Document: MAR-3-63-38

The hydrochemical consequence of catastrophic windthrow in a coastal temperate rainforest, High Island, southeast Alaska.

KRAMER, M.G.* ¹, B.T.BORMANN ², S.M.NAY ² and P.SOLLINS ¹

Oregon State University, Corvallis, OR 97331 USA ¹
USDA Forest Service, Corvallis, OR 97331 USA ²

Abstract:
The objective of the study was to determine the influence of windthrow disturbance on the hydrochemistry of small catchments. The study was conducted on a 200 hectare forested island in the panhandle of southeast Alaska. Four watersheds (0.1 to 0.8 ha in size) with contrasting disturbance histories were selected for the study. An event based sampling scheme was then used to compare hydrochemical properties of each catchment. Nine storms were sampled over a 14 month period, representing a range of antecedant and intensity conditions. Streamflow was measured, and solution samples were collected every 4 hours during each storm from each catchment. Streamflow on more-disturbed catchments peaked 4 to 12 hours later than in less-disturbed catchments. During storm events, streamwater temperatures were more equilibrated to ambient air temperatures in more-disturbed catchments than in less-disturbed catchments. Streams in more-disturbed catchments had higher pH, bicarbonate and base cation concentrations than streams in less-disturbed catchments. These results suggest that catastrophic windthrow disturbance smoothes hydrograph response to storm events, and increases the chemical interaction of rainwater with mineral soil horizons by increasing rainwater infiltration and storage in deeper soil profiles.

Keywords: hydrochemistry, soil disturbance, hydrology, windthrow

This abstract is being presented at: 10:45 AM in session:
Oral Session #42: Disturbance Ecology: Effects of Storms.