[Insert Figure 1 here]
A Meta-analysis of N and P Impacts on
CH4 Uptake in
Grasslands
To investigate the universality of these N and P effects on
CH4 uptake in grassland soils, we carried out a global
meta-analysis to quantify the responses of CH4 uptake
rates in grassland ecosystems to nutrient addition treatments (N-alone,
P-alone, and concurrent N + P additions) (Fig. 2 ). This global
meta-analysis showed that, relative to the control treatments, N
addition and concurrent N + P additions cause significant declines in
annual CH4 uptake: -27% (p < 0.01) and -14%
(p < 0.01), respectively (Fig. 2 ). The smaller
inhibition effect of concurrent N + P additions than the N-only addition
on CH4 uptake (p = 0.02) (Fig. 2 ) is consistent
with the results of our field experiment (Figs. 1a and2 ).