Plant and Microbial Dynamics Along Gradients in Soil Texture and Eolian Dust Accumulation in the Colorado Plateau.

The canyonlands region of Southwest Utah is made up of soils with a range of textures and chemistries. We have identified three transects of soils that range from high sand to high silt content in order to examine the effect of soil texture and chemistry on plant and microbial dynamics. We also take advantage of new techniques that allow separation of eolian-derived fine soil particles from in situ weathering and erosion products to evaluate the role that dust deposition plays in the chemistry of desert ecosystems. We present results from several studies along these transects including measurements of hydrologic fluxes and comparisons of soil and plant chemistry. We have also carried out experiments on microbial and plant processes along gradients with the aim of linking biological dynamics to variation in surficial chemistry and hydrology. Our initial results indicate that water holding capacity is substantially higher in silts vs. sandy soils but that increases in water availability in sands have a disproportionate effect on soil respiration rates with a more rapid and prolonged response to wetting in sands vs. silts. Comparisons of plant and soil chemistry suggest that plants and soils show similar increases in Mg and Mn concentrations along our textural transects. In addition, native bunch grasses growing in high eolian silt environments show elevated P content in their tissues and may reflect the input of P in eolian deposition. With these studies, we are beginning to build a mechanistic framework for understanding the relationship between eolian deposition and ecosystem response in arid environments.