Classifying and Restoring Pacific Northwest Streams and Riparian Zones for Water Quality and Anadromous Fish Habitat

EPA Grant Number: F13F11135
Title: Classifying and Restoring Pacific Northwest Streams and Riparian Zones for Water Quality and Anadromous Fish Habitat
Investigators: Hough-Snee, Nathaniel Wilson
Institution: Utah State University
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2014 through September 1, 2016
Project Amount: $84,000
RFA: STAR Graduate Fellowships (2013) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Fellowship - Ecology


Wadeable streams comprise large proportions of watersheds’ total stream area. These smaller, low-order streams harbor distinct habitats, biodiversity and hydrogeomorphic processes relative to larger rivers. Because relationships between riparian vegetation and environmental processes may be used to assess ecosystem integrity and future trajectories of change, their classification is a fundamental need for watershed managers. Accordingly, the overarching objective of this research is to effectively classify riparian vegetation communities and how they are likely to respond to multiple environmental processes that are sensitive to climate and land-use change.


This study will focus on wadeable streams of the Columbia and Missouri River Basins, two watersheds that provide crucial habitat for threatened and endangered salmonid species. Using existing riparian vegetation data collected by the USDA Forest Service, reaches will be clustered into community groups based on the compositional similarity of their riparian vegetation. Environmental attributes that filter vegetation from regional species pools down to those species that can occur at a given reach will be used to explain these patterns in riparian vegetation. These environmental filters originate at three major scales—the landscape, the watershed and stream buffer, and stream—and they will be grouped accordingly to partition the explanatory power of filters on vegetation composition. By correlating each riparian vegetation community to multiscale environmental filters, and the scales at which they originate, the realized niches of each community and component species can be identified. Those environmental filters that differ between communities also may be thresholds between vegetation transitions that can be modeled. By modeling vegetation under filters’ predicted global change scenarios, future distributions of riparian vegetation communities can be projected.

Expected Results:

Previous studies have predominantly looked at patterns in riparian plant diversity at either small spatial extents, or in large rivers. Because wadeable streams generally connect hill slopes to the fluvial environment, it is likely that distinct filters from some of the three scales will correspond to each riparian vegetation community. This is because it is likely that environmental processes will hierarchically shape riparian vegetation communities; that is, large-scale environmental filters will distinguish many communities’ environmental tolerances before watershed and stream-scale filters differentiate riparian vegetation communities. Due to the large spatial extent of the study area, it is likely that climatic gradients shape riparian vegetation before other processes. Climate and watershed setting will likely feedback on the hydrologic processes that influence channel form, creating hydroclimatic gradients across which vegetation will assemble. It also is anticipated that watershed disturbances, such as grazing, will create tipping points between vegetation types that otherwise have similar bioclimatic and fluvial niches.

Potential to Further Environmental/Human Health Protection

As broad global change occurs from shifts in climate, land use and disturbance regimes, wadeable streams and their riparian zones will be exposed to numerous perturbations. By identifying the environmental drivers of riparian and aquatic resources within watersheds that support threatened and endangered fish and wildlife, agencies will be better prepared to manage streams and riparian areas for resilience to global change. The results of this research will help inform decision making at the broad spatial scales relevant to land managers within the upper Missouri and interior Columbia River basins, while also elucidating the mechanisms that drive riparian plant community assembly across landscapes.

Supplemental Keywords:

Columbia River Basin, ecosystem assessment and modeling, stream habitat

Progress and Final Reports:

  • 2015
  • Final