A new collaborative research project funded by the National Science Foundation (NSF) at the Andrews Forest (AND) Long Term Ecological Research (LTER) program will examine how carbon is processed, exported and stored within small, steep, forested watersheds in the western Oregon cascades. Titled “Collaborative Research: How do hydrology and biogeochemistry control carbon flux from headwater streams to the atmosphere?” the project is led by Roy Haggerty (Oregon State University,Geosciences Dept.), Steve Wondzell (US Forest Service Research), Kevin Feris (Boise State Univ.) and Daniele Tonina (Univ. of Idaho),
With its rapidly growing 45-year-old forest, the much-studied Watershed 1 in the Andrews Forest is the focal point of field and modeling studies involving carbon dynamics and how they are influenced by interactions between atmospheric, hydrologic, and biogeochemical components of the ecosystem at the point they interface along the valley floor. Understanding how carbon is utilized and transported through small streams is significant to the hydrology and ecology of the watershed, as well as to regional and global carbon cycling. Forests of the western Oregon cascades have extremely high rates of primary production, absorbing significant quantities of carbon dioxide (CO2) from the atmosphere. Absorbed CO2 is transformed into organic carbon, the bulk of which is respired directly back to the atmosphere by the forest. The remaining is stored as biomass or transported through leaf fall, runoff, groundwater and episodic landslides to the stream system. The fraction that reaches the stream is known to be significant and may comprise as much as 25% of net ecosystem production.
The project will include experimental measurements of carbon processing rates in hyporheic mesocosms (experimental water enclosures in the hyporheic zone, the region beneath and alongside a stream bed where shallow groundwater mixes with surface water), and larger-scale direct observations from the Watershed’s well network. These observations will be used to identify and lay out the parameters of the simulation model known as PFloTran that will in turn be used to simulate the hydrologic and biogeochemical processes that control carbon processing at the watershed scale. PFloTran has the potential to link with the Community Earth System Model to provide a better understanding of the role of mountainous headwater ecosystems in global carbon dynamics.