Doctoral Dissertation Research: Interactions Between a Native Sedge (Carex nudata) and Physical River Processes: A Model of Coupled Biogeomorphic Development

河流恢复目前是整个西海岸巨大投资的重点，其动机是必须改善受威胁的太平洋鲑鱼种群的栖息地。这项研究将有助于这些努力：苔草nudata，本地莎草，发生在整个西海岸，越来越多地被视为恢复目标的促进者，但土地和河流管理人员缺乏一个清晰的了解，它如何可能改变通道形态和环境变量是至关重要的，它的可行性。本研究探讨了C. nudata，河岸莎草，及其河流环境。这项研究的特点在于它的目的是研究这种关系的两个方面：河流的物理环境和流动模式如何驱动C。nudata分布，以及C. nudata然后改变河流的物理过程。C.在中福克约翰戴河，随着牛群从河岸上撤离，nudata引起了调查人员的注意。C.裸贝沿着低流量河道的边缘、砾石坝上、切割堤岸的底部和岛屿生长，其密集的根系使其能够承受强大的水流。C. nudata似乎正在改变河道形态，使河流更加复杂，从而改善鱼类生境，促进河流恢复目标。研究人员假设C. nudata促进了复合通道的进化，其中C. Nudata使狭窄的低流量通道稳定，但是与许多植物不同，它不会减缓切割堤岸的侵蚀，使得满堤的通道继续移动或加宽。在某些情况下，这个过程被假设为导致C。位于银行底部的nudata补丁“分离”并成为孤岛，从而产生多线程通道。研究人员将使用多种方法来检验这些假设。将使用重复的地形测量和侵蚀针检查河岸后退和河床侵蚀/加积的变化。还将用航空图像检查河岸后退和岛屿形成。将使用声学多普勒海流剖面仪检查可能解释侵蚀/淤积模式的流速模式。 关于C. nudata分布，研究人员推测，C。nudata模式由水文变量和沉积物类型驱动。这些假设将通过C. nudata在三个不同的河流流域。直到世纪后半叶，河流地貌学只关注河流过程的物理尺度。直到最近，人们才认识到植被对河流的形状和形态有着重要的影响（Hughes 1997）。然而，目前的植物-河流相互作用的研究通常集中在这种关系的一个方面：即要么是河流环境对植物群落的影响，或植物对某些物理过程的影响。Corenblit等人（2007）强调植物-河流关系的相互性，并提出了河流形态演替的概念，以描述河流形状和形式与河岸植物群落的相关发展。

River restoration is currently the focus of enormous investment throughout the West Coast, motivated by the imperative to enhance habitat for threatened Pacific salmon populations. This research will contribute to these efforts: Carex nudata, a native sedge that occurs throughout the West Coast, is increasingly perceived as a facilitator of restoration goals, but land and river managers lack a clear understanding of how it may alter channel morphology and what environmental variables are critical to its viability. The proposed research explores the interactions between C. nudata, a riparian sedge, and its river environment. The research is distinguished by its aim to examine both sides of this relationship: how the river's physical environment and flow patterns drive C. nudata distribution, and how C. nudata then alters the physical processes of the river. C. nudata caught the attention of investigators in the Middle Fork John Day River where it has exploded in abundance following the withdrawal of cattle grazing from river banks. C. nudata grows along the edges of the low flow channel, on gravel bars, at the base of cut banks and as islands, its dense root system allowing it to withstand strong flows. C. nudata appears to be altering channel morphology in ways that enhance river complexity, thus enhancing fish habitat and facilitating river restoration goals. The investigators hypothesize that C. nudata facilitates the evolution of compound channels in which C. nudata stabilizes a narrow low flow channel but, unlike many plants, does not slow erosion of the cut banks, such that the bankfull channel continues to move or widen. In some cases, this process is hypothesized to lead to C. nudata patches at the base of banks "detaching" and becoming islands, giving rise to multi-threaded channels. The investigators will use multiple methods to examine these hypotheses. Changes in bank retreat and channel bed erosion/aggradation will be examined using repeated topographic surveys and erosion pins. Bank retreat and island formation will also be examined with aerial imagery. Flow velocity patterns that may explain patterns of erosion/aggradation will be examined with an Acoustic Doppler Current Profiler. With regards to C. nudata distribution, the investigators hypothesize that C. nudata patterns are driven by hydrological variables and sediment type. These hypotheses will be examined with headwaters-to-mouth surveys for C. nudata in three distinct river basins. Until the latter part of the 20th century, river geomorphology focused solely on physical dimensions of river processes. Only recently has vegetation been recognized as having significant effects on river shape and form (Hughes 1997). Nevertheless, current studies of plant-river interactions typically focus on one dimension of this relationship: i.e. either the effects of the river environment on plant communities or the effects of plants on certain physical processes. The proposed research follows Corenblit et al. (2007) who emphasize the reciprocal nature of plant-river relationships and propose the concept of biogeomorphological succession to describe the linked development of river shape and form with riparian plant communities.