Water Resources Research Act Program

Details for Project ID 2008MT165B

The Importance of Ecologically Connected Streams to the Biological Diversity of Watersheds: a case study in the St. Regis River subbasin, Montana

Institute: Montana
Year Established: 2008 Start Date: 2008-03-01 End Date: 2010-02-28
Total Federal Funds: $13,860 Total Non-Federal Funds: $27,720

Principal Investigators: Winsor Lowe

Project Summary: Headwater streams account for more than 70% of total stream channel length in the U.S. and they are guardians of rare and endangered species, clean water, and other important ecological services on which humans rely. But headwater streams may lose protection under the Clean Water Act (CWA) because a Supreme Court opinion interpreted the jurisdiction of the CWA to navigable waters and to only those non-navigable waters that function as a significant nexus to larger, downstream aquatic ecosystems. To satisfy the CWAs significant nexus clause and extend protection to headwater streams, we must improve understanding of the ecological processes in upper reaches that structure biodiversity in lower reaches. More importantly, to protect and restore these critical linkages, we must understand how they are altered by humans.

This proposed research will investigate the importance of healthy and connected headwater stream networks to Idaho Giant salamander (Dicamptodon atterimus; IGS) distribution, abundance, and persistence in headwater streams of the St. Regis River subbasin of western Montana. The IGS is listed as a state species of concern, but little is known about its natural history and ecology because there have only been five recorded observations in Montana prior to our preliminary research. This proposed research will provide specific information on IGS distribution and abundance, identify natural and anthropogenic factors that influence distribution and abundance, and provide critical information on the spatial extent of land management required to facilitate IGS population persistence.

This research has four objectives: (1) to map the distribution and abundance of IGSs, (2) to test how landscape-scale processes, including road activity and timber harvest, and local-scale processes affect IGS distribution and abundance, (3) to determine how connectivity along stream networks affects IGS persistence in upper and lower stream reaches, and (4) to identify best practices that allow for intact, ecological connections along a stream network and natural resource use by humans.

To accomplish these objectives, we will survey 48 headwater streams in the St. Regis River subbasin, which will be spatially nested within eight minimally-disturbed drainages and eight drainages impacted by timber harvest and active roads. Within each drainage, we will randomly select 3 headwater streams to sample. Each stream will be divided into two 50-m study reaches separated by 200 m and each reach will be surveyed for IGS occupancy (presence/absence) and abundance. We will characterize local and landscape-scale characteristics of each surveyed stream to identify variables that influence patterns of IGS distribution and abundance. We will use genetics (microsatellite DNA markers) and mark-capture-recapture (MCR) to assess the importance of connected stream networks to IGS population persistence and to determine the affect of human disturbance on stream connectivity. Finally, we will develop specific recommendations on the location and intensity of timber harvest and road activity that least affect IGS distribution and abundance.

This research will provide land managers with explanatory and predictive models that address the ecological outcomes of alternative management actions, such as the extent of timber harvest or road construction. In addition, these data will set the foundation for long-term monitoring of the IGS, an important indicator of healthy headwater ecosystems. Baseline data are critical to ascertain whether programs or practices are accomplishing management objectives and therefore to inform adaptive management strategies.