Figure 5.

Model bias in relation to soil variables. Partial residuals of the observed bias (%) in the maximum rate of Rubisco carboxylation predicted by the theoretical model ($V_{\mathrm{cmax}}^{\prime }$) by site plotted against soil cation exchange capacity (CEC, panel a), pH (panel b), carbon‐to‐nitrogen ratio (C:N, panel c), silt content (panel d), clay content (panel e), and an index of soil water availability (α; panel f) (black transparent circles). Model bias was defined as $\frac{V_{\mathrm{cmax}\left[\mathrm{pred}\right]}^{\prime }-V_{\mathrm{cmax}\left[\mathrm{obs}\right]}^{\prime }}{V_{\mathrm{cmax}\left[\mathrm{obs}\right]}^{\prime }}\ast 100$, where $V_{\mathrm{cmax}\left[\mathrm{pred}\right]}^{\prime }$ is the predicted optimal $V_{\mathrm{cmax}}^{\prime }$ and $V_{\mathrm{cmax}\left[\mathrm{obs}\right]}^{\prime }$ is the observed $V_{\mathrm{cmax}}^{\prime }$. Data points are sized logarithmically by $V_{\mathrm{cmax}\left[\mathrm{obs}\right]}^{\prime }$. Lines indicate the modelled response from the multiple linear regression models. Shading indicates 95% confidence intervals for regression lines. Only significant trends (P < 0.05) are shown. Data are plotted for each of the 193 sites that had available soil data. Colours are as in Figure 2.