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|Title: ||Factors limiting processes in freshwater wetlands: an agricultural primary stream riparian forest|
|Authors: ||Correll, David L|
Weller, Donald E.
|Issue Date: ||1989|
|Publisher: ||United States Department of Energy|
|Citation: ||Freshwater Wetlands and Wildlife. Proceedings of a Symposium held at Charleston, South Carolina, March 24-27, 1989|
|Abstract: ||We advocate a broader perspective for wetland studies and present a case study to
illustrate our approach. The case study focuses on the hydrology and belowground processing of
nitrate and sulfate in a riparian forest wetland that receives hydrologic inputs from a cropland
watershed and from direct precipitation. A conceptual model is presented that relates the
nitrate and sulfate uptake in the wetland to wetland processes, such as evapotranspiration,
plant uptake, oxidation-reduction reactions, and gaseous diffusion, and to external controlling
factors, such as temperature, groundwater input, and precipitation. The forest wetland transpired
an average of 67% of the sum of precipitation and groundwater inputs and took up averages
of 86% of the nitrate and 25% of the sulfate that entered in precipitation and groundwater.
Approximately 25% of this nitrogen was assimilated by trees and stored as woody biomass
accretion. The efficiency of nitrate uptake was relatively constant from year to year, but was
highest in the autumn (97%) and lowest in the winter (81%). The case study illustrates some
general features of the proposed broader perspective. A wetland process cannot be studied in
isolation but must be related to factors that may limit this process. A classification of important
wetland processes and potential limiting or controlling factors is presented. Limits on a
process can originate from geomorphic and climatic considerations or from human management.
In each of these categories, the controls can act directly within the wetland or act on a wetland
process externally by controlling the inputs to the wetland from its watershed or airshed. The
important internal and external controls that should be considered in studies of belowground
oxidation and reduction processes in wetlands are listed; examples of how those controls yield
negative feedback that limits the progress of a belowground process are given.|
|Appears in Collections:||SERC Staff Publications|
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