Vertebrate herbivory in managed coastal wetlands: A manipulative experiment
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Authors: L. A. Johnson, and A. L. Foote
Date: 1997
Journal: Aquatic Botany
Volume: 59
Number: 1-2
Pages: 17-32
Summary of Methods: Four marshes, two impounded (managed) next to two unmanaged marshes, in coastal Louisiana (29° 35’ N, 90° 05’ W) were used to evaluate the effects of water management and Nutria herbivory on above ground biomass of Spartina patens and Schoenoplectus americanus. Water flow in the impounded marshes was regulated by flap-gated culvert. The typical cycle of water management in this type of marsh was followed by impounding drainage in the spring, a drawdown period in the summer, and flooding during fall and winter. Within each marsh (managed and unmagaged) five unfenced and five fenced nine meter squared plots were constructed to test the effects of Nutria (Myocastor coypus) herbivory (grazed or ungrazed) on aboveground biomass. Aboveground biomass was measured by tagged-stem counts and calibrating stem height measurements with stem mass for both Spartina patens and Schoenoplectus americanus in 1991, before impoundment, and for three years following.
Article Summary / Main Points: Spartina aboveground biomass was comparable between managed and unmanaged marshes, although it increased for Schoenoplectus in the unmanaged marshes. Aboveground biomass was lower in grazed plots than ungrazed plots for Schoenoplectus. Spartina aboveground biomass was not affected by Nutria herbivory, though observations made during the study revealed belowground biomass was negatively affected. Nutria preferentially select for Schoenoplectus when feeding and this could increase marsh degradation.
Vegetation Types: Riparian and Wetlands
MLRA Ecoregions: 151 Gulf Coast Marsh
Agrovoc Control Words: Riparian zones Rangelands Wildlife
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: wetland management, myocastor coypus, aboveground biomass, nutria, salt marsh, spartina patens, scirpus americanus
Annotation: Management of coastal marshes is site dependent with a need for careful knowledge of each system. Impoundments may improve vegetation growth in some cases (Hartman and Cahoon 1990), but in others, like this study, it may not. Although this investigation is focused on Gulf Coast marshes and its applicability is limited to this region, there are general herbivory principles that are relevant to other rangeland setting such as selective grazing pressure. Based on this study, nutria herbivory should be a major concern for marsh managers. Another part of this study is presented in Johnson Randall and Foote, 2005, included in the RSIS database.
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