【目的】探索非结构性碳水化合物(non-structural carbohydrates,NSC)在落叶树种栓皮栎(Quercus variabilis)不同器官间的分配格局与调配机制,为进一步掌握树木生长规律并评估栓皮栎群落的固碳潜力提供参考。【方法】2016年5月—2017年6月,以秦岭东段栓皮栎为研究对象,通过旬尺度和月尺度相结合的周期性采样方法取得栓皮栎1、2年生枝条以及当年生健康叶片样品,采用蒽酮浓硫酸法测定栓皮栎叶片和枝条NSC的组分含量及变化。此外,对栓皮栎叶片物候进行周期性观测,测量叶片长度,运用Gompertz函数拟合叶片生长曲线,得到叶片物候主要日期阶段的变化。【结果】①栓皮栎叶片和枝条的NSC组分含量均随时间呈明显的动态变化(P < 0.05),叶片的NSC含量(质量分数)均值(8.94%)高于枝条的(7.90%)。②栓皮栎叶片和枝条的NSC组成均以可溶性糖为主,分别占62.5%和63.5%,这可能是本研究区栓皮栎对暖干生境的生理生态适应的结果。③两器官间NSC及其组分含量的显著性差异,主要出现在生长季前期(4—6月)和后期(10月),主要原因是两器官在碳存储和碳消耗的阶段存在功能性差异。生长季前期,枝条为萌芽展叶消耗能量,而叶片通过光合作用积累NSC;生长季后期,枝条为下一年树冠重建储存能量,而叶片光合作用减弱。④除可溶性糖与淀粉比值外,NSC及其组分含量在两器官间的Pearson相关系数均不显著。在生长季前期(3—6月),叶片和枝条NSC含量高度极显著正相关(R = 0.986, P < 0.001),但存在15~20 d的滞后。【结论】栓皮栎生长过程中叶片和枝条器官的碳水化合物储量表现出动态调配变化,但并非线性关系,可能是受滞后因素影响的非线性关系。因此,在使用模型估算栓皮栎群落固碳潜力时,需综合考虑碳分配在不同器官间的时滞效应。

【Objective】Non-structural carbohydrates (NSC) are important carbon reserves in trees, which are good indicators of tree carbon surplus or shortage stored. Research into the allocation of NSC contents among tree tissues will help to understand the mechanisms of carbon allocation within trees. This provides a scientific basis for further evaluation of the carbon sequestration potential of forest communities. 【Method】We conducted a field observational study by monitoring the NSC concentrations in the leaves and branches of Chinese cork oak (Quercus variabilis), and by synchronously observing the leaf phenology of those trees in some uneven-aged secondary oak forests growing in the east Qinling Mountain Range. By measuring the leaf length and fitting the leaf growth curve with the Gompertz function, the specific dates of the main phenological stages of leaves can be obtained. Sampling intervals were set semi-monthly/monthly during the leaf unfolding period from March to May, and monthly or bimonthly during the trees’ full growing season from June to November. The time series of observations and sampling spanned from May 2016 to June 2017. The content of NSC and its components in the leaves and branches of Q. variabilis was determined by the anthranone-sulfuric acid method. 【Result】① The dynamics of the content of NSC and its components in leaves and branches of Q. variabilis varied significantly with seasonal rhythms (P < 0.05). The average NSC content (mass fraction) in the leaves (8.94%) was higher than that in the branches (7.90%). ② The composition of NSC in leaves and branches of Q. variabilis was mainly soluble sugar, and comprised 62.5% and 63.5%, respectively. This physiological feature might be a life strategy for Q. variabilis, a deciduous tree species growing typically in the warm temperate zone, to survive in the local environment. ③ Significant differences in the NSC contents and their components between leaves and branches were observed mainly in the early (April-June) and late (October) growing seasons. Before entering the growing season, the NSC content of branches dropped rapidly to supply energy to bud-break and leaf development. In contrast, the leaves began to accumulate NSC by photosynthesis. In the late growing season, branches were inclined to store carbon to reconstruct the canopy for the next year. While, photosynthesis of leaves was reduced. ④ The Pearson correlation coefficients of the NSC content and their components between leaves and branches were not significant except for the ratio of soluble sugar to starch. The variation trend of NSC contents in leaves and branches was highly positive (R=0.986, P < 0.001) in the early growing season (March-June), but there was a time lag of 15-20 days.【Conclusion】It could be inferred that the distribution relationship of NSC contents between leaves and branches of Q. variabilis is not linear, but most likely non-linear. Therefore, when estimating the carbon sequestration potential of Q. variabilis, the nonlinear relationship of carbon distribution among different tissues should be comprehensively considered.