*3.2. Relationship Between Leaf* δ*13C,* δ*15N and N, P Concentrations as well as C:N Ratio*

For all leaf samples, δ13C was significantly positively correlated with leaf N and P concentrations, but negatively related to the C/N ratio (*p* < 0.001, Table 2). However, nutrient patterns did not differ among leaf ages as the leaf δ13C showed no significant relationship between leaf N, leaf P concentrations and the C/N ratio except for current-year-old leaves (*p* > 0.05).

Likewise, leaf δ15N showed significant positive correlation with leaf N and P concentrations but negative correlation with the C:N ratio in all leaf samples (*p* < 0.001). When examining the relationship between these leaf nutrients and δ15N at each leaf age level, a significant positive correlation between leaf N concentration and δ15N and a negative correlation between the C:N ratio and leaf δ15N were only observed in current-year-old and 1-year-old leaves, respectively, while there was no significant relationship between leaf δ15N and P concentrations at each leaf age group.


**Table 2.** Regression equations for leaf δ13C and δ15N values against leaf N and P concentrations and the C:N ratios for 4 years' leaves.

Note: \*\*\* *p* < 0.001,\* *p* < 0.05.
