Sponsor: INTECOL
Co-Chairs:
Dr. Jos T.A. Verhoeven
Landscape Ecology
Utrecht University
P.O. Box 80084
Utrecht, The Netherlands 3508 TB
Phone: 31-30-253-6700
Fax: 31-30-251-8366
E-mail: j.t.a.verhoeven@bio.uu.nl
and
Dr. D.F. Whigham
Smithsonian Environmental Research Center
P.O. Box 28
Edgewater, Maryland
USA 21037
E-mail: whigham@serc.si.edu
Overview of Symposium:
In wetland ecosystems, nutrient recycling as well as carbon storage are controlled by the decomposition of plant-derived detritus. The chemical quality of this detritus strongly influences the rate of decomposition. Initial nitrogen and phosphorus concentrations, and the organic chemistry (i.e., soluble as well as cell-wall-bound phenolics) are important in this respect. Chemical litter quality may change in wetland ecosystems in two ways. First, nitrogen and phosphorus concentrations can be influenced by anthropogenic nutrient enrichment. Second, the overall content of nutrient and secondary plant compounds in the detritus may change as a result of shifts in the species composition. Changes in decomposition process may have large impacts on the production of gases (carbon dioxide, methane and nitrous oxide) in the wetland ecosystem. In this symposium, field and mesocosm studies of the relation between decomposition and detritus quality in wetlands will be presented, with special emphasis on the effects of environmental change (climate, nutrient enrichment) on these interactions.
Scott Bridgham, Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA; ---, Department of Natural Resources, Cornell University, Ithaca, New York, USA; ---, Natural Resources Research Institute, University of Minnesota, Duluth, Minnesota, USA; and ---, Department of Forest Resources, University of Minnesota, St. Paul, Minnesota, USA - Controls over nitrogen and phosphorus cycling along ombrotrophic-minerotrophic gradients in northern peatlands.
The ombrotrophic-minerotrophic gradient in peatlands has often been thought to be synonymous with an oligotrophic-eutrophic gradient of nutrient availability, but little previous research has explicitly tested this assumption. We present an overview of a number of comparative and manipulative lab and field studies in various peatlands in the upper Midwest of the USA to test this assumption. Our data indicate that P availability tends to be higher in bogs, whereas N availability tends to be higher in fens. However, both N and P availability are very low compared to upland ecosystems. Net N and P mineralization are insufficient to explain plant nutrient uptake requirements, suggesting the inadequacy of this method to determine plant-available nutrients in peatlands or uptake of organic forms of N and P. Field liming treatments showed complicated responses in nutrient and carbon mineralization and availability. Fertilization and radiotracer experiments indicated tight retention of ambient levels of nutrients but minimal ability to retain increased loadings. We suggest that previous ideas of nutrient dynamics in peatlands need to be reexamined, and much greater research needs to be focused on understanding nutrient dynamics in peatlands.
