Collaborative Research: Biotic alteration of soil hydrologic properties and feedback with vegetation dynamics in water limited ecosystems

合作研究：水有限生态系统中土壤水文性质的生物变化及其与植被动态的反馈[j] . urugesu Sivapalan, Praveen Kumar, Kathleen Lohse, Peter Troch， Enrique Vivoni和Suresh rah .[摘要]土壤性质和相关结构的异质性对土壤水分的储存和利用起着重要的控制作用。水通过表层土壤流动，为临界带的生命提供栖息地和资源。临界带是陆地生物圈的一部分，从根带的底部延伸到冠层的顶部。此外，土壤的结构和性质也不是&amp；#64257；但会动态改变，部分是由居住在其中的生物造成的。土壤特性在控制资源可用性和初级生产方面的重要性构成了生态最优性假说的基础（Eagleson, 1978），该假说认为，随着时间的推移，生物过程会以这样一种方式改变土壤特性，从而提高生态系统的生产力，例如，通过增加土壤的渗透性。和/或增加沙质土壤的保持能力。本项目旨在了解土壤水文特性的生物变化对土壤水分的影响。水限生态系统中Uxes及其与相关植被动态的反馈。该研究的目的是验证一个总体假设，即土壤有机质的输入和大孔隙的发育改变了土壤环境，增加了植物对水和养分的获取，从而减少了植物消耗碳来获取这些资源的需求。我们将使用整体生态水文建模框架严格检查这一假设，并将用观察到的土壤特性测试模型预测。在新墨西哥州和亚利桑那州进行了实地测量。选定的集合&amp；#64257；野外地点，特别是在亚利桑那州，在三个海拔高度成对花岗岩和片岩下的集水区，代表沙漠灌木、橡树林和黄松林。Speci& # 64257;最后，我们将1)发展对新墨西哥州小流域土壤性质的生物介导变化的理解，为生态水文过程的相互作用建立基础；2)然后将土壤性质的生物效应纳入CRS冠层-根系模型中，该模型是另一个NSF项目（ATM 06-28687, PI Praveen Kumar）的一部分，该模型已在许多潮湿地区得到验证，我们现在将使用干旱地区的数据进行验证。3)根据适当的气候强迫和获得的新认识，对水文通量、植被动态和土壤特性进行预测；4)利用土壤结构数据和从几个气候-地形序列（包括亚利桑那州的卡塔利娜山脉的一个）沿线的地点获取的水文数据验证这些预测；5)利用水文制度的概念和现有的全球数据集开发一个解释框架。这项工作将与新成立的美国国家科学基金会资助的亚利桑那大学临界区天文台（特别是旱地生态学专家Travis Huxman， Scott Saleska和David Breshears）合作进行。对审稿人和小组总结评论的回应抽样策略：我们感谢审稿人对现场抽样缺乏细节的评论。共同项目负责人彼得·特罗克和凯瑟琳·洛斯曾与亚利桑那大学的土壤学家克雷格·拉斯穆森博士合作过，克雷格·拉斯穆森博士在这些干旱系统的土壤取样和分析方面有着丰富的经验。作为该项目的第一步，我们将与Rasmussen博士合作设计一个全面的实地采样计划。1-D CRS模型的充分性：我们承认三维空间格局在干旱土壤和生态系统中非常突出和重要。在水文方面，这些环境中的横向再分配主要发生在地表，受空间变化的土壤性质和地形的驱动。然而，一旦土壤被湿润，非饱和带的通量一般是垂直的，除了通过侧根外，几乎没有横向再分布。在考虑地表再分布对入渗的影响的同时，通过对景观上的冠下斑块和冠间斑块分别进行建模，我们相信利用一维模型可以准确地捕获相关的水文通量。与已资助项目ATM 06-28687重叠（PI Praveen Kumar）：确实与这个正在进行的项目重叠。然而，唯一的重叠之处是使用了作为该项目一部分开发的1-D CRS模型。然而，由于这种水、能量、碳和营养物质的综合一维耦合模型的关键作用，这种重叠是不可避免的，而且非常有用。作为先前资助项目的一部分，该模型已经使用来自伊利诺伊州、杜克森林和亚马逊的通量数据进行了验证。剩下的就是利用来自干旱地区（包括新墨西哥州和亚利桑那州）的数据来实施和验证这个模型，以及任何必要的改进。这将作为新项目的一部分来做。关于将不同的小气候对新墨西哥州北坡和南坡的影响从物种效应中分离出来：我们的目的不是将这些山坡视为不同的“处理”，它们与土壤的相互作用可以进行比较。如果是的话，那么很明显，不同的辐射输入将是一个混淆因素。然而，我们在这里看到了一个机会：我们认为，由于不同的小气候，两个山坡上的植被和土壤是不同的。从这个更广阔的角度来看，我们可以比较它们的小气候如何导致不同植被类型和策略的优势，以及它们对随后土壤发育的综合影响。Vivoni支持信：由于Vivoni博士正在从新墨西哥理工大学转到亚利桑那州立大学的过程中，我们在申请的时候无法获得这份支持信。我们将努力从他那里得到这封信，我们将在接下来的几天里转交给你。

Collaborative research: Biotic alteration of soil hydrologic properties and feedback with vegetation dynamics in water limited ecosystemsMurugesu Sivapalan, Praveen Kumar, Kathleen Lohse, Peter Troch, Enrique Vivoni and Suresh RaoAbstractHeterogeneity of soil properties and associated structure exert major controls on the storage and fluxes of water through the surface soils and provide habitat and resources for life in the critical zone - that part of the terrestrial biosphere extending from the bottom of the root zone to the top of the canopy. Also, soil structure and properties are not fixed, but are altered dynamically, in part by the organisms that inhabit it. The importance of soil properties in controlling resource availability and primary production formed the basis of the ecological optimality hypothesis (Eagleson, 1978) that biological processes alter soil properties over time in such a way that increases ecosystem productivity, e.g., by increasing the permeability of fine soils, and/or increasing the retention capacity of sandy soils. This project aims to understand the role of biologic alterations of soil hydrologic properties on soil moisture fluxes and the feedback with associated vegetation dynamics in water limited ecosystems. The objective is to test the overarching hypothesis that alteration of the soil environment by inputs of soil organic matter and the development of macropores increases the access of plants to water and nutrients and thus reduces the need for plants to expend carbon to access those resources. We will critically examine this hypothesis using a holistic ecohydrologic modeling framework, and will test model predictions of soil properties with observed field measurements in New Mexico and Arizona. The collection of chosen field sites, especially in Arizona, pairs granitic and schist-underlain catchments at three elevations representing desert shrub, oak woodland and ponderosa pine forest. Specifically, we will 1) develop understanding of biologically mediated alteration of soil properties in a small New Mexico watershed to establish a foundation for the interaction of ecohydrologic processes, 2) then incorporate biotic effects of soil properties into the CRS canopy-root-system model being developed as part of another NSF project (ATM 06-28687, PI Praveen Kumar), which has been validated in a number of humid sites, and which we now will validate using data from arid sites, including the New Mexico site, 3) generate predictions of hydrologic fluxes, vegetation dynamics and soil properties based on appropriate climate forcing and the new understanding gained, 4) validate these predictions using soil structure data and hydrologic data taken from sites located along several climo-topo-sequences, including one in the Catalina Mountains in Arizona, and 5) develop an interpretive framework using the concept of hydrologic regimes and available global data sets. The work will be conducted in partnership with the new NSF-funded Critical Zone Observatory at the University of Arizona (especially arid-land ecology specialists Travis Huxman, Scott Saleska and David Breshears). Responses to Comments of Reviewer and Panel Summaries1. Sampling strategy: We appreciate the comments of the reviewers about the lack of details on the field sampling. The co-PIs Peter Troch and Kathleen Lohse have a history of collaborating with pedologist Dr Craig Rassmussen of the University of Arizona, who has considerable experience in soil sampling and analysis in these arid systems. We will collaborate with Dr Rasmussen to design a comprehensive field sampling program as one of the first steps in the project.2. Adequacy of the 1-D CRS model: We accept that 3-dimensional spatial patterns are very prominent and very important in arid soil and ecosystems. Hydrologically, lateral redistribution in these environments occurs mainly on the surface, driven by spatially variable soil properties and topography. However, once the soil is wetted, unsaturated zone fluxes are generally vertical, with little lateral redistribution, except through lateral roots. By separately modeling under-canopy and between-canopy patches on the landscape, while accounting for the surface redistribution effects on infiltration, we believe it will be possible to accurately capture the relevant hydrologic fluxes using the 1-D model.3. Overlap with funded project ATM 06-28687 (PI Praveen Kumar): There is indeed an overlap with this ongoing project. The only overlap is however the use of the 1-D CRS model that has been developed as part of that project. However, due to the crucial role of this comprehensive 1-D coupled model of water, energy, carbon and nutrients, this overlap is inevitable and highly useful. As part of the previously funded project the model has been validated using flux data from Illinois, Duke Forest, and the Amazon. What remains is to implement and validate this model, and any needed refinements, using data from arid sites, including in New Mexico and Arizona. This will be done as part of the new project.4. On separating the effects of differing microclimates on the north and south-facing hillslopes at the New Mexico site from species effects: Our aim is not to consider these hillslopes as different 'treatments' whose interaction with the soils can be compared. If we were, then clearly the different radiation inputs would be a confounding factor. However, we see an opportunity here: we consider that the vegetation and soils on the two hillslopes are different as a result of the different microclimates. In this broader perspective, we can therefore compare how their microclimates may have led to the dominance of contrasting vegetation types and strategies and their combined effect on consequent soil development.5. Vivoni letter of support: we could not obtain this letter of support at the time of application because Dr Vivoni was in the middle of a move from New Mexico Tech to Arizona State University. We will endeavor to obtain this letter from him, which we will be forwarding to you in the next few days.