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

大气中二氧化碳浓度的上升可能会对陆地生态系统造成严重后果。这些影响通常是从对植物碳吸收和损失的直接影响的角度来考察的。然而，二氧化碳水平的升高可能会通过间接影响导致本地和作物生态系统的性能发生重大变化，包括对水和养分等其他资源的吸收和使用。在大多数本土生态系统中，水是最有限的资源。因此，二氧化碳水平上升对植被对水分的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。到目前为止，有一些证据表明，高二氧化碳可能会降低叶片对失水的抵抗力，但对土壤中、通过植物和大气的其他水流成分的潜在变化知之甚少。这项拟议的研究将审查大气二氧化碳预计上升对一些森林和作物物种的影响。更具体地说，将检查对根的水力传导性的影响，这通常是水流动的主要障碍。初步结果和理论考虑表明，高CO2可能会导致根系对水分的吸收和运输能力发生显着变化。这项拟议的研究还将研究最能解释为什么二氧化碳会影响根系水分运输特性的机制(S)。这些结果将对植物和生态系统对未来气候的生长响应模型具有重要的实用价值。这项研究还旨在确定物种反应的潜在差异，从而从机制上理解二氧化碳对生物多样性和种群动态的更大规模生态过程的影响。最后，这项研究将邀请K-12和本科生参与这项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.