3.2 Priming effect and C substrate mineralization
Glucose amendments had positive cumulative PEs under N and P additions while negative PE under Control, with the highest PE under P addition (Figure 2a). Vanillin amendments had negative cumulative PE for all nutrient treatments, with the highest PE under P addition. The PEs with glucose amendment were significantly correlated with soil and microbial C:N, C:P, N:P (Table 1). However, there were no significant relationships between PEs with vanillin amendment and stoichiometric characteristics of soil and microorganisms (Table 1).
Compared with control, nutrient additions increased C substrate mineralization, with much higher mineralization of vanillin than that of glucose (Figure 2b). Specifically, glucose mineralization was increased by 45%, 36%, and 33% under N, P and NP addition, respectively (Figure 2b). Vanillin mineralization was increased by 11%, 40%, and 48% under N, P and NP addition, respectively. Both C substrates (glucose and vanillin) mineralization was significantly correlated with soil and microbial C:N, C:P, N:P (except glucose mineralization and soil C:N) (Table 2).