Post-Fire Hydrology, Biogeochemistry, and Vegetation Response

今年9月，一场取代林分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。对SDEF火灾前条件的深入了解提供了一个千载难逢的机会，可以仔细研究火灾作为林荫生态系统中生态干扰的影响。SDEF的现有数据表明，与火灾较少的流域相比，火灾频繁的流域在长时间尺度上减少了河流流量和无机氮的输出。这一现有数据特别重要，因为它表明扰动状态与生态系统对大气沉积的易感性之间存在相互作用。更一般地说，我们的结果将与理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确定火灾频率对沉积物和养分输出的相对控制。其次，利用强大的观测网络，研究火灾后环境下蒸散发变化对流域水文的影响。该观测系统包括在1980年代作为规定火灾实验的一部分被烧毁的几个流域以及几个控制流域。第三，我们将通过对SDEF和南加州一个低沉降点的植被调查，研究高氮沉降率对火灾后环境中植被恢复的影响。最后，我们将探讨火灾历史对流域水文和生物地球化学输出的影响。我们还将为未来的研究做好准备，对森林的数字高程数据进行详细评估，利用火灾收集地面和遥感数据，并利用加州大学欧文分校捐赠的时间和设备，利用涡流通量系统对ET进行初步测量。更广泛的影响现有的设施和实验框架（详细的火灾历史与流域之间的差异）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要生态系统过程，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。该研究还将提供有关空气污染和干扰如何相互作用并影响加利福尼亚目前发生的大规模植被变化的信息，这些变化威胁着该地区独特的生物多样性。此外，圣迪马斯实验森林位于南加州，人口多样化，本科院校众多，为环境科学中代表性不足的群体（城市人口和少数民族）提供了一个绝佳的机会。加州大学河滨分校和长滩州立大学都主要招收少数族裔学生。

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.