Mosses stimulate soil carbon and nitrogen accumulation during vegetation restoration in a humid subtropical area

Mosses form a ground layer with a thickness of nearly 1 cm during the first decade of vegetation restoration, but their effects on the belowground microbial community and soil properties and the associated soil carbon (C) and nitrogen (N) accumulation in subtropical areas are unclear. Here, we measured soil C and N variables (soil organic C [SOC], total N [TN], dissolved organic C, ammonium [NH4+-N] and nitrate [NO3  -N]), soil microbial community and soil properties (soil water content [SWC] and pH) under four treatments (bare soil [BS], bare soil with transplanted moss, moss-covered soil [MS] and moss-covered soil with moss removed) in three vegetation types (forest plantations, forage grasslands and mixed plantations and forage grasslands) in a subtropical climate. We analyzed the effects of native mosses, moss transplantation and removal using BS and MS as references. One year post-treatment, moss transplantation increased NO3  -N and NH4+-N in the 0-5 cm and 2-5 cm soil layers, respectively. Conversely, moss removal decreased SOC and TN in the 0-2 cm soil layer and SWC in the 0-5 cm soil layer. Compared to BS and MS, native moss presence, moss transplantation and removal decreased the total microbial, bacterial and fungal biomass and altered the soil microbial community composition (ratios of fungi and bacteria and Gram-positive bacteria to Gram-negative bacteria) to varying degrees. Moss properties (biomass, C and N concentrations, C:N ratio and saturated water absorption content), as well as SWC, soil microbial biomass and community composition regulated by mosses affected soil C and N. These findings underscore the crucial role of mosses in facilitating soil C and N accumulation during vegetation restoration.