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United States Department of Agriculture

Agricultural Research Service

Title: Seasonal Relationships Between Dissolved Nitrogen and Woody Vegetation at Multiple Spatial Scales in the Calapooia River Watershed, Oregon, Usa

item Schoenholtz, Stephen - OREGON STATE UNIVERSITY
item Griffith, Stephen
item Wigington, Parker - US EPA
item Steiner, Jeffrey

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 31, 2005
Publication Date: June 30, 2005
Citation: Floyd, W.C., Schoenholtz, S.H., Griffith, S.M., Wigington, P.J., Steiner, J.J. 2005. Seasonal relationships between dissolved nitrogen and woody vegetation at multiple spatial scales in the Calapooia River watershed, Oregon, USA. In Proceedings of the AWRA Specialty Conference: Institutions for Sustainable Watershed Management: Reconciling Physical and Management Ecology in the Asia-Pacific. June 2005, Hawaii.

Technical Abstract: The Calapooia River is a major tributary of the Willamette River in western Oregon, and its watershed is typical of many found in the Willamette Basin. Public and private forested land occur in the steep upper watershed, mixed forest and agriculture lands occur in the middle portion, and the lower portion of the watershed is comprised primarily of grass seed agriculture on relatively flat topography with poorly drained soils. The Oregon Department of Environmental Quality has designated water quality in the Calapooia River as poor, identifying nitrate-nitrogen and ammonium-nitrogen levels as high. To gain a better understanding of the relationship between landuse/landcover (LULC) and dissolved nitrogen (DN) dynamics within the watershed, we selected 90 sites for monthly synoptic surface water quality sampling beginning in October 2003. During wet winter months, we observed a reduction in the apparent function of woody riparian vegetation within 30m of the stream network to reduce surface water nitrate concentration when compared to woody vegetation at the sub-basin level. These results support the hypothesis developed by other research in the region that during the wet winter season, much of the water entering the stream network completely bypasses the riparian buffers as overland flow, especially in areas characterized by poorly drained soils in agricultural settings.

Last Modified: 4/22/2015