CAREER: Fire management effects on Sierra Nevada ecohydrology - a dynamical systems approach

职业：火灾管理对内华达山脉生态水文学的影响——一种动力系统方法

• 批准号: 1555041
• 负责人: Sally Thompson
• 金额: $ 53.7万
• 依托单位: University of California-Berkeley
• 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 2021-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1555041&HistoricalAwards=false
• 关键词: CAREER; Fire; management; effects; Sierra

Forested mountain watersheds supply the majority of water to the western United States, and are fundamentally fire-prone ecosystems. Contemporary drought, and projected future climate change, simultaneously exacerbate fire risks in the Sierra Nevada and threaten the sustainability of the water supply. Management approaches that could simultaneously reduce fire risks while safeguarding water supplies are sorely needed. This research takes advantage of a unique pair of watersheds in the Sierra Nevada where fire suppression was practiced for almost a century prior to the 1970s, and managed wildfire has been practiced since then. These basins will be studied to determine how vegetation cover, snow and soil moisture behavior, and water yields have responded to the changed fire regime. The results will be synthesized in a modeling framework that can be applied to evaluate the potential consequences of similar shifts in fire regime elsewhere in the Sierra Nevada. Results of the research will provide an evidence basis to motivate new fire management in the Sierra Nevada, reducing fire risk and enhancing water security in a region that supplies 60% of California's 38 million residents. These results will be shared through an outreach program developed with the California Fire Science Consortium. The project will also include a citizen-science project involving middle-school students participating in outdoor environmental education programs run by NatureBridge at Yosemite National Park. The removal of fire from forested mountain ecosystems represents a century-long, massive, and poorly-understood experiment, altering the composition, demography, allometry and succession dynamics of forests, with presumed (although largely unquantified) effects on biogeochemistry, hydrology and ecosystem function. This research project leverages a unique opportunity to explore these effects by examining changes in vegetation, fire and hydrology in the only two watersheds in the Sierra Nevada where fire suppression has been deliberately alleviated and the natural fire regime allowed to re-establish. Historical and contemporary aerial photography will be used to reconstruct vegetation histories in the study watersheds. The resulting vegetation maps will be used as a basis for upscaling distributed soil moisture and fuel moisture measurements made throughout the study basins, and as input into distributed hydrological models. Weather stations, snow cameras and soil moisture observations will be installed in sites with distinct post-fire vegetation successions to characterize the effects of vegetation change on local meteorological and hydrological conditions. Laboratory experiments will be undertaken to evaluate the persistence of soil hydrophobicity under repeated freeze-thaw cycles, characteristic of the Sierra Nevada wet season. The process insights obtained through these field observations will be used to develop, parameterize and test a probabilistic model representing the dynamic interactions of fire, vegetation and water. The project will contribute new process understanding about the interaction of fire and hydrology in snow dominated landscapes, specifically how fire history impacts snowpack dynamics (such as interception, sublimation and melt timing), and how freeze-thaw processes impact post-fire soil hydrophobicity. It will generate unique spatial, temporal and historical datasets that will reveal the joint consequences of fire suppression and its alleviation on vegetation and hydrology in montane forests.

森林覆盖的山区分水岭为美国西部提供了大部分水，从根本上讲是容易起火的生态系统。当代干旱和预计的未来气候变化同时加剧了内华达山脉的火灾风险，并威胁到供水的可持续性。迫切需要能够在保障供水的同时降低火灾风险的管理办法。这项研究利用了内华达山脉的一对独特的分水岭，在20世纪70年代之前，那里实施了近一个世纪的灭火，自那时以来，一直在进行有管理的野火。将对这些盆地进行研究，以确定植被覆盖、积雪和土壤水分行为以及产水量对变化的火灾制度的反应。结果将在一个建模框架中综合，该框架可用于评估内华达山脉其他地区火力状况类似变化的潜在后果。研究结果将为推动内华达山脉新的火灾管理提供证据基础，降低火灾风险并加强该地区的水安全，该地区供应加州3800万居民中的60%。这些成果将通过与加州消防科学联合会制定的外展计划共享。该项目还将包括一个公民科学项目，让中学生参与约塞米蒂国家公园NatureBridge运营的户外环境教育项目。从森林覆盖的山区生态系统中除火是一项长达一个世纪的大规模实验，它改变了森林的组成、人口统计学、异速生长和演替动态，对生物地球化学、水文学和生态系统功能产生了推定(尽管基本上没有量化)影响。这项研究项目利用了一个独特的机会，通过检查内华达山脉仅有的两个流域的植被、火灾和水文变化来探索这些影响，在这些流域中，火灾抑制已被故意缓解，允许重新建立自然火灾制度。将使用历史和当代航空摄影来重建研究流域的植被历史。所产生的植被图将被用作扩大在整个研究流域内进行的分布式土壤水分和燃料湿度测量的基础，并作为分布式水文模型的输入。将在火灾后植被演替明显的地点安装气象站、积雪相机和土壤湿度观测仪，以表征植被变化对当地气象和水文条件的影响。将进行实验室实验，以评估土壤疏水性在反复冻融循环下的持久性，这是内华达山脉雨季的特征。通过这些实地观测获得的过程洞察力将用于开发、参数化和测试代表火、植被和水的动态相互作用的概率模型。该项目将有助于对积雪景观中火与水文相互作用的新过程的理解，特别是火灾历史如何影响积雪动态(如拦截、升华和融化时间)，以及冻融过程如何影响火灾后土壤的疏水性。它将产生独特的空间、时间和历史数据集，揭示火灾扑灭及其对山地森林植被和水文的缓解所产生的联合后果。