Abstracts of Papers - Harvard Forest - Harvard University

4) In mixtures, the competitively superior species
shows a relatively low degree of inequality, while
the competitively inferior species shows high
inequality.
The results support the dominance/suppression
model of plant competition.
Symposium: The Mire - Wetland Ecosystem
INTRODUCTION
Wetland and mire ecosystems possess a unique set of
characteristics that differentiate these systems from
both terrestrial and aquatic habitats. The abundant
research that has been done in Europe in these eco-
systems is in marked contrast to the state of our
knowledge in North America. However, in the past
decade or so, significant work has been completed in
the United States and Canada. This symposium hopes
to examine some of this recent research and present
the status of our knowledge of these ecosystems.
Organized by Dale H. Vitt, University of Alberta,
Edmonton, Alberta and Bruce Roberts, Canadian Forestry
Service, St. John's Newfoundland.
ANDRUS, RICHARD E. Department of Biological
Sciences, State University of New York at
Binghamton, N.Y. 13901.
- The ecology of Sphagnum.
Sphagnum species are ecologically unusual and prom-
inent wetland plants with xerophytic adaptations
and succession-directing acidification capabilities.
Species are differentiated along environment gra-
dients of pH, cation concentrations, hummock and
hollow, wet vs. dry, shade vs. sun, coastal vs. in-
land and cold vs. warm. The known factors respon-
sible for gradient differentiation include cation
exchange capacity, desiccation tolerance, desicca-
tion resistance, water-holding capacity, drying
rates and photosynthetic response at differing water
contents. Small-scale distribution of Sphagnum
species on ombrotrophic sites can be partially ex-
plained but for minerotrophic sites, where acid
precipitation influence is greatest, less is known.
BAYLEY, SUZANNE. Freshwater Institute,
501 University Crescent, Winnipeg, Manitoba.
R3T 2N6
- Comparisons of nutrient relationships in
freshwater wetlands from Canada to Florida.
Nitrogen and phosphorus dynamics in southern
swamp forests and fresh water marshes are compared
to northern bogs, fens, and marshes. Latitudinal
differences in nitrogen and phosphorus content of
vegetation, nutrient concentrations of surface
and pore water, and annual nutrient uptake are
not apparent in the data reviewed. Substrate and
hydrologic regimes appear to be more important.
Vegetation on organic substrates contains less
nitrogen and phosphorus in the above ground
biomass (Wigham and Bayley 1978). Cypress
wetlands in higher water flow contain higher
concentrations of phosphorus in above ground
biomass (Brown 1981). Other wetlands appear to
follow the same trend. The ability of a wetland
to retain added nutrients depends upon the
hydrologic regime and organic substrate.
Ecological Section 39
CARTER, VIRGINIA U.S. Geological Survey, 431
National Center, Reston, VA 22092 - Wetlands of
the United States- ecology, hydrology, and research
needs.
The wetlands of United States can be subdivided into
classes, subclasses, and dominance types on the basis
of vegetation, hydrology and soils using the "Classi-
fication of Wetlands and Deep Water Habitats" by
Cowardin et al. (1979). There is a tremendous
diversity in wetland types and wetland vegetation in
the United States, caused primarily by regional
topographic and climatic differences. Wetland
hydrology, a primary driving force influencing
wetland ecology and wetland development and persis-
tence, is as yet poorly understood. The interaction
between ground water and surface water, and the
discharge-recharge relationships in wetlands
influence water quality and nutrient budgets as well
as vegetative composition. Anthropogenic influences,
such as construction of drainage canals, diversions,
storage areas and industrial facilitites, or mining
of peat may have unforseen hydrologic consequences
because of our lack of knowledge of water movement
and water budgets. Expanded research and basic data
collection are needed to manage and protect wetlands
effectively.
DAMMAN, ANTONI W.H. Ecology Section, Biological
Sciences Group, University of Connecticut,
Storrs, CT 06268.
- Ecological processes in ombrogenic peat bogs
Ombrogenic peat bogs differ from soligenic and
topogenic peatlands in their hydrology and associated
differences in water chemistry, organic matter
accumulation and vegetation. The hydraulic potential
is positive in most of the raised peat mass, and
water flow is primarily through the relatively
undecompsed surface peat. The extreme nutrient-
deficiency of ombrotrophic peat and the growth of
the Sphagnum carpet create conditions for release
and accumulation of elements which are fundamentally
different from those on minerotrophic sites. In
ombrotrophic parts of these peatlands, productivity
affects peat accumulation, but on minerotrophic
sites decomposition overrides differences in
productivity and peat does not accumulate to any
significant degree above the water level. Potassium,
and to a lesser degree Ca, concentrations show
seasonal fluctuations in the drainage water with
high concentrations in spring and autumn, and
concentrations far below that of the precipitation
during the summer. Na and Mg concentrations remain
5-10 times that of the precipitation. The chemistry
of bog pool water depends on the topographical
position within the bog; it differs least from
rain water in the pools of the center or highest
part of bogs in oceanic regions.
GORHAM, EVILLE. Department of Ecology & Behavioral
Biology, University of Minnesota, Minneapolis,
MN 55455-0302.
- The biogeochemistry of Sphagnum bogs.
The following topics are discussed briefly from a
historical perspective and with modern examples; fac-
tors controlling peat accumulation and paludification
(waterlogging, nutrient limitation, roles of climate
and topography), hydrological and chemical differen-
tiation of bog from fen plant communities (surface
waters and peats, peat profiles, plants), the acidity
of bog waters (sources, ion-balances, sensitivity to