BE/CBC: Coupling of Carbon and Water Cycles in a Cold, Dry Ecosystem: Integrative Physical, Chemical and Biological Processes and their Controls on CO2 Exchange

Welker0221606这项研究工作将量化碳和水循环以及控制寒冷、干燥的陆地生态系统和大气之间碳交换的相互作用的物理、化学和生物(PCB)过程的耦合。他们将重点放在寒冷、干燥的生态系统上，因为：(1)对于这种极端环境来说，对碳和水的相互关系以及净碳交换的了解是最基本的，因此无法预测这一生态系统对预期的人类活动加剧的变暖的脆弱性；(2)这些冻土带系统足够简单，可以量化所有关键组成部分，并开发系统行为概念模型；(3)在这种寒冷、干燥的环境中，非冰冻水的重要作用凸显了阈值和多氯联苯过程之间高度非线性的相互作用的重要性。这些结果将有助于理解和量化全球碳和水循环，以及了解地球上的极端栖息地，可能还包括其他寒冷、干燥的行星体。它们将使用原位同位素方法量化树叶和生态系统尺度上碳和水耦合的季节变化，评估和量化物理、化学和生物过程的季节模式如何相互作用来调节净碳交换的动态，并使用生物地球化学模型研究当前气候和一系列可能的未来气候变化情景下的净二氧化碳交换和复杂的多氯联苯相互作用，并将这些与北极和全球碳收支估计相结合。该计划将基于阐明当前条件下碳和水耦合的复杂性，以及生物、化学和物理过程以及相互作用对冬季和夏季降水和变暖的田间操纵的反应。他们预计，这项研究将对植物和微生物在寒冷、干燥的生态系统中的适应能力以及生态系统中碳和水的耦合性质产生新的见解，这一生态系统与目前对这些过程的大多数理解起源的温带生态系统截然不同。此外，他们希望更准确地了解这个生态系统对未来气候变化的反应程度，以及这些变化对北极和全球碳预算的影响。

Welker0221606This research effort will quantify the coupling of the carbon and water cycles and the interacting physical, chemical and biological (PCB) processes that control C exchange between cold, dry terrestrial ecosystems and the atmosphere. They are focusing on cold, dry ecosystems because: (1) understanding of carbon and water interrelationships and net C exchange is only rudimentary for this extreme environment, making it impossible to predict the vulnerability of this ecosystem to the expected anthropogenically-exacerbated warming; (2) these tundra systems are sufficiently simple allowing the quantification of all key components and the development of a system behavior conceptual model and (3) the vital role of unfrozen water in this cold, dry environment underlies the importance of thresholds and highly nonlinear interactions between PCB processes. Results will contribute to the understanding and the quantification of global carbon and water cycling, as well as to the understanding of extreme habitats on Earth, and possibly on other cold, dry planetary bodies.They will quantify the seasonal changes in the coupling of C and water at the leaf and ecosystem scales using in situ isotopic approaches, evaluate and quantify how the seasonal patterns of physical, chemical and biological processes interact to regulate the dynamics of net C exchange, and use a biogeochemical model to investigate net CO2 exchange and the complex PCB interactions under current climates and a range of likely future climate change scenarios and integrate these with arctic and global carbon budget estimates. The program will be based on articulating the complexities of carbon and water coupling under current conditions, but also on the responses of the biological, chemical and physical processes and interactions in response to field manipulations of winter and summer precipitation and warming. They anticipate that the study will result in a new insight into the adaptations of plant and microbial life in cold, dry ecosystems and the coupled nature of carbon and water in an ecosystem that is very different from more temperate ecosystems where most current understanding of these processes has originated. Furthermore, they expect to gain a more precise understanding of the extent to which this ecosystem responds to future climate change and the consequences of these changes for arctic and global C budgets.