contemporary forest practices

Local and Downstream Impacts of Contemporary Forest Practices on Sediment Yield
Skaugset A., N. Zègre, A. Simmons, and H. Owens

The hydrological impacts of forest management remains a primary concern to resources managers yet much of our understanding about these effects comes from historic paired watershed studies conducted up to four decades ago. While these early studies play a critical role in the development of current best management practices and forest harvesting practices, results do not necessarily reflect the effects of modern forest harvesting. In this presentation we show results of a study conducted at the decade-long Hinkle Creek Paired Watershed Study that examines the local and downstream impacts of forest harvesting on streamflow. Streamflow was measured at the outlet of six (4 treatment|2 reference) headwater catchments and two (1 treatment|1 reference) 3rd –order watersheds. Regression-based change detection models were developed between reference and treated catchments using mean monthly streamflow, instantaneous maximum peak flow, and storm quick flow. Contemporary forest harvesting practices, defined by the Oregon Forest Practice Rule, were used to clear-cut harvest trees in four experimental headwater catchments, while reference catchments remained untouched. Forest harvesting treatments were initiated in the experimental headwater catchments in 2005 (1st entry) removing trees from 13% to 65% of catchment area following a fifteen to eighteen month calibration period.

DISCIPLINE: Hydrology & Water Quality    STUDY: Hinkle Creek    TYPE: Presentations    TAGS: sediment yield, contemporary forest practices, Discharge
The Influence of Contemporary Forest Management on Stream Nutrient Concentrations in an Industrialized Forest in the Oregon Cascades
Meininger, W. S.

The increased demand for wood and fiber from a continually shrinking land base has resulted in the use of intensively managed forest plantations. Because much of the water flowing in rivers in the U.S. originates as precipitation in forests, there is a justified concern about the impacts of forest management on water quality. Nutrient concentrations were measured in eight streams from October 2002 to September 2011 to assess nutrient response to contemporary forest practices at the Hinkle Creek Paired Watershed Study in the Oregon Cascades. This period of time included a two-year pre-treatment calibration between control and treatment watersheds, a fertilization treatment of both basins in October 2004, and a post-treatment period from 2005 to 2011. Stream water samples were analyzed for nitrogen, phosphorus, calcium, sodium, potassium, magnesium, sulfate, chloride, and silicon as well as specific conductance, pH, and alkalinity. All treatment watersheds showed a statistically significant increase in NO3 + NO2 concentrations after clearcutting (p < 0.001). The slope of the streambed through the disturbance was a stronger predictor of the magnitude of the response than was the magnitude of disturbance. Concentrations of NO3 + NO2 observed during the calibration period were similar to concentrations observed in an old-growth forest in the H.J. Andrews, suggesting that nutrient processing within the Hinkle Creek watershed had returned to levels that existed prior.

DISCIPLINE: Hydrology & Water Quality    STUDY: Hinkle Creek    TYPE: Theses    TAGS: Nutrient concentrations, contemporary forest practices, clearcutting, fertilization treatment
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