Biological Soil Crusts Effects on Surficial Processes in Sandy Soils of a Pinyon–Juniper Woodland

Biological soil crusts (biocrusts) are a broadly occurring and ecologically important ground cover on water-limited lands around the world. Biocrust cover and developmental stage alter soil structure, nutrient availability, surface roughness, and soil erodibility, thereby influencing hydrologic and erosion processes. However, biocrust effects on runoff and erosion are complex and highly variable. Although many studies have investigated these relationships, findings remain conflicting, particularly for coarse-textured soils in which biocrusts have been shown to both increase and decrease infiltration and runoff depending on biocrust composition, surface structure, and rainfall characteristics. We performed a suite of soil, ground surface, hydrology, and erosion experiments at the point and plot (0.5 m 2 ) scales on coarse-textured soils to quantify effects of Early versus Late biocrust succession on ground surface conditions and infiltration, runoff, and erosion processes. Soil aggregate stability and ground surface roughness were highest in later successional stages of biocrust development and were positively correlated with the percentage cover of dark cyanobacteria ( R 2 = 0.49–0.66). The runoff rates and cumulative sediment yields from rainfall simulation experiments (100 mm h −1 , 45 min) on dry antecedent moisture conditions were 2-fold and 6-fold greater for Early succession plots (25 mm h −1 and 153 g m −2 ) than Late-succession plots (11 mm h −1 and 24 g m −2 ). Runoff responses across Early and Late-succession plots were primarily controlled by and negatively related to the percentage cover of dark cyanobacteria, soil aggregate stability, and ground surface roughness. Sediment yield was regulated by the amount of runoff and negatively related to cover of dark cyanobacteria, soil aggregate stability, and ground surface roughness. Our study results offer land managers, researchers, and model developers valuable insights into the ecohydrologic role of biocrusts in drylands and provide context for forecasting ecosystem responses to biocrust perturbations due to natural disturbances and management actions.