Water Resources Research Act Program

Details for Project ID 2011WA328B

Ecohydrology of Invasive Reed Canary Grass

Institute: Washington
Year Established: 2011 Start Date: 2011-03-01 End Date: 2012-09-30
Total Federal Funds: $29,992 Total Non-Federal Funds: $59,999

Principal Investigators: Camille McNeely, Rebecca Brown, Carmen Nezat, Suzanne Schwab

Abstract: Ecohydrology of Invasive Reed Canary Grass (Philaris arundinacea) We will investigate the riparian ecohydrology of invasive Reed Canary Grass (Philaris arundinacea); our goal is to determine if summer stream discharge is altered by P. arundinacea domination of the riparian zone. Streams within the Eastern Washington Palouse and Scablands suffer from water quality and habitat impairments, including nutrient and sediment loading and high water temperature. These impairments are most significant during the summer; poor water quality is associated with low stream discharge, which lessens dilution of pollutants and allows water temperature to warm more quickly. We hope to determine whether invasion of riparian zones by P. arundinacea contributes to reduced summer stream flow. P. arundinacea is an invasive, European perennial grass that commonly develops monocultures in North American wetlands and riparian zones. It is a pervasive invader that threatens native plant diversity suspect that P. arundinacea monocultures may also modify local riparian hydrology as a result of their long growing season and high rates of evapotranspiration. We will use two complimentary techniques to test these hypotheses: direct measurements of evapotranspiration at leaf and plot scale using stomatal conductance and analysis of stable oxygen and hydrogen isotope tracers to determine the sources of water used by different vegetation types. We predict: 1.Timing of greatest declines in riparian water tables and discharge will correlate with periods of high evapotranspiration by riparian vegetation. 2.Stomatal conductance at the leaf scale will be highest in P. arundinacea, compared to other herbaceous and woody species. 3.Evapotranspiration at the plot scale will be higher for P. arundinacea dominated communities than for communities dominated by other herbaceous vegetation accessing the same shallow water sources. However, the higher per area biomass and leaf area of woody plants will result in higher ET at the plot scale compared to P. arundinacea, or other herbaceous vegetation. 4.Stable isotope analysis will reveal that P. arundinacea and other herbaceous plants use primarily stream water, soil water, and shallow groundwater, with increasing reliance on groundwater over the summer season. Woody vegetation will use a substantially larger portion groundwater. We hope our data will help assess one potential role of P. arundinacea in exacerbating water quality and watershed management concerns in the northwestern U.S., and provide useful information to management agencies. We also hope that this project will be a first step in a larger assessment of the role of reed canary grass in riparian and stream ecosystems, including effects on water quality, sediment and channel dynamics, and stream food webs.