Chin J Plant Ecol ›› 2020, Vol. 44 ›› Issue (9): 939-950.

• Research Articles •

### Plant size, branch age and environment factors co-drive variations of branch traits of Pinus koraiensis

YU Qing-Han, JIN Guang-Ze, LIU Zhi-Li*()

1. and Key Laboratory of Sustainable Forest Ecosystem Management- Ministry of Education, Northeast Forestry University, Harbin 150040, China
• Received:2020-05-27 Accepted:2020-08-07 Online:2020-09-20 Published:2020-09-03
• Contact: LIU Zhi-Li
• Supported by:
Supported by the National Natural Science Foundation of China(31971636);the Yong Elite Scientists Sponsorship Program by CAST(31971636);the Fundamental Research Fund for the Central Universities(31971636)

Abstract:

Aims Variations of many branch traits are affected by plant size, branch age and environment factors, but the relative importance of these factors to intraspecies variations of branch traits has rarely been evaluated simultaneously.
Methods In this study, we took Pinus koraiensis as the research object, to explore the effects of plant size (diameter at breast height (DBH) or tree height), branch age and environmental factors (light intensity, soil nutrient content and water availability) on branch traits, by measuring morphological traits, chemical traits and anatomical traits in different branch ages of 69 individuals with DBH in the range of 0.3-100.0 cm.
Important findings Our results showed that: (1) DBH and tree height had different effects on branch traits: wood density (WD), the xylem area-to-total cross-sectional area ratio (RXA), the phloem area-to-total cross-sectional area ratio (RPHA) and the pith area-to-total cross-sectional area ratio (RPA) were more sensitive to DBH, while the total resin canal area-to-total cross-sectional area ratio (RRC) and wood nitrogen content (WN) were more affected by the tree height; (2) branch age was the most important factor in driving intra-specific variations of branch traits of P. koraiensis, followed by plant size, while the impact of environment factors was minimal; (3) WD and RPHA were significantly positively correlated with DBH, while RPA was significantly negatively correlated with DBH; and RRC and WN were significantly positively correlated with tree height. Except for WN, the relationships between branch traits and branch age were significant, and as tree growth, the rate of RRC decreasing with branch age was enhanced, but the rate of RPA decreasing with branch age was weakened. The results of our study are helpful to understand the driving factors of intraspecific variation of branch traits at the local scale and the adaptation mechanism of branches to cope with environmental changes.