Grassland-Atmosphere Interactions: Analyses Using Coupled Ecophysiological, Ecosystem, Micrometeorology, and Mesoscale Atmospheric Models

本研究旨在发展草地生态系统对与温室气体（特别是二氧化碳）水平增加相关的大气变化的响应的数值评估能力。目前，我们进行这些评估的能力至少有三个主要缺陷。首先是缺乏针对草原上的二氧化碳暴露实验进行校准和测试的计算机模型。因此，这项研究的一个重点将是与正在堪萨斯州进行实地暴露研究的科学家合作。现有的草地生态系统功能和植物对二氧化碳和天气的响应模型将用于此目的。其次，忠实地代表当前对植物生理学理解的模型必须与代表土壤过程（如分解、养分循环和水储存和流动）的模型相结合，以了解整个生态系统如何响应大气变化。例如，养分循环速率可能会限制植物生长对二氧化碳升高的积极反应。相关的最先进的植物生理和土壤过程模型将在拟议的研究中使用。第三，陆地生态系统与大气的水、碳和能量交换过程对生态系统对大气变化的响应具有潜在的重大影响，但在过去的模拟研究中尚未得到充分的研究。这项研究将把生态和大气模式联系起来，以评估大气过程的作用，特别是水汽和能量的大尺度通量。这些结果将通过改变植物的水分利用效率和养分循环速率反馈到植物生长上。将这些不同的模型联系起来，探索草原、气候以及气候与草原之间的相互作用。

9524129 Coughenour This research is to develop capabilities for numerically assessing the responses of grassland ecosystems to atmospheric changes associated with increasing levels of greenhouse gases, particularly carbon dioxide (CO2). Currently, there are at least three major deficiencies in our abilities to perform these assessments. The first is a lack of computer models which have been calibrated and tested against field CO2 exposure experiments in grasslands. Accordingly, a focus of this research will be to collaborate with scientists working on an ongoing field exposure study in Kansas. An existing model of grassland ecosystem function and plant responses to CO2 and weather will be used for this purpose. Secondly, models that faithfully represent current understanding of plant physiology must be coupled with models that represent soil processes such as decomposition, nutrient cycling and water storage and flows to understand how whole ecosystems respond to atmospheric change. For example, it is possible that nutrient cycling rates will constrain otherwise positive plant growth responses to elevated CO2. Linked state-of-the-art plant physiological and soil process models will be employed in the proposed research. Thirdly, terrestrial ecosystem processes of water, carbon and energy exchange with the atmosphere have potentially significant effects on ecosystem responses to atmospheric change but have been poorly examined in past modeling research. This research will link ecological and atmospheric models to assess the role of atmospheric processes, particularly large-scale fluxes of water vapor and energy. These results will feedback onto plant growth through altered plant water use efficiency, and resultant responses of nutrient cycling rates. Grasslands, climate, and the interactions between climate and grasslands will be explored through linking these various models.