Effects of managed impoundments and herbivory on wetland plant production and stand structure
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Authors: L. A. Johnson Randall, and A. L. Foote
Date: 2005
Journal: Wetlands
Volume: 25
Number: 1
Pages: 38-50
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 measure the effects of Nutria(Myocastor coypus) grazing and water level management on annual production and vegetative stand structure. 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 five unfenced and five fenced nine meter squared plots were constructed to test the effects of Nutria herbivory (grazed or ungrazed). In all four study marshes, annual aboveground biomass, stem density and height were measured for two wetland plant species, Spartina patens and Schoenoplectus americanus in 1991, before impoundment, and for three years following.
Article Summary / Main Points: Biomass, stem density and height were similar between managed and unmanaged marshes for Spartina, but for Schoenoplectus all of these were higher in unmanaged marshes. Nutria select for Schoenoplectus when feeding. Grazing reduced annual aboveground production, stem density and height for Schoenoplectus. Though Nutria herbivory did not affect Spartina production, increases in Schoenoplectus density and stem height in plots without herbivory led to increases in Spartina stem height.
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, nutria, myocastor coypus, annual production, plant stand structure, spartina patens, schoenoplectus americanus
Annotation: Although the authors followed the normal management of coastal marshes in this region, which has been shown to increase vegetation growth, the water heights during the drawdown period was much lower in the managed versus the unmanaged marshes which could have affected plant growth. Different management of the impounded marshes may create different results. Selective grazing pressure by the nutria in this study is similar to other types of herbivores in other systems. This study is part of a larger investigation on water impoundment and nutria herbivory (Johnson and Foote, 1997, included in the RSIS database).
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