Microbiotic crust influence on unsaturated hydraulic conductivity

Microbiotic crusts occur extensively in I rangeland soils. Developed by filaments of cyanobacteria and algae, and thalli of lichen and moss entanglement of soil particles, they create a physical discontinuity in the surface profile with greater concentrations of clay, silt, and potentially hydrophobic organic matter. These conditions potentially contribute to variability in soil hydrology of arid land and should be considered in the development of hydrologic and erosion models. However, there is limited manipulative rescarch examining the functional relationships between soil and microbiotic crusts. We investigated the influence of cyanobacterial-dominated microbiotic crust on measured hydraulic conductivity (K) in a sandy loan soil at a southeastern 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. We applied treatments to spatially interspersed intact surface soils within shrub interspaces. Microbiotic crusts at this site and in this stage of successional development had no discernible influence on K. This finding supports results from research conducted in a variety of soils from sandy to silt dominated with a range of microbiotic development. Because this research was site and time specific, and because the role of microbiotic crusts in the environment continues to be debated, additional research is warranted to determine how Stage of development of microbiotic crust influences soil hydrology.