4. DISCUSSION
N and P additions differently affected the magnitude and direction of
PEs, decomposition of plant-derived substrate and SOC, microbial CUE,
and thus C accumulation. This was mainly associated with the N and P
additions-induced differences in soil nutrient status and microbial
ecological stoichiometric ratios, as well as differences in substrate
decomposability due to changes in plant community composition and plant
species’ predominance. Glucose induced positive PEs while vanillin
induced negative PEs. These results were in accordance with our
hypotheses. However, the positive PEs with glucose amendment was mainly
generated by “nutrient mining” while negative PEs with vanillin
amendment was generated by the balanced two mechanisms “co-metabolism”
and “nutrient mining”. This partially supported our hypotheses. The
comprehensive effects on C decomposition and accumulation led to
declines in SOC contents in response to N and P additions.