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

森林覆盖的山区流域为美国西部提供了大部分的水资源，并且基本上是容易发生火灾的生态系统。当前的干旱和预计的未来气候变化，同时加剧了内华达州的火灾风险，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减少火灾风险的管理办法。 这项研究利用了内华达州的一对独特的流域，在那里，在20世纪70年代之前，灭火已经进行了近世纪，从那时起，管理野火一直在进行。将对这些盆地进行研究，以确定植被覆盖、雪和土壤水分行为以及水量如何对变化的火灾状况作出反应。 结果将被合成在一个建模框架，可应用于评估潜在的后果，类似的变化在其他地方的火灾制度在内华达州。 研究结果将提供一个证据基础，以激励新的火灾管理在内华达州，减少火灾风险和提高水安全的地区，供应60%的加州的38万居民。 这些结果将通过与加州消防科学联盟开发的外展计划分享。 该项目还将包括一个公民科学项目，涉及中学生参加由自然之桥在约塞米蒂国家公园举办的户外环境教育项目。 从森林覆盖的山区生态系统中消除火灾是一个长达一个世纪的大规模和知之甚少的实验，改变了森林的组成，人口，异速生长和演替动态，对土壤地球化学，水文和生态系统功能产生了推定的影响（尽管基本上没有量化）。 这个研究项目利用了一个独特的机会来探索这些影响，通过检查植被，火灾和水文的变化，在只有两个流域在塞拉利昂内华达州，灭火已被故意减轻和自然火灾制度允许重新建立。 历史和当代航空摄影将用于重建研究流域的植被历史。 由此产生的植被图将被用作基础，扩大分布式土壤水分和燃料水分测量整个研究流域，并作为输入到分布式水文模型。 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装置，以描述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，以评估反复冻融循环下土壤疏水性的持久性，这是Sierra内华达州雨季的特征。 通过这些实地观察获得的过程见解将用于开发，参数化和测试代表火灾，植被和水的动态相互作用的概率模型。 该项目将有助于对雪主导景观中火与水文相互作用的新过程理解，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疏水性。它将产生独特的空间、时间和历史数据集，揭示灭火及其缓解对山地森林植被和水文的共同影响。

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.