Burning, bulldozing, and the effectiveness of rehabilitation: A study of disturbance response pathways in subalpine vegetation

While plants have evolved a range of strategies to help them persist in the landscape, vegetation response may alter with different types of disturbance.  This research investigates vegetation recovery following (a) bushfire disturbance and (b) massive soil disturbance caused by machine grading of fire containment lines as part of bushfire suppression operations, in the subalpine woodlands of south-eastern Australia. Specifically the study asks: Are patterns in the regeneration response dependent on disturbance type? Can the early regeneration response after disturbance be predicted, and does active assistance in the form of rehabilitation/restoration alter response pathway? Vegetation recovery of three different slope rehabilitation treatments applied to bulldozed fire containment lines constructed in 2003 were compared 2 years and 4 years post-disturbance with the vegetation on sites burnt in 2003, and sites which have remained long undisturbed. Rehabilitation treatments included (1) drainage works, (2) drainage works plus topsoil/windrow replacement, (3) drainage works, topsoil/windrow replacement, and revegetation. Vegetation response was assessed in terms of cover conditions, vegetation height and species composition. Initial (2 year) surveys showed cover conditions of bulldozed sites receiving different rehabilitation treatments was similar, but lower than that of burnt and long undisturbed sites. After 4 years the cover conditions of bulldozed sites showed an increase, but showed more variability with treatment type.  Differences in the composition of the bulldozed and burnt and long undisturbed areas were evident at both 2 and 4 years, with a greater presence of exotics in bulldozed sites irrespective of rehabilitation treatment. Results indicate that response pathways of subalpine vegetation differ with disturbance type in the early stages of recovery and that response patterns may change through time. The outcomes of this research will help inform land managers of the likely response of subalpine vegetation to different disturbances, and the implications of current rehabilitation practices.