Contribution of moss crusts to soil multifunctionality in karst ecosystems under extreme climate conditions

Frequent extreme climate events globally threaten ecosystem services and functions, particularly in fragile regions. As one of the vital “ecosystem engineers” and “living skin”, mosses have been demonstrated to impact soil biogeochemical cycles markedly, yet their role in shaping the soil multifunctionality of fragile regions under extreme climates remains unclear. A one-year in-situ field experiment was conducted to simulate the effect of moss crust on soil multifunctionality in intense karst rocky desertification regions under extreme drought and heavy precipitation. Compared with bare soil, the moss crust significantly enhanced soil multifunctionality, with increases of 44.0 %, 32.7 %, and 54.8 % in extreme drought, ambient precipitation, and heavy precipitation conditions, respectively. This was primarily attributed to moss crust promoting the related variable on soil carbon cycling, such as improving β-1,4-glucosidase and microbial biomass carbon under extreme climate conditions. Furthermore, moss crust reduced the dependency of soil on precipitation by boosting above-ground biomass and modulating microbes to enhance soil multifunctionality. Collectively, this finding underscores the critical role of moss crusts in sustaining soil multifunctionality of vulnerable ecosystems under extreme climate contexts, and provides new insights into soil protection. However, the limited biomass input of moss crusts and the potential imbalance in nitrogen fraction conversion are critical issues that require careful consideration. Accordingly, combining moss crusts with diverse vegetation restoration approaches may be an effective strategy for ecological restoration and carbon sequestration enhancement in fragile ecosystems affected by climate change. Schematic diagram of the driving mechanism comparison with moss crusts and bare soil on soil multifunctionality under changes in precipitation conditions. Black and white numbers next to the lines represent positive and negative correlation, respectively. *** p < 0.001, ** p < 0.01, and * p < 0.05. • Moss boosts soil multifunctionality by 44.0 % under extreme drought. • Moss enhanced soil multifunctionality by 54.8 % under heavy precipitation. • Moss lessens the dependence of soil multifunctionality on water availability. • Nitrogen conversion induced by moss crust may be imbalanced.