THE PINE CANYON WATERSHED PROGRAM: UNDERSTANDING IMPACTS OF GLOBAL CHANGE ON SOIL FUNGAL BIODIVERSITY IN AN ARID ENVIRONMENT

In arid environments, biodiversity and productivity tend to increase with increasing elevation. The basis for this pattern appears to reflect positive changes in soil moisture and temperature that are associated with increasing elevation in arid landscapes. Although there have been several studies that have examined these patterns with respect to plant biodiversity, there have been no studies that have attempted to examine the relationship between soil fungal biodiversity and elevation in a rid landscape. In that soil fungi are responsible for the majority of the decomposition that occurs in terrestrial ecosystems, an understanding of the mechanisms that account for landscape level patterns in fungal biodiversity is needed. Our research efforts to evaluate the relationships between soil moisture, soil temperature, and both taxonomic and functional diversity of soil fungi is one component of the larger Pine Canyon Watershed program at Big Bend National Park. Soil fungal biodiversity data has been collected twice yearly (January and August) since 1999 from the five vegetations zones that exist along the watershed. Although fungal taxonomic diversity does not differ significantly along the elevational gradient, species composition of the associated fungal assemblages and functional diversity does change with increasing elevation. The greatest functional diversity is associated with the forested and grassland sites along the gradient. Step-wise Discriminate Function Analyses have been conducted to examine the relationships in fungal functional diversity among the vegetation zones and across season. These analyses have shown that the fungal functional diversity of the Oak-Forest site is the most distinct of the vegetation zones. The Soto-Grassland and the high elevation Oak-Pine sites have similar fungal functional diversity. The low elevation Creosotebush-Bajada and Lowland Scrub sites also are more closely related functional to each other then to the other locations along the gradient. These data are critical if we are to understand and evaluate impacts of climate change of soil fungal biodiversity.