Effects of long-term military training traffic on forest vegetation in central minnesota

Abstract

We studied vegetation on traveled and on traveled loamy sands on military training land in central Minnesota to identify traffic-induced differences in species composition, cover, diversity, growth rates, and tree condition. Long-term military traffic resulted in a 23% reduction in overstory basal area, a 14% reduction in canopy cover, a 43% reduction in overstory stem density, and a 20% reduction in overstory species diversity compared with adjacent untraveled areas. Most of the overstory basal area reduction was accounted for by a 78% reduction in quaking aspen basal area. Crown dieback was not significantly affected by traffic. Midstory tree and shrub density was 70% lower on traveled areas. Herbaceous vegetation was denser and more diverse in traveled areas. Traffic caused a six-fold increase in bare soil area on sloping soils, but had no effect on bare soil area on level sites. Our data suggest that moderate, long-term traffic on loamy sand soils results in a relatively stable system which can he thought of as in equilibrium between traffic, natural regenerative forces, and management activities. We caution managers that quaking aspen may decline under traffic, and remind them of the risk of erosion on traveled slopes.