Figure 8 The Structural equation model of ecosystem nitrogen (a) and phosphorus (b) stocks. The number near the arrow are standardized path coefficients. Red arrow denote significant positive (* < 0.05, ** < 0.01, *** < 0.001) correlation and green arrow denote significant negative (* < 0.05, ** < 0.01, *** < 0.001) correlations. The solid arrow indicates a positive and negative relationship and the dotted arrow indicates a non-significant relationship. The proportion of variance explained (r2) near endogenous variables represents the proportion of variance explained by the mode.
Supplementary table 1: The allometric equations used to estimating the biomass of the tree components (Y, kg per tree) and CBH (circumference at breast height X cm), acceding to regression equation (ln Y=a+b ln X, where a=intercept, and b= slope) and logarithmic regression relation to biomass of alder tree components dry weight in gram with the function of tree diameter at breast height (DBH, cm).