RAPID: How does reduced snowpack in winter impact the availability and processing of stream nutrients in summer?

Oregon State University, Corvallis OR

Investigators

Abstract

Declining snowpack is a growing environmental, social and economic concern across the western United States. The climate of the Pacific Northwest provides little rainfall during middle of summer and early fall, so that streams rely on the legacies of winter snow to maintain higher discharge during spring and into the summer. In 2015, the snowpack was at record low levels in the Cascade Mountains and with severely diminished snowpack in winter, streams that drain Cascade Mountain catchments across Oregon, Washington and California are expected to experience record low summer discharge this year. This project will measure the variation in stream nitrogen concentrations across a large forested watershed in Oregon and determine how nitrogen and life in streams change under these severe drought conditions. Forecasts for the Pacific Northwest suggest that droughts associated with reduced snowpack will be more common in the future, with associated ecological, social and economic consequences, including effects on fish species that rear in headwater ecosystems. This project will support two undergraduate interns. Because it will be conducted in association with other long-term university and U.S. Forest Service research projects, it will leverage the outreach and broader network infrastructure for extending results and engaging with the public and forest managers. Extreme low flow conditions are expected to increase variability in background nutrient concentrations as dilution by surface water declines. In headwater streams, areas with both elevated nutrients and elevated light have higher primary production which in-turn enhances biogeochemical activity. Determining how patterns of nitrogen availability change as flow declines is therefore important in understanding not only where primary production may be elevated but also where biogeochemical hotspots are likely to develop. This work will quantify inorganic nitrogen, light, and in situ chlorophyll a in a synoptic sampling effort that will encompass 12 km of a 4th-order stream network in the Cascade Mountains of Oregon. Working in a drought year will maximize the potential to identify the influences of spatial heterogeneity in nutrient availability.