Doctoral Dissertation Research: The Impact of Historical Logging Activities on the Ecology and Geomorphology of Mountain Streams

本博士论文研究改进项目是关于历史河道干扰及其对生态系统功能的影响。先前的研究已经证明了河流地貌与河流代谢等生态系统过程之间的密切关系，但对于过去的河道干扰如何影响这些关系或河流如何从这些历史干扰中恢复知之甚少。了解地貌过程和生态系统功能之间的联系，以及这些关系如何受到干扰的影响，对河流的环境管理，特别是河流恢复的实践具有重要意义。生态系统代谢是指藻类和水生植物群落的总初级生产（GPP）过程与生态系统呼吸（ER）过程之间的平衡，ER是系统中所有水生群落对有机碳的总消耗。光、温度、流流量和通道复杂性都相互作用并影响GPP和ER的速率。这项研究将解决过去的河道干扰和最近的恢复工作对这些控制的影响程度。该项目的研究问题是：1)受干扰、未受干扰和恢复河道条件下的结构和功能地貌特征是如何变化的？2) GPP和ER如何响应这些变化？在过去，山间溪流受到一种被称为“系带驱动”的森林采伐策略的影响，在这种策略中，人们系统地清理和疏导溪流，以帮助铁路的运输。这种做法在怀俄明州和科罗拉多州非常普遍，这种做法的遗产今天仍然很明显。我们假设：1)与未受干扰的河流相比，系带驱动的河流的GPP更高，因为较薄的河岸覆盖和较低的河道岸增加了光的可用性；2)与未受干扰的河流相比，系带驱动的河流的ER最低，因为有机质存量减少，河道复杂性降低。3)所有河流的ER率都大于GPP率，这表明社区依赖于来自渠道外的能源补贴。本研究的结果将解决与河流地貌、河岸组成和生态系统代谢之间相互作用相关的知识空白，并将为理解河流恢复项目的生态结果奠定综合基础。该项目的研究结果将有助于通过对干扰环境下河流地貌和生态系统功能的综合调查，为未来的河流恢复和管理工作提供信息。改善这些学科联系将导致更高效和有效的河流恢复项目，并更有效地利用联邦和州的恢复投资。在该项目的实施过程中，研究结果和相关数据将直接与美国农业部林业局和美国鱼类和野生动物管理局等当地机构共享，确保研究成果将迅速有效地纳入机构管理工作。作为博士论文研究进步奖，该项目将为有前途的研究生建立独立的研究生涯提供支持。

This Doctoral Dissertation Research Improvement project is about historic stream channel disturbances and associated implications for ecosystem functioning. Previous research has demonstrated strong relationships between stream geomorphology and ecosystem processes such as stream metabolism, but little is known about how past stream channel disturbances influence these relationships or how streams recover from these historic disturbances. Understanding the link between geomorphic processes and ecosystem function as well as how these relationships are affected by disturbance has implications for the environmental management of streams, particularly the practice of stream restoration. Ecosystem metabolism refers to the balance between the processes of gross primary production (GPP) by algal and aquatic plant communities and ecosystem respiration (ER), which accounts for the total consumption of organic carbon by all aquatic communities in the system. Light, temperature, stream flow, and channel complexity all interact and influence rates of GPP and ER. This research will address the degree to which past stream channel disturbances and recent restoration efforts affect these controls. The project's research questions are 1) how do structural and functional geomorphic characteristics vary between disturbed, non-disturbed, and restored channel conditions?; and 2) how do GPP and ER respond to these changes? In the past mountain streams were impacted by a forest harvesting strategy known as 'tie-driving,' during which there was systematic clearing and channelizing of streams to aid in the transport of railroad ties. This practice was very common in Wyoming and Colorado and the legacy of this practice is still evident on the landscape today. We hypothesize that 1) GPP will be higher in tie-driven streams as compared to non-disturbed streams because of increased light availability as a result of thinner riparian cover and lower channel banks, 2) ER will be lowest in tie-driven streams compared to non-disturbed streams because of decreased organic matter standing stocks and decreased channel complexity, and 3) rates of ER will be greater than rates of GPP in all streams indicating that communities are reliant on energy subsidies originating from outside the channel. Results from this study will address knowledge gaps related to the interactions between stream geomorphology, riparian composition, and ecosystem metabolism and will develop an integrative foundation for understanding ecological outcomes of stream restoration projects.Results of this project will help to inform future stream restoration and management efforts through the integrative investigation of stream geomorphology and ecosystem function within the context of a disturbance regime. Improving these disciplinary links will result in more efficient and effective stream restoration projects and more efficient use of federal and state restoration investments. Over the course of this project, results and associated data will be shared directly with local agencies such as the USDA Forest Service and the U.S. Fish and Wildlife Service, ensuring that research findings will be incorporated in agency management efforts quickly and efficiently. As a Doctoral Dissertation Research Improvement award, the project will provide support to enable a promising graduate student to establish an independent research career.