Can biological soil crusts be prominent landscape components in rangelands? A case study from New Mexico, USA

Abstract

To sustainably manage rangelands, it is paramount that all agents of soil health are considered in conservation practices. Yet, our understanding of the extent and importance of biological soil crust (hereafter biocrust) as a component of rangeland health and quality is limited. The objective of this project was to quantify and characterize rangeland biocrusts within a region of New Mexico, USA, for which soil microbes have yet to be considered in rangeland health assessments: the Rio Puerco Watershed. Moreover, we examined the influence of biocrust on soil aggregate stability as key ecosystem service in a landscape prone to erosion. We further assessed the relationships between biocrust abundance and community composition with soil properties. We found that biocrusts covered an average of 41% of plant interspaces throughout all sampling locations (n = 20), with the most abundant types being incipient and light cyanobacterial crusts, which tend to be more cryptic in appearance. Soil surface stability was greater than subsurface stability and biocrust cover was positively related to soil surface stability. Light cyanobacterial and cyanolichen crusts were the primary biocrust types related to soil surface stability, especially on sites with unconsolidated subsurfaces. Physical soil crusts were also a major landscape component covering an average of 21% of the soil and were important for subsurface stability. These findings reflect the importance of biological and physical soil aggregating processes in dryland systems. Several environmental variables were related to biocrust community composition and aggregate stability, with surface soil texture, salt contents, pH, and soil nitrogen ions having the strongest relationships. This study expands the biocrust characterizations of drylands in a region that has received little attention. It further contributes new insights on how biocrust and soil microbial communities may play a role in influencing rangeland health, providing much needed data for a watershed characterized by its high susceptibility to soil loss.