Biocrust restoration in novel climates: Assisted migration, habitat amelioration, and varied community composition as climate-smart techniques
Introduction Successful restoration of terrestrial drylands depends on stable, fertile soils that retain water. These functions are provided by biological soil crusts (biocrust), suggesting their reestablishment is a critical step in dryland restoration. Restoration may be hindered by the increasingly documented negative effects of climate change, while new climate-smart biocrust restoration methods may improve short- and long-term restoration outcomes. Objectives In this study, we evaluated three approaches to climate-smart biocrust restoration: assisted migration, habitat amelioration via shading, and varied community composition. Methods We collected biocrusts from across wide geographic gradients spanning multiple climate regimes, including wide ranges of mean annual temperature, mean annual precipitation, and precipitation seasonality. We used biocrust from these different environments as inoculum in two common garden restoration trials, in a research greenhouse testing shading and drying, and at a rangeland field site evaluating shading and warming. Results Community composition was related to climate across the natal (inoculum source) sites, and differences in the initial proportion of moss, lichen, and cyanobacteria resulted in different responses to experimental restoration treatments. We found mixed support for the efficacy of assisted migration and likely not enough success to outweigh the potential risks at present. Shading facilitated moss establishment even under warmer and drier conditions but inhibited lichen establishment and had little effect on cyanobacteria, which colonized quickly between mosses and lichens. Conclusion Overall, our results suggest several potential paths forward for biocrust restoration in warming drylands.