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

合作研究：RUI：快速重复野火后山坡绿水循环的恢复轨迹

• 批准号: 1738228
• 负责人: Kevan Moffett
• 金额: $ 28.67万
• 依托单位: Washington State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-07-01 至 2021-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1738228&HistoricalAwards=false
• 关键词: Collaborative; Research; RUI; Recovery; trajectories

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.

随着气温上升，降雨和降雪变得更加间歇性，森林地区的野火预计会再次发生。尽管在过去30年里，仅在短时间(10年)后重新燃烧一个地区的野火非常常见，但管理这些火灾的机制是什么？快速重新燃烧？是不完全理解的。这可能是因为森林覆盖的山坡上可用水的减少，即改变了水文循环，改变了对火灾后植物重新生长的控制，从而改变了随后的野火。然而，几乎没有关于植物在火灾后所需的土壤水资源、火灾后多年火烧区土壤水分的时空变化、或植被再生过程中的水分反馈的数据。这项研究解决了再燃烧后山坡水文和生态水文系统恢复方面的数据随着时间的推移的这一关键差距，并将有助于确定再燃烧是否可能缓解或恶化下游洪水和滑坡风险，这些风险往往伴随着火灾后较高的水流。这项研究产生的新知识将与联邦和州水和森林管理者密切协调，包括举办一系列研究-管理讲习班，以改进研究与管理实践的交流。该项目还将通过一个与实地有关的志愿者组织与非营利性社区接触，并通过创建一个临时科学展览在当地博物馆展出，并在与科学家见面期间在当地学前班和小学开展便携式教育，与公众接触。这项研究旨在了解(1)随着自然复燃次数的增加和自上次火灾以来的时间，山坡的水文响应是如何不同的；(2)坡地土壤水分和蒸散通量的恢复之间的模式和反馈如何与植被的恢复有关，以及它们如何随复燃次数、种源距离和起火时间的变化而变化；(3)在不同的气候影响下，山坡水平衡的逐渐变化如何与下游河流流量动态相关。这项研究将检验一个重要假设的多个组成部分，即存在时空(相关)和生物物理(因果)两种因素，将土壤水分和土壤水力过程在重新燃烧后的变化联系起来。此外，它还阐述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，下游水流和洪水风险如何随着时间的推移而消退。土壤水分、基质潜力、质地、憎水性、渗透性和水力特性测量、活的植被和木质碎屑将在六个0.25公顷的田野上进行测绘，并在整个研究期间进行监测，建立在另外两个季节初步数据的基础上。现场方法包括现场传感器和数据记录器、土壤湿度的3D地球物理调查、微气象监测以及详细的植被生态调查，包括树苗的存在和存活。山体南侧的六个示范性野外遗址。华盛顿州亚当斯的生态、气候、坡度、海拔、坡向、距离未燃烧的森林的距离和过去的每次火灾严重程度相似，但在过去的火灾次数(过去13年中为1至3次，未燃烧的对照)和火灾发生后的时间上有所不同。将对主要植被和裸地覆盖类别进行蒸散模拟，并借助遥感数据和长期气候、干旱和径流时间序列，在空间和时间上广泛应用于两个相关流域。这一模拟分析将寻求更好地了解火灾后坡面水循环的时空动态及其与不同野火再燃次数和火灾后不同恢复间隔的径流动力学的关系。