[Variation in leaf functional traits of different-aged Robinia pseudoacacia communities and relationships with soil...

On the basis of various leaf functional traits of different-aged Robinia pseudoacacia communities, as well as the relationships between the traits and soil nutrients, the adaptation strategy of R. pseudoacacia in relation to soil conditions was analyzed in Ansai County, the Loess Plateau, China. The results showed that specific leaf area, leaf area, leaf water content, leaf total nitrogen content and leaf organic carbon content first increased and then decreased with the increasing stand age. The peak values of specific leaf area (279.18 cm²·g^-1), leaf area (12.33 cm²), leaf water content (0.09%), leaf total nitrogen content (33.01 g·kg^-1) and leaf organic carbon content (523.08 g·kg^-1) were obtained at 30 years old. With the increasing stand age, leaf tissue density, leaf total phosphorus content, leaf thickness and stomata density increased, and stomata length and stomata width decreased. Leaf area, specific leaf area, leaf total phosphorus content, leaf water content, leaf thicknessand stomata density were the main indexes based on principal component analysis (PCA), for R. pseudoacacia leaf functional traits responding to the increased stand age. The indexes were correlated with each other, indicating that R. pseudoacacia was capable of changing leaf morphological structure to adapt to environmental changes. Soil total nitrogen content was the main factor influencing leaf area, leaf water content, specific leaf area and stomata length, while soil organic carbon content mainly affected stomata width, leaf tissue density, leaf thickness, leaf total phosphorus content, leaf total nitrogen content and stomata density. Therefore, soil total nitrogen and organic carbon content were main factors that affected leaf functional traits of R. pseu-doacacia in different stand ages. Soil nutrients in R. pseudoacacia communities were improved with the increasing stand age, which eventually affected leaf functional traits. The flexibility of leaf functional traits indicated that R. pseudoacacia communities had great potential to adapt to environmental change in Loess Plateau hilly region.