兴安落叶松天然林新老枝叶光合能力及水分利用效率研究

【目的】兴安落叶松林是我国大兴安岭地区顶级植被,每年长出的新枝和老枝间有明显的特征差异,而这种差异可能会引起新枝叶和老枝叶光合能力及水分利用效率的差异。笔者探究新枝叶和老枝叶间光合能力的差异,分析兴安落叶松光合能力对环境变化的响应,以准确估算大兴安岭地区顶级群落的光合及水分利用情况。【方法】于2016年6—9月在黑龙江漠河森林生态系统定位研究站对不同分化等级的兴安落叶松新枝叶和老枝叶的光合能力(P_n,max)、蒸腾速率(T_r)、水分利用效率(C_WUE)等指标进行测定。【结果】兴安落叶松新枝叶和老枝叶平均P_n,max分别为5.654和3.248 μmol/(m²·s),平均T_r分别为1.291和0.779 μmol/(m²·s),新枝叶P_n,max和T_r分别比老枝叶高74.1%和65.7%。新枝叶和老枝叶平均C_WUE分别为5.077 和4.762 μmol/mmol,新枝叶比老枝叶高6.61%。【结论】兴安落叶松林各分化等级间P_n,max、T_r和C_WUE均差异不显著(P>0.05); 但新枝叶及老枝叶的P_n,max和T_r均表现为差异极显著(P<0.01),新枝叶和老枝叶平均C_WUE则差异不显著(P>0.05),仅6月中旬与其他月份间C_WUE差异极显著(P<0.01)。因此,兴安落叶松新老枝叶在光合能力和蒸腾速率上存在较大差异,而水分利用效率的差异较小。

A study on new and old branch's leaf photosynthetic capacity and water use efficiency of natural Larix gmelinii forest in the northern Great Xing'an Mountains

【Objective】Larix gmelinii is the climax vegetation in the northern Great Xing'an Mountains. The pronounced differences between new and old branches may cause significant variations of photosynthetic capacity and water use efficiency. Exploring the difference of photosynthetic capacity between new branch and old branch and the response of photosynthetic capacity of L. gmelinii can definitely help to accurately estimate the photosynthetic capacity and water use efficiency of the climax vegetation in Great Xing'an Mountains.【Method】The leaf photosynthetic capacity(P_n,max), transpiration rate(T_r)and water use efficiency(C_WUE)of the new and old branches of different differentiation grade L. gmelinii were examined in the study site of Mohe Forest Ecosystem Research Station from June to September in 2016.【Results】The results showed that the average P_n,max of new and old branches were 5.654 and 3.248 μmol/(m²·s), The average T_r were 1.291 and 0.779 μmol/(m²·s)respectively. The P_n,max and T_r of new branch were 74.1% and 65.7% higher than those of the old branch. The C_WUE of new branch was 6.61% higher than that of the old branch with the average values of 5.077 and 4.762 μmol/mmol, respectively. 【Conclusion】The analysis indicated that the differences of P_n,max and T_r between new and old branches were significant(P<0.01). The difference of average C_WUE between new and old branches was not statistically significant(P>0.05), although the C_WUE in June was significantly(P<0.01)different from those in the other months. Thus, we concluded that the P_n,max and T_r of L. gmelinii between new and old branches exhibited great differences, while the difference of C_WUE was much small.