Camels Hump Mountain, Huntington, VermontCamels Hump
Long-Term
Vegetation Study

Timothy D. Perkins, Ph.D
Forest Decline Project
Department of Botany & Agricultural Biochemistry
University of Vermont

 

Vegetation surveys on Camels Hump mountain in the Green Mountains of Vermont were initiated by Thomas Siccama as part of his doctoral research in 1964 (Siccama 1968).  Visible mortality of trees in high elevations led to a follow-up survey in 1979, which revealed significant reductions in red spruce density and basal area (Siccama et al. 1982).  Subsequent surveys were conducted in 1983, 1986, 1990, and 1995 (Vogelmann et al. 1985, 1988, Klein and Perkins 1992, Perkins unpublished).  The next survey is tentatively scheduled to take place in the year 2000.

Sampling is conducted at 200 ft elevational intervals from 1800 to 3800 ft on the southwest slope of Camels Hump along the Burrows trail.  Ten 10' x 100' plots are used at each elevation from 1800 to 2800 ft, and five plots from 3000 to 3800 ft. 

Density (the number of trees) and basal areas (a measure of the cross-sectional area of live standing wood) of trees > 2.0 cm diameter at breast height (dbh) are shown for each sampling year in the table below. Calculations are based upon areas within the natural distribution zone for each species (Vogelmann  et al. 1988).


DENSITY

% Change

% Change

(stems/ha)

1965

1979

1983

1986

1990

1995

1965-1995

1990-1995

Abies balsamea

1950

1999

1842

1710

1713

1953

0.2

14.0

Betula cordifolia

306

242

189

160

175

237

-22.5

35.4

Picea rubens

560

261

286

194

276

375

-33.0

35.9

Sorbus americana

155

77

96

65

53

96

-38.1

81.1

Betula allegheniensis

124

124

70

79

77

88

-29.0

14.3

Acer spicatum

746

203

212

99

56

118

-84.2

110.7

Acer pensylvanicum

185

95

81

69

88

172

-7.0

95.5

Acer saccharum

863

558

616

547

452

459

-46.8

1.5

Fagus grandifolia

439

234

283

256

269

460

4.8

71.0

BASAL AREA

% Change

% Change

(m2/ha)

1965

1979

1983

1986

1990

1995

1965-1995

1990-1995

Abies balsamea

15.20

14.85

13.28

12.90

13.97

15.97

5.1

14.3

Betula cordifolia

4.58

5.17

3.32

3.38

3.78

3.49

-23.8

-7.7

Picea rubens

8.21

4.75

2.54

2.13

2.08

2.73

-66.7

31.3

Sorbus americana

0.47

0.36

0.28

0.31

0.26

0.38

-19.1

46.2

Betula allegheniensis

5.76

6.85

6.15

5.51

6.06

6.30

9.4

4.0

Acer spicatum

0.74

0.38

0.33

0.15

0.06

0.10

-86.5

66.7

Acer pensylvanicum

0.54

0.44

0.46

0.37

0.52

0.47

-13.0

-9.6

Acer saccharum

18.70

15.37

14.00

13.55

14.04

15.13

-19.1

7.8

Fagus grandifolia

8.86

6.18

6.64

5.78

4.64

5.43

-38.7

17.0


Figure 1. Density of red spruce and balsam fir   
by diameter size class                                         
Density of red spruce and balsam fir by size class

By looking at the diameter distributions of red spruce and balsam fir (Figure 1), we can see that the majority of the increase in density of red spruce has resulted from new recruitment and growth of seedlings (< 2.0 cm dbh) into the sapling size (2-5 cm dbh).  This follows a trend which started in 1990.  Some of the red spruce saplings have grown enough to move up to the next larger size class (5-8 cm dbh) as well.  Only small changes were observed in the larger diameter size classes.

Balsam fir density increased in most size classes (except 8-10 cm) due to recruitment of seedlings into the sapling size class and also because of growth of surviving trees into larger size classes.

This leads us to the question of whether or not red spruce decline is over.   Recent evidence supports the notion of at least a temporary recovery.  Radial increment growth  has increased in surviving trees in recent years (Siccama unpublished).   Density of red spruce trees is increasing, at least in the smaller size classes.   Basal area is also increasing slightly. Vigor of red spruce has also been higher in the last two vegetation surveys (Figure 2)

Figure 2. Vigor of red spruce trees (> 2.0 cm dbh)
on Camels Hump, Vt.
wpe1E.jpg (14243 bytes)
In this figure, the green color indicates healthy trees, yellow represents moderate levels of defoliation, and red indicates severe defoliation. Vigor of the red spruce tree population (measured as defoliation) decreased sharply in 1986, but has increased steadily since.Winter Injury in Red Spruce Tree 2.jpg (382495 bytes)

All of these indicators seemingly point to a recovery of health in the high-elevation forest on Camels Hump.  It is important to note however, that winter injury has been relatively light over the past several years.  Severe, repeated winter injury to current-year red spruce foliage is believed to be mechanism which precipitates decline in red spruce.  Although the precise physiological mechanisms and mode of damage (extreme cold, thaw-induced dehardening, rapid freezing, freeze-thaw cycling) are not known, it is clear that acidic deposition in some manner renders red spruce foliage susceptible to winter conditions.


For further information about this research contact Dr. Tim Perkins at (802) 899-9926 or  tperkins@zoo.uvm.edu


References

Siccama, T.G.  1968.  Altitudinal distribution of forest vegetation in the Green Mountains of Vermont.  Ph.D. Dissertation, Dept. Botany, Univ. of Vermont, Burlington, Vermont

Siccama, T.G. 1974.  Vegetation, soil, and climate in the Green Mountains of Vermont.  Ecol. Monogr. 44: 325-349.

Siccama, T.G., M. Bliss, and H.W. Vogelmann.  1982. Decline of red spruce in the Green Mountains of Vermont. Bull. Torrey Bot. Club 109: 162-168.

Vogelmann, H.W., M. Bliss, G.J. Badger, and R.M. Klein.  1985.  Forest decline on Camels Hump, Vermont.  Bull. Torrey Bot. Club 112: 274-287.

Vogelmann, H.W., T.D. Perkins, G.J. Badger, and R.M. Klein. 1988. A 21-year record of forest decline on Camels Hump, Vermont. Eur. J. For. Path. 18: 240-249.

Klein, R.M. and T.D. Perkins.  1992.  Long-Term Fates of Declining Forests. Chapter 19. pp. 360-373. In: D. Dunnette and R.J. O'Brien (Eds.). The Science of Global Change. American Chemical Society, Washington, D.C.


Acknowledgements

This research was funded in part by the A.W. Mellon and R.K. Mellon Foundations and the Conservation & Research Foundation.