SGER: Branch Carbon Balance and Allocation During an Extreme El Nino and La Nina in a Wet Neotropical Forest

马尔基9805908 在许多热带地区，厄尔尼诺南方涛动（ENSO）导致干燥，阳光明媚的年份（厄尔尼诺）与潮湿，多云的年份（拉尼娜）交替。在阳光年际变化的背景下，我们将记录ENSO对树木生产力的影响，通过操纵两个湿林冠层树种的树枝的碳收支。这将通过增加树冠中的光照和在碳增益的关键时期对实验树枝上最近一批叶子进行遮光来实现。照明将增加与体育场灯竖立在塔以上的天篷和发电机供电，而阴影将提供遮阳布。将从大型独立式起重机进入顶篷。在实验期间和之后的碳分配将从光合作用，非结构性碳水化合物的变化和生殖输出的措施进行评估。分支碳平衡的经验模型将被用来评估综合碳增益和补偿反应的操作分支，并将这些数据与碳水化合物积累在分支木材。除了记录这一全球气候事件对树木生产力的作用外，这项工作还将测试雨季云层覆盖限制雨林生产力的假设。

Mulkey 9805908 In many parts of the tropics, the E1 Nino Southern Oscillation (ENSO) causes dry, sunny years (E1 Nino) alternating with wet, cloudy years (La Nina). Against this background of interannual variation in sunlight, we will document the effect of ENSO on tree productivity by manipulating carbon budgets of branches of two wet-forest canopy tree species. This will be accomplished through augmentation of light in the canopy and shading of the most recent crop of leaves on experimental branches during critical periods for carbon gain. Light will be augmented with stadium lamps erected on towers above the canopy and powered by a generator, while shading will be provided with shade cloth. The canopy will be accessed from a large, freestanding crane. Carbon allocation during and following experimental periods will be assessed from photosynthesis, variation in nonstructural carbohydrate, and measures of reproductive output. An empirical model of branch carbon balance will be used to assess integrated carbon gain and compensatory responses of manipulated branches, and relate these data to carbonhydrate accumulation in branch wood. In addition to documenting the role of this global climate event on tree productivity, this work will test the hypothesis that wet-season cloud cover limits the productivity of rainforests.