Yan‐gui Su, Jie Liu, Yuan‐ming Zhang, Gang Huang
Biocrusts (composed of bryophytes, lichens, cyanobacteria and algae) provide important cover on the soil surface in drylands, improve soil health, and provide key ecosystem functions and services. Drylands are globally extensive, supporting up to 38% of the human population, and thus can vary substantially in physical and biotic characteristics, including the development of biocrusts. We lack understanding of how variations across drylands in climate, biocrust development, and plant and soil microbial diversity affect soil functions, and this knowledge gap limits our capacity to effectively understand and improve ecosystem services in drylands. Here, we investigated soil bacterial and plant diversity, biocrust development, and a soil multifunctionality index (indicated by nine soil C, N and P cycling parameters) across a 2200 km gradient spanning hyper-arid to semi-arid climatic zones in northern China. Relationships between plant and soil bacterial communities and biocrust development differed depending on aridity. Increases in both plant and soil bacterial diversity positively affected biocrust in the most arid regions, but the opposite was the case in more mesic, semi-arid regions. Further, biocrust development directly affected soil functioning in more arid regions, but biocrust effects were indirect through changing soil microbial functioning in semi-arid regions. Overall, our findings illustrate the differing role of biocrusts in regulating ecosystem functions depending on aridity and emphasize the importance of maintaining biocrust integrity for conserving soil qualities in drylands.