RAPID: Interactive effects of wildfire and severe drought on plants, soil microbes and C storage in a semiarid shrubland ecosystem

RAPID：半干旱灌木丛生态系统中野火和严重干旱对植物、土壤微生物和碳储存的相互作用

• 批准号: 2154746
• 负责人: David Lipson
• 金额: $ 19.9万
• 依托单位: San Diego State University Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-12-01 至 2024-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2154746&HistoricalAwards=false
• 关键词: RAPID; Interactive; effects; wildfire; severe

Like many semiarid ecosystems around the world, southern California is subject to increasingly frequent and intense wildfires and droughts. These extreme events can cause long-term changes in the ecosystem by allowing invasive weeds to replace native shrubs and disrupting the physical structure of soil and the communities of microscopic organisms (microbes) like bacteria and fungi that live in the soil. These changes to plants, microbes and soils can affect how the whole ecosystem works, including how effectively the ecosystem can absorb carbon dioxide (CO2) from the atmosphere and store carbon for a long time as organic matter. The ability of land to absorb and store carbon is very important because it can slow down the accumulation of CO2 in the atmosphere, slowing down its effects on the climate. Computer models predict how future changes in ecosystems will influence atmospheric CO2. However, there is not enough information to make confident predictions of how wildfire and drought will change semiarid ecosystems like southern California shrublands. Studying the combined effects of wildfire and drought requires experiments where otherwise similar parts of the landscape are either burned or unburned, and the amount of rain falling on an experimental plot can be controlled. For safety reasons, prescribed burns are carried out under conditions that are very different from natural wildfires, and might represent how real wildfires will affect ecosystems. On the other hand, wildfires are unpredictable. This makes it hard to plan an experiment that requires comparable burned and unburned landscape, access to the location, preliminary information about the area before the fire, and the time to establish rain shelters before the onset of seasonal rains. This NSF RAPID project takes advantage of such an opportunity, in which a wildfire burned part of a well-studied nature preserve, and a rainfall experiment could be established before the main rainy season, given immediate action.This project takes advantage of a rare and time-sensitive opportunity to combine a natural wildfire with a controlled rainfall experiment in a factorial design and incorporate the data into an improved model for predicting the response of semiarid ecosystems to episodic and gradual aspects of climate change. This RAPID award allows rainfall shelters to be constructed in burned and unburned areas prior to the onset of seasonal rains. The project tests the hypotheses that fire and drought will interact to promote invasion by grasses and other herbaceous species, and cause 1) earlier phenology of ecosystem C gain as well as a shorter growing season, and 2) an increase in the vulnerability of the ecosystem to loss of C and N via changes in soil structure and microbial communities. Thus, together fire and drought will synergistically contribute to lower ecosystem C stocks. This project will (1) establish a factorial drought × wild fire experiment, (2) measure ecosystem responses (including plant and soil components) to the factorial treatments, and (3) organize these data for incorporation into the Millennial Model and the Community Earth System Model (CESM), enabling predictions for both the U.S. Southwest, and other semiarid ecosystems around the world. C and N will be measured in soil physical fractions (various size classes of aggregates, particulate organic matter, microbial biomass, etc.), and the microbial community structure will be characterized using shotgun metagenomic sequencing. Plant measurements will include community composition, phenology, and ecophysiological measurements at the canopy and leaf level, and remotely sensed imagery at the landscape level. The ecosystem modeling activities will place these data into an ecosystem-level framework. This one-year project will lay the groundwork for longer-term studies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

像世界各地的许多半干旱生态系统一样，南加州也越来越频繁地遭受强烈的野火和干旱。这些极端事件可以通过允许侵入性杂草代替天然灌木并破坏土壤的物理结构以及微生物（如微生物）（如细菌和居住在土壤中的真菌）来引起生态系统的长期变化。这些变化对植物，微生物和土壤的变化会影响整个生态系统的运作方式，包括生态系统可以从大气中吸收二氧化碳（CO2）的有效程度，并长期以来将碳作为有机物。土地吸收和储存碳的能力非常重要，因为它可以减慢大气中二氧化碳的积累，从而减慢其对气候的影响。计算机模型预测生态系统的未来变化将如何影响大气二氧化碳。但是，没有足够的信息来对野火和干旱将如何改变南加州灌木丛等半干旱生态系统做出自信的预测。研究野火和干旱的综合作用需要实验，在这些实验中，否则景观的相似部分要么被燃烧或未被燃烧，并且可以控制落在实验图上的雨量。出于安全原因，在与天然野火截然不同的条件下进行规定的烧伤，可能代表真正的野火如何影响生态系统。另一方面，野火是不可预测的。这使得很难计划一个实验，该实验需要可比的燃烧和未燃烧的景观，进入位置，有关大火前区域的初步信息，以及在季节性降雨开始之前建立雨庇护所的时间。这个NSF快速项目利用了这样的机会，在这种机会中，野火燃烧了一个良好的自然保护区的一部分，并且可以在主要雨季之前建立降雨实验，并立即采取行动。此项目利用了一个罕见且敏感的机会，将自然火与自然野火相结合，并将其融合到往返的模型中，以将自然野生火与自然野生动作结合到往返的范围内，以进行响应，以预测往返的模型，以进行循序渐进的模型，以进行循环的模型，以进行验证，并将其融合到循环设计中。气候变化的等级方面。这项快速奖励允许在季节性降雨开始之前在燃烧和未燃烧的地区建造降雨避难所。该项目检验了火灾和干旱将相互作用以促进草和其他草本物种的侵袭的假设，并引起1）生态系统C增益以及较短的生长季节的早期物候学，以及2）生态系统脆弱性通过土壤结构和微生物社区的变化而增加C和N的脆弱性。这将共同开火和干旱协同作用，从而有助于降低生态系统C股票。项目将（1）建立一个阶乘干旱×野生火灾实验，（2）测量对阶乘治疗的生态系统反应（包括植物和土壤组件），以及（3）将公司的这些数据组织到千禧年模型和社区地球系统模型（CESM）中，为美国西南部和其他Semiariarid Ecossems提供了预测。 C和N将在土壤物理分数（各种大小的聚集体，有机物，微生物量等）中进行测量，并使用shot弹枪元基因组测序来表征微生物群落结构。植物测量值将包括在冠层和叶片水平上的社区组成，物候和生态生理测量，以及在景观水平上远程感知的图像。生态系统建模活动将将这些数据置于生态系统级别的框架中。这个为期一年的项目将为长期研究奠定基础。该奖项反映了NSF的法定任务，并通过使用基金会的知识分子优点和更广泛的影响标准来评估，以诚实的方式表示支持。