CAREER: The Role of Ecosystem Rooting Depth in Predicting Global Carbon and Water Fluxes

摘要该项目将执行一项为期五年的研究、教学和推广计划，该计划将结合生态学、全球变化和科学教育的长期利益。该研究考察了根系分布，特别是深层根系对陆地生态系统中碳和水循环的重要性。需要验证的假设包括：1)深根灌木在草原的引入有助于植被和土壤中超过草原最大生根深度的碳储存。2)灌丛侵蚀导致土壤动物向深层移动，增强了深层碳循环，并向剖面深层转移养分和碳。3)与草地相比，灌丛的水分吸收将来自更深的土层，从而导致生产力的提高和蒸散的季节性降低。提案中的三项研究活动分别是野外深土取心、3m深管控制实验和建模整合。野外工作比较了美国中部沿降水梯度的邻近深根和浅根系统的生态系统特性（包括四个长期生态研究点（LTERs））。栅栏线比较用于检查在土壤性质没有初始差异的情况下改变生根深度的影响。一系列10米深的土壤岩心已经在CPER LTER和德克萨斯州弗农成功取样。在3米深的管道中进行的研究提供了与现场实验相对应的受控对照；水和营养物质将精确地施用于深层，以便从机械上考察深层根系的重要性。模型集成建立在检验根系分布和土壤深度对碳和水循环影响的实验基础上。它也很适合我实验室的其他研究项目，包括陆地生态系统全球变化的任务1.3.1（“根系分布和碳水通量”），以及国家气象分析与综合中心的一项附带活动，以改善全球模型中地下过程的表现。教学和推广活动充分利用了德克萨斯大学奥斯汀分校对生态学和科学教育的巨大需求。1994年，该大学开设了一个新的本科专业——生态、进化与保护（EEC），为现在入学的400名本科生提供了一个极好的教学和指导机会。所教授的课程（植物生态学、野外生态学、植物生理生态学和全球环境变化）很好地结合了这些学生的需求，并为研究计划带来了许多好处。最重要的是能够让有才华的本科生参与研究，同时补充他们传统的课堂教育的协同作用。自1995年以来，已有10名本科生在我的实验室做过这样的研究项目，另外还有7名勤工俭学的学生。正是在这种指导下，科学家和教师的双重角色真正融合在一起——学生通过教授的榜样学习科学，而研究也在这个过程中取得进展。

ABSTRACTJACKSON9733333This project will execute a five-year research, teaching, and outreach plan that combines long-term interests in ecology, global change, and science education. The research examines theimportance of root distributions, particularly deep roots, for carbon and water cycling in terrestrialecosystems. A subset of the hypotheses to be tested are: 1) The introduction of deep-rooted shrubs into grasslands lends to carbon storage in the vegetation and in soil layers beyond the maximum rooting depth of grasslands. 2) Shrub encroachment results in the movement of soil fauna to deeper layers, enhancing carbon cycling at depth and transferring nutrients and carbon deeper in the profile. 3) Water uptake in shrublands will come from deeper soil layers than in grasslands, resulting in increased productivity and decreased seasonality of evapotranspiration.The three research activities in the proposal are deep-soil coring in the field, controlledexperiments in 3-m-deep tubes, and integration through modeling. The field work compares ecosystemproperties of adjacent deep- and shallow-rooted systems along a precipitation gradient in the centralUnited States (including four Long Term Ecological Research sites (LTERs)). Fenceline comparisonsare used to examine the effects of altered rooting depth in the absence of initial differences in soilproperties. A series of 10-m-deep soil cores have been successfully sampled at the CPER LTER and atVernon, TX. The studies in 3-m-deep tubes provide a controlled counterpart to the field experiments;water and nutrients will be applied at precise depths so that the importance of deep roots can beexamined mechanistically. The modeling integration builds on the experiments to examine theconsequences of root distributions and soil depth for C and water cycling. It also fits well with otherresearch projects in my lab, including Task 1.3.1 of Global Change in Terrestrial Ecosystems ("Rootdistributions and carbon and water fluxes") and an accompanying activity at the National Center forEcological Analysis and Synthesis to improve the representation of belowground processes in globalmodels. Teaching and outreach activities take advantage of a large demand for ecology and scienceeducation at the University of Texas at Austin. In 1994 the university created a new undergraduatemajor - Ecology, Evolution, and Conservation (EEC) - providing an excellent opportunity for teachingand mentoring among the 400 undergraduates now enrolled. The courses that are taught (Plant Ecology, Field Ecology, Plant Physiological Ecology, and Global Environmental Change) integrate well with the needs of those students and lead to numerous benefits for the research program. Foremost is the synergy of being able to involve talented undergraduates in research, while supplementing theirtraditional classroom education. Ten undergraduates have done such research projects in my lab since1995, with seven additional work-study students. It is in this mentoring that the dual roles of scientist and teacher truly blend - students learn science by the professor's example, and research progresses in the process.