Carbon Dioxide and Water Cycling in Tropical Forests

将在白天和夜间在两个热带雨林（一个季节性森林和一个季节性森林）的不同高度上测定水蒸气和周围二氧化碳的同位素组成和浓度。这些气体的同位素值将与潜在来源的同位素值进行比较：土壤呼吸和大气中的二氧化碳；而土壤蒸发，蒸腾，和大气中的水蒸气。这些测量将回答以下关于亚马逊雨林中二氧化碳和水循环的问题：亚马逊森林中什么水平的土壤剖面为热带树木提供水分？土壤蒸发、蒸腾和大气湿度对森林环境湿度的贡献是什么？被光合作用修复的呼出的二氧化碳的量是多少？光合作用过程中与叶片水分的平衡如何影响环境二氧化碳的氧同位素组成？这些问题的答案将促进我们对世界上最大的连续林分中二氧化碳和水循环动态的了解；亚马逊。

9315697 Sternberg Isotopic composition and concentration of water vapor and ambient carbon dioxide will be determined at various heights in two tropical rain forests, (a seasonal and an aseasonal forest), during the day and night. Isotopic values of these gases will be compared with that of potential sources: soil respiration, and atmospheric for carbon dioxide; and soil evaporation, transpiration, and atmospheric for water vapor. These measurements will answer the following questions about carbon dioxide and water cycling in the Amazonian rain forest: What levels of the soil profile provide water for tropical trees in the Amazonian forest? What is the contribution of soil evaporation, transpiration, and atmospheric moisture to the ambient humidity in the forest? What is the amount of respired carbon dioxide refixed by photosynthesis? How is the oxygen isotopic composition of ambient carbon dioxide influenced by equilibration with leaf water during photosynthesis? The answers to these questions will advance our knowledge on the dynamics of carbon dioxide and water cycling in the largest stand of continuous forest in the world; the Amazon.