研究通过西双版纳热带雨林中连续7年(20032009)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.
英文摘要:
Seven years (20032009) 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 forest. 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.