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以中国东北温带森林两个散孔材树种白桦和紫椴为对象,研究落叶后树干木质部中非结构性碳水化合物(NSC)浓度的空间变异.结果表明:两种树种的可溶性糖与淀粉的总和(TNC)与可溶性糖浓度均随树干径向深度增加而缓慢下降,淀粉的径向变化不明显,即使在树干径向深处仍存有大量的NSC.两种树种树干的TNC、可溶性糖和淀粉浓度从根颈到胸高降低,之后逐渐升高,最大值出现的高度因树种和TNC组分而异.两种树种树干糖淀粉比值的纵向变化趋势为:白桦随树干升高而增大,紫椴则随之减小.树干NSC储量估算的误差主要来源于NSC浓度的纵向变化,其次是径向变化.喜光树种白桦的树干TNC浓度(1.0%干质量)显著低于耐阴树种紫椴(4.3%干质量),可能与其生活史对策差异有关.采用考虑了树干NSC纵向和径向变化的取样方法,可以有效地降低树木或林分水平上NSC储量估算的不确定性.
Spatial variability of non-structural carbohydrate (NSC) concentrations in the xylem of the trunk xylem after defoliation was studied using two diffuse porous tree species Betula platyphylla and Tilia amurensis in temperate forest of northeastern China.The results showed that the sum of soluble sugar and starch (TNC) and soluble sugar concentration decreased slowly with the increase of tree trunk radial depth, but the radial change of starch was not obvious, and there were still a large number of NSC in the radial direction of tree trunk.The TNC, soluble sugar and The starch concentration decreased from the root of the neck to the chest height and then increased gradually, the height of the maximum appeared to vary with tree species and TNC components.The longitudinal variation trend of the ratio of starch to starch of the two tree species was as follows: Tilia diminish.Therefore, the error of estimation of trunk NSC reserves mainly comes from the vertical change of NSC concentration, followed by the radial change.The TNC concentration (1.0% dry weight) of trunk of Betula luminifera is significantly lower than that of tolerant Tilia amurensis (4.3% dry mass), may be related to the differences in their life history strategies.Using sampling methods that take into account the longitudinal and radial variations of the NSC in the trunk can effectively reduce the uncertainties in estimating NSC reserves at the tree or stand level.