Fig. 6
From: Trajectories in nitrogen availability during forest secondary succession: illustrated by foliar δ15N
Changes in foliar δ15N with forest succession in different climatic regions. Foliar δ15N was standardized to the mean value of foliar δ15N in the first 50 years of succession at the regional level. Blank black circles represent the mean value of foliar δ15N in the same succession time. Blank circles in other colors represent foliar δ15N in different succession sequences. The black solid circle in c represents the outlier. The red line represents the trajectory of foliar δ15N with forest succession. The blue line represents the piecewise linear regression line. The inflection points in temperate and tropical forests were at the 66th and 23rd years, respectively. No inflection point was found in the boreal forest