Responses of Root Hydraulic Conductivity to Elevated CO2: Patterns and Mechanisms

大气中二氧化碳浓度上升可能对陆地生态系统造成严重后果。这些影响通常是根据对植物碳吸收和损失的直接影响来研究的。然而，二氧化碳水平升高可能通过间接影响，包括水和养分等其他资源的吸收和利用，导致本地和作物生态系统的性能发生重大变化。在大多数原生生态系统中，水是最有限的资源。因此，CO2水平的上升对植被水分吸收和利用的任何影响都将影响植物和生态系统的生产力，并影响水文生物圈-大气反馈。迄今为止，有一些证据表明，二氧化碳浓度升高可能会降低树叶对水分流失的抵抗力，但对土壤内、植物和大气中水流的其他组成部分的潜在变化所知甚少。拟议的研究将检查预计大气中二氧化碳的增加对许多森林和作物物种的影响。更具体地说，将研究对根系水力导电性的影响，这通常构成水流的主要障碍。初步结果和理论上的考虑表明，高CO2浓度可能导致根系对水分的吸收和运输能力发生显著变化。拟议的研究还将检验可能最好地解释为什么二氧化碳会影响根系水分运输特性的机制。这些结果将对植物和生态系统生长对未来气候的响应模型具有重要的实用价值。该研究还旨在确定物种响应的潜在差异，从而为二氧化碳对生物多样性和种群动态的更大范围生态过程的影响提供机制理解。最后，本研究将吸引K-12以及本科生参与本研究的概念和实验方面。

Rising atmospheric CO2 concentration could have serious consequences for terrestrial ecosystems. These effects are often examined in terms of direct influences on carbon uptake and losses by plants. However, elevated levels of CO2 may result in significant changes in performances of native and crop ecosystems via indirect effects involving uptake and usage of other resources such as water and nutrients. In most native ecosystems, water is the most limiting resource. Therefore, any impact of rising CO2 level on water uptake and usage by vegetation will affect plant and ecosystem productivity as well as affecting the hydrologic biosphere-atmosphere feedbacks. To date, there is some evidence that elevated CO2 may reduce foliage resistance to water loss but considerably less is known about potential changes in other components of water flow within the soil, through the plant and to the atmosphere. The proposed study will examine the effects of projected rise in atmospheric CO2 on a number of forest and crop species. More specifically, effects on root hydraulic conductivity which often constitutes a major barrier to water flow will be examined. Preliminary results along with theoretical considerations indicate that high CO2 may result in a significant change in root uptake and transport capacity of water. The proposed study will also examine the mechanism(s) that may best explain why CO2 would affect root water transport properties. The results will have significant utility for models of plant and ecosystem growth responses to future climates. The study is also designed to determine potential differences in species responses thus providing a mechanistic understanding of CO2 affect on the larger scale ecological processes of biodiversity and population dynamics. Finally, the study will engage K-12 as well as undergraduate students in conceptual and experimental aspects of this research.