The composition and structure of beech gaps in Great Smoky Mountains National Park 15

years after beech bark disease infestationJulia Roberts and Dr. David Vandermast

Elon University

IntroductionAmerican beech

(Fagus grandifolia) Beech gaps

Beech bark disease (BBD)Insect-fungal complex

(Cryptococcus fagisuga, and Nectria coccinea)

Photo by: David Vandermast

Introduction (cont’d)Fungal infection after

insect infestationThree phases:

Invasions and buildupsSmall beech trees in

aftermath forestsDemographics change to

adjustBoston in 1929; GRSM in

1993Permanent plots sampled

during summers 2000 and 2008 Photo by: David Vandermast

Purpose of studyTo understand how beech bark disease is

altering the community composition and structure of tree-sized stems in high-elevation beech gaps in the Great Smoky Mountains National Park

Hypotheses1) Since 2000, BBD will continue to cause the

loss of tree-sized (dbh ≥ 10 cm) beech stems as measured by density and basal area (BA)

2) Beech gaps with the highest mortality in 2000 would show evidence of recovery (the development of aftermath forests)

Methods11 permanent

plots in high-elevation forests in GSMNP

Identified individual trees using tree “maps” created in 1985

Photo by: David Vandermast

Locations of permanent plots in high-elevation beech forests

Methods (cont’d)Visited 11 permanent plots (total area = 1.39

ha) in high-elevation beech forestsRecorded DBH and identity of all living tree

(DBH ≥ 10cm) species during summer 2008Compared results to community composition

recorded in summer 2000Paired Wilcoxon ranked sign tests in Sigma

stat 3.1

ResultsAcross all 11 plots, BA declined by 10% and

stem numbers declined by 14% (though neither change was statistically significant)

Roughly half of all plots gained BA and stems Losses in BA and stems sustained by

declining plots were statistically significant as were the gains realized by the plots with increases

Plots that gained stems and BAFive plots that gained stems also gained

basal areaOne plot gained one stem but lost basal area

The average gain in stems was 12.4% (p = 0.004)

The average gain in basal area was 16.3% (p = 0.03)

Plots that lost stems and BAFive plots that lost stems also declined in

basal areaAs mentioned above, one plot lost BA but

gained one stem

Average loss of stems was 24.6% (p = 0.004)

Average loss of basal area was 43.5% (p = 0.04)

2000 2008

Species RD RBA RD RBA

Fraser fir 0.6 0.2 0.4 0.2

Striped maple 0.2 0.1

Sugar maple 1.7 2.3 5.1 6.2

Buckeye 7.1 12.2 5.8 11.3

Serviceberry 0.4 0.8 2.4 1.8

Yellow birch 3.1 4.5 3.9 6.9

American beech 79.5 67.1 74.0 60.2

Silverbell 0.1 0.1

Red spruce 6.8 9.1 7.3 9.8

Black cherry 0.4 1.7 0.4 1.5

No. red oak 0.3 1.5 0.2 1.2

Hemlock 0.1 0.6 0.1 0.7

Relative densities and basal areas of tree-sized (dbh ≥ 10 cm) stems in 11 high-elevation beech plots 2000-2008

DS2 DS1 IG1 IG2 IG3 BG1 BG2 BG3 BM1 BM2 PHG0

20

40

60

80

100

120

140

160

Total stem density (stems/ha) in 11 high-elevation beech plots in

2000 and 2008

20002008

Plots

Ste

m d

en

sity

(st

em

/ha)

DS2 DS1 IG1 IG2 IG3 BG1 BG2 BG3 BM1 BM2 PHG0

0.5

1

1.5

2

2.5

3

3.5

Total Basal Area (m2/ha) in 11 high-elevation beech plots in 2000

and 2008

20002008

West Plots East

Basa

l A

rea (

m2/h

a)

DiscussionThere continued to be overall declines in BA

and stem #s from 2000-08However, some beech gaps show signs of

recovering from BBDBeech forests in GRSM are a mosaic of dying

and recovering patchesPlots with increasing stem numbers

demonstrated the structural and compositional characteristics expected of aftermath forests

AcknowledgmentsElon University Honors ProgramGreat Smoky Mountains National Park for

license and campingSarah Galliher, Alexandra Kay – field

assistance and moral support!

Questions?