Conserved Forest Ecosystems: Outreach and

Research

ADAPTIVE MANAGEMENT PROJECT

Adaptive Forest Management in Pine Flatwoods:

Research Results and Tour

Carrabelle, FL

September 21, 2012

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TABLE OF CONTENTS Page

Acknowledgements............................................................................................................................ 2

Project Overview and History ............................................................................................................. 3

Maps and Treatments Implemented ................................................................................................... 4

Road/site map with research blocks superimposed ............................................................................. 4

Post–harvest aerial photographs of research blocks ............................................................................ 5

Block 1 ................................................................................................................................... 5

Block 2 ................................................................................................................................... 5

Block 3 ................................................................................................................................... 5

Descriptions of the harvest treatments................................................................................................. 6

Uncut control ........................................................................................................................ 6

Group selection ..................................................................................................................... 7

Shelterwood ......................................................................................................................... .8

Stutter-step .......................................................................................................................... .9

3rd row thin .......................................................................................................................... 10

Cut 2 Leave 3 row thin ........................................................................................................ 11

Ongoing/Future Activities for Field Study ......................................................................................... 12

Current Research Results ................................................................................................................. 13

1. Modeling conversion of stand from even-aged to uneven-aged structures ................................... 13

Input values/ Initial stand structure ........................................................................................ 13

Description of the conversion scenarios .................................................................................. 13

Forest Vegetation Simulator (FVS) outputs (structure, carbon, timber) ................................. 14

Optimizing multiple objectives ................................................................................................ 15

2. Light regimes as affected by uneven-aged harvests. ...................................................................... 16

3. Examination of soil seed bank for its potential to restore understory in-situ. ............................... 18

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ACKNOWLEDGEMENTS

Principal Investigators:

Kimberly Bohn, University of Florida

Ajay Sharma, University of Florida

Sponsors:

Florida Forest Service

Florida Park Service

Northwest Florida Water Management District

Suwannee River Water Management District

UF/IFAS Dean for Research

Supporters:

Gilchrist Club

Nokuse Plantation

St. Johns River Water Management District

Southwest Florida Water Management District

Normandeau Associates, Inc.

USDA Forest Service- National Forests in Florida

USDA Forest Service-Southern Research Station

UF/IFAS School of Forest Resources and Conservation

Scientists:

Shibu Jose, University of Missouri

Dale Brockway, USDA Forest Service

Kenneth Outcalt, USDA Forest Service

Edward Loewenstein, Auburn University

Field Operations:

David Morse, Florida Forest Service

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PROJECT OVERVIEW AND HISTORY

Management of conserved forests must consider the sustainability of a variety of ecosystem products and values. Increasingly, uneven-aged forest management is considered an ideal strategy for maintaining ecosystem function and structure to ensure the sustained production of both commodity products and other ecosystems services including wildlife habitat, carbon sequestration, and recreational value. However, our experiences with uneven-aged management are limited, particularly in mesic to hydric flatwoods, and with slash pine sites, such as existing at the Tate’s Hell State Forest. Further, a majority of forest lands are currently even-aged, plantations and would require a series of conversion cuttings to transition to uneven-aged management.

Objective: To evaluate various harvesting strategies (traditional even-aged thinning methods as well as two-aged and uneven-aged methods) to convert plantations to sustainable uneven-aged longleaf/ slash pine ecosystems in terms of species composition (both overstory and understory), forest structure, and productivity (timber yield and carbon sequestration potential) using long term field experiments and simulation modeling.

Status of the project: Stand data was collected at Tate’s Hell State Forest in 2009 which formed the basis of tree marking for implementing the experimental stand conversion harvests. Five harvest treatments (Group selection, Shelterwood, “Stutter-step”, 3rd row thin, and Cut 2 leave 3 row thin) were completed in 3 research blocks in December 2011. Simultaneous with the harvests, soil seed bank assessment was carried out for proactive planning of understory restoration. Currently, the post-harvest overstory and understory data are being collected. The stands are scheduled for prescribed burn in fall/winter 2012, and a regeneration study in the group selection gaps (described later) will be installed in January 2013.

The project also included a modeling study using the U.S.D.A Forest Vegetation Simulator (FVS) model to simulate various harvest treatments over a 100 year time frame. Input data for the model utilized tree data collected at plots at Tate’s Hell before harvesting. The two main initial harvest treatments simulated to convert plantations were low thinning vs. a traditional uneven-aged ‘BDq’

selection system, at two residual basal areas (50 or 20 ft2/acre) and two cutting cycles (10 or 20

yrs).

Preliminary results suggest that different cutting strategies optimized different objectives. The BDq method at any residual basal area or cutting cycle reached a maximum structural diversity in tree sizes sooner than any other treatment. On the other hand, using thinning to a high residual basal to

convert stands resulted in the greatest annualized timber production (ft2/acre/year) and carbon sequestration ( tons/acre/yr) over the simulation period, and resulted in a similar structural diversity to BDq ( within 10%) by year 50.

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MAPS AND TREATMENTS IMPLEMENTED FOR CONVERSION HARVEST STUDY

Road/site map with research blocks superimposed

Block 1

Block 2

Block 3

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Post–harvest aerial photographs of research blocks

BLOCK 1

BLOCK 2

BLOCK 3

BLOCK 2

Each treatment plot was replicated 3 times by

installing all treatments within every block.

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Descriptions of the harvest treatments- Schematic diagrams, post-harvest aerial and site photographs

All the treatment plots are 15.4 acre (820 x 820 ft) in size.

Uncut control

Dense unthinned slash pine plantation established in 1976-77, BA= 110-160 ft2/ac.

Pre-harvest Post-harvest

Schematic: No harvest was performed in the experimental controls. Red dots represent cypress trees existing in the treatment plots

Aerial perspective Terrestrial perspective

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Group selection

Pre-harvest Post-harvest

Schematic: Create 4 gaps (2, 1.0, 0.5, 0.25 ac) in each treatment plot, third row thin within “matrix” of the remaining forest. Cypress trees (red dots) existing in the treatment plots were left uncut.

Aerial perspective

Terrestrial perspective

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Shelterwood

Lowest basal area among all treatments ~30-40 ft2/ac

Creates an open “park-like” condition suitable for regeneration across the entire area

Pre-harvest Post-harvest

Schematic: The best trees (large size, healthy, large crowns) uniformly distributed over the stands were left at residual basal area of 30-40 ft2/ac. Cypress trees (red dots) were left uncut.

Aerial perspective

Terrestrial perspective

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Stutter-step/Staggered 3rd Row Thin

Closely resembles single tree selection, BA~50-70 ft2/ac

Pre-harvest Post-harvest

Schematic: 150’-200’ in a row were cut followed by side stepping over to next row and cut another 150’-200’, then side step back to create a checker-board effect. Cypress trees (red dots) were left uncut.

Aerial perspective Enlarged aerial

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3rd Row Thin

Reduced pre-thin BA by 33 percent.

Typical thinning operation used as a preliminary step to open up stand before implementing uneven-aged methods

Pre-harvest Post-harvest

Schematic: alternate rows cut, while keeping cypress trees (red dots).

Aerial perspective Terrestrial perspective

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Cut 2 Leave 3 row thin

Reduced pre-thin BA by 40 percent

Schematic: Somewhat typical thinning operation to open up stand prior to uneven-aged methods. Alternatively, try under-planting seedlings in the open rows to initiate a second age class. Cypress trees (red dots) were left uncut.

Aerial perspective

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ONGOING/FUTURE ACTIVITIES FOR FIELD STUDY

Permanent measurement plots are being established and marked Post-harvest overstory and understory data (baseline data) being collected The stands are scheduled for prescribed burn in fall/winter 2012 A regeneration study in the group selection gaps will be installed.

o Natural and artificial regeneration studies following harvests o Comparative performances of slash pine and longleaf pine.

Effect of gap opening size and microenvironmental variation within gaps

Figure 1. Seedling planting design inside the group opening. The circle represents the border of the gap and the lines represent the planting rows of slash and longleaf pine.

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CURRENT RESEARCH RESULTS

1. Modeling conversion of stand from even-aged to uneven-aged structures using Forest Vegetation Simulator (FVS) Model Input values/ Initial stand structure

32-year old, BA= 127 ft2/ac, DBH= 7.1 in

–

Figure 2. The initial stand conditions exhibiting a typical bell-shaped diameter distribution of even-aged stands

Conversion scenarios

Two harvest types (BDq and “low thin”)

-BDq scenarios: tree marking based on theoretical reverse J-shaped diameter distribution of the target stand from first harvest onwards.

-“low thin” scenarios: removal of trees of lower diameter classes first in 1st harvest, removal across diameter classes in 2nd harvest, and BDq harvests from 3rd harvest onwards.

-“low thin” scenario depicts AMP shelterwood treatment.

Two residual BA (20 and 50 ft2/ac)

Two cutting cycles (10 and 20 yr)

6 levels of regeneration (0, 100, 300, 500, 700, and 900 established seedlings/ac)

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Forest Vegetation Simulator (FVS) Outputs

Forest structural diversity Carbon sequestration

(a) (b)

Timber production

(c) (d)

Figure 3. Structural diversity (a), C stocks (b), total merchantable timber (c), and sawtimber production under different scenarios of harvest type (Thin or BDq), residual basal area (50 or 20 ft2/ac), and cutting cycle (10 or 20 yr) as affected by level of regeneration simulated over 100 years.

None of the scenarios maximized all criteria variables simultaneously

BDq scenarios resulted in higher average structural diversity while ‘low thin’ scenarios were more effective in C- stocks and timber production

Greatest gains in structural diversity, timber production, and C stocks were observed when scenarios shifted from no regeneration to 100 seedlings/ac

In general, sensitivity of the variables to increases in regeneration above 100 seedlings/ac was low except, in a few scenarios with a low basal area and longer cutting cycle

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Optimizing multiple objectives

Table 1. Structural diversity, C stocks, and timber production in top scenarios providing multiple benefits at BA= 50 ft2/ac

BDq harvest from the beginning followed by successful regeneration of 300-700 seedlings/ac will maximize multiple objectives.

Managing at 20 yr cutting cycle, “low thin” at first cycle followed by 500 seedlings/ac will also maximize multiple objective

Table 2. Structural diversity, C stocks, and timber production in top scenarios providing multiple benefits at BA= 20 ft2/ac

“Low thin” at 20 yr cutting cycle followed by regeneration of 300-900 seedlings/ac will maximize multiple objectives

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2. Light regimes as affected by uneven-aged harvests

The study carried out at Blackwater River, Goethe, and Tate’s Hell State Forests examined

light regimes in slash pine-longleaf pine ecosystems in transition to uneven-aged structures.

Figure 4. Boxplot showing different measures of light conditions (sky, direct fraction of Absorbed Photosynthetically Active Radiation (fAPAR), and diffuse fAPAR) for stands managed under different system in Goethe State Forest (GSF) and Blackwater River State Forest (BRSF). Line in the middle of each box represents median, lower and upper ends of the boxes are first and third quartiles (hinges) and the whiskers extend to the extreme data points in either direction that is within 1.5 factor of the hinge. The outliers are shown as black dots.

Group selection cuttings produced desirable conditions similar to those of the traditionally used shelterwood cuttings but with highest variability (Sharma et al., 2012).

The high amount as well as variability in group selection system is correlated with high regeneration and species richness (Brockway, pers. comm.)

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(a) (b)

Figure 5. Understory light conditions (a)sky, cover fraction, direct fAPAR, and diffuse fAPAR) and (b) leaf area index (LAI) in various areas of the group selection system plots as compared to the uncut control plots approximately 5 years following reproduction cuttings at Goethe State Forest. The values with the same letter did not differ significantly

After 5 years of uneven-aged harvests, light conditions in regeneration clusters was comparable to either matrix forest or uncut control.

Figure 6. Effect of overstory species composition (different proportion of longleaf pine and slash pine) on Leaf Area Index in longleaf pine-slash pine stands

For a given BA, longleaf pine (LLP) transmitted more light to understory than slash pine. In mixed stands, significant reduction in understory light occurred only when slash pine ≥ 70%

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3. Examination of Soil Seed Bank for its potential to restore understory

In addition to the AMP project stands, soil seed bank assessment was also carried out in other stands representing a restoration gradient at Tate’s Hell State Forest to enhance our understanding of seed bank dynamics in pine flatwoods ecosystems. The stands were classified as

Degraded: Highly degraded conditions included AMP project stands which had never been thinned and long unburned

Partially restored: Mature slash pine stands subjected to low to moderate restoration activities

Restored: Slash pine stands subjected to intense restoration activities in past two decades

Table 3. Seed bank characteristics at different soil depths and stand conditions

Highest seed density, number of species and diversity was observed in top 2 inch of soil in all stands except seed density in degraded stands (AMP stands) which was highest at 2 to 4 inch depth.

Overall, a total of 26, 39, and 64 species germinated from seed bank of degraded, partially restored, and restored stands.

Since highest density of seed was found in 2-4 in soil depth, management activities which protect as well as expose this layer could help speed recovery of the understory.

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For more information please contact:

Melissa Kreye Coordinator, Conserved Forest Ecosystems: Outreach and Research

School of Forest Resources and Conservation University of Florida PO Box 110410,

342 Newins-Ziegler Hall Gainesville, FL 32611-0410 Phone: (352) 846-0546

Fax: (352) 846-1277 mkreye@ufl.edu

http://www.sfrc.ufl.edu/CFEOR/