落叶作为热带雨林水分亏缺适应对策的研究:以西双版纳热带雨林为例

Leaf shedding as an adaptive strategy for water deficit: a case study in Xishuangbanna's rainforest

研究通过西双版纳热带雨林中连续7年(2003—2009)的生态系统监测数据,探讨了土壤水分亏缺的季节和年间波动对冠层叶片物候的影响.研究表明西双版纳热带雨林冠层物候具有明显的季节构型,叶片在土壤水分亏缺最严重的旱季末期发生集中凋落.并且,叶片的凋落主要发生在冠层高度超过20 m的冠层上部,冠层下部以及林下植物则为常绿状态.同时发现叶片凋落量存在较大的年间波动,进一步分析表明,土壤水分亏缺的年间动态是造成这种波动的主要原因.最后,对西双版纳热带雨林叶片物候动态,进行了成本-收益分析.分析的结果进一步确认了水分亏缺是造成该森林季节性落叶的主因.研究从生态系统的尺度上,对冠层叶片物候动态进行了研究,是一种全新的尝试.同时,也为多年以来,关于西双版纳热带雨林落叶原因的争议,提供了具体的科学数据.

Seven years （2003--2009） ecosystem -level monitoring data was collected to examine how seasonal and inter - annual soil water deficit affect the canopy leaf phenology in a tropical rainforest of Xishuangbanna, China. This study found that ： there is distinctive seasonal pattern of canopy leaf phenology in the studied for- est. Intensive leaf shedding occurred in the latter dry season when peaked in soil water deficit and evaporation demand. Moreover,leaf - shedding mainly occurred in canopies higher than 20 m. There was no obvious intensive leaf - shedding in canopy between 5 and 20 m during dry season. A close positive relationship was found between leaf - shedding amount and cumulative soil water deficit at inter - annul scale. Leaf - shedding amount was higher in the dry year. A cost - benefit analysis indicated that shedding leaves during the driest period was a good way for canopy carbon gain. Therefore, the leaf shedding was regarded as an adaptive strategy for water deficit in Xishuangbanna tropical rainforest.