The effects of herbivory on neighbor interactions along a coastal marsh gradient
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Authors: K. L. Taylor, J. B. Grace, and B. D. Marx
Date: 1997
Journal: American Journal of Botany
Volume: 84
Number: 5
Pages: 709-715
Summary of Methods: The effects of nutria (Myocastor coypus) herbivory on neighbor competition between three dominant grasses (Panicum virgatum, Spartina patens, and Spartina alterniflora) in three coastal marsh communities (fresh, oligohaline, and mesohaline) along the lower Pearl River on the Louisiana-Mississippi border were examined over one growing season. Mixtures and monocultures of plants were transplanted to the test sites and either protected from nutria grazing or not. Biomass of protected and unprotected dominant grasses was measured at the end of the growing season.
Article Summary / Main Points: Nutria herbivory reduced biomass of all three grass species on all marsh types, however, the level of impact varied by species. Neighboring plants had positive (mutualism) and negative effects (competition), depending on plant species and salt marsh type. Neighbor competition did not vary with Panicum virgatum and Spartina patens in the absence of herbivores, but varied considerably between environments. Neighbor competition intensified for Panicum virgatum and decreased for Spartina patens with increasing salinity. However, when plants were grazed by nutria, all neighbor effects, positive and negative, were absent. Intense herbivory was able to override other biotic interactions such as competition and mutualism.
Vegetation Types: Riparian and Wetlands
MLRA Ecoregions: 151 Gulf Coast Marsh 152A Eastern Gulf Coast Flatwoods
Agrovoc Control Words: Riparian zones Marshes Herbivory
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: coastal marshes, communities, competition, herbivory, neighbor effects, positive interactions, wetlands
Annotation: This was a replicated study over one year and is only applicable to coastal marshes. Results suggest that salinity and herbivory can affect competitive and symbiotic relationships among neighboring plants within salt marsh types. Grazing can reduce neighbor effects dramatically in some cases. One season of data and small sample size prevent land managers from making generalizations about grazing effects at this time and indicate a need for more studies of this type across multiple years. Additionally, Taylor et al. (1994, Wetlands 14:82-87) studied the interactive effects of fire and herbivory on a southern oligohaline marsh and Taylor and Grace (1995, Wetlands 15:68-73) studied the effects of nutria herbivory on plant community structure on three southern coastal marshes; also available on the RSIS website.
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