Abstracts of Papers - Harvard Forest - Harvard University

degree of variability within each population was,
large and for most characters the mean values, and
the variance, decreased with increasing pasture age.
It is argued that the overall high diversity has
resulted from the heterogeneity of the biotic
environment, and the general decrease in diversity is
attributable to continuous elimination of the less
fit genotypes by competition and grazing.
ACKERMAN, JAMES D.* ana ARLEE M. MONTALVO.
Department of Biology, University of Puerto RicQ,
Rio Piedras, PR 00931. -- Limitations to natural
fruit production in Epiaend-rum ciliare, a tropical
orchid.
Natural fruit set of Epidendxrum ciliare (Orchidaceae)
at one large population in Puerto Rico was 6 %
during the first of two flowering seasons studied.
The flowers are allogamous ana self-compatible.
They lack pollen anda nectar rewards. In the second
season, handa-pollinated
more fruits (74k % fruit
plaxits produced substaxntially
set) than control groups
(13 %), which suggests that the paucity of pollinations
is one factor limiting natural fruit production
at this population. However, other constraints are
likely operating as well. Correlation anaalysis shows
that large inflorescences have a higher percent fruit
set than small inflorescences, yet most inflorescences
are small. Thus, factors affecting the vigor
of a planat may also contribute to the low fruit
production of this species.
ADAMS, JILL D. Department of Botany, University
of Washington, and MILTON SMITH. College of
Forest Resources, University of Washington,
Seattle, WA 98195.
- Using LANDSAT images to study plant
A case in Hawaii.
succession:
LANDSAT images have been used for rapidly defining
and classifying successional sequences on the lava
flows of Mauna Loa, Hawaii. Mauna Loa, a shield-type
volcano (elevation
recorded ages that
13,680
extend
feet), has flows of various
from high elevations to sea
level on both the wet and dry sides of the Island of
Hawaii.
primarily
Successional patterns on the flows
on the roughness of the substrate,
depend
the
rainfall, and the elevation. The rougher aa flows
have slower vegetation development than the smoother
pahoehoe flows in all except the wettest regions. In
addition, succession
fern sparse forest,
on aa often leads to an Ohia/
whereas pahoehoe flows of the
same age and aspect will give rise to savannah and
mixed Koa forest. On a given flow succession proceeds
more slowly at higher elevations, thus it is
often possible to observe a range of successional
stages by examining the changes occuring in the
LANDSAT spectral
of the flow.
signature from the top to the base
ANTLFINGER, ANN E. Biology Department,
University of Nebraska at Omaha, Omaha, NE 68182.
- The genetic and ecological consequences of
outcrossing in Impatiens capensis.
Because genetic transmission occurs through the
process of mating, a plant's mating system has signi-
ficant effects on the genotypic structure and the
dynamics of evolutionary change of plant populations.
The mixed mating system of Impatiens capensis takes
the form of floral dimorphism where chasmogamous and
cleistogamous flowers are produced on the s-ame indi-
vidual. To estimate the fitness of cleistogamous
Ecological Section 43
(CL) and chasmogamous (CH) individuals, germination,
growth and survival of seedlings in field and green-
house populations were compared. Mean percent field
germination for spring, 1982, was 63.4 for CL seeds
and 39.8 for CH seeds. CH seedlings were larger in
size than CL seedlings. However, under uniform
greenhouse conditions, growth rates were similar in
both mating types. These experiments were repeated
with seeds germinated in spring, 1983. Genetic
variation was assessed using starch gel electrophore-
sis and family-structured common garden experiments.
ARMBRUSTER, W. SCOTT. Department of Biology,
University of Alaska, Fairbanks, AK 99701.
- Phenological Organization and Pollination
Ecology of the Plant Communities on South-facing
bluffs in the Subarctic.
Flowering phenology and plant-pollinator relationships
were observed on a series of south-facing bluffs in
interior Alaska. The communities comprise a distinctive
assemblage of plant and insect sp-ecies; many of the
species are endemics, disjuncts, or vicariants of taxa
of temperate North America or Asia. The major
pollinators of the zoophilous flora include solitary
bees (Andrenidae, Halictidae, Megachildae, Anthophoridae),
Bombus (Apidae), and bee flies
(Bombyliidae). Three functional flower classes were
distinguished: open flowers, short-tube flowers, and
long-tube flowers. Each class has a characteristic
assemblage of pollinators. Overlap of flowering period
among members of the same flower class was measured and
compared with the overlap among members of different
flower classes. Members of the open and short-tube
flower classes had significantly less overlap than the
null expectation, whereas long-tube flowers had more
overlap. This difference may be a consequence of the
fact that members of the open and short-tube classes
share locations of pollen placement on pollinators with
members of their own class, whereas long-tube species
place pollen in 2-3 distinct locations on the
pollinators' bodies.
BASKIN, CAROL C.* and JERRY M. BASKIN. School
of Biological Sciences, University of Kentucky,
Lexington, KY 40506. - Germination ecophysi-
ology of eastern deciduous forest herbs:
Stylophorum diphyllum.
Stylophorum diphyllum is an herbaceous perennial
of mesic deciduous forests in the eastern USAo
Seeds are dorrnant at dispersal in spring, and
dormancy is due to a rudimentary embryo which
requires incubation at low moist temperatures
f or growth. In nature embryo elongation occurs
during the cold season, and seeds germinate in
early spring. A warm pretreatment is not re-
quired for subsequent embryo growth and germ-
ination. Embryos in freshly-matured seeds
averaged 0.41 mm long, but after 10 w of
chilling at 5 C they averaged 1.41 mm. Germ-
ination of seeds incubated continuously at 5 C
began after 11 w; after 19 w 80?% had germinated.
Seeds chilled for 6 w germinated to 75 and 65?h
at daily thermoperiods of 15/6 and 20/10 C,
respectively, while 12 w of chilling were re-
quired for comparable germination at 25/15 C.
Seeds of S. diphyllum fit Nikolaeva's (1977)
definition omrpophysiologica). complex
dormancy .