Effects of Disturbances Along Hydroelectrical Transmission Corridors Through Peatlands in Northern Manitoba, Canada

Abstract

Understory vegetation and soil factors were studied in forested peatlands along two power lines extending between 50 and 56°N in Manitoba. At 16 sites, comparisons were made between the cleared right-of-ways and adjacent undisturbed forest communities. The primary sources of disturbances in the right-of-ways were (1) initial clearance and line construction, (2) traffic, and (3) vegetation management with herbicides.

Vegetation in the right-of-way is distinguished by altered species abundances rather than changes in floristic composition. The right-of-way community had generally lower abundances of Sphagnum fuscum and ericoid shrubs and a significantly greater extent of exposed peat. Polytrichum strictum was the only species with a higher abundance in the right-of-way. Water chemistry indicated a slight enrichment of the right-of-way environment. The thawing of permafrost in the northern right-of-way sites and subsequent erosion occurred only in areas of heavy traffic. Use of the tree/shrub herbicide picloram in the right-of-way has led to the additional and ecologically undesirable disappearance of such nontargeted species as Sphagnum fuscum.