Quantifying the impacts of contemporary harvesting strategies on sediment and associated nutrient transport dynamics in forested watersheds

量化当代采伐策略对森林流域沉积物和相关养分输送动态的影响

• 批准号: RGPIN-2014-06712
• 负责人: Stone, Micheal
• 金额: $ 2.19万
• 依托单位: University of Waterloo
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=633980
• 关键词: Quantifying; impacts; contemporary; harvesting; strategies

Forested landscapes are critical source water regions that produce the majority of drinking water supplies in Canada and the United States. Previous research demonstrates that traditional landscape activities/disturbances (forest harvesting, site preparation, road construction/use and stream crossings) can negatively impact water quality, quantity and availability. In addition to the production of forestry products, contemporary harvesting practices are also used as a primary tool to manage increasing, climate-associated wildfire risks, which can have catastrophic impacts on water quality as well as the treatability of drinking water supplies. Given increasing demands on water supplies from forested source water regions, there is an urgent need to better understand the water quality impacts of contemporary forest harvesting practices used to manage forests to decrease the impacts of potentially catastrophic disturbances (wildfire) in forested watersheds. This work provides a rare opportunity to conduct a paired catchment study to investigate impacts of various forest harvesting strategies on sediment and associated nutrient transport dynamics in Alberta’s Oldman River Basin (ORB). Two previously undisturbed, fully instrumented watersheds for which 10 years of pre-disturbance data (hydrology and water quality) have been collected will be used thereby enabling comparison of effects before and after forest harvesting. One watershed will remain undisturbed while three sub-catchments of the other will be harvested using three harvesting techniques (variable retention, strip-shelter wood and partial cut). A key impact of forest disturbance on water is the delivery of fine sediments and associated nutrients to receiving streams. In Alberta, our research demonstrates that post fire water quality impacts downstream are severe, can last for decades and increase costs of water treatment and drinking water supply. In response to recent changes in upstream water quality of the Elbow River, the City of Calgary has spent over $600 million to upgrade the Glenmore water treatment plant. To provide a comparison to wildfire as a landscape disturbance on water quality, I plan to conduct field and laboratory studies in two well-described forested catchments to characterize the source, transport and fate of sediment and associated nutrients delivered to receiving streams as a result of contemporary forest harvesting disturbances. To date, no such comparisons of contemporary harvesting practices have been conducted. Knowledge generated from this study will enable land managers to select harvesting strategies to manage wildfire risks while potentially mitigating downstream propagation of sediment and associated nutrients. While some effects of forest harvesting on water have been documented elsewhere, information from other climatic regions is not applicable to the Alberta’s eastern slopes because of geographical differences that govern impacts on water. It is actually possible that in the longer term, the impacts from resource management may be less detrimental to water values than protective policies prohibiting land uses. The outcome of these strategies must be understood to sustain water supplies. While traditional drinking water source protection policies aim to minimize anthropogenic disturbances such as forest harvesting to protect water quality, forest management policies aim to protect communities and water supplies from potentially catastrophic effects of common disturbances (wildfire) that pose significant threats to water. A novel impact of this work is that it will enable these contradictory policies to be addressed from an informed, scientific perspective.

森林景观是重要的水源地区，生产加拿大和美国的大部分饮用水。先前的研究表明，传统的景观活动/干扰（森林采伐、整地、道路建设/使用和河流穿越）会对水质、水量和可用性产生负面影响。除了林业产品的生产外，当代的采伐实践也被用作管理日益增加的与气候相关的野火风险的主要工具，这可能对水质以及饮用水供应的可处理性产生灾难性影响。鉴于对森林源水区供水的需求不断增加，迫切需要更好地了解用于管理森林的当代森林采伐做法对水质的影响，以减少森林流域中潜在灾难性干扰（野火）的影响。这项工作提供了一个难得的机会来进行配对流域研究，以调查各种森林采伐策略对阿尔伯塔省奥德曼河流域（ORB）沉积物和相关养分输送动态的影响。将使用两个以前未受干扰、仪器齐全的流域，这些流域已收集了 10 年的干扰前数据（水文和水质），从而可以比较森林采伐前后的影响。一个流域将保持不受干扰，而另一个流域的三个子流域将使用三种采伐技术（可变保留、条形防护林和部分砍伐）进行采伐。森林扰动对水的一个关键影响是将细小的沉积物和相关营养物质输送到接收溪流中。在艾伯塔省，我们的研究表明，火灾后下游水质影响非常严重，可能持续数十年，并增加水处理和饮用水供应的成本。为了应对最近Elbow河上游水质的变化，卡尔加里市花费了6亿多美元对Glenmore水处理厂进行升级改造。为了与野火对水质的景观干扰进行比较，我计划在两个描述良好的森林流域进行实地和实验室研究，以描述由于当代森林采伐干扰而输送到接收溪流的沉积物和相关养分的来源、运输和归宿。迄今为止，尚未对当代采伐实践进行此类比较。这项研究产生的知识将使土地管理者能够选择收获策略来管理野火风险，同时有可能减轻沉积物和相关营养物质的下游传播。虽然其他地方已经记录了森林采伐对水的一些影响，但由于控制对水的影响的地理差异，来自其他气候地区的信息不适用于艾伯塔省的东坡。事实上，从长远来看，资源管理对水价值的影响可能小于禁止土地使用的保护性政策。必须了解这些策略的结果才能维持供水。传统的饮用水源保护政策旨在最大限度地减少人为干扰，例如为了保护水质而采伐森林，而森林管理政策则旨在保护社区和供水免受对水构成重大威胁的常见干扰（野火）的潜在灾难性影响。这项工作的一个新颖影响是，它将使得这些相互矛盾的政策能够从知情、科学的角度得到解决。