Data from: Necromass carbon but not microbes constrain soil carbon release in restoration of degraded alpine grassland

Alpine grassland restoration, a critical strategy for enhancing soil
organic carbon (SOC) sequestration in high-altitude ecosystems, profoundly
influences plant‒soil‒microbe interactions that govern the magnitude of
carbon (C)-climate feedback. However, mechanisms driving plant and
microbial regulation of SOC mineralization (i.e., soil CO2-C release)
during degraded alpine grassland restoration remain unresolved, limiting
predictions of SOC cycling in these vulnerable ecosystems. Here, by
integrating passive and active restoration experiments with aerobic
incubation, high-throughput sequencing, and biomarker analyses, we
disentangled how restoration-induced shifts in SOC composition (plant- and
microbial-derived C) and microbial activity and diversity regulate soil
CO2-C release in degraded alpine grassland on the Qinghai-Tibetan Plateau.
Our results showed that soil CO2-C release increased significantly with
restoration progression under both passive and active approaches. Alpine
grassland restoration markedly enhanced plant-derived C accumulation and
its SOC contribution, while microbial-derived C remained unchanged due to
reduced necromass accumulation coefficients. Notably, although active
restoration accelerated plant-derived C accumulation, its oxidation
decomposition degree was lower compared to passive restoration and even to
unrestored heavily degraded grasslands, increasing the SOC pool lability.
Fungal community restructuring, particularly in the saprophytic fungal
community, emerged as a hallmark of restoration. More importantly, we
found that elevated soil CO2-C release during degraded alpine grassland
restoration was not primarily mediated by microbial activity and diversity
shifts but strongly linked to divergent plant- and microbial-derived C
accumulation patterns, especially the dynamics of plant-derived C. These
insights underscore the critical roles of plant- and microbial-derived C
redistribution in grassland restoration and suggest new mechanisms for
restoration-induced soil C dynamics.