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

马尔基9805908在热带的许多地区，厄尔尼诺南方涛动(ENSO)导致干旱、晴朗的年份(厄尔尼诺)和潮湿、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，我们将通过控制两种湿林树种树枝的碳收支来记录ENSO对树木生产力的影响。这将通过在获得碳的关键时期增加树冠上的光照和对实验树枝上最新的叶子进行遮荫来实现。灯光将通过安装在天篷上方的塔楼上并由发电机供电的体育场灯具来增强，而遮阳将用遮阳布提供。天篷将从一台大型独立起重机上进入。在实验期间和之后的碳分配将通过光合作用、非结构性碳水化合物的变化和生殖产出的测量来评估。树枝碳平衡的经验模型将被用来评估被操纵的树枝的综合碳增益和补偿响应，并将这些数据与碳水化合物在树枝中的积累联系起来。除了记录这一全球气候事件对树木生产力的影响外，这项工作还将检验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.