis. Iowa State University (Libr. Congr. Card No. Mic. 73-3940). 162 pp. University Microfilms, Ann Arbor, Michigan.

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79

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Whigham, D. F., and R. L. Simpson. 1976a. The potential use of freshwater tidal marshes in the management of water quality in the Delaware River. Pages 173-186 J. Tourbier and R. W. Pierson, Jr., eds. Biological control of water pollution. University of Pennsylvania, Philadelphia, Pennsylvania. 340 pp.

Whigham, D. F., and R. L. Simpson. 1976b. Sewage spray irrigation in a Delaware River freshwater tidal marsh. Pages 119-144 D. L. Tilton, R. H. Kadlec, and C. J. Richardson, eds. Freshwater wetlands and sewage effluent disposal. The University of îlichigan, Ann Arbor, Michigan. 343 pp.

80

SECTION III. NITROGEN, PHOSPHORUS, AND THE DECOMPOSITION OF TYPHA

GLAUCA AND SPARGANIDM EURYCAEPUM IN A PRAIRIE MARSH

81

ABSTRACT

Sparganixm eurycarpum shoot litter with an initial nitrogen con­

centration of 1.41% lost 27% more dry weight over a 505-day period

than did Sparganivm with an initial nitrogen concentration of 0.59%.

Typha glauca shoot litter with an initial nitrogen concentration of

0.55% lost 2% more dry weight during 505 days than Typha tissues with

an initial nitrogen concentration of 0.48%. Elevation of available

nitrogen and phosphorus concentrations in marsh surface waters to 20 ppm

NO^-N, 25 ppm NH^-N, and 5 ppm PO^-P did not alter the rate of

Sparganium or Typha shoot decomposition. After 505 days, losses of

shoot material totaled 39% for both species under fertilized and

unfertilized conditions. Fertilization also had no effect on decompo­

sition of root and rhizomes of both species. The below-ground tissues

lost 28-50% of their dry weight over 505 days.

During the 505-day sampling interval, quantities of nitrogen

in shoot litter increased 31% for Sparganium and decreased 10% for

Typha under unfertilized conditions. Nitrogen quantities increased

35% for the two species under fertilized conditions. The quantity

of phosphorus in Sparganium and Typha shoot litter increased 7% and

121%, respectively, with fertilization. Under unfertilized conditions,

Sparganium shoot litter lost 2% and Typha litter gained 25% of original

phosphorus quantities. Sparganium shoot litter with a high initial

nitrogen concentration lost 50% of its original quantity of nitrogen

over 505 days; but high nitrogen Typha shoot litter gained an additional

82

19% nitrogen. Below-ground litter consistently lost nitrogen through­

out the 505-day sequence under unfertilized and fertilized conditions:

a 24% loss from Sparganium litter in unfertilized areas, 50% from

Sparganium litter in fertilized areas, 54% from Typha litter in

unfertilized areas and 49% from Typha litter in fertilized areas.

Key words: Sparganium, Typha, bur-reed, cattail, decomposition,

nitrogen, phosphorus, freshwater wetland, prairie marsh, C:N ratio,

C:P ratio, litter, nutrient cycling.

83

INTRODUCTION

A nimber of studies have demonstrated that at least during the

growing season wetland ecosystems can act as effective nutrient sinks

(Seidel 1971, 1976; Toth 1972; Lee et al. 1975; Kitchens et al. 1975;

Steward and Omes 1975; Spangler et al. 1976; Tilton et al. 1976;

Tourbier and Pierson 1976; Fetter et al. 1978; van der Valk. et al.

1978; Davis et al. 1981; and others). The fallen emergent litter

compartment has been postulated as a major compartment for the

accumulation and storage of some nutrients in wetlands (Richardson

et al. 1976; Davis and Harris 1978; Davis and van der Valk 1978a,

1978b, 1978c). Nitrogen and phosphorus removal associated with

fallen litter is the result of microbes using the litter as a carbon

source, but obtaining nutrients from surrounding waters. The

microbe-litter association (detritus) is a complex entity with an

endogenous primary source of carbon (litter) and an endogenous (litter)

as well as exogenous (water) source of nutrients for the associated

microorganisms (Figure III-l). High C:N and C:P ratios within litter

(>16-23:1 and 200:1, respectively) are indicative of microbial nitro­

gen and phosphorus demands exceeding the initial content of the litter

and require the microbial populations to utilize exogenous sources of

nitrogen and phosphorus (Gosz et al. 1973; Enwezor 1976; Brinson 1977;

Prentki et al. 1978).

The effectiveness of emergent litter as a nutrient sink during

decomposition depends on 3 criteria: (1) the quantity of nutrients

84

Ni IC^ PC ^ h Surface Waters

CK

'2

u

' '

Microbes

Litter

Figure III-l. Sources of carbon, nitrogen, and phosphorus for microbial decomposers

85

leached from the litter, (2) the rate of decomposition and mineraliza­

tion, and (3) the rate nutrients are accrued through microbial activity.

When the rate of litter decomposition is slower than the rate of litter

deposition, the nutrient content of the litter is eventually incor­

porated into the sediment and retained in the system (Davis and Harris

1978). Factors which affect the rate of decomposition will therefore

determine to some extent the capacity of the litter to function as a

nutrient sink. The concentration of nitrogen and phosphorus in the

litter and in the surrounding waters are the major factors that can

influence the rate of litter decomposition. The rate of emergent

decomposition has been suggested as positively correlated with the

initial nutrient concentration of the litter (Kaushik and Hynes 1971;

Almazan and Boyd 1978; Coulson and Butterfield 1978; Davis and

van der Valk 1978b). In laboratory stream microcosms (Kaushik and

Hynes 1971; Howarth and Fisher 1976) and in natural stream ecosys­

tems (Elwood et al. 1981), high concentrations of nitrogen and

phosphorus in waters have also been shown to accelerate decomposition

of litter. This may also be true in lentic systems (Andersen 1978;

Davis and Harris 1978).

The major emphasis of this investigation was to assess the sig­

nificance of initial litter nutrient concentrations versus concentra­

tions of nitrogen and phosphorus in ambient waters for emergent plant

litter decomposition rates and nitrogen and phosphorus accumulation

and/or losses by this litter. This was accomplished by comparing

under field conditions the decomposition of Typha glauca and Sparganium

86

eurycarpum shoot litter obtained from 2 sources, each source with

litter of a different initial nutrient content; and by determining

the effect of surface water fertilizer application on decomposi­

tion of Typha and Sparganitim tissues with the same initial nutrient

content. A second objective of this study was to characterize the

decomposition of below-ground tissues of emergent macrophytes. The

contribution of root and rhizome decomposition to wetland nutrient

cycles is poorly understood. In only a few instances has root

decomposition even been described (Heal et al. 1978; Hackney and

De La Cruz 1980; Puriveth 1980). Our study compared root-rhizome

decomposition with the decomposition of above-ground plant parts

under fertilized and unfertilized conditions.

87

METHODS

Study Site

Eagle Lake, Iowa is a 365-ha natural prairie marsh of glacial

origin. The center of the marsh is a semi-permanent zone of open

water that rarely exceeds 1 m in depth. During this study, nitrogen

and phosphorus concentrations within the marsh water averaged approx­

imately 0.41 ppm PO^-P, 0.56 ppm total dissolved phosphorus (as

PO^-P), 0.21 ppm particulate phosphorus (as PO^-P), 0.56 ppm NO^N, 0.47

ppm NH^-N, and 7.36 ppm organic nitrogen (as NH^-N). The sediments are

highly organic (99 - 115 kg organic material/ha for a 16.51 cm depth)

with a total nitrogen content of 2.3% and total phosphorus quantities

of about 16.5 kg/ha. Althou^ more than 40 aquatic plant species

occur in Eagle Lake (Currier 1979), during years of high water levels

such as 1979-1980 the marsh is dominated by two emergent macrophytes,

Sparganium eurycarpum and Typha glauca.

Fertilization Experiments

In early May, 1979 a series of 6 watertight enclosures (6 x 6 m )

were erected in monodominant stands of Sparganium and Typha, 3 enclo­

sures per species. During the 1979 and 1980 growing seasons, each

enclosure was fertilized at 28-day intervals with (NE^) 2^^^ and

NE^NOg. Each fertilizer application was calculated to restore

available nitrogen and phosphorus concentrations in the water

column to 45 ppm available nitrogen (25 mg NH^-N/l; 20 mg NO^-N/l)

and 5 ppm available phosphorus (5 mg P-PO^/1). Near each ferti­

88

lized enclosure, an unfertilized control plot was established

by staking a 6- x 6-m area of open marsh. Although the unfertilized

plots were not enclosed and do not represent true controls. Eagle Lake

is a fairly stagnant system; thus, the difference between open and

enclosed areas was assumed minimal.

Shoot tissues

Standing 1978 litter was collected in March, 1979 in monodominant

stands of Typha and Sparganium at Eagle Lake. This material was

dried at 60 C for 1 week, weighed, subsampled, and used to prepare

144 mesh (1 mm) fiberglass litterbags (30 x 20 cm) for each species.

Each bag contained approximately 10 gm of Typha or Sparganium tissue.

On 31 May, 1979, 24 litterbags of Typha or Sparganium were placed in

each unfertilized and fertilized plot. Three bags were removed

from all plots after 1, 14, 30, 50, 100, 150, 350, and 505 day inter­

vals; thus, on each sampling date 9 bags were collected from the

unfertilized and fertilized plots for each species.

All litterbags were rinsed in distilled HgO, dried at 60 C

for 1 week, weighed, and subsampled. The subsamples were ground

in a Wiley mill with a #20 mesh and analyzed for total nitrogen and

total phosphorus. Litter weights were used to determine the rate

of decomposition as an expression of the percentage of original

weight.

89

Root-rhizome tissues

Root—rhizome tissues were collected in April, 1979 by excavating

2 0.25 m samples of Typha and Sparganium below-ground material Oroot

and rhizome). In the laboratory, the root-rhizome material was

washed in distilled HgO, killed by drying at 60 C for 1 week, weighed,

and used to prepare 98 litterbags for each species. 14 root litter-

bags were placed in each control and fertilized plot. These bags

were buried at approximately 30 cm. Two bags were collected from

each plot after 14, 30, 50, 100, 150, 350, and 505 day intervals.

Root-rhizome litter bags were processed in the same manner as the

shoot litterbags; however, because of funding constraints, only

total nitrogen was determined.

Shoot Decomposition and Initial Nutrient Content

Standing litter was obtained in March, 1979 from artificial

marshes used in the treatment of raw swine-waste (Werblan 1979).

Initial nitrogen concentrations in this litter were 1.41% and

0.55% for Sparganium and Typha, respectively. Nitrogen concen­

trations in the litter obtained from Eagle Lake were 0.59% for

Sparganium and 0.48% for Typha. This litter was rinsed,

dried, weighed, and placed in 48 litterbags for each species. 24

bags of each species were distributed in two control areas. Three

bags were collected from each area after 1, 14, 30, 50, 100, 150,

350, and 505 day intervals and processed the same as all other litter­

bags. Only total nitrogen analyses were performed. Litter in

90

fertilized plots, in unfertilized plots, and from the artificial,

swine-waste treatment marshes are referred to as fertilized litter,

unfertilized litter, and enriched litter, respectively, throughout

the remainder of this paper.

Statistical Analyses

The decomposition and change in nitrogen and phosphorus content

of litter was tested by using 3-way analyses of variance (ANOVA).

The ANOVA's were used to determine whether the following factors or

interactions affected decomposition: site, species, treatment,

species x treatment, site x species x treatment, time, time x species,

time x treatment, and time x species x treatment. This model was

used to compare the breakdown of shoot and root-rhizome material

between unfertilized and fertilized plots. The model was also used

to contrast the breakdown of litter initially high in nutrient con­

centrations with the breakdown of Eagle Lake litter in unfertilized

plots-

Wetlands typically exhibit high intrinsic variation; thus,

statistical significance was set at o = 0.1 (see Richardson et al.

1976). Because multiple measurements within the same treatment

plot, e.g., 3 bags from 1 plot on a single date, and measurements

over time do not represent true replicates, the analyses of variance

were modified in two ways. First, when computing site, species,

treatment, and species x treatment mean square values, the site x

species x treatment interaction was used as an error term. Secondly,

91

mean square values for the remaining ANOVA terms were computed by

using conservative degrees of freedom (personal communication,

D. F. Cox, Iowa State University Statistics Department).

92

RESULTS

Shoot Decomposition

Dry weight

The percentage remaining of dry shoot weight is presented in

Figure III-2. Fertilized and unfertilized Sparganium and Typha litter

lost 20% and 16%, respectively, of their original weight within 24

hours after being submerged. The loss of dry weight continued for

approximately 50 days. After 50 days, dry weights of Sparganium in

unfertilized and fertilized litterbags had declined 39%, and Typha

losses during that period were approximately 26%. After these initial

losses, Typha dry weight dropped slightly, but Sparganium dry weight

remained relatively constant. After 505 days, 61% of the initial litter

weight remained in Sparganium unfertilized and fertilized litterbags,

and 61% of the initial material remained in the Typha unfertilized

and fertilized litterbags.

The pattern of dry-weight loss from the enriched litter paralleled

the weight losses in Eagle Lake litter; however, the rate of decomposi­

tion was statistically greater in the swine-waste enriched litter.

24-hour dry-weight loss from the enriched litter was 27% for Sparganium

and 19% for Typha. After 50 days, 55% of the Spargam'urn dry material

and 31% of the Typha dry material was lost. Over the remaining period,

Sparganium continued to decompose rapidly; only 34% of the original

dry weight remained after 505 days. In contrast, 59% of the original

dry weight of the enriched Typha tissues remained after 505 days.

SHOOT ROOT 100-t-

$ s 60 z < s 20

H

gioo-

: it-'.——1 LL'.'jJ^Tî:^

TYPHA

100 200 300 400 500

20+ SPARGANIUM

1 1 h—H f 100 200 300 400 500

100-t-

100 200 300 400 500

100

60

20

f

SPARGANIUM

100 200 300 400 500

vo w

TIME ELAPSED (DAYS)

FERTILIZED UNFERTILIZED — ENRICHED

Figure III-2. The average percentage of original dry weight remaining in submerged Typha and

Sparganium shoot and root-rhizome litterbags

94

Although decomposition of both species was significantly accelerated

by the waste enrichment, the Sparganium response to the treatment

was greater than the Typha response, i.e., a significant species x

treatment interaction.

Nitrogen content

Figure III-3 illustrates the change in nitrogen concentration of

unfertilized, fertilized, and enriched litter. Over the entire

sampling interval, nitrogen concentrations of shoot litter increased

under all treatments. Sparganium percentages increased from an initial

concentration of 0.59% to a final concentration of 1.26% in control

plots (an increase of 114%) and 1.30% in fertilized plots (+ 120%).

Typha nitrogen concentrations increased from an initial concentration

of 0.48% to final concentrations of 0.70% (+ 46%) and 1.05% (+ 119%)

in control and fertilized plots, respectively. Sparganium and Typha

enriched litter increased from 1.41% to 2.06% (+ 46%) and from 0.55% to

1.12% (+ 104%), respectively. All nitrogen increases with time were

significant. Among treatments, nitrogen concentrations in the enriched

litter were significantly greater than concentrations in the unfertilized

litter. In contrast, no significant difference was observed between

nitrogen concentrations of litter in fertilized and unfertilized plots.

Nitrogen concentrations were converted to absolute quantities

remaining in litterbags by adjustment for dry-weight loss (Boyd 1970).

These data are presented in Figure III-4. Most of these curves show

an initial loss of nitrogen, corresponding to the loss in dry weight.

2.0- - SHOOT

100 200 300 400 500

V

8 1.0

-r*

SPARGANIUM

100 200 300 400 500

2.0-1-ROOT

TYPHA

100 200 300 400 500 VO Ui

2.0

1.0

SPARGANIUM

100 200 300 400 500

FERTILIZED

TIME ELAPSED (DAYS)

UNFERTILIZED ENRICHED

Figure III-3. The average concentration of nitrogen in submerged Typha and Sparganium shoot and root-rhizome litterbags

o z z < s 111 K

z

140

100

BO- •

20

' *

SHOOT ROOT ...»

TYPHA

1 4 h—1-

...—

SPARGANIUM

H 1 1—H h 100 200 300 400 500

20 -

140- '

100

60* "

20--SPARGANIUM

-4 h 1 1 h 100 200 300 400 500

TIME ELAPSED (DAYS)

FERTILIZED UNFERTILIZED ENRICHED

VO o\

Figure III-4. The average percentage of original nitrogen remaining in submerged Typha and Spar-ganiym shoot and root-rhizome litterbags

97

followed by a gradual accrual of nitrogen. Typha litter in unferti­

lized plots and Sparganium enriched litter represent the only

exceptions to this trend. Amounts of nitrogen declined in unfertilized

Typha litter between 150-505 days. In Sparganium enriched litter,

nitrogen declined slowly throughout the entire 505 day period. Both

of these variations reflect the pattern of dry-weight loss (Figure

III-2).

After 505 days, the percentage of the initial quantity of nitrogen

remaining in litterbags were as follows: 131% in unfertilized Sparganium

litter, 135% in fertilized Sparganium litter, 50% in swine-waste

enriched Sparganium litter, 90% in unfertilized Typha litter, 135% in

Typha fertilized litter, and 119% in swine-waste enriched Typha litter.

Over the entire sampling interval, litter in fertilized plots contained

significantly greater quantities of nitrogen than did the litter in

unfertilized plots. Also, the enriched litter contained significantly

less amounts of nitrogen than did litter in unfertilized plots. The

latter response is clearly evident, with the exception of day 505 for

Typha (Figure III-4). In addition to the significant treatment effects,

the accumulation of nitrogen in enriched litter was species-specific.

Sparganium lost 50% of its original nitrogen content, but Typha con­

tained an additional 19% nitrogen.

Phosphorus content

Figure III-5 presents the change in phosphorus concentration in

unfertilized and fertilized shoot litter. Initial concentrations in

the litter were 0.079% for Sparganium and 0.025% for Typha, and final

1.5-

GO.5-

Z o % H z 1.5-Ul V

11.0

U 0.5

TYPHA

r-1 1 1 1 L

SPARGANIUM

200-

0

Z 100-z

1 a!

Z 200-lU

% Ul

100-

TYPHA

—

SPARGANIUM VO 00

!

100 200 300 400 500 100 200 300 400 500

TIME ELAPSED (DAYS)

FERTILIZED UNFERTILIZED

Figure III-5. The average concentration of phosphorus and the percentage of original phosphorus remaining in submerged Typha and Sparganium shoot litterbags

99

concentrations were 0.12% in unfertilized Sparganium litter (an

increase of 52%), 0.13% in fertilized Sparganium litter C+ 65%),

0.05% in Typha unfertilized litter (+ 100%), and 0.09% in Typha

fertilized litter (+ 260%). The effect of fertilization on phosphorus

concentrations was not significant- Although the data suggest a

species-specific increase to fertilization, the species x treatment

and species x treatment x time interactions were not significant.

Figure III-5 also illustrates the change in absolute amounts of

phosphorus in litterbags. After 505 days, quantities of phosphorus

remaining in Sparganium unfertilized and fertilized litter were 98%

and 107%, respectively. Amounts of phosphorus in Typha litter in­

creased to 125% of the initial amount in unfertilized plots and 221%

of the initial amount in fertilized plots over 505 days. Despite the

discrepancy between amounts of phosphorus accumulated by each

species, the species x treatment interaction was not significant;

however, the time x species, time x treatment, and time x species x

treatment interactions were all significant.

Root-rhizome Decomposition

Dry weight

The percentage remaining of root-rhizome dry weight is presented

in Figure III-2. Weight loss from below-ground tissues was similar

to the pattern of loss from shoot tissues. Initial loss of material

extended from 30-50 days. Dry weight of unfertilized and fertilized

Sparganium root-rhizome tissues initially declined by 33%. Typha

root-rhizomes declined by 42% in unfertilized plots and 36% in the

100

fertilized plots during the same period. For Sparganium, the percen­

tages of initial dry weight lost in the first 30-50 days were similar

between shoots and roots-rhizomes. In Typha, however, initial root-

rhizome losses were approximately 22% greater than shoot losses in

unfertilized plots and 10% greater in fertilized plots. Further dry-

weight losses from root-rhizome tissues after the initial phase were

minimal. By day 505, only 28% and 47% of the original Sparganium

tissue had disappeared in unfertilized litterbags and fertilized

litterbags, respectively. Loss of Typha tissue totaled 50% in

unfertilized plots and 38% in fertilized plots. Fertilization did

not statistically alter the loss of dry weight from the root-rhizome

tissues•

Nitrogen content

The change in nitrogen concentration of root-rhizome tissue is

presented in Figure III-3. Spargaaium values fluctuated between 1.15%

and 1.73%, and Typha values between 1.10% and 1.66%. Slight declines

in nitrogen concentration with time, however, seem obvious. Initial

nitrogen percentages for Sparganium and Typha roots-rhizomes were

1.38% and 1.49%, respectively. With one exception, the concentration

in Sparganium root-rhizomes of control plots (1.49%), final concen­

trations were lower than the initial concentrations. Final nitrogen

concentrations in the remaining treatment plots were 1.28% in

Spargam' urn fertilized plots (a decrease of 7%), 1.37% in Typha control

plots (-8%), and 1.19% in Typha fertilized plots (-20%). The fertili­

101

zation treatment did not cause an increase in concentrations of

roots and rhizomes. Rather, nitrogen concentrations of below-ground

tissues were significantly lower in fertilized plots. Seasonal

averages were 1.46% in Sparganium control plots and 1.36% in fertilized

plots. Similarly, Typha averages were 1.44% in control plots and

1.26% in fertilized plots.

The absolute quantities of nitrogen remaining in root-rhizome

litterbags appear in Figure III-4. This pattern is in contrast to

that for shoot material. Significant quantities of nitrogen were

lost early from below-ground tissues after placement in the unferti­

lized and fertilized plots. During the first 100 days, 58% (unferti­

lized) and 52% (fertilized) of the original quantity of nitrogen was

lost from Typha root-rhizome tissues. The losses from Sparganium

below-ground tissues occurred over a shorter period of time, 14 days,

and were smaller, 26% in unfertilized plots and 23% in fertilized

plots. After the initial period of loss, remaining quantities of

nitrogen were constant (Figure III-3).

102

DISCUSSION

Dry Weight

Shoot litter

Most studies of emergent plant decomposition have been conducted

by placing material collected soon after shoot death into marsh water

or artificially prepared water. After inundation, the litter undergoes

two phases of decomposition: an initial period of rapid weight loss

because of leaching of soluble compounds and a longer period of

microbial breakdown (Boyd 1970; Mason and Bryant 1975; Howard-Williams

and Howard-Williams 1978; Davis and van der Valk 1978a, 1978b;

Puriveth 1980; Rogers and Breen 1982). In contrast to the submerged

litter, standing litter is affected primarily by leaching and frag­

mentation (Davis and van der Valk 1978a). The loss of soluble com­

pounds is a slower process in standing litter (Boyd 1970) and is

essentially a function of the timing and quantity of precipitation

events (Davis and van der Valk 1978a). We collected standing shoot

litter approximately 7 months after shoot death; hence, leaching

should have been virtually complete. Fertilized, unfertilized, and

enriched litter, however, lost 16-27% of their original weight

within 24 hours after being submerged (Figure III-2). These rates

are comparable to a 24-hour loss of 22% dry weight from anaerobic

Fraxinus excelsior leaf litter (Nykvist 1959). The dramatic Eagle

Lake losses suggest that leaching by precipitation immediately after

103

shoot death was incomplete or that exposure of standing litter to

alternate periods of drying, wetting, freezing, and thawing through

the winter rendered the vegetation more susceptible to leaching once

in the fallen litter compartment. Because fall, 1978 through spring,

1979 was a period of near normal precipitation (Table III-l), the

latter alternative seems more probable.

Neither leaching or the rate of decomposition of shoot litter

was affected by the application of fertilizer (Figure III-2).

Andersen (1978) found a 10% increase in the rate of decomposition

of Phragmites communis between a nutrient-rich lake and a nutrient-

poor lake. Fertilization studies in the laboratory and field have

also shown that rates of decomposition in stream ecosystems can be

accelerated by increased nitrogen and phosphorus concentrations in

the water (Kaushik and Hynes 1971; Howarth and Fisher 1976; Elwood

et al. 1981). The decomposition of litter in a bog ecosystem,

however, was not altered by fertilization; rather, decomposition

in that study was positively correlated with the initial concentration

of nitrogen in the litter (Coulson and Butterfield 1978). Davis and

van der Valk (1978b) also alluded to an increase in the rate of

dry-weight loss with an increase in initial nitrogen concentration;

and, Almazan and Boyd (1978) demonstrated a positive correlation

between oxygen consumption by microbial decomposers and nitrogen

concentrations of various macrophytes and algae. In a terres­

trial system, initial concentrations, however, have been shown

important only during the early phase of leaf litter decomposition

Table Ill-l. The amount of precipitation (cm) at Eagle Lake between fall, 1978 and spring, 1979

1978 1979

Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr.

Precipitation 6.99 12.37 2.77 3.76 4.47 1.60 4.72 1.19 5.79

Departure from normal -1.12 +4.22 -1.85 +0.61 +0.89 -1.04 +2.01 -4.26 -1.12

105

(Staaf 1980). Initial Sparganium and Typha nitrogen values in

the enriched litter were 138% and 15% higher than initial values

from litter collected in Eagle Lake. These enriched tissues exhibited

statistically faster rates of decomposition, with the effect most pro­

nounced in Sparganium tissues (Figure 111-2).

Root-rhizome litter

Root-rhizome tissues at Eagle Lake had high rates of dry-wei^it

loss at the outset of the study. The results of this study are compara­

ble to a reported dry-weight loss of over 20% from Sparganiurn and Typha

latifolia below-ground tissues in a Wisconsin marsh after 1 month

(Puriveth 1980). These early losses from Sparganium and Typha roots-

rhizomes are greater than early losses described for other wetland

species. Early losses from Juncus roemerianus and Sparina cynosuroides

root-rhizome tissues have been reported as minimal (Hackney and

De La Cruz 1980) . In fact, raoemerianus below-ground tissues

buried at depths of 15 and 25 cm increased 8.7% and 6.1% in weight

after 43 days. Heal et al. (1978) also reported very slight losses

of weight from below-ground tissues of Eriophorum vaginaturn and

Calluna vulgaris. After 1 year, decomposition of these latter two

species had progressed by only 0.6% and 5.0%, respectively.

After 505 days in the field, Sparganium had lost as much as 47%

of its dry weight and Typha as much as 50%, with fertilization having

no effect on the loss. These losses are more than twice as great

as the losses from roots and rhizomes of Juncus and Spartina after

106

360 days (Hackney and De La Cruz 1980); and approximately 4-40 times

greater than losses from Eriophorum and Calluna after 2 years.

Puriveth reported losses of 27.8% from 2- latifolia and 42.1% from

Sparganium after 348 days. Puriveth's values are lower than comparable

data for the species at Eagle Lake on day 350, i.e., 37% for Spargam" imi

and 48% for Typha in control plots. Hackney and De La Cruz (1980)

reported that rhizomes decompose faster than roots. Both Sparganixim

and Typha below-ground structures are predominantly rhizomatous,

which may partially account for their high rates of decomposition.

It is certainly possible that our results and those of Puriveth

(1980) may have been affected by the initial drying of the live root

and rhizome tissues. That drying alters organic compounds and cell

wall components and increases leaching has been observed or suggested

for submergent macrophytes (Harrison and Mann 1975; Godshalk and

Wetzel 1978; Rogers and Breen 1982). Similar alteration may have

occurred in our study. Hackney and De La Cruz (1980) have cited the

possible alteration of chemical constituents as a reason for air

drying roots and rhizomes instead of oven drying them.

Nutrient Content

Shoot litter

An eventual rise in nitrogen and phosphorus concentrations of dead

tissues is typical (Kaushik and Hynes 1968, 1971; Odum and De La Cruz

1967; Maystrenko et al. 1969; Boyd 1970; Klopatek 1975; Mason and

Bryant 1975; Andersen 1978; Richardson et al. 1976; Davis and Harris

107

1978; Davis and van der Valk 1978a, 1978b, 1978c; Puriveth 1980; Staaf

1980; and others). Concentration increases of N and P in litter may be

caused by more rapid loss of organic material than nitrogen or phosphorus,

accumulation of nitrogen and phosphorus, or a combination of these

two factors (Brinson 1977). Although this study does not address

the relative importance of these two processes specifically, the

assumption is probably valid that increases in the fertilized and

and unfertilized Typha and Sparganium tissues were due to nutrient

accumulation by microbes (Kaushik and Hynes 1971; De La Cruz

and Gabriel 1974; Brinson 1977; Davis and van der Valk 1978a,

1978b) . C:N ratios of 16-23 (Enwezor 1976; Brinson 1977) and

a C:P ratio of 200 (Brinson 1977) are presumably minimum levels for

complete mineralization of detritus by microbes. Ratios above these

values are indicative of a microbial nitrogen and phosphorus demand

in excess of the nitrogen and phosphorus content of the litter. Thus,

nitrogen and phosphorus concentrations within the litter increase

because of microbial immobilization from the surrounding water and

adjacent soil particles. Table III-2 summarizes the initial and

final C:N and C:P ratios in the litter at Eagle Lake. These ratios

suggest a nitrogen and phosphorus demand by the microbes. Over the

course of this study, both C:N and C:P ratios did decline, and Typha

ratios were consistently higher than Spargam'iini ratios.

Nitrogen concentration increases in the enriched litter were as like­

ly due to a differential loss of carbonaceous material and nitrogen con­

taining compounds as to an actual accumulation of nitrogen (Figure III-2).

Table III-2. Approximate C:N and C:P ratios (assuming C as 45% of dry weight - Prentkl et al. 1978) of unfertilized, fertilized, and swine enriched litter

C:N C:P

Typha Sparganlum Typha Sparganium

Shoot Root-rhizome Shoot Root-rhizome Shoot

Unfertilized

Initial 94 30 76 33 1800 570

Final 64 33 36 30 882 385

Fertilized

Initial 94 30 76 33 1800 570

Final 43 38 35 35 500 354

Enriched

Initial 82 — 32 — —

Final 41 — 22 — ——

109

The C:N ratios for both species do indicate that some accumulation

should have occurred (Table III-2), but the Spargani nm ratios (an

initial ratio of 32 and a final ratio of 22) do approximate ratios

sufficient to insure complete microbial decomposition.

Kaushik and Hynes (1971) presented data which indicate that

nitrogen immobilization in excess of demand can occur, i.e., luxuriant

uptake. In that study, an ambient concentration of 10 ppm nitrogen

was more than the nitrogen quantity required for breakdown of leaf

litter, but an increase to 100 ppm stimulated even greater immobiliza­

tion. Fertilization did not cause any significant elevation in nitro­

gen or phosphorus concentration in our work. But, absolute quantities

of nitrogen and phosphorus immobilized in the litter of fertilized

' plots were significantly greater than those amounts in the litter of

unfertilized plots.

Absolute quantities of nitrogen and phosphorus in submerged

litter of some species have been reported to exceed temporarily the

original quantities of nitrogen or phosphorus (Boyd 1970; Brinson

1977; Davis and Harris 1978; Davis and van der Valk 1978a, 1978b).

In each of these studies the quantity of nutrient eventually declined.

But, at Eagle Lake only nitrogen in Typha unfertilized litter declined

after an increase. At 505 days, all other nitrogen values were at

their highest level (Figure III-4). Similarly, phosphorus values

continued to rise or remain stable (Figure III-5).

In contrast to the fertilized and unfertilized litter.

110

Sparganium enriched litter was a nitrogen source (Figure III-3).

After 505 days, 50% of the original nitrogen had disappeared. Al­

ternately, Typha enriched litter eventually functioned as a nitrogen

sink, but was less effective than the fertilized litter (final

quantities of 119% and 135%, respectively, of original amounts).

Thus, it seems that the ability of litter to function as a nutrient

sink is closely related to initial nutrient content, and to a

lesser extent the amount of structural tissue. These data indicate

that plants with high initial nutrient content, are likely to act

as sinks only while living.

Below-ground litter

Table III-2 indicates a range of C:N ratios from 33-38 for the

below-ground detritus of Sparganium and Typha at Eagle Lake, thereby

indicating that nitrogen immobilization should have occurred. But,

nitrogen concentrations were stable or increased only slightly

(Figure III-3). Hackney and De La Cruz (1980) have reported slight

elevations of nitrogen in root-rhizome tissues over a 360-day period.

Although nitrogen concentrations of roots-rhizomes were significantly

lower in fertilized enclosures, the absolute quantities of nitro­

gen remaining in litterbags were not statistically different between

fertilized and unfertilized sites. Based on the absolute nitrogen

values within the litterbags, the below-ground material of Sparganium

and Typha was a net exporter of nitrogen (Figure III-4). Similar

trends have been reported by Puriveth (1980) for below^ground tissues

Ill

of the same genera. Puriveth, however, observed major increases in

nitrogen quantities after 3-8 months of decomposition. Any increases

in the Eagle Lake species were minimal.

The absence of a change in nitrogen quantities with, fertiliza­

tions was unexpected, particularly because the above-ground litter

responded to fertilization, and analyses of interstitial waters

substantiated that concentrations of available nitrogen and phosphorus

in 15-cm interstitial waters were significantly elevated by fertiliza­

tion (unpublished). Because decomposition rates can be limited by

oxygen (Chamie and Richardson 1978; Heal et al. 1978), the effects

of fertilization may have been minimized by subsurface anaerobiosis.

The interaction of microbial demands for oxygen and available nutrients

is not understood, but is probably complex and seasonally variable

(Brinson 1977).

112

CONCLUSIONS

Table III-3 summarizes the final amounts of dry weight, nitrogen

and phosphorus remaining in Sparganlum and Typha litter after 505

days decomposition. On the basis of these data, decomposition of

emergent plant shoot litter was evidently limited by the initial

nutrient supply in the litter rather than the supply of nutrients

in surrounding waters; and shoot litter with a high initial nutrient

content was less effective as a nutrient sink than shoot litter

with an initially low nutrient concentration in high nutrient waters.

At Eagle Lake, an increase in initial nutrient concentrations of

emergent shoot litter, including a 138% increase in nitrogen concen­

tration of Sparganium litter and a 15% increase in nitrogen concen­

tration of Typha litter, resulted in a loss of 27% and 2% more dry

weight than unfertilized and fertilized Sparganium and Typha litter

with a lower initial nutrient content. During the 505 day period,

the enriched Sparganium shoot litter lost 50% of its original quantity

of nitrogen. Enriched Typha shoot litter was also a nitrogen expor­

ter through 350 days of decomposition, but by 505 days exhibited a

net gain of 19% nitrogen. On the other hand, quantities of nitrogen

in fertilized Typha and Sparganium shoot litter increased by 35%;

and quantities of phosphorus in fertilized Typha and Sparganium

shoot litter increased by 121% and 7%, respectively.

Sparganium and Typha roots-rhizomes decomposed at nearly the

same rate as shoot litter (Table III-3), but the role of below-ground

113

Table III-3. Percentage remaining of original dry-weight, nitrogen, and phosphoinis quantities in Typha glauca and Sparganium eurycarpum litter after 505 days

% Remaining

Typha glauca

fertilized

unfertilized

enriched

Shoot

Dry Wt.

61

61

59

N

135

90

119

221

125

Root-rhizome

Dry Wt.

62

50

N

51

46

Sparganium eurycarpum

fertilized

unfertilized

enriched

61

61

34

135

131

50

107

98

53

72

50

76

114

litter in wetland nutrient cycles seems quite different from that of

shoot litter. Our data suggest decomposing below-ground litter is

a continuous source of nitrogen under both fertilized and unfertilized

conditions. After 505 days decomposition, maximum nitrogen losses

were between 50 and 54% of original quantities in root-rhizome

litter of both species.

115

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119

Tilton, D. L., R. H. Kadlec, and C. J. Richardson. 1976. Freshwater wetlands and sewage effluent disposal. University of Michigan, Ann Arbor, Michigan. 343 pp.

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Tourbier, J. and R. W. Pierson. 1976. Biological control of water pollution. University of Pennsylvania Press, Philadelphia, Pennsylvania. 340 pp.

van der Valk, A. G., C. B. Davis, J. L. Baker, and C. E. Beer. 1978. Natural freshwater wetlands as nitrogen and phosphorus traps for land runoff. Pages 457-467 P. E. Greeson, J. R. Clark, and J. E. Clark, eds. Wetland functions and values: The state of our understanding. American Water Resources Association, Minneapolis, Minnesota. 674 pp.

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120

SUMMARY

The goal of this project was to determine the impact of nitrogen

and phosphorus loading on three wetland compartments: interstitial

water, living emergent vegetation, and submersed emergent litter.

Repeated application of NH^NO^ and (NH^) 2^^^^ in 1979 and 1980 indicated

that (1) interstitial concentrations of nitrogen and phosphorus increase

with an elevation of surface water concentrations, (2) that emergent

plant production can be a function of the fertility of the surface water,

and (3) that the rate of emergent litter decomposition, and thus its

capacity to act as a nutrient sink, is controlled by the initial nutrient

concentration of the litter itself and not the nutrient concentration of

the surrounding water.

The impact of fertilization has been considered separately for each

marsh compartment in the three sections of this dissertation; however,

this does not imply that the compartments responded independently to

fertilization. Rather, the movement and effect of applied nitrogen was

a sequential process involving the interaction of all 3 compartments

(Figure 4)• Applied nitrogen and phosphorus moved first from the sur­

face water into the interstitial water, causing an increase in PO^-P

(+47% in 1979 and +60% in 1980) and NH^-N (+144% in 1979 and +189% in

1980) in the top 15-cm of interstitial water beneath stands of Spar-

ganitm eurycarpum and Typha glauca» Fallen emergent plant litter was

found to function as a physical and biological (microbial uptake)

barrier to the downward movement of surface nutrients across the sedi-

121

Emergen* Vtgrtatîon

Shoot N

Sporgonium +34* + 14* Typho

d*nitrifî<otion

^— Surface HgO

NH4 (25mg/l)

Spargonium +20* PO4 Typho +30*

(Sms/i) N,P

Shoot NPP

Litter-Microbe Complex litter-Micrbbe Complex Sporganium +57*

I+«>*> Sporgonium +25* V Typho Interstitial HgO

Figure 4. The movement and effect of nitrogen and phosphorus fertilizer in Eagle Lake marsh. After application, the fertilizer moved through the litter layer into the interstitial water column.

As a result, nitrogen and phosphorus concentrations in both compartments were elevated. Emergent plant uptake and accu­mulation of nitrogen from interstitial waters in 1979 and 1980 stimulated an increase in shoot density in 1980, an increase in net primary production (ïîPP) in 1980, and even­tually an increase in the rate of decomposition. Percentages denote the 1980 post—fertilization changes in nitrogen and phosphorus concentration of interstitial water and live tissues; the change in the absolute quantity of nitrogen and phosphorus in litter; the change in shoot density; the change in NPP; and the change in the rate of decomposition

122

ment-water interface. With fertilization, absolute quantities of nitro­

gen (+35% for both species) and phosphorus (+7% for Sparganium and +121%

for Typha) accumulated in the fallen litter over 505 days of decomposi­

tion. After movement of the added PO,-P and NH,-N into the inter-4 4

stitial water column in 1979, percentage nitrogen increased in the roots-

rhizomes of Sparganium (+14%) and the shoots of both species (+30% for

Sparganium and +7% for Typha); however, these increases did not signif­

icantly alter plant production. In 1980, root-rhizome nitrogen concen­

tration (+25% for Sparganium and +38% for Typha), shoot nitrogen concen­

tration (+34% for Sparganium and +14% for Typha), shoot density (+20%

for Sparganium and +30% for Typha), and net primary productivity (+57%

for Sparganium and +19% for Typha) increased. The 1-year delay for a

production response was presumably related to the storage of the nutri­

ents in overwintering below-ground tissues (see Section II for furthur

discussion). Eventually, the elevated nitrogen concentration of the

live tissues resulted in an acceleration of emergent litter decomposi­

tion (+138% .nitrogen in Sparganium litter caused a loss of 27% more dry

weight over 505 days, and +15% nitrogen in Typha litter resulted in a

loss of 2% more dry weight over 505 days).

123

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125

ACKNOWLEDGEMENTS

This study was supported by grants from the Iowa Agriculture

and Home Economics Experiment Station (Project 2071), the U.S.

Environmental Protection Agency (Grant #805826-012), the U.S. Office

of Water Resources Technology (Grant #A-080-IA), and Sigma Xi, the

Scientific Research Society. Gratitude is expressed to each of my

committee members, James Baker, Craig Davis, Richard Smith,

Cecil Stewart, and Arnold van der Valk, for their constructive

comments on this dissertation. Special thanks are given to James

Baker and Richard Smith for donation of their laboratory facilities.

I would also like to thank Rose Griffin, Mike Martin, Steven Schaff,

and Scott Thompson for their help in the field and laboratory, and

Sandy Wade for her careful typing of this dissertation. Very special

appreciation goes to my wife. Renée, for her long hours of assistance

in the laboratory and field, and her secretarial help in finishing

this manuscript.