Factors affecting individual growth of Pinus koraiensis and Tilia amurensis in coniferous and broadleaved mixed forests in Jiaohe, Jilin Province of northeastern China

Objective Pinus koraiensis and Tilia amurensis, the dominant tree species in coniferous and broadleaved mixed forests in Jiaohe, Jilin Province of northeastern China, were taken as the research object. We investigated the interspecific differences in leaf traits, correlations among leaf traits, and the effects of biotic factors (neighborhood competition, initial DBH, leaf traits) and abiotic factors (topographical factor) on growth rate of trees.

Method Welch ANOVA was used to quantify the interspecific differences in leaf traits of Pinus koraiensis and Tilia amurensis. Principal component analysis (PCA) and Spearman correlation coefficient were used to evaluate the correlations among leaf traits. The relative effects of different factors on growth rate of Pinus koraiensis and Tilia amurensis were calculated by ordinary least squares model (OLS).

Result The light-saturated photosynthetic rate and leaf dark respiration of Pinus koraiensis were significantly higher than those of Tilia amurensis; light-saturated stomatal conductance and specific leaf area of Tilia amurensis were significantly higher than those of Pinus koraiensis. The light-saturated photosynthetic rate of Pinus koraiensis was positively correlated with light-saturated stomatal conductance and specific leaf area. The light-saturated photosynthetic rate of Tilia amurensis was positively correlated with light-saturated stomatal conductance and negatively correlated with specific leaf area. Initial DBH, neighborhood crowding index and slope had significant negative effects on average annual DBH growth of Pinus koraiensis. Initial DBH had significantly positive effect on average annual biomass growth of Pinus koraiensis, neighborhood crowding index and slope had significantly negative effect. Initial DBH had significantly negative effect on average annual DBH growth and positive effect on average annual biomass growth of Tilia amurensis. Altitude had significant negative effects on the average annual DBH growth and annual biomass growth of Tilia amurensis.

Conclusion The leaf traits of Pinus koraiensis and Tilia amurensis have significantly interspecific differences, the correlation of leaf traits of two species has different patterns. The growth of Tilia amurensis is affected by the initial DBH and elevation. The larger the initial DBH is, the lower the average annual DBH growth is, and the higher the average annual biomass growth is. The higher the elevation is, the lower the average annual DBH growth and biomass growth is. The growth of Pinus koraiensis is affected by the initial DBH, neighborhood crowding index and slope. The larger the initial DBH is, the lower the average annual DBH growth is, while the higher the average annual biomass growth is. The larger the neighborhood crowding index and slope is, the lower the average annual DBH growth and average annual biomass growth are.