西双版纳片断化热带雨林常绿乔木幼树水分利用效率的边缘效应研究

EDGE EFFECTS OF PLANT WATER USE EFFICIENCY INDICATED BY FOLIAR δ^(13) C VALUE IN A FRAGMENTED SEASONAL RAINFOREST IN XISHUANGBANNA

以植物叶片 δ1 3 C值为植物水分利用效率的指示值 ,通过研究一个片断化森林方位对常绿乔木幼树叶片δ1 3C值的影响以及对各样线上从林缘到林内不同取样点植物叶片δ1 3 C值的影响 ,探讨了片断化森林方位对植物长期水分利用效率边缘效应的影响。研究结果显示 :城子龙山林常绿乔木幼树叶片δ1 3C值的范围为 - 35 .32‰～ -2 7.6‰ ,平均值为 - 31.6 0 1‰± 0 .148‰ ;城子龙山林不同方位样线上叶片δ1 3 C值之间存在显著差异 ,其中 ,城子西样线叶片δ1 3C的平均值高于城子北和城子东样线叶片δ1 3C平均值 ;在距林缘 0～ 10 m处 ,东、西、南、北四方位叶片δ1 3C值差异极显著 ,而在距林缘 2 0～ 30 m,5 5～ 6 5 m和 95～ 10 5 m处则差异不显著。这表明 :对该研究地点的常绿乔木幼树而言 ,东、西、南、北 4方位相比 ,边缘的产生对西面植物水分利用效率的影响最大 ,而北面则最小 ;方位对植物水分利用效率影响的范围至少进入林内约 10 m;方位对边缘效应的影响的确存在 。

Using foliar δ 13 C value as an indicator of plant water use efficiency (WUE), we tested the effects of exposure at forest edges facing each of four different aspects on evergreen tree seedling leaves in a fragmented rainforest in Xishuangbanna, Yunnan. In the edge transects, foliar δ 13 C value ranged from -35 32‰ to -27 6‰, averaging -31 6‰±0 15‰. There were significant differences between the average foliar δ 13 C values of the four aspects, with the western aspect higher than those of the northern and eastern aspects of the forest. At sampling areas 0-10 m from the forest edge, the foliar δ 13 C value differed significantly among the four aspects, however at distances of 20-30 m, 55-65 m and 95-105 m from the edge differences were no longer significant. These results indicate that the effect of forest edges on WUE was the largest in the western and the smallest in the northern aspects and that the distance of edge effects on plant water use efficiency was at least 10 m in from physical edges. Therefore we conclude that the influence of aspect should not be neglected when investigating the edge effects on plant species in fragmented forests.