The impact of vertebrate herbivores on wetland vegetation in Atchafalaya Bay, Louisiana
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Authors: D. E. Evers, C. E. Sasser, J. G. Gosselink, D. A. Fuller, and J. M. Visser
Date: 1998
Journal: Estuaries and Coasts
Volume: 21
Number: 1
Pages: 1-13
Summary of Methods: The effects of herbivory by waterfowl and nutria were measured because of vegetation loss in Sagittaria spp. dominated marshes along the coast of Louisiana. One set of study plots was set up on islands in Atchafalya Delta (fall 1985), while the other set was established on islands in Wax Lake Delta (winter 1986). Each set of plots included an exclosure that barred just nutria, one that barred just waterfowl, one that barred both, and an open grazing plot. Aboveground biomass and species composition were measured at the end of the growing season in 1986 and 1987. Belowground biomass was collected and analyzed at the same time and at the beginning of the growing season in 1987. Waterfowl were aerially counted bi-weekly during winter 1985-86 and 1986-87 and nutria were estimated via total reported trap counts from the area during 1985 and 1986.
Article Summary / Main Points: There were over 50,000 birds at Atchafalaya Delta and over 94,000 birds in Wax Lake Delta. Nutria estimates were inconclusive. Biomass and species richness increased with removal of waterfowl and nutria. The amount of biomass removal was similar between plots grazed by waterfowl or nutria. The open grazed plots had the most biomass removal.
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: coastal marsh, nutria, myocastor coypus, biomass, species composition, waterfowl, muskrat, ondatra zibethicus, sagittaria latifolia, sagittaria platyphylla
Annotation: The results from this study could be applicable to other Gulf Coast marshes with rodent and waterfowl herbivory. According to the authors, attempts to control rodents are often implemented but waterfowl populations are encouraged to increase. This management could be hampering marsh recovery along the Louisiana coast. The two deltas were not compared directly, probably due to different proportions of Sagittaria and other plant species.
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