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