Impacts of road disturbance on soil properties and on exotic plant occurrence in subalpine areas of the Australian Alps

The construction and maintenance of roads in the Australian Alps has caused profound disturbance to the natural existing soil and vegetation, as well as the introduction and proliferation of exotic plant species. This study examined three ecotypes associated with roads. These ecotypes were tested for differences in soil characteristics and occurrence of different plant species. Differences in chemical and physical soil properties were found between road verges and adjacent native vegetation areas. Soils from natural areas had higher humus levels, less gravel and sand, higher levels of nutrients, and higher pH and electrical conductivity than road verges. A relationship was found between soil properties and the occurrence of different exotic plant species along roadsides. Exotics dominated in areas along the road verge and road drainage lines. The dominant exotic found in these ecotypes was Achillea millefolium (yarrow). These ecotypes were characterized by high water and sediment wash off, which had significantly higher soil pH and exchangeable levels of calcium and potassium than natural areas and disturbed areas without yarrow.