植株大小、枝龄和环境共同驱动红松枝性状的变异

许多枝性状的变异受植株大小、枝龄或环境的影响, 但少有研究同时评估这些因素对枝性状种内变异的重要性。该研究以红松(Pinus koraiensis)为研究对象, 通过测定69株胸径(DBH) 0.3-100.0 cm范围内植株不同年龄枝的形态性状、化学性状和解剖性状, 探讨植株大小(DBH或树高)、枝龄与环境因素(光照强度、土壤养分及土壤含水率)对枝性状的影响。结果表明: (1) DBH与树高对枝性状的影响存在差异: 木质密度(WD)、木质部面积占比(R_XA)、韧皮部面积占比(R_PHA)及髓面积占比(R_PA)对DBH更敏感, 而树脂道总面积占比(R_RC)和枝氮含量(WN)受树高影响更大; (2)枝龄是导致红松枝性状种内变异的最主要因素, 植株大小次之, 而环境因素的影响最小; (3) WD、R_PHA与DBH显著正相关, R_PA与DBH显著负相关, R_RC、WN与树高显著正相关; 除WN外, 其余枝性状与枝龄均显著相关, 且随着树木生长, R_RC随枝龄增大而减小的速率加剧, 相反, R_PA随枝龄增大而减小的速率减缓。研究结果有助于了解局域尺度上枝性状种内变异的影响因素以及枝条应对环境变异的适应机制。

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

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 (R_XA), the phloem area-to-total cross-sectional area ratio (R_PHA) and the pith area-to-total cross-sectional area ratio (R_PA) were more sensitive to DBH, while the total resin canal area-to-total cross-sectional area ratio (R_RC) 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 R_PHA were significantly positively correlated with DBH, while R_PA was significantly negatively correlated with DBH; and R_RC 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 R_RC decreasing with branch age was enhanced, but the rate of R_PA 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.