Microbiotic crust influence on unsaturated hydraulic conductivity

Microbiotic crusts occur extensively in I rangeland soils. Developed by fil aments of cyanobacteria and algae, and thalli of lichen and moss entangleme nt of soil particles, they create a physical discontinuity in the surface p rofile with greater concentrations of clay, silt, and potentially hydrophob ic organic matter. These conditions potentially contribute to variability i n soil hydrology of arid land and should be considered in the development o f hydrologic and erosion models. However, there is limited manipulative res carch examining the functional relationships between soil and microbiotic c rusts. We investigated the influence of cyanobacterial-dominated microbioti c crust on measured hydraulic conductivity (K) in a sandy loan soil at a so utheastern Utah site. Using a tension infiltrometer, we determined K under three surface treatments: undisturbed, chemically killed (representing dead microphytes within the crust), and removed (scalped) microbiotic crusts. W e applied treatments to spatially interspersed intact surface soils within shrub interspaces. Microbiotic crusts at this site and in this stage of suc cessional development had no discernible influence on K. This finding suppo rts results from research conducted in a variety of soils from sandy to sil t dominated with a range of microbiotic development. Because this research was site and time specific, and because the role of microbiotic crusts in t he environment continues to be debated, additional research is warranted to determine how Stage of development of microbiotic crust influences soil hy drology.