Biocrusts enhance short-term carbon cycling and long-term sequestration in a restored semiarid shrubland

Biocrusts are a common component of semiarid shrublands worldwide. Yet, while the isolated influence of shrubs and biocrusts on carbon (C) cycling has been extensively studied, much less is known about their interactive influence, which limits our capacity to predict the future of carbon stocks in drylands. In this study, we conducted incubation experiments to compare C mineralization in soils from isolated Artemisia ordosica shrub patches (without biocrusts) and those including shrub-biocrust coexistence patches in a restored shrubland on the northern Chinese Loess Plateau. Our results showed that, compared to isolated shrub patches, the presence of biocrusts increased mean C mineralization rates by 17.1–19.5 % and cumulative C mineralization by 16.8–26.5 %. The enhanced soil C mineralization in the presence of biocrusts was primarily driven by the increased quantity and quality of mineralizable organic substrate which promote microbial assimilation of nutrients and stimulate extracellular enzyme activities. An increase in the abundance of particular fungal groups, such as Mortierellomycota and Ascomycota may also boost the production of extracellular enzymes which could speed up the breakdown of complex organic compounds. Importantly, the enlarged soil C pool in shrub-biocrust patches reduced the relative proportion of C lost through mineralization. Moreover, the temperature sensitivity of C mineralization tended to decline, although the effect was not significant. Overall, our study highlights the crucial role of biocrusts in the stabilization and accumulation of organic C when coexisting with shrubs in semi-arid drylands, thereby supporting the sustainability and resilience of restored shrubland ecosystems.