Afforested and abandoned land ecosystems exhibit distinct soil microbial biomass stoichiometric homeostasis over chronosequence

Abstract

AbstractRevegetation influences microbial biomass stoichiometry by altering the substrate conditions, yet the differences in microbial stoichiometry homeostasis and the underlying drivers under different revegetation approaches remain unexplored. Here, we selected sites across three age classes of Robinia pseudoacacia plantation (RP) and abandoned land (AL), and quantified the microbial stoichiometric characteristics during farmland‐initiated restoration. Plant community composition, leaf and soil nutrients, and microbial community composition and diversity were also measured. We found that revegetation of former farmland under both restoration types resulted in non‐isometric changes in soil carbon (C), nitrogen (N), and phosphorus (P) contents, that is, decoupling of soil C and N from P. However, AL and RP succession exhibited homeostatic and plastic microbial biomass stoichiometry, respectively, in response to altered substrate stoichiometry. These differences were associated with adjustments in the above‐ and belowground biomes. Specifically, the synergistic increase of Compositae and Actinobacteria in the late AL succession allowed the ecosystem to reduce P demand and maintain microbial stoichiometric homeostasis. In contrast, higher leaf C and N input during RP succession may have resulted excessive microbial storage of elements, which in turn leads to stoichiometric convergence between microbial biomass and soil resources. In addition, RP succession caused changes in microbial community structure, mainly the continuous increase of Proteobacteria (copiotrophs, r‐strategists), which also potentially increased the requirement for resources to maintain homeostasis and ensure the rapid growth. These findings demonstrate that AL has a comparatively greater efficacy in maintaining microbial stoichiometric homeostasis during long‐term revegetation. Our study also highlights the importance of appropriately managing existing RP plantations to alleviate the pressure of P deficiency and sustainably maintain this fragile ecosystem.