SGER: The Interactions of Nitrogen Eutrophication and Fire on Invasive Annuals in California Coastal Sage Shrublands

SGER：氮富营养化和火灾对加州沿海鼠尾草灌木丛入侵一年生植物的相互作用

• 批准号: 9408079
• 负责人: Edith Allen
• 金额: $ 5万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-03-01 至 1996-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9408079&HistoricalAwards=false
• 关键词: SGER; Interactions; Nitrogen; Eutrophication; Fire

9408079 Allen Exotic annuals have been invading southern California shrublands at increasing rates over the past 40-50 years. A number of factors may be responsible for the invasion, including fore, anthropogenic nitrogen deposition, soil disturbance, grazing, and fragmentation. Of these potential causes, N deposition has received no attention, and the effects of frequent fire are just beginning to be realized. Southern California shrublands are subject to aerial N deposition rates as high rates as high as 30 kg/ha/yr, with lower rates at a distance from agricultural and urbanized areas. Many of the colonizing annuals are probably nitrophilous, e.g., they have high rates of growth with added N. By contrast, we hypothesize that the native shrubs have relatively little response to increased N. Fire alone can explain the increased weediness and decrease in shrub cover in some sites, but areas that have not been burned in 30-40 years have and increase in exotics. These include primarily annual grasses in the genera Bromus, Hordeum, and Avena. The native vegetation that is most subject to weed invasion is the coastal sage scrub, a type that is limited in extent, is threatened by urbanization, and harbors a number of sensitive species. %%% Our objective is to examine the interaction between fire and nitrogen deposition on plant growth. We request funding through the SGER Program to take advantage of the recent fires in California. We have located two sites that were burned in November, one with high and one with low N deposition. We propose to set up a factorial experiment at each site, with burned and unburned vs. fertilized and unfertilized plots. We hypothesize that annual grass growth will be increased more than shrub growth after N fertilization, and that fire hastens the conversion from native shrubland to annual grassland. This research has important implications for the conservation of coastal sage shrub. A reduction in the fire cycle will be important to prevent a rapid conv ersion to weedy annuals, but we may also recommend a reduction in anthropogenic N deposition.

在过去的40 - 50年中，9408079 Allen Exotic Mentials一直以增加的速度入侵南加州灌木丛。 许多因素可能是侵袭的原因，包括前胎，人为氮沉积，土壤干扰，放牧和碎片化。 在这些潜在原因中，n的沉积没有得到关注，频繁火的影响才刚刚开始实现。 南加州灌木丛的空中N沉积率高达30 kg/ha/yr，距离农业和城市化地区的距离较低。 许多殖民一年的殖民年度可能是硝基嗜酸的，例如，它们的生长率很高，而添加了N。相比之下，我们假设，对单独的火灾的天然灌木对n的反应相对较小。仅北火的反应就可以解释某些地点的杂草和灌木覆盖率的增加，但是在30-40年中，Exotics却没有燃烧的区域，并且没有燃烧。 这些主要包括Bromus属，Hordeum和Avena中的一年草。 最受杂草入侵的本地植被是沿海鼠尾草磨砂膏，这种植被在范围内受到限制，受到城市化的威胁，并拥有许多敏感的物种。 我们的目标是检查植物生长对火与氮沉积之间的相互作用。 我们要求通过SGER计划进行资金，以利用加利福尼亚最近发生的大火。 我们找到了两个在11月燃烧的地点，一个地点较高，一个含量很低。 我们建议在每个地点建立一个阶乘实验，并用燃烧和未燃烧的且未施肥的地块和未施肥的图。 我们假设在氮肥后，每年的草生长将比灌木增长更多，而火灾加速了从本地灌木丛到一年一度的草地的转变。 这项研究对沿海鼠尾草灌木的保护具有重要意义。 减少火灾周期对于防止快速对杂草的年度群体的转变至关重要，但是我们也可能建议降低人为n的沉积。