Natural Regeneration of Ground Storey Vegetation in a Semi-Arid Woodland Following Mechanical Disturbance and Burning. 1. Ground Cover Levels and Composition.

Abstract

A study was made over a period of 12 years of the natural regeneration of vegetation along a corridor corridor cleared for the construction of a natural gas pipeline in a semi-arid woodland in central- western New South Wales. Total cover, proportion of grasses, and species composition were assessed on the infilled trench and on areas from which topsoil had been bladed, as well as on adjacent undisturbed areas and areas burned by a wildfire. All areas were grazed continuously by sheep under normal station management, and by native animals. After four years of about average rainfall, total cover on disturbed areas had regained levels as high or higher than on adjacent areas, and was maintained thereafter. On many individual sites this period was as short as eighteen months. The proportion of grasses remained much lower on disturbed areas, except for some periods of annual grass dominance. Species composition remained very different between disturbed and undisturbed areas, the main difference being in perennial species. However, composition also varied markedly between years, according to rainfall seasonality and competition from previously established plants. Little difference was apparent between undisturbed areas and similar areas which had burned twelve months before the first measurements. Mechanical disturbance caused by trenching and blading had a much greater effect on vegetation than did fire, and the effects were still obvious after twelve years.