Latitudinal gradients in vegetation along a disturbed transmission line right-of-way in Manitoba

Abstract

A floristic survey was conducted along the high voltage direct current transmission line right-of-way in Manitoba. The right-of-way extends over 895 km, from 50 to 56° N latitude, intersecting six of the natural vegetation zones. The disturbed right-of-way communities differ from the adjacent undisturbed communities in both species composition and physiognomy. The majority of disturbed communities are characterized by high graminoid richness and cover, principally as a result of such secondary disturbances as grazing, mowing, herbicide treatment, and fire. In contrast, the majority of undisturbed communities are woodland or forested areas consisting of species from a variety of growth forms. Species richness in most plant growth forms (graminoid, forb, and tall shrub) decreases significantly with an increase in latitude in both the undisturbed and disturbed communities; the only exception being the low shrub group, which occurs predominantly in the northern latitudes. The composition of the undisturbed communities is highly influenced by changes in latitude and three major vegetation zones are recognizable. This strong latitudinal gradient is absent from the disturbed communities where the majority of species are ubiquitous.