The availability of metallic nutrients in dryland soils, many of which are essential for the metabolism of soil organisms and vascular plants, may be altered due to climate change-driven increases in aridity. Biocrusts, soil surface communities dominated by lichens, bryophytes and cyanobacteria, are ecosystem engineers known to exert critical functions in dryland ecosystems. However, their role in regulating metallic nutrient availability under climate change is uncertain. Here, we evaluated whether well-developed biocrusts modulate metallic nutrient availability in response to 7 years of experimental warming and rainfall reduction in a Mediterranean dryland located in southeastern Spain. We found increases in the availability of K, Mg, Zn and Na under warming and rainfall exclusion. However, the presence of a well-developed biocrust cover buffered these effects, most likely because its constituents can uptake significant quantities of available metallic nutrients. Our findings suggest that biocrusts, a biotic community prevalent in drylands, exert an important role in preserving and protecting metallic nutrients in dryland soils from leaching and erosion. Therefore, we highlight the need to protect them to mitigate undesired effects of soil degradation driven by climate change in this globally expanding biome.

干旱地区土壤中金属养分的有效性可能会发生变化，其中许多对于土壤生物和维管植物的新陈代谢是必不可少的。生物外壳是由地衣，苔藓植物和蓝细菌控制的土壤表面群落，是生态系统工程师，已知在旱地生态系统中发挥关键作用。然而，在气候变化下它们在调节金属养分供应方面的作用尚不确定。在这里，我们评估了发达的生物结皮是否能响应西班牙东南部地中海干旱地区7年的试验变暖和降雨减少而调节金属养分的利用率。我们发现，在变暖和降雨排除条件下，钾，镁，锌和钠的有效性增加。然而，发达的生物结皮覆盖层的存在可以缓和这些影响，这很可能是因为其成分可以吸收大量可用的金属养分。我们的研究结果表明，生物结皮是干旱地区普遍存在的生物群落，在保护和保护旱地土壤中的金属养分免受淋溶和侵蚀方面发挥着重要作用。因此，我们强调需要保护它们，以减轻这种全球扩张的生物群落因气候变化而导致的土壤退化的不良影响。