Drylands, ~40% of Earth’s terrestrial surface, rely on biocrusts (a consortium of bacteria, cyanobacteria, lichens and bryophytes) for key ecosystem functions including soil stability, biogeochemical cycling and water capture. Climate change is expanding drylands and land use practices are rapidly degrading them. Little is known about biocrust adaptability to novel climates. To test biocrust adaptability, we set up three transplant common gardens along an elevational-climate gradient on the Colorado Plateau (1200, 1600, and 2000m) with fence protection. Mature biocrusts (15cm x 15cm by 5cm deep) were collected intact from each site and reciprocally transplanted. We tested three non-exclusive hypotheses: 1. Biocrust transplants planted at their home site will show local adaptation, with higher productivity and lower species turnover than in a novel environment. 2. Biocrust transplants in a novel environment would perform better at elevations higher than their origin, and worse at elevations lower than their origin. 3. More ruderal and/or more cosmopolitan biocrust taxa would be more adaptable to novel environments than later successional species and/or species restricted to more mesic sites. We measured visible species composition and cover and took cores to assess the cyanobacterial communities, using qPCR on the 16S region, over two years in the field.
Results/Conclusions
Climate varied along the elevation gradient during the time of the experiment with mean annual temperatures of 13C, 11C and 10C from low to high elevation, and mean annual precipitation of 80mm, 120mm and 260mm, respectively. Biocrust source, garden, time, and time by source and garden were strong predictors of biocrust community composition, abundance, and richness (both visible and cyanobacterial; p<0.01). Hypothesis one was supported in that mid and low elevation biocrusts maintained higher richness and cover at home. Hypothesis two was not supported consistently. Instead, we found that the lowest elevation biocrusts maintained greater cover and species richness at the high elevation site and lowest at the mid elevation site, whereas the mid-elevation transplants maintained the highest cover and species richness in the low elevation garden with the lowest cover and richness at the highest elevation site. Hypothesis three was supported: ruderal mosses (Byrum sp.), early colonizing lichens (Collema), as well as early colonizing cyanobacterial cover increased, and later successional lichens (Peltula and Placidium), and species restricted to more mesic sites (Syntrichia ruralis and Fulgensia) cover decreased when transplanted to novel environments. These results suggest that biocrust communities, but not all community members, are adaptable to climate change.