View
226
Download
1
Tags:
Embed Size (px)
Citation preview
Sphagnum bogs…Sphagnum bogs…
…would they be as acid by any other name?
Louise Kulzer
Water quality specialist, Aquatic ecologist
King County Department of Natural Resources
(Scott Luchessa, Fred Weinmann, Sarah Cooke collaborators)
Why we’re here...Why we’re here...
““In the end, we will conserve only what we love, we will love only what we understand, and
we will understand only what we are taught.”
-- Baba Dioum, Senegal
Goals Goals
To understand the unique characteristics of sphagnum bogs
To understand how human influences can adversely impact sphagnum bogs
To see a peat system first-hand
What you’ll learn about...What you’ll learn about...• Where & how bogs are formed
• How sphagnum moss creates it’s own niche
• Physical & chemical gradients in wetlands & where bogs fit in
• Plant & animal communities in bogs
• How human activities can disrupt bogs
Definitions Definitions (after Bridgham, (after Bridgham, 1998)1998)
Peatland is a generic term applied to wetlands in which the rate of accumulation of organic matter exceeds the rate of decomposition, and where at least 1 foot ( 30 - 40 cm) of peat has accumulated (Glaser, 1987)
(Mire is the European name for peatlands)
Two basic divisions in peatlands:bogs -- acidic peatlands, Sphagnum moss forms dense mat
fens-- depends on classification-- usually more sedges, less acidic
Definitions, cont’d
Other peatland typesOther peatland typesmuskeg-- northern peatlands covered with
stunted black spruce (Crum, 1992) rooted in Sphagnum
moors-- in Britain, bleak, uncultivated land, not necessarily peaty. “High-moor” is characterized by calcium poor substrates and Sphagnum mosses.
heath--in Britain, areas of infertile, often peaty soils supporting shrubby vegetation. Typically over-grazed historically.
carr-- a peat system, usually not Sphagnum-dominated, supporting deciduous trees
Types of bogsTypes of bogs• lake-fill or kettle-hole bogs
– flat basin– plateau or raised bogs
• Blanket bogs– flat valley– slope bogs
carpets, lawns (use differs with authors)
open hummock/hollow, usually w/ shrubs
forested
terrestrialization
paludification
Bogs form in specific Bogs form in specific environmental situations environmental situations
Precipitation exceeds evaporation
Bogs form in specific Bogs form in specific environmental situationsenvironmental situations
• Drainage is poor (plateaus, drainage divides)
• Poor soils, often glaciated
• Kettle holes
• Cool temperatures
• Oceanic influence common-- rainfall higher in Na & Cl
• Northern latitudes
• in lakes, protected from wind, upstream flowpaths
Distribution of bogsDistribution of bogs
Sequence /age of peat Sequence /age of peat profileprofilePuget Sound region– Often underlain by blue clay– sedge peat
– pumicite layer (laid down 6,700 yr b.p. (151 obs.))– sphagnum peat
• 11,900 yr. b.p. average for beginning of peat accumulation
• 41 years/ inch of peat accumulation (151 obs, Puget Sound lowlands)
Other NW bogs: 49 years / inch (55 obs in NE Wa, Idaho, BC)
Northern Minnesota-- 4,000 yr. BP (mid-holocene)
Characteristics of sphagnum Characteristics of sphagnum bogsbogs
• form mats which are at least somewhat buoyant
• mats often form hummocks & hollows, support a unique assemblage of plants
• water acidic
• bacterial communities severely depressed, but aquatic fungi thrive
• lack of dissolved oxygen, minerals and nutrients in water
• typically have a moat or “lagg” at periphery
Gradients operating in Gradients operating in peatlandspeatlands
• source of water
rain runoff groundwater
• water mobility
stagnant flowing
• water chemistry (pH, cations, anions, nutrients)
low high
• water levels
stable fluctuating
More gradients More gradients
• sunlight shade
• summer winter
• hummock hollow
• mat lagg or moat
What’s in a name?What’s in a name?rich fen poor fen
rheophilous
geogenous(minerotrophic)
Vegetation community gradients responding to abiotic gradients, made up of many attributes.
Different investigators draw the line between the names (fens vs. bogs) in different ways.
Bridgham, et al., 1996, call for new paradigm
(“Multiple limiting gradients in peatlands, a call for a new paradigm.” Wetlands, Vol. 16, No. 1, March 1996, pp. 45-65)
bogbog
ombrophilousombrophilous
ombrogenousombrogenous (ombrotrophi(ombrotrophic)c)
What’s in a name?What’s in a name?
Makes sense to use a “weight of evidence” approach in referring to peatlands as either bogs or fens rather than a single indicator. Vegetation, esp. Sphagnum, should be one of the indicators. Variable, especially across latitudinal and altitudinal gradients
Sphagnum
BOG FEN
GenerallyGenerally
water source
mobility
chemistry
pH
cations
anions
nutrients
water level
bogsbogs fens fens
rainwater surface & groundwater
stagnant flowing
acid neutral or basic
scarce abundant
Cl dominant CO3, HCO3 dominant
low high
stable stable or fluctuating
Bottom line:Bottom line:
Sphagnum bogs are isolated from the influences of groundwater &/or surface water runoff in some way
• topography (small watershed, flat area)
• impermeable layers– blue clay– decomposed peat itself
• raised character of hummocks or plateau
• moat or lagg
SphagnumSphagnum moss moss• Indeterminate growth
• upper portion actively grows,bottom portion sloughs away, may sink to bottom or be suspended
• dozens of species, w/ own growth habits, tolerances for pH, light, wetness
• leaves thin, only 1 cell thick
• cell walls w/ perforations, high concentrations of polyuronic acid, an active cation exchanger
• high water-holding capacity (15-23X dry weight)
Sphagnum ecologySphagnum ecology• Numerous species, 61 in European mires
• wide range of pH tolerances
• some species are specialists, some generalists
• Coastal BC-- 6 species groups– degree of shading
– height above water table
– surface water chemistry
• No definitive local taxonomy done for WA, OR
Profile through a sphagnum Profile through a sphagnum hummockhummock
2’2’
Zone 1 interstitial spaces aerated
Zone 2 interstitial spaces saturated, water oxygenated
Zone 3 interstitial spaces saturated, water anoxic
acrotelm
catotelm
Dissolved oxygen in bogsDissolved oxygen in bogsincreasing depth within matincreasing depth within mat
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
4" 12" 20"
site1site2site3site4
Little Lake, Snohomish county, WA
depth from surface
DOmg/ L
/ L
pH of natural waterspH of natural waters
Small streamSmall stream
RainRain
BogBog
L. WashingtonL. Washington
Typical wetlandTypical wetland
1 2 3 4 5 6 7 8 9 10 11 12 13 14
acidic pH (log scale) basic
(data from the Puget Sound area)
Sources of acidity in bogsSources of acidity in bogs
• decomposition of peat in the acrotelm yields organic acids– humic acids
– fulvic acids
• redox reaction of sulfur compounds yields acids
• Cation exchange by sphagnum -- H+
Bog/fen gradientBog/fen gradient
Bog Fen
Mitch &Grosselink, 1993
Moss (Sphagnum) -dominated
Grass & sedgedominated
Gignac& Vitt,1990
Sphagnum-dominated
Mod. richfens
Rich fens
Sjors,1950
Moss Extremepoorfen
TransPoorfen
Intermedrich fen
Transrichfen
Extremerich fen
Weber1909
Hochmoore Ubergangs-moore
Niedermoore
Cation exchangeCation exchangeCa++ Na+ H+ Mg++
Mg++ K+
Ca++
2 H+
Na+
Polyuronic acid on sides of cell wall
Buffering systems in Buffering systems in waterswaters
Atmosphere: CO2
CO2 + H2O = H2CO3
H2CO3 H++ HCO3- 2H++ CO3
--
organic CO2 HCO3
- HCO3-
acids H2CO3 bicarbonate
carbonic acid CO3--
carbonatepH 3 4 5 6 7 8
Typ. wetlandsbogs
Carbonate - bicarbonate Carbonate - bicarbonate buffering systembuffering system
Buffers in natural waters, Buffers in natural waters, cont’dcont’d
Cations Solution
Na+
K+
Ca++
Mg++
organic acid+
pH 6 8
Salts
NaHCO3
K2CO3
CaCO3
MgCO3
organic salt
1 0
HCO3- H+
H+ CO3--
HCO3- H+
H+ H+
H+ CO3--
Chemistry of waters: Chemistry of waters: cationscationsdata from Puget Sound area (typical)data from Puget Sound area (typical)
hardness (Ca + Mg)hardness (Ca + Mg)
alkalinity (... mg/L alkalinity (... mg/L CaCOCaCO33))
1 10 20 30 40 50 60 70 80 901 10 20 30 40 50 60 70 80 90Urban runoff
Typical wetlands
Tea-stained lake
L. Wa.
groundwaterBogs, sm. streams
Chemistry of waters: nutrientsChemistry of waters: nutrientsdata from Puget Sound areadata from Puget Sound area
Total phosphorus concentrations
.01 .01 * * 0.05 0.1 0.5 1.0 5.0 10 0.05 0.1 0.5 1.0 5.0 10 Total Phosphorus (mg/L)Total Phosphorus (mg/L)
Urban runoff/groundwater Typ. wetland
rain
L.Wa
*
bog
.001 .005 .01 .05 .1 * .5 1
Chemistry of waters: nutrientsChemistry of waters: nutrientsdata from Puget Sound areadata from Puget Sound area
Nitrogen(Nitrogen(NONO33)) mg/L mg/L
Urban runoff
Rain
L. WashingtonTypical wetland
bog
Nitrogen concentrations
Groundwater
Cations in surface watersCations in surface watersELS21, April 26, 1993ELS21, April 26, 1993
Inlet stream
• Ca++ 2.0
• Mg++ 0.9
• Na+ 2.0
• K+ 0.4
Units: mg/L
• pH 6.3
lagg Sphagum Mat
1.9 0.70.7
0.8 0.30.3
1.8 0.60.6
0.6 0.5
5.6 4.24.2
Cations in surface & Cations in surface & groundwatergroundwater LCR16, 1998-9LCR16, 1998-9
groundwater*
• Ca++ 4.7
• Mg++ 8.4
• Na+ 0.9
• K+ 3.0
• Alkalinity 30.0
Units: mg/L
• pH 6.2
* Avg, 60 m from bog
sphagnum
lagg mat
4.9 0.4
2.1 0.2
2.5 0.8
0.6 1.3
16 <1
6.9 4.2
Mauncha diagramMauncha diagram
H+H+ K+ K+
HCOHCO33-- Na+ Na+
ClCl-- Ca++Ca++
SOSO44== Mg++Mg++
Microbial characteristicsMicrobial characteristicsBog water Moat area
heterotrophic A 85 11,000
plate countB 119 13,700
yeast A 400 6,800
plate count B 310 5,800
filamentous A 20 3,500
mold B 18 2,800
Units: CFU/ ml
Hypothetical plant Hypothetical plant gradientsgradients• Emergents (sedges, skunk cabbage,
etc.)
• sedge peat
• sphagnum moss
– lawns
– hummocks & hollows
– ericacious shrubs
– stunted trees
• closed canopy forest over peat
Gradients in herbaceous Gradients in herbaceous species:species:Minnesota peatlands (Glasser, 1987)Minnesota peatlands (Glasser, 1987)BogsBogs
Carex oligospermaCarex oligosperma
Eriophorum spissumEriophorum spissum
Poor fensPoor fens
Rhynchospora albaRhynchospora alba
Carex limosaCarex limosa
Rich fensRich fens
Carex chordorrhiza, C. lasiocarpaCarex chordorrhiza, C. lasiocarpa
Common bog plantsCommon bog plants(Based on fall 1998 survey, 30 Puget Sound
bogs)
30 Ledum groenlandicum Ledum groenlandicum (Labrador tea)(Labrador tea)
25 Tsuga heterophylla (hemlock)
20 Kalmia microphyllaKalmia microphylla (bog laurel) (bog laurel)
17 Spirea douglasii
17 Vaccinium oxycoccusVaccinium oxycoccus (cranberry) (cranberry)
15 Thuja plicata (w. red cedar)
Pink font = family EricaceaePink font = family Ericaceae
Other common bog plantsOther common bog plantsDrosera rotundifolia (sundew)
Cladium (reindeer lichen)
Rhynchospora alba (beakrush)
stunted Sitka spruce, shorepine, white pine
crabapple, cascara, willow, birch
blueberry, huckleberry
Eriophorum (cottongrass), Menyanthes (bogbean)
Scirpus atrocinctus (= cyperinus)
skunk cabbage
Uncommon bog plantsUncommon bog plantsCarex pauciflora (few-flowered sedge)
Olympic peninsula
Myrica gale (sweet gale)
Rhododendron macrophyllum
Gentianan sp. (bog gentian)
Habenaria dilatata (bog orchid)
British Columbia
Andromeda sp. (bog rosemary)
Rubus sp. (cloudberry)
Unique bog beetles--Unique bog beetles--WA state sensitive statusWA state sensitive status
Effects of human activity Effects of human activity
Uses of sphagnumUses of sphagnum• soil amendment
• fuel source, ancient times to present
• acid-loving crops– cranberries
– blueberries
• truck farms (Ravenna P-patch)
• paleo-botanical record
• historical record
• absorbent material -- bandages WW1, diapers
Historical changes in Historical changes in sphagnum acreage -- King sphagnum acreage -- King County, WACounty, WA
24 King County Bogs, 1930s to 1990
Sphagnum acres
1930 1980 1990
Total 458 140 132
71% reduction in acreage
1930 acres from Rigg, Peat Resources of Washington
1980, 90 acres estimated from from air photos
Urbanization of watershed Urbanization of watershed • volume of annual runoff increased ~ 40%
• increases winter high
water level
• increases water level fluctuation
• concentration of cations, nutrients
greatly increases ( changes buffer equilibrium)
• bacterial concentration increase
• physical disturbance increases (pets, people)
Responses to urban runoffResponses to urban runoff• Binding of cations+ greatly increased,
may use up exchange sites and kill moss
• buffering system equilibrium disturbed
• WLF causes – increased depth of D.O., increased area of
acrotelm, more decomposition of mat
– higher winter, lower summer water levels
• increased bacteria, more decomposition
• higher nutrients favor typical emergents
Recent changes in Recent changes in sphagnum acreage -- King sphagnum acreage -- King CountyCountyLoss of Sphagnum acreage in inventoried bogs since 1980
Sphagnum acresBog name 1980 1995 Impact
Mill Creek 18 12 0 Housing development,utility placement
LCR22 10 0 Housing developmentLCR25 2.1 0 Housing developmentJenkins Cr17 9 0 MiningHylebos Cr 34 1.4 0 Housing development
Total 34.5 0Loss of sphagnum communities in 5 out of 55 inventoriedwetlands having bog components in 1980 = 9%
Recent changes in Recent changes in sphagnum acreage -- King sphagnum acreage -- King CountyCountyOf the 50 remaining bogs in King Co. WA Of the 50 remaining bogs in King Co. WA most show damagemost show damage
– drainingdraining– dirt paths, roadsdirt paths, roads– cuts for ROW, ditchescuts for ROW, ditches– invasion by non-acid loving plantsinvasion by non-acid loving plants
(more overland runoff)(more overland runoff)– erosion of mat (increased Oerosion of mat (increased O22, WLF), WLF)– tramplingtrampling
Recent changes in Recent changes in sphagnum acreage -- King sphagnum acreage -- King CountyCounty
Impacts of recent drainage, LCR14Impacts of recent drainage, LCR14 hemlock growth taller near cut face of bog # years of accelerated growth increase
closer to the cut face height of Ledum increases, little Kalmia
near cut face Dry hummocks, no bog beetles near cut face
The case of LCR14 The case of LCR14 1934 air photo1934 air photo
1995 air photo1995 air photo
Drainage from cut face
LCR14LCR14
T r e e g r o w t h v s d i s t a n c e
0
5
1015
20
25
8 16 23 152
D i s t a n c e ( m )
# r
i n
g s /
2 c
m # rings
King County Surface Water King County Surface Water Design ManualDesign Manual
Sphagnum bog protection menu applied throughout watershed
Goals: reduce TP by 50%
reduce N by 40%
alkalinity < 10 mg/L
pH < 6
3-facility WQ treatment train
facilities which contribute organic acids
ALSO: match pre-developed volumes
Consequences of accelerated Consequences of accelerated peat system decaypeat system decay
• Excess nutrients to downstream lakes
• Release of greenhouse gases (methane)
• Loss of unique wetland type
• Loss of unique habitat for plants, invertebrates
• Loss of hydrological “sponge” depresses summer low flows, increases winter high flows
• Loss of paleobotanical, geological records
Are we doing enough?Are we doing enough?• Stormwater treatment facilities remove
about half of increased cations, nutrients
• Construction impacts
• Logging & agricultural impacts
• Air pollution, urban climate modification
• Extraction (sphagnum peat use by gardeners widespread)
• Roads can block drainage recharge
• Trampling problem “walking on meringue”
So what to do?So what to do?
• Keep entire catchment forested-- no logging
• Keep roads out of catchment
• Limit any construction/ land disturbance to dry season
• No cement use in catchment
• Don’t give mining permits, stop using peat
• Construct modest, low-impact trails
• Show people! You can’t long protect what people don’t value.
LCR16 from moat looking to bog LCR16 from moat looking to bog matmat
gift of the gift of the glaciersglaciers