Little is known about the role of biocrusts in regulating the responses of N₂O and CH₄ fluxes to climate change in drylands. Here, we aim to help filling this knowledge gap by using an 8-year field experiment in central Spain where temperature and rainfall are being manipulated (~ 1.9°C warming, 33% rainfall reduction and their combination) in areas with and without well-developed biocrust communities. Areas with initial high cover of well-developed biocrusts showed lower N₂O emissions, enhanced CH₄ uptake and higher abundances of functional genes linked to N₂O and CH₄ fluxes compared with areas with poorly developed biocrusts. Moreover, biocrusts modulated the responses of gases emissions and related functional genes to warming and rainfall reductions. Specifically, we found under rainfall exclusion and its combination with warming a sharp reduction in N₂O fluxes (~ 96% and ~ 197%, respectively) only under well-developed biocrust cover. Warming and its combination with rainfall exclusion reduced CH₄ consumption in areas with initial low cover of well-developed biocrust, whereas rainfall exclusion enhanced CH₄ uptake only in areas with high initial cover of well-developed biocrusts. Similarly, the combination of warming and rainfall exclusion increased the abundance of the nosZ gene compared to the rainfall exclusion treatment and increased the abundance of the pmoA gene compared to the control, but only in areas with low biocrust cover. Taken together, our results indicate that well-developed biocrust communities could counteract the impact of warming and altered rainfall patterns on soil N₂O and CH₄ fluxes, highlighting their importance and the need to preserve them to minimize climate change impacts on drylands.

关于生物结皮在调节N ₂ O和CH ₄通量对干旱地区气候变化的响应中的作用知之甚少。在这里，我们的目标是通过在西班牙中部进行为期8年的田间试验来弥补这一知识鸿沟，该试验在有无好雨的地区控制了温度和降雨（约1.9°C的变暖，减少了33％的降雨及其组合），发达的生物地壳群落。最初发育良好的生物外壳的高覆盖区域显示出较低的N ₂ O排放量，增加的CH ₄吸收量以及与N ₂ O和CH ₄相关的功能基因的丰度较高通量与生物结皮较差的地区相比。此外，生物结壳调节了气体排放和相关功能基因对变暖和降雨减少的响应。具体而言，我们发现在降雨排除及其加温的结合下，只有在发达的生物壳覆盖下，N ₂ O通量才会急剧减少（分别为〜96％和〜197％）。变暖及其与降雨排除的结合，在生物发达的初始覆盖率较低的地区减少了CH _4的消耗，而降雨排斥仅在生物发达的初始覆盖率较高的地区提高了CH _4的吸收。同样，变暖和降雨排除的结合增加了nosZ的丰度与降雨排除处理相比，该基因的表达水平更高，而与对照相比，pmoA基因的丰度却增加了，但仅限于生物结皮覆盖率较低的地区。综上所述，我们的结果表明，发达的生物地壳群落可以抵消变暖和降雨模式对土壤N ₂ O和CH ₄通量的影响，突出了它们的重要性以及需要加以保护以最大程度地减少气候变化对旱地的影响。