Eco-enzymatic stoichiometry unveils resource limitations in soil microorganisms during subtropical vegetation restoration

Eco-enzymatic stoichiometry offers insights into how soil microorganisms allocate resources to fulfil their energy and nutrient demands. Subtropical ecosystems are known to be limited in resources, particularly by phosphorus (P) limitation. Vegetation restoration often leads to sustained changes in the relative availability of soil carbon (C), nitrogen (N) and P. However, the patterns of microbial resource limitations and their driving factors during vegetation restoration remain largely unclear. Here, we used eco-enzymatic stoichiometry modelling to investigate soil microbial resource limitations and to identify the key driving factors across five stages of vegetation restoration including grassland (GL), shrubland (SL) and early-, mid- and late-stage forests (EF, MF and LF) in the subtropical region of China. The activities of beta-1,4-glucosidase (BG), beta-N-acetyl glucosaminidase (NAG) and acid phosphatase (ACP) in forest stages (EF, MF and LF) were significantly higher than those in the GL and SL stages. The activities of cellobiohydrolase (CBH) and leucine aminopeptidase (LAP) increased consistently only across the forest stages (EF, MF and LF). Soil microbial resources wereco-limited by C and P. Soil nutrients had the strongest overall impact, positively affecting microbial C limitation and negatively affecting P limitation, while litter biomass positively regulated P limitation. Synthesis and applications. This research provides key insights into microbial resource limitations associated with vegetation restoration and could inform the design of more effective forest restoration strategies aimed at enhancing the recovery and stability of subtropical ecosystems.