基于空间变异性的树冠非结构性碳含量估算:以胡桃楸和春榆为例

Estimating nonstructural carbon content of tree crown considering its spatial variability: A case study on Juglans mandshurica and Ulmus japonica

以胡桃楸和春榆为例,采用枝解析法测定不同基径枝条的非结构性碳水化合物（NSC）浓度的变异,进而估算并评价不同取样方法对树冠NSC含量估算的误差.结果表明：器官对两种树种树冠NSC浓度的影响显著,叶、新枝、老枝和死枝的可溶性糖与淀粉的总和（TNC）的平均浓度分别为17.6%、12.6%、5.7%和2.9%.叶和新枝的NSC浓度随枝基径、枝龄、枝长和枝相对高度的变异多不显著,但老枝的NSC浓度随枝基径、枝龄和枝长增大而降低,而随枝相对高度增加而增加,其中枝基径是老枝NSC浓度的最佳预测变量（R2在0.87-0.95）.两树种叶、新枝和老枝平均TNC含量分别占其树冠TNC含量的28%、2%和70%.分析树冠枝NSC的空间变异性对树冠NSC含量估算误差的影响发现,采用新枝和直径约3 cm老枝枝段的NSC浓度估算冠层NSC含量是较简易而精确的方法.

Using Juglans mandshurica and Ulmus japonica as test materials,we examined the variability in nonstructural carbohydrates（ NSC） concentrations in the branches with different basal diameters with a branch analysis method and explored potential errors in estimating the crown-scale NSC content introduced from various sampling protocols. The results showed that organs significantly influenced the crown NSC concentrations for both species. The mean concentrations of the sum of soluble sugars and starch（ TNC） of the leaves,new twigs,old branches,and dead branches were17. 6%,12. 6%,5. 7% and 2. 9%,respectively. Most of the NSC concentrations in leaves and new twigs varied insignificantly with basal diameter,age,length and height of the branch. However,the NSC concentration in old branches increased significantly with decreasing the basal diameter,age and length of the branch,and with increasing the relative height of the branch. Among the branch traits,basal diameter was the best predictor for the NSC concentration of the old branch（ the R2 between 0. 87 and 0. 95）. The mean TNC contents of leaves,new branches,and old branches for the two species accounted for 28%,2% and 70% of the crown TNC content,respectively.Considering the effect of the spatial variability in the estimation of NSC content,we recommend the sampling protocol that applies the NSC concentration of new twigs and old branches with a diameter of 3 cm to up-scale the crown NSC content as a simple and practical method.