Controls on carbon exchange in Boreal ecosystems

要从机制上理解碳交换的生物物理控制，就必须研究年际和年际气候趋势如何影响地表-大气交换。拟议的研究将量化寒带生态系统与大气之间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林和泥炭地生态系统上，将使用微气象方法连续测量基于塔的二氧化碳通量数年。这两个地点彼此相距几公里，因此受到相同的环境条件的影响。光利用效率（LUE）将从基于塔的吸收光合有效辐射和总生态系统生产力的测量中得出。将使用微气象和生物物理变量集调查环境控制对每个站点LUE变化的影响。在不同的空间尺度上，遥感植被指数与LUE存在相关性。因此，通量的升级将通过结合遥感技术来实现。安装在塔上的辐射计将用于提供植被指数的高分辨率连续测量。将从这些实地测量中发展植被指数与塔基通量之间的关系。地面算法将应用于可比较的卫星指数，从而产生生态系统尺度的碳交换估计。这项研究的目的是增加对在瞬时、季节、年度和年际等时间尺度上驱动大气生态系统C交换的关键过程和环境强迫的认识。关于生态系统生理反应的详细信息可以进一步用于修改和验证生态系统模型，从而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.