The Effects of Clearcutting and Selection Cutting on Streamwater Quality, Vegetative Cover, and Soil Exposure in Northern Wisconsin
University of Wisconsin-Stevens Point, College of Natural Resources
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A clearcut and a selection cut were studied to determine their impacts on stream water quality, vegetative ground cover, and soil exposure. Water samples were taken above and below harvest sites to detect changes in water quality as the streams flowed through the harvest areas. Water samples were collected at 2 week intervals from June through September of the first year after harvesting, and in March, May, and June of the second year after harvesting. Random sample plots were established along transects within the harvested areas and in undisturbed control areas. Estimations of vegetative cover and soil exposure were made on each plot. On the clearcut site dissolved oxygen, turbidity, pH, total alkalinity, total hardness, and calcium concentrations in stream-water increased, while concentrations of total nitrogen, total Kjeldahl nitrogen, and non-filtrable residue in streamwater decreased. Most of the water quality changes were probably due to increased interflow transporting dissolved substances to the stream, and dilution from increased streamflow. Vegetative cover in the clearcut averaged almost 70% during the first growing season and almost 90% in the second growing season. Soil exposure averaged less than 1% during the first growing season, and declined to 0% during the second growing season. Selection cutting affected only one water quality parameter. Nitrite+ nitrate decreased as the stream flowed through the harvested area. This may have been due to dilution from increased streamflow following the harvest. Vegetative cover increased after partial opening of the forest canopy. Coverage increased from a control average of about 25%, to almost 45% during the first growing season, and to almost 60% during the second growing season. Soil exposure was less than 1% during both growing seasons. Neither clearcutting nor selection cutting degraded the integrity of the soil and water resources on these sites.