Table 1.
Results of linear models examining global-scale variation of riparian litter traits [nitrogen (N) and phosphorus (P) concentrations, log-transformed N:P ratio, magnesium (Mg) and tannin (Tan) concentrations, and log-transformed specific leaf area (SLA)], depending on key climatic and soil predictors (mean annual temperature, MAT; mean annual precipitation, MAP; soil pH, SoilpH; and soil N concentration, SoilN) and on other litter traits.
| Litter trait | Model | Factor | Estimate | Std. Error | t | p | %Variance |
|---|---|---|---|---|---|---|---|
| N | N ~ P + Tan + MAT + MAP + MAT × MAP + SoilpH | ||||||
| Variance explained: 37% | Intercept | 1.0282 | 0.0383 | 26.87 | <0.001 | ||
| Total df: 164 | P | 0.1880 | 0.0133 | 14.17 | <0.001 | 66.30 | |
| Residual df: 157 | Tan | −0.0910 | 0.0232 | −3.92 | <0.001 | 15.34 | |
| MAT | 0.0306 | 0.0442 | 0.69 | 0.489 | 3.05 | ||
| MAP | 0.4176 | 0.0652 | 6.41 | <0.001 | 12.49 | ||
| MAT × MAP | −0.1550 | 0.0416 | −3.72 | <0.001 | 1.27 | ||
| SoilpH | 0.1866 | 0.0340 | 5.49 | <0.001 | 1.55 | ||
| P | P ~ N + MAT + SoilpH + SoilN | ||||||
| Variance explained: 34% | Intercept | 0.0461 | 0.0014 | 33.92 | <0.001 | ||
| Total df: 164 | N | 0.0143 | 0.0017 | 8.55 | <0.001 | 84.88 | |
| Residual df: 159 | MAT | −0.0043 | 0.0022 | −1.98 | 0.049 | 6.55 | |
| SoilpH | 0.0042 | 0.0019 | 2.24 | 0.026 | 3.33 | ||
| SoilN | 0.0068 | 0.0019 | 3.65 | <0.001 | 5.23 | ||
| N:P | Log N:P ~ Tan + MAT + MAP + MAT × MAP | ||||||
| Variance explained: 18% | Intercept | 3.8256 | 0.0333 | 114.73 | <0.001 | ||
| Total df: 165 | Tan | −0.0753 | 0.0206 | −3.66 | <0.001 | 11.00 | |
| Residual df: 160 | MAT | 0.2091 | 0.0515 | 4.06 | <0.001 | 71.25 | |
| MAP | −0.0013 | 0.0487 | −0.03 | 0.979 | 15.32 | ||
| MAT × MAP | −0.0818 | 0.0412 | −1.99 | 0.049 | 2.43 | ||
| Mg | Mg ~ N + P + N:P + MAP + SoilpH + SoilN | ||||||
| Variance explained: 14% | (Intercept) | 4.3896 | 0.1723 | 25.48 | <0.001 | ||
| Total df: 164 | N | 0.3710 | 0.1357 | 2.73 | 0.007 | 4.09 | |
| Residual df: 157 | P | −0.4528 | 0.2042 | −2.22 | 0.028 | 3.51 | |
| N:P | −0.8064 | 0.2391 | −3.37 | 0.001 | 25.55 | ||
| MAP | −0.8824 | 0.2555 | −3.45 | 0.001 | 21.49 | ||
| SoilpH | −0.9425 | 0.1800 | −5.24 | <0.001 | 6.95 | ||
| SoilN | −0.9481 | 0.1482 | −6.40 | <0.001 | 38.41 | ||
| Tan | Tan ~ N + Mg + MAT + MAP + MAT × MAP + SoilpH | ||||||
| Variance explained: 17% | Intercept | 8.789 | 0.778 | 11.30 | <0.001 | ||
| Total df: 164 | N | −1.958 | 0.405 | −4.83 | <0.001 | 48.59 | |
| Residual df: 157 | Mg | −1.153 | 0.266 | −4.34 | <0.001 | 20.86 | |
| MAT | −1.913 | 0.845 | −2.26 | 0.025 | 1.64 | ||
| MAP | 4.420 | 1.083 | 4.08 | <0.001 | 12.06 | ||
| MAT × MAP | −1.714 | 0.741 | −2.31 | 0.022 | 15.11 | ||
| SoilpH | −1.260 | 0.469 | −2.69 | 0.008 | 1.74 | ||
| SLA | Log SLA ~ P + Tan + MAT + SoilN | ||||||
| Variance explained: 34% | Intercept | 5.019 | 0.023 | 219.30 | <0.001 | ||
| Total df: 138 | P | 0.106 | 0.024 | 4.36 | <0.001 | 20.96 | |
| Residual df: 133 | Tan | −0.172 | 0.023 | −7.53 | <0.001 | 46.24 | |
| MAT | −0.170 | 0.025 | −6.94 | <0.001 | 25.72 | ||
| SoilN | −0.136 | 0.031 | −4.34 | <0.001 | 7.08 | ||
We show the proportion of variance explained by each model and the total and residual degrees of freedom (df; numerator df = 1 in all cases) and, for each factor, we show the mean estimate and standard error, t-statistic, p-value and proportion of variance explained; bold type indicates significant relationships at the p < 0.05 level.