Plant biomass, soil chemical properties, and microbial biomass
Aboveground and belowground biomass increased along the N addition gradient, but the increasing magnitude was higher aboveground than belowground (Table S1). The N input increase led to an increase in plant N concentration, soil NH4+-N, and NO3-N (Table S2). In contrast, soil pH significantly decreased by 0.58 units from 7.02 in control (F0) to 6.44 under the highest N addition (F120) level. Soil total C and N remained stable among treatments.
Fertilization termination led to the quick recovery of aboveground plant biomass, plant N concentration, and soil pH, as the values were not significantly different from the control plots (R0). NO3-N also remained statistically unchanged across all treatments after nutrient addition ceased. NH+4-N content was significantly lower in previously fertilized soil. Total soil C and N tended to be lower than control (R0), but statistically insignificant (Table S2). Microbial biomass N increased after N inputs cessation while microbial biomass C remained stable (Table S1).