Post-Fire Hydrology, Biogeochemistry, and Vegetation Response

0327071Meixner去年9月，一场取代标准的野火烧毁了圣迪马斯实验森林(SDEF)。SDEF有60年的流域水文记录和20年的流域氮输出记录。SDEF对火灾前情况的深入了解提供了千载难逢的机会，可以近距离研究火灾对生态系统的影响，这是一种生态干扰。SDEF的现有数据表明，与火灾频率较低的流域相比，火灾频率较高的流域在长时间尺度上减少了径流和无机氮的输出。这一现有数据特别重要，因为它表明了干扰制度与生态系统对大气沉积的敏感性之间的相互作用。更广泛地说，我们的结果将与了解生态系统中的干扰以及干扰对水文和生物地球化学过程的影响有关。我们打算在火灾后的环境中调查四个主要问题。首先，我们将通过观测网络和基于过程的研究来确定火灾频率对沉积物和养分输出的相对控制。其次，我们将通过一个强大的观测网络，研究火灾后环境中ET的变化对流域水文的影响。这个观测系统由几个流域和几个对照流域组成，这些流域是在1980年代作为规定的火灾实验的一部分被S烧毁的。第三，我们将通过在SDEF和南加州低沉积地点的植被调查来研究高N沉积速率如何影响火灾后环境中的植被恢复。最后，我们将调查火灾历史如何影响流域水文和生物地球化学输出。我们还将为未来的研究做好准备，利用火收集地面和遥感数据的森林数字高程数据的详细评估，以及利用加州大学欧文分校捐赠的时间和设备的涡流系统对ET的初步测量。广泛的影响预先存在的设施和实验框架(详细的火灾历史和不同流域的差异)提供了一个真正独特的机会来调查火灾对人类可用水量的影响以及火灾对水质的影响。由于火灾是美国西部许多生态系统的主导生态系统过程，因此更好地了解火灾对水资源和水质的影响对土地管理者来说是至关重要的信息。这项研究还将提供有关空气污染和干扰如何相互作用和影响加州目前正在发生的威胁该地区独特生物多样性的大规模植被变化的信息。。此外，圣迪马斯实验森林位于加利福尼亚州南部，有着多样化的人口和众多的本科院校，为接触环境科学中代表性不足的群体提供了一个完美的机会：城市人口和少数族裔。加州大学河滨分校和长滩州立大学都以少数族裔人口为主。

0327071MeixnerA stand-replacing wildfire burned through the San Dimas Experimental Forest (SDEF) this past September. The SDEF has a 60-year record of watershed hydrology and a 20-year record of watershed nitrogen export for several watersheds. The intense understanding of pre-fire conditions at the SDEF presents a once in a lifetime opportunity to closely investigate the impacts of fire as an ecological disturbance in a chaparral ecosystem. Existing data at SDEF indicates that watersheds with more frequent fires have reduced streamflow and inorganic nitrogen export on long timescales compared to watersheds with less frequent fires. This existing data is especially important because it indicates an interaction between disturbance regime and the susceptibility of ecosystems to atmospheric deposition. More generally our results will be relevant to understanding disturbance in ecosystems and disturbance influences on hydrologic and biogeochemical processes. We intend to investigate four major questions in this post-fire environment. First, we will determine the relative control of fire frequency on sediment and nutrient export with an observational network and process based studies. Second, we will investigate the impact of changes in ET on watershed hydrology in the post-fire environment with a robust observation network. This observation system consists of several watersheds that were burned during the 1980's as part of a prescribed fire experiment as well as several control watersheds. Third, we will investigate how the high rates of N deposition influence vegetation recovery in the post-fire environment with vegetation surveys at SDEF and at a low deposition site in southern California. Finally, we will investigate how fire history affects watershed hydrologic and biogeochemical export. We will also prepare the ground for future studies with detailed assessment of digital elevation data at the forest taking advantage of fire to collect both on the ground and remotely sensed data as well as with preliminary measurements of ET with an eddy-flux system with time and equipment donated by the University of California, Irvine.Broader ImplicationsThe pre-existing facilities and experimental framework (detailed fire history with differences between watersheds) provide a truly unique opportunity to investigate the impact of fire on the amount of water available for human use and the impacts of fire on water quality. Since fire is such a dominant ecosystem process in many ecosystems of the western United States, better information on the impact of fire on water resources and water quality is critical information for land managers. The research will also provide information on how air pollution and disturbance interact and influence the large-scale vegetation change currently occurring in California that threatens the unique biodiversity of the region. . Additionally the location of the San Dimas Experimental Forest in southern California with its diverse population and numerous undergraduate institutions provide a perfect opportunity for outreach to underrepresented groups in the environmental sciences: urban populations and minorities. The University of California, Riverside and Long Beach State University both serve predominantly minority populations.