Distribution, frequency and density of the weed Achillea millefolium Yarrow in the Snowy Mountains, Australia

Abstract

This paper examines the distribution of Achillea millefolium L. (Yarrow, Asteraceae), in the Snowy Mountains. Location data from species specific surveys, field experiments and 18 general vegetation surveys were mapped in relation to altitude/floristic zone, climatic parameters (rainfall and temperature) and location of roads and tracks. Achillea millefolium is less common with increasing altitude and benefits from human disturbance. Using all location data, Yarrow was found at 376 sites; nearly all associated with human disturbance (91% of sites) mostly road or trail verges (72%) and around buildings and other ski tourism infrastructure. It occurred along ~100 km of public access roads, management trails and walking tracks, from the tableland to the alpine zone (800 m to 2100 m altitude). The general vegetation surveys, however, indicate that although it can be found in 15% of disturbed sites, it is uncommon in undisturbed vegetation (4%). Yarrow occurred at high density around buildings and low density along walking tracks in the species specific surveys. The distribution of A. millefolium demonstrates that human disturbance provides favourable habitats for weeds even in mountains. Although its distribution was affected by altitude, A. millefolium was able to establish and grow on some of the highest mountains in Australia, along tracks. Increased disturbances as well as climate change are likely to facilitate its spread.