Dynamics of Carbon Export to the Atmosphere and Oceans from Fluvial Systems of the Humid Tropics: Southeast Asia

摘要在这项提案中，我们要解决的总体问题是：“在潮湿热带地区的碳循环中，二氧化碳从河流系统向大气的逃逸(放气)相对于向海洋输出的河流碳起到了什么作用？”我们最近证明，亚马孙流域中部河流和湿地的二氧化碳排放量为1.2 0.3 mg C ha-1 y-1，或者，当在整个流域外推时，比河流向海洋输出的有机碳大一个数量级。这样的流量将是一个重要的损失，因为它大约相当于亚马逊地区碳封存的较低估计。这些结论导致了这一提议的工作假设，即地表水二氧化碳逃逸是潮湿热带河流系统碳损失的主要来源(超过向海洋出口的10倍)，总体上协调了热带地区在全球碳收支中的作用。逃避主要是由有机碳的流内呼吸驱动的，有机碳从陆地和河岸来源在空间和时间上转移。虽然亚马逊地区的估计受到了更好的限制，但热带其他地区的估计却并非如此，特别是在人为影响更大的地区。通过这一提议，我们打算将我们基于亚马逊的工作假说扩展到另一个重要的地区，东南亚。我们建议(1)改进现有的模型，根据地形条件改进水的路线和淹没、沉积物和碳模块，(2)进行实地采样活动，以确定区域特定的过程并为模型验证提供数据，以及(3)使用由此产生的改进模型来分析有关东南亚河流环境中碳动态的问题，这将检验我们的工作假设。我们建议的最重要的智力优点是(1)全球碳循环中的一个显著异常正在得到解决，以及(2)这项工作代表了地球科学历史上不同路线的汇聚，形成了陆地-水-大气耦合过程和程度的全球重要性的重要“新”观点。这项工作最重要的更广泛的影响很可能来自改善工具和信息网络，以便在一个面临多重跨界环境压力的区域实现“可持续性”。

AbstractThe overall question we are addressing in this proposal is, "What role does the evasion (outgassing) of CO2 from the river system to the atmosphere play relative to fluvial carbon export to the ocean in the carbon cycle of the humid tropics?" We have recently demonstrated that outgassing of CO2 from rivers and wetlands of the central Amazonian basin is 1.2 0.3 Mg C ha -1 y -1 , or, when extrapolated across the entire basin, an order of magnitude greater than fluvial export of organic carbon to the oceans. Such a flux would be an important loss, as it is approximately equal to lower estimates of carbon sequestration in the Amazon. These conclusions lead to the working hypothesis for this proposal, that Surface water CO2 evasion is the dominant source of carbon loss (exceeding export to the oceans by a factor of 10) in fluvial systems of the humid tropics, and in the aggregate reconciles the tropics in the global carbon budget. Evasion is driven primarily by in-stream respiration of organic carbon translocated in space and time from its terrestrial and riparian origins. While estimates are becoming better constrained in the Amazon, they are not elsewhere in the tropics, particularly in regions of much greater anthropogenic impact.With this proposal we intend to extend and test our Amazon-based working hypothesis to another significant region, Southeast Asia. We propose to (1) enhance an existing model with improved water routing and inundation, sediments, and carbon modules as a function of landscape condition, (2) conduct a field sampling campaign to determine region-specific processes and provide data for model validation, and (3) use the resulting improved model to analyze questions concerning the dynamics of carbon in the fluvial environments of Southeast Asia which will test our working hypothesis.The most significant intellectual merit of our proposal is (1) that a significant anomaly in the global carbon cycle is being addressed, and (2) the work represents a convergence of historically separate lines of earth science into a significant "new" view of the global importance of the processes and magnitudes of land-water-atmosphere coupling. The most important broader impact of the work will most likely come via improved tools and information networks for "sustainability" in a region of multiple transboundary environmental pressures.