Defoliation, waterlogging and dung influences allocation patterns of Deschampsia caespitosa

Abstract

Wet meadows are some of the most productive communities in the northern Rocky Mountains, USA but are also among the most sensitive to grazing by native ungulates and domestic livestock. These meadows typically are inundated with floodwater in spring and early summer but are relatively dry in summer. To determine the interactive effects of clipping and flooding on plant recovery after clipping, we subjected plants of tufted hairgrass (Deschampsia caespitosa (L.) Beauv) to 6-week and 10-week waterlogging treatments in combination with 1 and 2 clipping events, with and without dung amendment in a greenhouse experiment. The experiment was designed to mimic early and late growing-season patterns of herbivory by native and domestic herbivores on a dominant species of wet meadows of this region. Waterlogged plants produced a higher percentage of roots at the surface, elongated stems to the first axial leaf, increased the proportion of tillers that flowered, but increased aboveground yield and tiller height only with the addition of dung. Root biomass declined with waterlogging when dung was not added, and a second defoliation exacerbated the negative effects of waterlogging on roots. Defoliation with short-duration waterlogging increased shoot nitrogen (N) concentration and N yield/root biomass, while continuous waterlogging reduced shoot N concentration of aboveground biomass. Dung amendment did not reverse this effect. Although extended flooding in combination with moderate rates of defoliation did not reduce aboveground biomass of Deschampsia caespitosa, it aggravated total root loss, caused shifts to a shallower root distribution, and altered N concentration of aboveground biomass for herbivores.Key Words: flooding, tufted hairgrass, herbivory, nitrogen dynamics, wet meadows Riparian and wet meadow systems are among the most productive foraging areas for both native ungulates and domestic livestock in the western rangelands of the United States; yet they are also among the most sensitive of North American habitats to grazing impact (Johnson et al. 1977). These areas typically are inundated with floodwater in spring and early summer, but are relatively dry in late summer depending on snowpack and the timing of snow melt. Studies in upland systems have shown that plant recovery after defoliation depends largely on environmental Research was funded by the Basic Research Grants Program at the University ofWyoming.Manuscript accepted 8 Oct. 02. ResumenLas praderas humedas son una de las comunidades mas productivas del norte de las Montaflas Rocallosas del E.U.A, pero tambien estan entre las mas sensitivas al apacentamiento por ungulados nativos y ganado domestico. Estas praderas tipicamente estan inundadas en primavera a inicios de verano pero son relativamente secas en el verano. Para determinar el efecto interactivo del corte y la inundacion en la recuperacion de las plantas despues del corte condujimos un experimento de invernadero en el que sometimos plantar de "Tufted hairgrass" (Deschampsia caespitosa (L....

Flooding and grazing promote germination and seedling establishment in the perennial grass Paspalum dilatatum

“…1999; Insausti et al . 2001), yet only a few studies have addressed the interactive effects of flooding and grazing on individual growth (Oesterheld & McNaughton 1991; Gough & Grace 1998; Merrill & Colberg 2003). None of these papers have considered these interactive effects upon population recruitment.…”