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.