What does the changing climate hold for biocrusts?
Climate change with its many expressions threatens the stability of ecological systems, yet difficulties arise when predicting different ecological consequences without understanding the impacts arid communities experience under changing conditions. Although biocrusts are generally composed of stress tolerant species, they are still sensitive to physical compression, frequent sub-optimal hydration periods, and hydration periods with high temperatures (Reed et al . 2012; Ferrenberg et al . 2015; Doherty et al . 2018). Ongoing climate perturbations and land use practices that result in soil disturbance will further cause habitat unsuitability and we will witness a strong decline in the cover of biocrusts globally (Rodríguez-Caballeroet al . 2018). Studies focused on climate disturbances, ours included, indicate not only a decline in biocrust cover in the future, but also the retrogression of the developmental states of these communities. However, we demonstrated that biocrusts could broadly maintain the integrity of their species composition after long-term climatic disturbance, while having noticeable structural shifts with greater impact on mosses.
The diversity of species in biocrusts has been documented to influence productivity and multifunctionality but has not been studied with respect to its influence on community resistance. Although we limited our study to the diversity of lichens and mosses, more diverse communities seem to be more susceptible to experiencing a greater change in their composition. Press perturbations are also driving biocrusts to less functional states, in which the decrease in richness will directly impact the dynamics of the ecosystem. The combined impacts on well-developed and richer biocrust communities calls for urgent conservation actions on standing dryland biodiversity and the mitigation of climate change impacts to assure the preservation of their ecosystem functions and services. In addition, adding knowledge on long-term effects of climate change on the community maturity and composition of Southwest dryland communities will facilitate future climate projections of ecosystem function and feedbacks to the climate system.
Acknowledgements
The project was supported by the National Science Foundation Dimensions of Biodiversity Program grants awarded to MAB (1638966), KKC (1638955), BDM (1638956), MJO (1638972), LRS (1638943), KMF (1638996) as well as the US Geological Survey Ecosystems Mission Area. MCRF was also supported by the Canyonlands Research Center Graduate Research Scholars Programs. We thank Erika Geiger and Ed Grote for data support and L. Bailey for her support in the field data collection. This research comprised part of the doctoral dissertation of MCRF. Any use of trade, product or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.