Controls on carbon exchange in Boreal ecosystems

要从机制上理解生物物理对碳交换的控制，就必须研究年内和年际气候趋势如何影响地表-大气交换。这项拟议的研究将量化北方生态系统和大气之间的二氧化碳净生态系统交换的动态。在北方森林东部詹姆斯湾地区的黑云杉森林和泥炭地生态系统上，将使用微气象方法连续几年测量基于塔的二氧化碳通量。这两个现场位置彼此相距几公里内，因此受到相同的环境条件的影响。光能利用效率(LUE)将通过对吸收的光合作用有效辐射和总生态系统生产力的塔式测量得出。将使用一组微气象和生物物理变量来调查环境控制对每个地点LUE变化的影响。遥感植被指数已被证明在各种空间尺度上与LUE相关。因此，通量的放大将使用遥感技术的组合来实现。安装在塔上的辐射计将用于提供高分辨率的植被指数连续测量。植被指数和基于塔的通量之间的关系将从这些现场测量中得到发展。地面算法将应用于可比的基于卫星的指数，从而产生碳交换的生态系统规模估计。这项研究旨在提供更多关于推动大气生态系统碳交换的关键过程和环境作用力的知识，时间尺度从瞬时、季节性、年度到年际不等。关于生态系统生理反应的详细信息可进一步用于修改和验证生态系统模型--成为研究对气候变化的反应的工具。

A mechanistic understanding of the biophysical controls on carbon exchange necessitates a study of how intra- and inter-annual climate trends affect surface-atmosphere exchanges. The proposed research will quantify the dynamics of net ecosystem exchange of carbon dioxide between a boreal ecosystem and the atmosphere. Tower-based fluxes of CO2 will be continuously measured using micrometeorological methods over a black spruce forest and peatland ecosystem for several years in the eastern James Bay region of the boreal forest. The two field locations are located within several kms of each other and are therefore subjected to the same environmental conditions. Light use efficiency (LUE) will be derived from tower-based measurements of absorbed photosynthetically active radiation and gross ecosystem productivity. The influence of environmental controls on the variation in LUE at each site will be investigated using the set of micrometeorological and biophysical variables. Remotely sensed vegetation indices have been shown to be correlated with LUE at a variety of spatial scales. Upscaling of fluxes will therefore be accomplished using a combination of remote sensing techniques. Tower-mounted radiometers will be used to provide high resolution continuous measurements of vegetation indices. Relationships between vegetation indices and tower-based fluxes will be developed from these field measurements. Ground based algorithms will be applied to comparable satellite-based indices resulting in ecosystem scale estimates of carbon exchange. The research is designed to provide increased knowledge of the critical processes and environmental forcings which drive the atmosphere ecosystem C exchange on time scales ranging from instantaneous, seasonal, annual through inter-annual. Detailed information on ecosystem physiological responses can further be used to modify and validate ecosystem models - becoming tools for studying responses to changing climate.