Document: MAT-3-59-5

Effects of biodiversity manipulation on soil nutrient availability in the Jornada Basin, New Mexico.

WALLENSTEIN, M.D.* and W.H.SCHLESINGER

Duke University, Durham, NC 27708 USA ¹

Abstract:
During the last century, large areas of semiarid grasslands in the southwestern U.S. have been replaced by arid shrublands. Previous research has shown that invasion by arid shrubs results in a redistribution of soil nutrients into "islands of fertility" and may cause a decrease in biodiversity. A large, blocked experiment was established in 1995 to examine the role of species diversity in ecosystem functioning. In August 1999, we examined the effects of alterations to biodiversity on soil nutrient availability using ion exchange membranes. We found significant differences between treatments in the availability of nitrate (p < 0.001) but not for ammonium. Plots with reduced vegetation, including removal of the dominant invasive shrub (Larrea tridentata) had the greatest concentrations of nitrate. This may be due to increased rates of nitrification, especially in former intershrub microsites. Labile phosphorus was not detected in any plot, possibly due to very dry soil conditions. There was also a significant block effect for nitrate (p < 0.001), suggesting that geomorphology and soil characteristics also play an important role in determining nutrient availability and losses.

Keywords: biodiversity, nutrient availability, ion exchange membranes, Jornada Basin

This abstract is being presented at: 3:30 PM in session:
Poster Session #15: Nutrient Cycling.