Collaborative Research: RUI: Recovery trajectories of the hillslope green water cycle after rapidly repeated wildfires

随着气温上升，降雨和降雪变得更加间歇，预计森林地区的野火复发将增加。尽管在过去的30年里，在很短的时间（10年）内重新燃烧一个地区的野火非常常见，但控制这些野火的机制是什么？快速再燃？并不完全理解。这可能是因为水的可用性下降，即，在森林覆盖的山坡上，水文循环的改变正在改变对火灾后植物再生的控制，以及随后的野火。然而，几乎没有关于火灾后植物所需的土壤水资源的数据，火灾后多年来被烧毁地区土壤水分的时空变化，或植被再生的水分反馈。这项研究解决了这一关键差距的数据后再烧山坡水文和生态水文系统恢复随着时间的推移，也将有助于确定再烧是否可能减轻或恶化下游洪水和滑坡的风险，往往伴随着更高的火灾后水流。这项研究产生的新知识将与联邦和州水和森林管理人员密切协调，包括一系列研究管理讲习班，以改善研究与管理实践的沟通。该项目还将通过一个与实地有关的志愿者组织与非营利社区接触，并通过在当地博物馆举办临时科学展览，以及在当地幼儿园和小学开展便携式教育，与公众接触。认识科学家本研究旨在了解（1）随着自然再烧次数的增加和自上次火灾以来的时间的推移，山坡水文响应如何不同;（2）坡面土壤水分恢复与蒸散通量之间的模式和反馈与植被恢复的关系，以及它们如何随复烧次数而变化，种子源的距离，和火灾后的时间;（3）如何在山坡水平衡的逐渐变化涉及到下游河流的水流动态火灾或再烧后，在可变的气候影响。这项研究将测试一个总体假设的多个组成部分，有时空（相关）和生物物理（因果关系），连接土壤水分和土壤水力过程的变化后，再烧。此外，它还讨论了植被再生如何为随后的火灾提供燃料负荷，以及在多次野火之后，下游流量和洪水风险如何随着时间的推移而消退。土壤水分，基质势，质地，防水性，渗透和水力特性测量，活植被，和木质残体将绘制在6个0.25公顷的现场，并在整个研究过程中，随着时间的推移进行监测，建立在额外的两个赛季的初步数据。实地方法包括原位传感器和数据记录器，土壤湿度的3D地球物理调查，微气象监测和详细的植被生态调查，包括树苗的存在和存活。在山南翼的六个示范现场。亚当斯，华盛顿州，是相似的生态，气候，坡度，海拔，方面，距离未烧毁的森林，和过去的严重程度每火灾，但不同的是在过去的火灾（1至3在过去的13年，和未烧毁的控制）和时间，因为火灾。将对主要植被和裸地覆盖类进行蒸散模拟，并借助遥感数据和长期气候、干旱和径流时间序列，在两个相关流域以时空广泛的方式应用。这种建模分析将寻求更好地了解火后山坡水循环的时空动态及其与径流动态的关系后，不同数量的野火再烧和不同的恢复间隔后火灾。

As temperatures rise and rain and snowfall become more intermittent, wildfire recurrence is expected to increase in forested areas. Although wildfires that re-burn an area after only a short time (10 years) have been unusually common over the last 30 years, the mechanisms governing these ?rapid reburns? are incompletely understood. It may be that decreasing water availability, i.e., an altered hydrological cycle, on forested hillslopes is changing the controls on plant regrowth after fire, and so on subsequent wildfires. However, there are almost no data on the soil water resources that plants need following fires, the spatial and temporal changes in soil moisture in burned areas over multiple years after fires, or moisture feedbacks with vegetation regrowth. This research addresses this critical gap in data on post-reburn hillslope hydrology and ecohydrologic system recovery over time and will also help identify whether reburns might mitigate or worsen the downstream flood and landslide risks that often accompany higher post-fire water flows. The new knowledge generated by this research will be produced in close coordination with federal and state water and forest managers, including a series of research-management workshops to improve research communication with management practices. The project will also engage with the nonprofit community via a volunteer organization related to the field area and with the public via creation of a temporary science exhibit for display at a local museum and also for portable education at local preschools and elementary schools during ?meet-a-scientist? visits and will expand research a opportunities for undergraduate and graduate researchers.This research aims to understand (1) how hillslope hydrological response differ with increasing numbers of natural reburns and with time since last fire; (2) how the patterns and feedbacks between the recovery of hillslope soil moisture and evapotranspiration fluxes are linked to the recovery of vegetation, and how they vary with number of reburns, seed-source distances, and time since fire; and (3) how the gradual change in the hillslope water balance relates to downstream river flow dynamics after a fire or reburn under variable climate influence. This research will test multiple components of an overarching hypothesis that there are both spatio-temporal (correlative) and biophysical (causative), linking soil moisture and soil hydraulic process changes following reburns. In addition, it addresses how the vegetation regrowth provides the fuel load for subsequent fires, and how downstream flows and flood risks recede over time following multiple wildfires. Soil moisture, matric potential, texture, water repellency, infiltration, and hydraulic property measurements, live vegetation, and woody debris will be mapped across six 0.25 ha field sites and monitored over time throughout the study, building on an additional two seasons of preliminary data. Field methods include in situ sensors and data loggers, 3D geophysical surveys of soil moisture, micrometeorological monitoring, and detailed vegetation ecology surveys including tree seedling presence and survival. The six exemplary field sites on the southern flank of Mt. Adams, WA, are of similar ecology, climate, slope, elevation, aspect, distance to unburned forest, and past severity per fire, but differ in the number of past fires (1 to 3 in the last 13 years, and an unburned control) and time since fire. Modeling of evapotranspiration will be conducted for major vegetation and bare land cover classes and applied in a spatially and temporally extensive manner across two relevant watersheds with the aid of remote sensing data and long-term climate, drought, and streamflow time-series. This modeling analysis will seek to better understand the spatiotemporal dynamics of the post-fire hillslope water cycle and its relation to streamflow dynamics after different numbers of wildfire reburns and different recovery intervals after fire.