Importance of organ age in driving intraspecific trait variation and coordination for three evergreen coniferous species

Abstract

Plant functional traits play an important role in plant growth and community composition in forest ecosystem. However, how the intraspecific trait variations for both leaf and branch were driven by organ age is less clear. We chose three evergreen coniferous species in the mixed broadleaved-Korean pine (Pinus koraiensis) forest in Northeast China and measured the functional traits for leaf and branch across organ ages. We mainly evaluated the influences of needle or branch age on the intraspecific trait (both leaf and branch) variations and bivariate correlation of traits for three species. We found that organ age had the largest contributions to the intraspecific variations in most traits for the three species. Current organ had high specific leaf area, high leaf nitrogen content, high specific branch length and low leaf and branch dry matter content, while perennial organ showed the opposite trend, indicating the differentiation of ecological strategies at different organ ages. The organ age significantly modified most of the trait-trait relationships, indicating that the transformation of the plant ecological strategy was driven by organ age. Unexpectedly, the variation in plant hydraulic traits was not affected by branch age and decoupled with most other traits for the three species. Our results suggest that the organ age effect should be incorporated into future studies of trait-based ecology for evergreen coniferous species.