Abstracts of Papers - Harvard Forest - Harvard University

BILDERBACK, DAVID E., CLINTON E. CARLSON, J. HENRY
SLONE and STEPHEN C. MARVEL. Department of Botany,
University of Montana and Forestry Sciences Laboratory,
U.S. Forest Service, Missoula, MT 59812.
- The effects of ash from Mount St. Helens on
chlorophyll content, photosynthesis and radial stem
growth of Douglas. fir (Pseudotsuga menziesii).
During the eruption of Mount St. Helens on May 18,
1980, a forest site south of Coeur d'Alene, Idaho received
1.0 cm or more of ash. Needles of Douglas fir
at this site retained 422 mg of ash/gm needle dry
weight during the summer and fall of 1980. Trees
northeast of Coeur d'Alene received a light dusting
of ash. Chlorophyll content and radial growth of
trees were compared at the two sites. Chlorophyll
content of 1979 and 1980 needles heavily coated with
ash was significantly less than the chlorophyll from
needles lightly dusted with ash. There was no significant
difference in the chlorophyll content of 1981
needles or the radial stem growth. Seedlings of
Douglas fir were artificially dusted with ash. Eight
weeks later, needles had significantly less nonstructural
carbohydrates than did needles of undusted
plants. Ash-coated and control seedlings had similar
dark respiration rates, compensation points and light
saturation levels; however, ash-coated seedlings exhibited
an enhanced photosynthetic rate.
BRADFIELD, GARY E. and DANIEL GAGNON. Department
of Botany, U.B.C., Vancouver, BC V6T1W5;
Departement des Sciences biologiques, Universite
du Quebec a Montreal, Montreal, PQ H3C3P8.
- Correlations among strata and environmental
gradients in forests of Vancouver Island, B.C.
West central Vancouver Island vegetation data were
used to investigate if forest strata patterns (trees,
saplings, seedlings, shrubs, herbs and bryophytes)
are correlated and if these strata respond similarly
to environmental gradients. These hypotheses were
evaluated with three data sets: (1) a moist coastal
sector of the study area, (2) a dryer inland sector,
and (3) a combined data set to provide greater envi-
ronmental diversity. Product moment correlations
and cononical correlation analyses were used to
assess the degree of correlation among strata, and
with environmental gradients. Patterns of correla-
tion were different in each sector, with different
strata showing the strongest correlation among them,
as well as with environmental gradients.
BRUEDERLE, LEO P.* and FOREST STEARNS. Biological
Sciences (Botany), Rutgers University, New Bruns-
wick, NJ 08854 and Department of Botany, University
of Wisconsin, Milwaukee, WI 53211. - Ice storm
damage to a southern Wisconsin mesic forest.
In March 1976, an ice storm followed by strong winds
struck southern Wisconsin. This storm deposited up
to 12 cm of glaze causing substantial damage to wood-
ed areas. At the UWM Cedar-Sauk Field Station a
forest fuel sampling technique was modified to meas-
ure macro-litter volume by species resulting from
the storm. Changes in the canopy were photoassayed
using wide-angle3and fish-eye lenses. The storm re-
sulted in 19.1 m /ha macro-litter with approximately
43 percent of the canopy removed. Damage was uneven,
influenced by geographic and climatic factors. Wind
and aspect of slope were found to be of particular
Ecological Section 45
ieportance with macro-litter volume virying from 22.6
m /ha on the windward slope to 10.4 m /ha on the lee-
ward. Ulmus rubra and Fraxinus americana suffered the
heaviest damage and Ostrya virginiana and Tilia amer-
icana the least. Biotic factors responsible for
species susceptibility include growth form, wood me-
chanical properties, age, decay, and phytosociological
position.
CARTER, M. El-OISE BROWN* AND WILLIAM H. MURDY.
Biology Department, Agnes Scott College,
Decatur, GA 30030 and Biology Department,
Emory University, Atlanta, GA 30322.
- Cha racte r D i sp l acemen t i n Ta l i n um menges i i
(Po rtulacaceae).
Character displacement was investigated in popula-
tions of Talinum mengesii and T. teretifolium,
which were sampled from granite outcrops along a
100 mile transect, including both sympatric and
allopatric populations. The results from analysis
of floral traits, diurnal flowering times, herita-
bility estimates, and experiments in the field,
greenhouse and laboratory supported the hypothesis
of unilateral reproductive character displacement
in T. mengesii. The sympatric populations
exhibited large flowers with long, exserted styles
and early flower opening; characteristics which
were shown to be important in reducing interspecific
hybridization. Heritability estimates for the
displaced traits were greater than 75%. Exserted
styles in the sympatric populations resulted in
a primarily outcrossing breeding system requiring
insect-assisted pollination. Reproductive losses
in these plants during periods of low pollinator
activity may be compensated by a large number
of ovules and extensive vegetative reproduction.
CAZA,* CAROLINE L. and PAMELA t1. STOKES.
Department of Botany, Universit y of Toronto,
Toronto, Ontario, M5S lAl.
-Variation in the distribution of Populus
tremuloides on an unamended uranium tailings site,
Ontario, Canada.
Spatial variation in the biotic and abiotic environ-
ment was studied in an aspen population on an un-
amended uranium tailings site near Bancroft, Ontario.
The site was divided into four zones based on type of
ground cover. Vegetation and substrate character-
istics were measured within each zone. Principal
components analysis was used to summarize physical,
chemical and biological differences between zones.
The distribution of aspens on the site was correlated
with substrate characteristics such as elevation,
temperature, moisture and nutrient content. Other
parameters displayed large variation within the site
but were not related to aspen distribution. Addition-
al data were collected from aspen populations on
non-tailings (reference) sites. There was no indi-
cation of differences in factors influencing dis-
tribution between uranium tailings and these sub-
strates. All physical and chemical factors measured
on the tailings were within ranges reoorted for
natural substrates. It is suggested that large vari-
ation in these factors, occurring over small dis-
tances on the tailings, is the most important deter-
minant of aspen distribution on these wastes.