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

在热带的许多地区，厄尔尼诺-南方涛动（ENSO）导致干燥、晴朗的年份（厄尔尼诺）与潮湿、多云的年份（拉尼娜）交替发生。在这种日照年际变化的背景下，我们将通过操纵两种湿林冠层树种树枝的碳收支来记录ENSO对树木生产力的影响。这将通过增加树冠的光照和在碳获取的关键时期对实验树枝上最近收获的叶子进行遮荫来实现。灯光将通过安装在天篷上方的塔上的体育场灯来增强，并由发电机供电，而遮阳将由遮阳布提供。顶篷将从一个大型的独立式起重机进入。从光合作用、非结构性碳水化合物的变化和生殖产量的测量来评估试验期间和之后的碳分配。树枝碳平衡的经验模型将用于评估综合碳增益和补偿响应，并将这些数据与树枝木材中的碳水合物积累联系起来。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.