Effectiveness of streamside management zones in Maine

 

Forestry Best Management Practices (BMPs) have been developed, tested, and implemented through public-private partnerships to protect water quality and aquatic habitats. Streamside management zones (SMZs) are an important component of BMPs in states and provinces throughout North America.

A recurring topic of discussion in BMP programs is the appropriate SMZ prescription in small headwater catchments. This question was addressed in a recent field study in Maine conducted by scientists with the Manomet Center for Conservation Sciences. Timber harvest caused statistically significant increases in chlorophyll a concentration and algal feeding organisms in streams with no streamside buffer. Chemical measures of water quality were not significantly affected by harvest in this study, regardless of SMZ prescription.

Results from this study are presented in “The effectiveness of different buffer widths for protecting water quality and macroinvertebrate and periphyton assemblages of headwater streams in Maine, USA” (Canadian Journal of Fisheries and Aquatic Sciences 67:177-190). The authors are E. Wilkerson, J.M. Hagan, and A. A. Whitman. The study was conducted on lands owned by Plum Creek Timber Company, Seven Islands Land Company, International Paper, and MeadWestvaco Corporation. Funding was provided by NCASI, the Cooperative Forest Research Unit at the University of Maine, Plum Creek Timber Company, the National Fish and Wildlife Foundation, and the Maine Department of Environmental Protection. The abstract follows.

“We evaluated the effect of timber harvesting on water quality and macroinvertebrate and periphyton assemblages in first-order streams in Maine, USA. Fifteen streams were assigned to one of five treatments: clearcutting without a stream buffer, clearcutting with 11 m buffers, clearcutting with 23 m buffers, partial harvesting with no designated buffer, and unharvested controls. Harvest blocks on both sides of the stream were 6 ha and partial harvesting within buffers was allowed. Specific conductivity, pH, dissolved oxygen, turbidity, and soluble reactive phosphorus did not change significantly for 3 years after harvesting in all treatments. Unbuffered streams had significantly elevated concentrations of chlorophyll a as well as increased abundance of algal feeding organisms (Diperta Cricotopus and Diptera Psectrocladius). Streams with 11 m buffers had substantial (10-fold) but nonsignificant increases in chlorophyll a. No other significant changes were detected in other treatment groups. In all treatment groups, the dominant taxa (periphyton Achnanthes minutissimum and macroinvertebrate Chironomidae) are adapted to disturbed environments. We attribute the limited harvest-induced changes to lack of soil disturbance within 8 m of the stream, the small (<40%) proportion of watersheds harvested, and the resilient nature of aquatic organisms. However, small-scale changes may not be detected due to the small sample size, an inherent limitation of field-based studies.”

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