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

河流修复目前是整个西海岸巨大投资的重点，其动机是为受威胁的太平洋鲑鱼种群改善栖息地。这项研究将有助于这些努力：Carex NuData是一种遍及西海岸的本土莎草，越来越多地被视为恢复目标的促进者，但土地和河流管理者缺乏对它可能如何改变河道形态以及哪些环境变量对其生存至关重要的清楚了解。这项拟议的研究探索了河岸莎草C.NuData与其河流环境之间的相互作用。这项研究的独特之处在于它的目的是考察这种关系的两个方面：河流的物理环境和水流模式如何驱动C.NuData的分布，以及C.NuData如何改变河流的物理过程。C.NuData引起了中福克John Day河调查人员的注意，在河岸上放牧的牛撤离后，NuData在那里大量爆炸。C.NuData沿着低流量渠道的边缘、砾石坝、路堤底部和AS岛生长，其密集的根系使其能够承受强大的水流。C.NuData似乎正在以增加河流复杂性的方式改变河道形态，从而改善鱼类栖息地，促进河流恢复目标。研究人员推测，C.NuData促进了复合水道的进化，在复合水道中，C.NuData稳定了狭窄的低流量渠道，但与许多植物不同，它不会减缓切割河岸的侵蚀，从而使河岸满的渠道继续移动或加宽。在某些情况下，这一过程被假设为导致C·NuData补丁在银行的底部“分离”并成为孤岛，从而产生多线程通道。调查人员将使用多种方法来检验这些假说。河岸后退和河床冲刷/淤积的变化将使用重复的地形测量和冲蚀钉进行检查。岸边撤退和岛屿形成也将通过航空图像进行检查。可以解释冲刷/淤积模式的流速模式将用声学多普勒水流剖面仪进行检查。关于C.nuData的分布，研究人员假设C.nuData的分布模式是由水文变量和沉积物类型驱动的。这些假设将通过C.NuData在三个不同的河流流域进行的源头到嘴巴的调查来检验。直到20世纪后半叶，河流地貌学只关注河流过程的物理维度。直到最近，人们才认识到植被对河流形状和形态有重大影响(Hughes，1997)。然而，目前对植物-河流相互作用的研究通常集中在这种关系的一个维度上：即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。这项拟议的研究是在Corenblit等人之后进行的。(2007)，他强调了植物-河流关系的互惠性质，并提出了生物地貌演替的概念，以描述河流形态和形态与河岸植物群落的联系发展。

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.