Figure 3

The values of δ15N in forest floor litter and soil layers in natural forests and plantations at six sites across the eastern China. The error bars indicate standard deviation (n = 3). MH (Mohe), QY (Qingyuan), XY (Xinyang), HT (Huitong), DH (Dinghushan), JF (Jianfengling). *, ** and *** indicate a significant level at p < 0.05, p < 0.01 and p < 0.001, respectively.