Effects of soil disturbance from roadworks on roadside shrub populations in South-Eastern Australia

In many fragmented agricultural regions of south-eastern Australia, roadside vegetation provides important refuges for threatened native fauna and isolated populations of plant species. However, as roads are transport corridors for humans and their vehicles, species survival is affected through destruction and modification of remaining habitat by human activity. The effects of soil disturbance from roadworks on the structural dynamics and spatial patterning of roadside Acacia populations was investigated in the Lockhart Shire study area, NSW, Australia. Classification and ordination of size structures of Acacia pycnantha, A. montana and A. decora showed distinct groups of colonising, stable and senescent populations. Soil disturbance from previous roadworks was recorded in 88 percent of populations, and there was a significant relationship between major recruitment pulses and roadworks events in Acacia populations. Spatial pattern analysis using the Network K-function showed significant clustering of older senescent populations, and Discriminant Function Analyses revealed that road verge width, road category, disturbance intensity, and distance to nearest town were highly significant variables in relation to disturbance regimes from roadworks activities. These results have highlighted the importance of understanding human logic regarding roadworks activities, in ongoing management of roadside vegetation, and has important consequences regarding conservation of these unique environments.