Tradeoffs between microbial life-history strategies drive soil carbon cycling during revegetation in karst ecosystems: A metagenomic perspective

Cai, Xiaoyi

JOURNAL OF ENVIRONMENTAL MANAGEMENT

2025

395

Zhu, XA; Liu, WJ

Revegetation strongly influences the dynamics of soil organic carbon (SOC) and microbial communities. While microbial communities are known to drive carbon (C) cycling, the specific traits responsible for C stabilization and mineralization during the revegetation of degraded karst ecosystems are not well understood. This study used a combination of metagenomic and instrumental methods to investigate variations in soil physicochemical properties, organic C fractions, C-cycle microbial community traits (diversity, life strategies, and co-occurrence patterns), and C-cycling (fixation and degradation) genes across four karst ecosystems representing a revegetation chronosequence encompassing cropland, grassland, shrubland, and primary forest. Our findings demonstrated that revegetation increased total SOC and recalcitrant OC (ROC) contents, while it decreased dissolved inorganic nitrogen (DIN) and reduced the ratio of labile OC (LOC) to SOC. This indicates enhanced C pool stabilization and storage, alongside reduced soil nutrient availability. These shifts favored the development of C-cycle microbial communities with low diversity and high proportions of K-strategists, which efficiently utilize recalcitrant C under oligotrophic conditions. Consequently, the increased dominance of K-strategists redirected microbial resource acquisition, manifested in a 29 % decrease in C-fixation gene abundances (rTCA, WL, and DC/4-HB pathways) and a 27 % decrease in genes degrading labile C compounds (starch, hemicellulose, cellulose, and chitin). Conversely, genes involved in degrading recalcitrant C compounds (pectin and lignin) increased by 19 %. Furthermore, the elevated proportion of K-strategists enhanced the complexity and stability of microbial taxonomic and functional networks, potentially strengthening community resilience and nutrient cycling efficiency. These results reveal a causal link between shifts in the soil C pool and nutrient availability during revegetation and the subsequent reshaping of C-cycling microbial communities. Such restructured communities, in turn, drive the expression of genes associated with C stabilization and mineralization, thereby impacting the soil C pool. This study provides mechanistic insights into microbial-mediated biochemical processes governing soil C decomposition and stabilization in karst ecosystems, offering critical guidance for ecological restoration in these degraded and fragile regions.