干旱区生态环境知识资源中心

We studied the importance of effective rainfall for interannual variation in water use efficiency (WUE) and tree-ring growth of Chinese pine (Pinus tabulaeformis Carr.) and black locust (Robinia pseudoacacia L.) by examining correlations of seasonal precipitation with annual values of stable carbon isotope ratio (delta C-13) and tree-ring width in early and late wood. The correlations with precipitation were examined for each month and for periods of all possible lengths from 2 to 22 months starting from January of the previous year to October of the current year. The period with the highest correlation was adopted as the most effective rainfall season for interannual variations in WUE and tree-ring width. In early wood, precipitation during the dry season (October to May) before the growing season was negatively correlated with delta C-13 in pine trees and positively correlated with ring width in pine and locust trees. In late wood, rainfall during the growing season in the current year was negatively correlated with delta C-13 in pine and locust trees, and positively correlated with ring width in locust trees. Our results demonstrated the differences in the water use strategies of pine and locust trees. The delta C-13 in pines indicated higher WUE and more conservative water use than in locust trees. Precipitation during the dry season affected the interannual variation in WUE and tree-ring growth in pine and locust trees, indicating that rainfall during the dry season is important for carbon gain and tree-ring growth during the following growing season.