Species-specific effects of biocrust-forming lichens on soil properties under simulated climate change are driven by functional traits

Biocrusts are key drivers of ecosystem functioning in drylands, yet our understanding of how climate change will affect the chemistry of biocrust-forming species and their impacts on carbon (C) and nitrogen (N) cycling is still very limited. Using a manipulative experiment conducted with common biocrust-forming lichens with distinct morphology and chemistry (Buellia zoharyi, Diploschistes diacapsis, Psora decipiens and Squamarina lentigera), we evaluated changes in lichen total and isotopic C and N and several soil C and N variables after 50 months of simulated warming and rainfall reduction. Climate change treatments reduced δ13C and C:N ratio in B. zoharyi, and increased δ15N in S. lentigera. Lichens had species-specific effects on soil dissolved organic N (DON), , β-glucosidase and acid phosphatase activity regardless of climate change treatments, while these treatments changed how lichens affected several soil properties regardless of biocrust species. Changes in thallus δ13C, N and C:N drove species-specific effects on DON, , β-glucosidase and acid phosphatase activity. Our findings indicate that warmer and drier conditions will alter the chemistry of biocrust-forming lichens, affecting soil nutrient cycling, and emphasize their key role as modulators of climate change impacts in dryland soils.We thank D. Callen, M. Ladrón de Guevara, J. L. Quero, M. D. Puche, N. Simón, R. Chaves, V. Felde, D. Sánchez-Pescador and S. Asensio for their help during the setup, maintenance and harvest/analysis of the experiment and its samples, and R. Maia for the isotope and elemental analysis. We also thank two anonymous reviewers for helpful comments that improved an earlier version of the manuscript. This research was funded by the European Research Council (ERC Grant Agreements 242658 [BIOCOM] and 647038 [BIODESERT] awarded to F.T.M), and by the Marie Skłodowska-Curie Actions (MSCA Grant Agreement 795380 [INDECRUST] awarded to L.C-Z.). E.V. was supported by the 2017 program for attracting and retaining talent of Comunidad de Madrid (no. 2017‐T2/ AMB‐5406). F.T.M. also acknowledges support from Generalitat Valenciana (CIDEGENT/2018/041)