Abstract: Competition is one of the main drivers for forest decline and restoration. In this study, we investigated 293 target trees in aLarix gmeliniiplantation in a semiarid area of eastern Inner Mongolia. We used Heygi individual competition index model to quantify the competition intensity at both individual and plot levels and analyzed the determinant factors. Results showed that the competition intensity ofL. gmeliniidecreased with the increases of diameter at breast height (DBH). Their relationship followed the power function. Results from Pearson’s correlation analysis indicated that individual competition index was negatively correlated with tree height and crown width, and positively correlated with tree decline index. A multiple linear regression model analysis demonstrated that the competition intensity at the plot level was mainly influenced by stand density. Our results had implications for uncovering the mechanism for the forest decline in eastern Inner Mongolia.

Key words: ammonium N, ammonium chloride, nitrate N, nitrification potential, nitrification inhibitor