3.1 Variations in root and foliar N and P
The foliar N and P concentrations were the most variable, and root N and P concentrations were least variable, across the three study site and along the elevational gradients, as inferred by the CV values (Table 1). The mean root N concentration was significantly lower (P< 0.05) than the mean foliar N concentration, whilst the root N:P ratio was significantly higher (P < 0.05) than the foliar N:P ratio, across study areas and elevations.
Variance partitioning shows that the root N and P concentrations were mainly influenced by soil factors (Figure 2), with the root P concentration further affected by ECM traits with an explained variance of 10.8%. The variance in foliar N was mostly explained by the joint effect of the climate factors and the ECM traits. Among the different categories of factors, soil environmental conditions were most influential on the root and foliar N:P ratios, explaining 33.9% and 39.9% of the variations, respectively; whilst the ECM traits were secondary in affecting the root and foliar N:P ratios, explaining 14.8% and 9.18% of the variations, respectively.