A study was made over a period of 12 years of the natural regeneration of vegetation along a 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 areas from which topsoil had been bladed, as well as on adjacent undisturbed areas or areas burned by a wildfire. All areas were grazed continuously by sheep under normal station management. The effects of mechanical disturbance and of burning on individual species were measured in terms of species dominance and occurrence. Some insight was also gained in to the successional process on bared sites and in to the effects of the timing of seasonal rainfall on species composition. Of the 75 major species recorded, 15 were found to have greater occurrence on trenched sites, 46 decreased in occurrence and 14 showed no clear trend. Perennial grasses and small annual plants were the main decreasers, whilst Medicago spp., Erodium crinitum, Hordeum leporinum and certain 'weedy' annuals were the main increasers. Some of the early colonisers lasted only a few years or even less in any quantity, thereafter to be replaced by other increasers. Burning had little effect on the long-term occurrence of Stipa variabilis, Wahlenbergia spp., Helipterum spp., Calotis cuneifolia and some minor species. Eragrostis lacunaria appeared to decrease, while several annual plants were more common on burned areas.
Does mechanical disturbance affect the performance and species composition of submerged macrophyte communities?
