Figure captions
FIGURE 1 Effects N and P addition on stoichiometric characteristics of soil (a) and microorganisms (b) (means ± 1SE, n=5). Abbrevation: Control the control without any nutrient addition, N N-alone addition, P P-alone addition, NP N and P together addition. The statistics are from a two-way ANOVA, *, **, *** and ns denotingp <0.05, p <0.01,p <0.001, and p >0.05, respectively. Letters indicate significant difference among N and P additions atp < 0.05. Numbers above N, P, and NP are effects of N and P compared to Control
FIGURE 2 Effects N and P addition on priming effect (PE) with glucose or vanillin substrate amendment (a) and carbon substrate mineralization (b). Values shown are means ± 1SE (n=5 per treatment). Abbrevation: Control the control without any nutrient addition, N N-alone addition, P P-alone addition, NP N and P together addition. The statistics are from a two-way ANOVA, *** and ns denotingp <0.001, and p >0.05, respectively. Letters indicate significant difference among N and P additions atp < 0.05. Numbers above N, P, and NP bars are effects of N and P compared to Control
FIGURE 3Effects N and P addition on soil organic carbon (SOC) decomposition (a), and soil net carbon balance (NCB) (b). Values are mean ± 1SE (n=5 per treatment). Abbrevation: Control the control without any nutrient addition, N N-alone addition, P P-alone addition, NP N and P together addition. The statistics are from a two-way ANOVA, *** denotingp <0.001. Letters indicate significant difference among N and P additions at p < 0.05. Numbers above N, P, and NP bars are effects of N and P compared to Control
FIGURE 4 Effects of N and P additions on the microbial carbon use efficiency (CUE) (Mean ± 1SE, n=5) of 13C-glucose and 13C-vanillin. Abbrevation: Control the control without any nutrient addition, N N-alone addition, P P-alone addition, NP N and P together addition. The statistics are from a two-way ANOVA, *, *** and ns denoting p <0.05,p <0.001, and p >0.05, respectively. Letters indicate significant differences among N and P additions atp < 0.05. Numbers above N, P, and NP bars are effects of N and P compared to Control
FIGURE 5 A conceptual diagram illustrating the main effects of N and P additions on C decomposition and accumulation in Tibetan alpine meadows. Abbrevation: SOC soil organic carbon, CUE microbial carbon use efficiency. The red, green and yellow symbols and numbers denote the processes influenced by N-alone addition, P-alone addition, and NP together addition, respectively. The short arrows ↑and ↓ represent the increase or decrease in soil C processes in response to N and P additions, respectively. The numbers in red, green and yellow denote increase or decrease in % under N, NP and P addition compared with Control.