Biological soil crusts provide a myriad of ecosystem functions and are highly sensitive to physical disturbance. In addition to physical disturbance, contemporary data suggest that climate change can alter biocrust community composition and function on fast (sub-decadal) timescales. While we have a strong sense of the vulnerability of biocrusts to change, few studies have tracked trajectory of biocrust community composition and function recovery after disturbance. Here, we used physical and climate disturbance experiments to follow recovery of biocrusts in an effort to build a ‘clock’ from which we can better predict how biocrust communities and the processes they regulate fluctuate over the course of recovery. We use a study at three sites on the Colorado Plateau, where we applied climate change and physical disturbance treatments for nearly a decade. We used a physical disturbance experiment at two sites, and a climate disturbance experiment at one site, which included active warming and altered precipitation treatments. We ceased the strongest disturbance factors (physical trampling and altered precipitation) and allowed the communities to recover for five years. We assessed the recovery of community composition and key functions – for example, soil stability and fertility – by comparing the treated plots with paired control plots.
Results/Conclusions
Biocrust communities under both the shrub canopies and within the interspaces were distinct between disturbed and undisturbed controls (p = 0.002 and 0.001, respectively). Undisturbed control plots possessed a higher abundance of late successional biocrust constituents (i.e. mosses and lichens), whereas both physically and climate-disturbed treatments were dominated by early successional biocrust constituents (i.e., cyanobacteria). While the communities remain distinct 5 years after the removal of the stressors, recovery rates were faster than anticipated – overall, biocrust cover at some of the sites was similar between control and disturbed treatments. Additionally, while late successional biocrust cover was lower in disturbed treatments, mosses and lichens were not completely absent, indicating that recovery is occurring. Notably, recovery patterns were non-linear and showed strong spatial variability pointing to interactive drivers of recovery. Furthermore, these data suggest that a given year’s climate has a strong role in biocrust recovery, and directional changes in climate such as warming will likely interact with physical disturbance to slow recovery. These data lend key insight into how biocrust communities will respond to continued, interactive anthropogenic change drivers with important implications for predicting biocrust community change and improving biocrust restoration efforts.