Table 1.
Summary of the meta-regression model, P values <0.05 are significant.
| Fine root traits | Moderator variables | Tree species | Covariate | Coefficient | Standard Error | 95% Lower | 95% Upper | Z-value | Two-tailed P-value | R2 |
|---|---|---|---|---|---|---|---|---|---|---|
| FRB | Warming magnitude | Overall | Intercept | 2.13 | 0.581 | 0.99 | 3.27 | 3.67 | 0.00 | 0.28 |
| Warming magnitude | -0.53 | 0.178 | -0.87 | -0.18 | -2.99 | 0.00 | ||||
| Coniferous | Intercept | 3.21 | 0.796 | 1.64 | 4.77 | 4.03 | 0.00 | 0.56 | ||
| Warming magnitude | -0.84 | 0.235 | -1.30 | -0.38 | -3.59 | 0.00 | ||||
| Deciduous | Intercept | 1.02 | 0.733 | -0.41 | 2.46 | 1.40 | 0.16 | 0.01 | ||
| Warming magnitude | -0.11 | 0.255 | -0.61 | 0.38 | -0.44 | 0.66 | ||||
| Soil depth | Overall | Intercept | -0.00 | 0.58 | -1.16 | 1.14 | -0.01 | 0.98 | 0.07 | |
| Soil depth | 0.05 | 0.04 | -0.02 | 0.13 | 1.38 | 0.16 | ||||
| Coniferous | Intercept | 0.21 | 0.96 | -1.67 | 2.10 | 0.22 | 0.82 | 0.08 | ||
| Soil depth | 0.05 | 0.05 | -0.06 | 0.16 | 0.85 | 0.39 | ||||
| Deciduous | Intercept | -0.34 | 0.93 | -2.18 | 1.49 | -0.37 | 0.71 | 0.20 | ||
| Soil depth | 0.12 | 0.09 | -0.06 | 0.32 | 1.28 | 0.20 | ||||
| SRA | Warming magnitude | Overall | Intercept | -1.06 | 1.78 | -4.55 | 2.42 | -0.60 | 0.54 | 0.42 |
| Warming magnitude | 0.73 | 0.46 | -0.18 | 1.64 | 1.57 | 0.11 | ||||
| Soil depth | Intercept | -1.03 | 1.36 | -3.70 | 1.63 | -0.76 | 0.44 | 0.65 | ||
| Soil depth | 0.14 | 0.07 | 0.00 | 0.29 | 1.99 | 0.04 | ||||
| SRL | Warming magnitude | Overall | Intercept | -1.06 | 1.78 | -4.55 | 2.42 | -0.60 | 0.54 | 0.42 |
| Warming magnitude | 0.73 | 0.46 | -0.18 | 1.64 | 1.57 | 0.11 | ||||
| Soil depth | Intercept | -1.03 | 1.36 | -3.70 | 1.63 | -0.76 | 0.44 | 0.65 | ||
| 0.14 | 0.07 | 0.00 | 0.29 | 1.99 | 0.04 | |||||
| D | Warming magnitude | Overall | Intercept | 0.49 | 0.51 | -0.52 | 1.50 | 0.95 | 0.34 | 1.00 |
| Warming magnitude | -0.13 | 0.06 | -0.25 | -0.00 | -2.06 | 0.03 | ||||
| Soil depth | Intercept | -2.82 | 0.95 | -4.68 | -0.95 | -2.97 | 0.00 | 1.00 | ||
| Soil depth | 0.16 | 0.05 | 0.04 | 0.27 | 2.77 | 0.00 |
Figure 1.
Effect sizes of fine root traits, including fine root biomass (FRB), and fine root morphological traits, such as specific root length (SRL), specific root area (SRA), and diameter (D) of coniferous and deciduous trees to soil warming. Error bars represent 95% confidence intervals (CI). The vertical line shows an effect size of zero. The effect of soil warming on fine root traits was considered significant if the 95% CI of the effect size for a variable did not overlap zero.
Figure 2.
Meta-regression slops showing fine root biomass variation in relation to the warming magnitude and soil depth. The sizes of the circles correspond to the weight given to each individual study in the meta-analysis. Larger circles represent a higher weighting.