The effects of vertebrate herbivory on plant community structure in the coastal marshes of the Pearl River, Louisiana, USA

Abstract

In this study, we investigated the impacts of herbivory by the introduced aquatic herbivore, nutria (Myocastor coypus), on three marsh communities of the Pearl River using fenced exclosures and control plots. Although total community above-ground biomass was reduced by 30% in the plots exposed to herbivory as compared to those protected from herbivory, we found species richness to be unaffected. When individual species were examined within each community, Panicurn virgatum and Aster subulatus were found to be significantly reduced by herbivory in the freshwater community, Panicum virgaturn and Vigna luteola were significantly increased by herbivory in the oligohaline community, and no species were significantly affected in the mesohaline community. We conclude that this herbivory has some specific effects on some plant species as well as having a general community effect.

Litter Decomposition of Spartina alterniflora and Juncus roemerianus: Implications of Climate Change in Salt Marshes

“…In recent years, however, consumers have been identified as important controllers of salt marsh productivity, whether the consumer is mammalian (feral horses (Turner 1987, Furbish andAlbano 1994), rodents (Gough andGrace 1998, Crain 2008), hares (van der Wal et al 2000) or nutria (Evans 1970, Taylor andGrace 1995)), avian (snow geese Odum 1983, Jeffries 1997)), or invertebrate (crabs (Jackewicz 1973, Kraeuter and Wolf 1974, Pennings et al 1998, Bortolus and Irabarne 1999 or periwinkle snails Bertness 2002)). Insects also affect salt marsh biomass, at least in some cases (Bertness et al 1987, Bertness and Shumway 1993, Daehler and Strong 1995, Daehler and Strong 1996.…”

The interactive effects of fire and herbivory on a coastal marsh in Louisiana

“…Results from exclosure studies conducted in mesohaline marshes by Chabreck (1959) indicated that plots protected from herbivory possessed 40% greater standing crop than unprotected plots. In an earlier study of the Pearl River (Taylor and Grace 1995), biomass increased 30% in plots protected from herbivory in fresh, oligohaline, and mesohaline marshes. Since that earlier study, which took place in 1990-91, our observations indicate that populations of nutria and wild boar (Sus scrofa L.) have increased substantially.…”

“…Among the most intense examples of herbivory reported are those dealing with muskrat (Ondotra zibethica rivalicius Bangs;O'Neil 1949), snow geese (Chen caerulescens L.; Adams 1956, Bazely andJefferies 1986), and nutria (Myocastor coypus Molina;Chabreck 1959, Fuller et al 1985, Shaffer et al 1992, Nyman et al 1993, Taylor and Grace 1995, Taylor et al 1995. Throughout the region, however, a range of different effects has been observed (Nyman et al 1993, Taylor and Grace 1995, Grace and Ford 1996. The effects of herbivores on coastal wetlands have also been shown to depend on a number of factors such as food preference (Shaffer et al 1992), animal density (Linscombe et al 1981), and habitat conditions (Shaffer et al 1992).…”

“…This paper reports results of a two-year study of the effects of herbivory and fire on three contrasting marsh communities: Panicum virgatum L-dominated, Sagittaria lancifolia L-dominated, and Spartina patens-dominated. The study site for this work was the Pearl River basin in Louisiana (Taylor and Grace 1995). The Pearl River drains about 2.3 million ha from south central Mississippi into the extreme southeastern part of Louisiana.…”

Interactive effects of herbivory and competition on blue vervain (Verbena hastata L.: Verbenaceae)

“…To measure the effect of herbivory, investigators usually compare the growth, survival, or reproduction (henceforth called performance) of target plants in experimental treatments with herbivores excluded versus herbivores not excluded. Results of herbivore-exclusion experiments conducted in wetlands suggest that herbivory may reduce plant performance signficantly (Smith 1983, Jensen 1985, Bazely and Jefferies 1986, Belanger and Bedard 1994, Taylor and Grace 1995, Mulder 1998. To measure the effect of competition, investigators usually compare the performance of target plants in experimental treatments with neighboring plants removed versus neighbors left intact.…”