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Effects of Warming on Forested Streams

Researchers examine how climate change impacts carbon in streams

An important basis for stream function is the input of carbon through leaves and wood from surrounding forests. As global temperatures rise and stream waters warm, the ecological processes within them begin to change. This research by RBC affiliates and collaborators examines the consequences of warming on how the carbon contained in leaves, fallen trees, and other natural organic materials is processed within streams. The goal of this project is to understand how warming impacts not only the rates of carbon processing in streams, but also the fate of carbon — whether inputs are released as carbon dioxide, sent downstream, or consumed by stream organisms.

The fate of carbon may have implications for the health of the ecosystem.  For example, if warmer temperatures lead to carbon being processed more quickly, organisms may run out of food sources. Additionally, if increased amounts of carbon dioxide are released into the atmosphere when streams warm, warmer streams may contribute more to climate change.

To understand these processes, researchers examine how streams respond to temperature at scales from the individual organism to the entire landscape. Some of these experiments were performed in constructed channels to mimic stream conditions at small scales. These artificial streams are used to test how stream organisms, particularly aquatic insects that fish rely on for food, respond to increasing temperature. Other parts of the project include a long-term (3-year) experimental warming of a whole stream to compare the realistic response of organisms and carbon dynamics to a reference stream. The team also leveraged the temperature variation across elevation, season, and topographic aspect to determine relationships between temperature and carbon dynamics. These findings are now being used to predict how carbon processes will play out over hundreds of square miles of the Southern Appalachian landscape.

In addition, this team is collaborating with community groups to develop an understanding of how temperatures currently vary across Southern Appalachian streams, and have used this data to predict how fish habitat will change in the future. The team built a statistical model of stream temperatures to predict how Brook trout habitat may change with climate warming. This study included partnerships with Trout Unlimited and Mainspring Conservation Trust. Former River Basin Center research technician Emily Chalfin and RBC Research Coordinator Phillip Bumpers led the temperature modeling effort, which is summarized in this ArcGIS StoryMap.

This project provides information on the amount of change that is predicted to occur in Southern Appalachian streams due to climate warming to inform stewardship and management of these valuable ecosystems.  It has been made possible through funding by the NSF, site access and research infrastructure provided by the USDA Forest Service, and the contributions of faculty, staff, graduate students, and undergraduate students at the collaborating institution.  These include faculty members Jon Benstead (lead PI, UA), Co-PIs Amy Rosemond, (UGA) Vlad Gulis (CCU), Ashley Helton (UCONN), Erin Hotckiss (VT), and Senior Personnel Seth Wenger (UGA). Project managers, technicians, and graduate students include Kaity Ackerman (CCU), Phillip Bumpers (research coordinator, UGA), Emily Chalfin (UGA), Carolyn Cummins (UGA), Danielle Hare (UCONN), Kyle Madoni (UA), Laura Naslund (UGA), Hunter Pates (CCU), Phoenix Rogers (UA), and Nathan Tomczyk (UGA). Scholars who were undergraduates when they contributed to the project based at UGA include Charlie Bond, Garrett Frandson, Maggie England-Johns, Anna Kaz, Quentin Rice, Jessica Mitchell, Olivia Allen, and Ally Whiteis. Funding for the UGA portion of this work was supported by NSF DEB #1655789.