Collaborative Research: Water partitioning between trees, soils, and streams following forest disturbance

合作研究：森林干扰后树木、土壤和溪流之间的水分配

• 批准号: 1807165
• 负责人: Salli Dymond
• 金额: $ 4.31万
• 依托单位: University of Minnesota Duluth
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-07-15 至 2020-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1807165&HistoricalAwards=false
• 关键词: Collaborative; Research; Water; partitioning; between

Over half of the freshwater supply in the contiguous United States originates in forested watersheds. It is thus critical that forested headwater catchments are properly managed to ensure clean and ample water supplies for aquatic ecosystems and downstream communities. Research on forested experimental watersheds has established that reducing forest cover generally increases water yield and that afforestation decreases water yield. However, there is still not agreement on the magnitude and persistence of changes in streamflow, particularly during periods of the highest and lowest streamflow. This is because the connection between forest harvesting, or other forest disturbances, and streamflow is essentially a "black box", whereby the mechanisms influencing streamflow are not understood. This research will broaden our process-based understanding of forest hydrology by investigating how contemporary forest management affects water movement and storage in a well-studied coastal California watershed. Results of this research will provide evidence to motivate new forest management in coastal watersheds and lead to better foundational knowledge of the linkages between vegetation and water supply. These results will be generated in conjunction with the USDA Forest Service and the California Department of Forestry and Fire Protection, which will use the results to update California's Forest Practice Rules. It is increasingly critical to improve our quantitative understanding of how forest disturbances affect the storage and release of water through catchments. However, it is not yet understood how disturbances impact water compartmentalization at time scales other than the annual water balance. This is because the mechanisms by which streamflow increases can only be inferred in paired watershed studies, which have been the most popular tool for quantifying hydrological effects of forest disturbance. A combined mass balance and dual water isotope approach offers the potential to critically improve our understanding of the effects of disturbances on the processes and mechanisms that drive water storage and release. Here, it is hypothesized that the ecohydrological response of a forested watershed is proportional to the severity of disturbance. Using different intensities of forest harvesting (0%, 35%, 55%, and 75% removal of pre-treatment vegetation) as a mechanism for studying forest disturbances, the following research questions will be addressed: How do increasing levels of disturbance affect the water budget at different hillslope positions? How does forest disturbance affect the separation of water between soils, groundwater, streams, and trees? To answer these questions, this study takes a novel approach to connect the processes by which forest disturbance affects water budgets, subsurface water movement, and plant water use by combining a mass balance analysis and dual water isotopes. All components of the water budget (i.e., streamflow, soil moisture, groundwater, evapotranspiration, and fog) will be monitored and coupled with dual stable isotopes (2H and 18O). This study also addresses critical calls for field-based hydrologic research to inform hydrologic models to answer key questions about disturbance impacts on water resources.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

美国本土超过一半的淡水供应源自森林覆盖的流域。因此，正确管理森林覆盖的源头集水区至关重要，以确保为水生生态系统和下游社区提供清洁和充足的水源。对森林实验流域的研究表明，减少森林覆盖通常会增加产水量，而植树造林会降低产水量。然而，对于水流变化的幅度和持续性仍然没有达成一致，特别是在最高和最低水流期间。这是因为森林采伐或其他森林干扰与水流之间的联系本质上是一个“黑匣子”，影响水流的机制尚不清楚。这项研究将通过调查当代森林管理如何影响经过充分研究的加利福尼亚沿海流域的水运动和储存，扩大我们对森林水文学的基于过程的理解。这项研究的结果将为推动沿海流域的新森林管理提供证据，并更好地了解植被与供水之间的联系。这些结果将与美国农业部林务局和加利福尼亚州林业和消防局共同生成，该部门将使用这些结果来更新加利福尼亚州的森林实践规则。提高我们对森林干扰如何影响集水区水的储存和释放的定量理解变得越来越重要。然而，目前尚不清楚扰动如何影响除年度水平衡之外的时间尺度上的水分区。这是因为水流增加的机制只能在配对流域研究中推断，而配对流域研究是量化森林干扰水文影响的最流行的工具。质量平衡和双水同位素相结合的方法有可能极大地提高我们对扰动对水储存和释放的过程和机制的影响的理解。在这里，假设森林流域的生态水文响应与干扰的严重程度成正比。使用不同强度的森林采伐（0％、35％、55％和75％去除预处理植被）作为研究森林干扰的机制，将解决以下研究问题：干扰水平的增加如何影响不同山坡位置的水预算？森林干扰如何影响土壤、地下水、溪流和树木之间的水分离？为了回答这些问题，本研究采用一种新颖的方法，通过结合质量平衡分析和双水同位素，将森林扰动影响水收支、地下水运动和植物用水的过程联系起来。水预算的所有组成部分（即水流、土壤湿度、地下水、蒸散量和雾）都将受到监测，并与双稳定同位素（2H 和 18O）结合起来。这项研究还满足了对实地水文研究的迫切需求，为水文模型提供信息，以回答有关水资源扰动影响的关键问题。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响进行评估，被认为值得支持审查标准。