Table 2.
Linear correlations between the variations (log of response ratio: lnRR) of foliar C:N ratio and N:P ratio with latitude, MAP, MAT under warming, increased precipitation, N addition and eCO2.
| Treatment | Independent variables | Dependent variables | a | b | × 0 | y0 | r2 | P |
|---|---|---|---|---|---|---|---|---|
| Warming | Latitude | C:N | – | – | – | – | – | – |
| N:P | – | – | – | – | – | – | ||
| MAP | C:N | – | – | – | – | – | – | |
| N:P | – | – | – | – | – | – | ||
| MAT | C:N | – | – | – | – | – | – | |
| N:P | – | – | – | – | – | – | ||
| Increased precipitation | Latitude | C:N | − 0.214 | 9.465 | – | – | 0.340 | 0.036 |
| N:P | 0.085 | − 3.634 | – | – | 0.190 | 0.029 | ||
| MAP | C:N | 0.001 | − 0.159 | – | – | 0.340 | 0.036 | |
| N:P | 0.726 | 78.638 | 267.856 | − 0.351 | 0.686 | < 0.0001 | ||
| MAT | C:N | − 0.02 | 0.199 | – | – | 0.340 | 0.036 | |
| N:P | − 0.042 | 0.309 | – | – | 0.458 | 0.000 | ||
| N addition | Latitude | C:N | 0.014 | − 0.725 | – | – | 0.173 | < 0.0001 |
| N:P | – | – | – | – | – | – | ||
| MAP | C:N | − 0.001 | 0.107 | – | – | 0.115 | 0.002 | |
| N:P | – | – | – | – | – | – | ||
| MAT | C:N | – | – | – | – | – | – | |
| N:P | – | – | – | – | – | – | ||
| eCO2 | Latitude | C:N | – | – | – | – | – | – |
| N:P | – | – | – | – | – | – | ||
| MAP | C:N | – | – | – | – | – | – | |
| N:P | – | – | – | – | – | – | ||
| MAT | C:N | – | – | – | – | – | – | |
| N:P | – | – | – | – | – | – |
The correlations were significant when P < 0.05.
MAP: mean annual precipitation (mm), MAT: mean annual temperature (°C), [CO2]: carbon dioxide concentration, N: nitrogen, C:N: foliar carbon to nitrogen ratio, N:P: foliar nitrogen to phosphorus ratio.