Rehabilitating Biocrusts and Understanding the Influence of Seasonality on the Actively Eroding Pinyon-Juniper Mesa-Top Soils in Bandelier National Monument, NM.

Soil erosion is a persistent problem in many dryland systems globally.  Continuous soil erosion can lead to loss of top soil, decreased plant-available water, extreme soil surface temperatures, and freeze-thaw activity, all of which hinder vegetation establishment and reduce site productivity.  An exemplar of this problem are the Pinyon-Juniper woodlands of Bandelier National Monument, NM, which has seen erosion rates as high as one centimeter of soil loss per decade. This threatens not only ecosystem processes, but also archaeological sites the Monument is tasked to protect. We hypothesized that dryland biological soil crusts (biocrusts) – a community of mosses, lichens, cyanobacteria, and heterotrophs aggregating the soil surface – may be an effective tool for stabilizing soil surfaces.  Here, in a full factorial design, we inoculated plots on the actively eroding Pinyon-Juniper mesa tops of Bandelier National Monument with greenhouse cultured native biocrusts, and administered the erosion intervention treatments of flashing, slash placement, and seeding.  We measured soil stability and biocrusts cover before and after inoculation, which occurred before the summer monsoon, to understand how our treatments and seasonal changes influence soil aggregate stability.  While we did not detect an effect of inoculum addition or erosion intervention treatments on soil stability, we did see significant changes to the soil quality between seasons, with the system experiencing a significant reduction in soil aggregate stability.  Simultaneously, we saw an increase in the formation of physical crust – an abiotic soil crust formed by compaction, rain-splash, or other abiotic forces. This result points to dynamic seasonal changes, presumably induced by the monsoons, which by forming physical crust maintain the cycle of erosion within this system.  Taken together, this research provides an understanding of the intra-annual variation within these dryland systems and bring us closer to developing effective techniques to arrest soil loss in these important social-ecological systems.