DISSERTATION RESEARCH: Woody plant encroachment into grasslands: Impacts on landscape-scale patterns of soil carbon, nitrogen, and phosphorus storage and dynamics

论文研究：木本植物侵占草原：对土壤碳、氮、磷储存和动态的景观尺度模式的影响

• 批准号: 1600790
• 负责人: Thomas Boutton
• 金额: $ 1.93万
• 依托单位: Texas A&M AgriLife Research
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-06-01 至 2018-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1600790&HistoricalAwards=false
• 关键词: DISSERTATION; RESEARCH; Woody; plant; encroachment

Lands that receive small amounts of rain or snow occupy approximately 40% of the Earth's land surface. Large portions of these areas are experiencing a replacement of plants that are mostly grasses with increased numbers of trees and shrubs. This change generally increases the amount of carbon found in both plants and soils, and impacts how other elements that are important for plant growth, such as nitrogen and phosphorus, are used; carbon accumulation may also impact climate. Nitrogen and phosphorus are nutrients that often limit the rates at which plants grow, and the supply of one or the other can affect other elements. Despite the importance of carbon, nitrogen and phosphorus in plants and soils, very few studies have been conducted that consider all three elements together in dry landscapes, where the numbers of trees and shrubs are increasing. This project will measure patterns of storage of carbon, nitrogen, and phosphorus within the soils in areas where trees and shrubs have largely replaced grasses. The results will provide knowledge on why trees and shrubs are replacing grasses and what these changes mean for those environments. The information gained by this research will be used to improve mathematical models that describe the interactions of climate and nutrient cycles that in turn can inform the conservation and management of these dry lands. Educational materials about the research will be prepared for the general public in cooperation with the Texas A&M AgriLife Extension program.Modification of soil nutrient pool sizes following woody proliferation has long been of interest to grassland, savanna, and desert ecologists. However, most previous studies examining nutrient dynamics following woody encroachment have been confined to small spatial scales, limited to the uppermost portions of the soil profile, and focused primarily on C and/or N. This research will quantify soil organic C, total N, and total P throughout the entire soil profile in order to make the first assessment of landscape-scale C:N:P soil stoichiometry following woody plant encroachment into grassland. Specific objectives are: (1) Examine whether vegetation cover change alters the 3-dimensional spatial patterns of soil C, N, and P storage at the landscape scale; and (2) Test whether soil P scales isometrically with respect to C and N, and whether these isometric patterns change with soil depth in N-fixer encroached systems. Nutrient stores will be quantified in spatially-specific soil cores taken to a depth of 1.2 meters in a subtropical savanna landscape where N-fixing woody plants have encroached into grasslands during the past century. Results will offer new perceptions on the effects of woody encroachment on interactions between C, N, and P cycles in arid and semi-arid ecosystems across the globe, and enhance our ability to represent these interactions in linked biogeochemistry-climate models.

接收少量雨或雪的土地占地约40％。这些地区的很大一部分正在替代植物，这些植物主要是草和灌木数量增加的草。这种变化通常会增加植物和土壤中发现的碳量，并影响对植物生长重要的其他元素（例如氮和磷）如何使用；碳积累也可能影响气候。 氮和磷是通常限制植物生长速率的营养素，而一个或另一个的供应会影响其他元素。尽管碳和土壤中碳，氮和磷的重要性，但很少进行研究，这些研究在干燥的景观中将所有三个元素一起考虑在一起，在干燥的景观中，树木和灌木的数量正在增加。该项目将测量在树木和灌木中大部分取代草地的土壤中碳，氮和磷的储存模式。结果将提供有关树木和灌木为何取代草的知识，以及这些变化对这些环境意味着什么。这项研究获得的信息将用于改善数学模型，这些模型描述了气候和营养周期的相互作用，进而可以为这些干地的保护和管理提供信息。关于这项研究的教育材料将与得克萨斯州A＆M Agrialife扩展计划合作为公众准备。在木质增殖后，土壤养分池大小的修改长期以来对草地，稀树草原和沙漠生态学家感兴趣。 However, most previous studies examining nutrient dynamics following woody encroachment have been confined to small spatial scales, limited to the uppermost portions of the soil profile, and focused primarily on C and/or N. This research will quantify soil organic C, total N, and total P throughout the entire soil profile in order to make the first assessment of landscape-scale C:N:P soil stoichiometry following woody plant encroachment into grassland.具体目标是：（1）检查植被覆盖是否改变了景观尺度上土壤C，N和P存储的3维空间模式； （2）测试土壤P量表是否相对于C和N，以及这些等距模式是否随着N-Fixer侵占系统中的土壤深度而变化。在亚热带的稀树草原景观中，将在空间特异性的土壤岩心上量化营养店，在过去的一个世纪中，n固定的木本植物侵占了草原。 结果将为木质侵占对全球干旱和半干旱生态系统中C，N和P循环之间相互作用的影响提供新的看法，并增强了我们在链接的生物地球化学气候模型中代表这些相互作用的能力。