Dissertation Research: Does Hydraulic Redistribution Increase Microbial Activity in the Rhizosphere?

论文研究：水力再分配是否增加了微生物在淡水界的活动？Z.G.公司Cardon和P.M. Herron单个植物的根系可以跨越土壤的深度，表现出很强的水分梯度。通常，在干旱地区，表层土壤干燥，深层土壤湿润。 这种水分梯度提供了一种驱动力，使水分通过根系从较深的土壤被动地重新分布到较浅的、养分丰富的土壤中，通常是在夜间。 这种“水力再分配”现在在全世界近60个物种中得到承认，并已被证明可以增加蒸腾速率，增加邻近植物的生长，并改变整个地区的水文。 已经出现了一些假设，重点是水分的水力再分配到浅的，营养丰富的土壤层，以维持土壤微生物活性的潜在重要性，从而可能提高养分的可用性，植物根系周围。该项目探讨了水力再分配以及由此产生的水资源可用性模式是否会影响根际微生物生物量、生长速率和活性。 我们将测试是否植物根系周围的养分循环，以及植物的养分有效性，通过温室和田间的水力再分配得到增强。 重点植物种类是山艾树（蒿tridentata），一个根深蒂固的灌木，往往是一个社区占主导地位的半干旱，在美国西部景观在野外工作中，我们将探讨水力再分配和蒿属的生殖适合度之间的关系;在温室里，我们将使用基因工程土壤细菌来报告土壤水势，根周围有微米和毫米级的鳞片。 在温室和田间，将使用标准土壤分析和土壤湿度计来跟踪微生物活动和土壤湿度。 本研究的结果将揭示深根蒿影响半干旱系统浅层土壤养分动态和水分含量的机制。

Dissertation Research: Does Hydraulic Redistribution Increase Microbial Activity in the Rhizosphere?Z.G. Cardon and P.M. Herron The root systems of single plants can span a depth of soil exhibiting strong gradients of water availability. Often, in arid regions, dry soils are found at the surface and moister soils at depth. This gradient of water availability provides a driving force for the passive redistribution of water through the root systems from the deeper soils to the shallow, nutrient rich soils, usually at night. Such "hydraulic redistribution" is now recognized in almost 60 species worldwide, and has been shown to increase rates of transpiration, increase growth in neighboring plants, and alter the hydrology of entire regions. A number of hypotheses have emerged focusing on the potential importance of hydraulic redistribution of water into the shallow, nutrient-rich soil layers for maintenance of soil microbial activity, and thus potentially enhanced nutrient availability, around plant roots. This project explores whether hydraulic redistribution, and resulting patterns of water availability, affect rhizosphere microbial biomass, growth rates, and activity. We will test whether nutrient cycling around plant roots, and nutrient availability to plants, are enhanced by hydraulic redistribution in the greenhouse and in the field. The focal plant species is sagebrush (Artemisia tridentata), a deep-rooted shrub that is often a community dominant in semi-arid, western landscapes in the U.S. In field work, we will explore the relationship between the presence of hydraulic redistribution and the reproductive fitness of Artemisia; in the greenhouse, we will use soil bacteria that are genetically engineered to report soil water potentials to provide the first glimpse of soil water potentials at micro- and millimeter scales around roots. In both the greenhouse and the field, standard soil assays and soil psychrometers will be used to track microbial activity and bulk soil moisture. Results from this study will suggest mechanisms by which deep-rooted Artemisia tridentata can affect nutrient dynamics and water contents in shallow soils of semi-arid systems.