Experimental gaps and biodiversity responses in the Vermont Forest Ecosystem Management Demonstration Project
Bill Keeton
Graduate student contributors:
Nicholas Dove, Sarah Ford, Heather McKenny, and Kimberly Smith
University of Vermont, Rubenstein School of Environment and Natural Resources
Rothwald Old-growth Forest, Austrian AlpsPhoto credit: Sarah Ford
Vermont Forest Ecosystem Management Demonstration Project
Structural Objective Silvicultural Technique Multi-layered canopy Single tree selection using a target
diameter distribution Release advanced regeneration Establish new cohort
Elevated large snag densities Girdling of selected medium to large sized, low vigor trees
Elevated downed woody debris densities and volume
Felling and leaving, or Pulling over and leaving
Variable horizontal density Harvest trees clustered around “release trees”
Variable density marking Re-allocation of basal area to larger diameter classes
Rotated sigmoid diameter distribution
High target basal area Maximum target tree size set at
90 cm dbh Accelerated growth in largest trees Full and partial crown release of
largest, healthiest trees
Structural Complexity Enhancement (SCE)
Gaps are an Element of the Study• Crown release in SCE resulted
in clustered harvesting and small gaps (mean opening size = 0.02 ha)
• Modified group selection (mean opening size = 0.05 ha)
Artificial gaps (“groups”) specifics:
•Gap sizes based on mean 0.05 ha (1/8 acre) disturbance scale (from Seymour et al. 2002)
•Gap sizes are irregular
•Gap shapes are irregular
•Light retention within gaps
Study Areas:
Mount Mansfield State Forest
Jericho Research Forest
Paul Smith’s College (FERDA cooperation)
• Mature, multi-aged northern hardwoods
• History of thinning and selection harvesting
• Mid-elevation, moderate productivity
Study Sites
N
100 0 100 200 Meters
Response Indicators: Growth and yield Stand structure and dynamics Herbaceous vegetation Birds Small mammals Amphibians Fungi Soil invertebrates Soil OM and macro-nutrients Economic tradeoffs and
feasibility Biomass and carbon Tree Regeneration
© Al Sheldon
FEMDP Research
ANOVA:Fcrit, 0.05 = 2.867F = 11.435P < 0.001
F tests for variance:SCE > STS: P = 0.031GS > STS: P = 0.010SCE > GS: P = 0.296
Leaf Area Index Changes: Pre-Treatment to Post-Treatment
-40
-35
-30
-25
-20
-15
-10
-5
0
5
10
Controls StructuralComplexity
Enhancement
Single-TreeSelection
Group Selection
LAI P
erce
nt C
hang
e
Spatial Variability: •SCE v. GS; not sign.•SCE & GS > STS; P < 0.05
Keeton. 2006. For. Ecol. and Mgt.
Coarse Woody Debris Enhancement
log(λ )(β0 + β1*density CWD 1-2 + β2*density CWD 3-5 + β3*site + β4*% relative density overstory trees)
0
5
10
15
20
25
30
35
40
-3 -2 -1 0 1 2 3
Standardized covariates
Mea
n ab
unda
nce λ i
Density CWD 1-2
Density CWD 3-5
Relative densityoverstory trees
Red-backed Salamander Response Based on Occupancy Modeling
McKenny, Keeton, and Donovan. 2006
Response of Late-successional Understory
Plant Species
Richness:* p = 0.012 SCE > GS
Shannon Index:* p = 0.009 SCE > CON
-0.6
-0.3
0
0.3
0.6
0.9
1.2
-1 1 2 3 4Year
Div
ersi
ty
-4
-2
0
2
4
-1 1 2 3 4Year
Ric
hnes
s
ControlGroup selectionSCESingle-tree selection
Smith, Keeton, Twery, and Tobi. 2008. CJFR* Following Hill’s (1973) series of diversity Indices
Locally Extirpated Species
ANOVA:
p = 0.07
Percent Species Lost by Treatment
0
4
8
12
16
GS STS SCE CONTreatment
% S
pecie
s Los
t
Fungal Responses;Aboveground Sporocarps
Dove and Keeton. 2014. Fungal Ecology
Fungi Responses: Classification and Regression Tree
Dove and Keeton. 2014. Fungal Ecology
Initial formula included 7 structural variables
Biomass and carbon in downed logs 10 years post-harvest
Mg/
ha
Treatment Type
Closing Thoughts
• Silvicultural gaps promote some elements of late-successional biodiversity, depending on within gap structure
• Spatial configuration w/closed canopy patches also important
• Manage for temporal and spatial variability
• There is no “one-size-fits all” approach; mix it up!
• Adapt, learn from unanticipated results
Acknowledgements
• Vermont Monitoring Cooperative
• U.S. National Science Foundation
• Northeastern States Research Cooperative
• USDA McIntire-Stennis Forest Research Program
• USDA National Research Initiative