Year

2000

Degree Name

Master of Science (Hons.)

Department

Department of Biological Sciences

Abstract

This project investigated the regeneration capacity of a remnant of the endangered plant community Cumberland Plain Woodlands. Many studies have investigated the effect of disturbances such as fire, grazing and trampling on the regeneration ability of species in many different communities. Few studies, however, have measured the interaction between these disturbance factors. In the Sydney region, even fewer studies have measured the interaction which different disturbances have on species within the endangered plant communities of the Cumberland Plain, with most research concentrating on the vegetation growing upon Hawkesbury sandstone.

This research was undertaken within one of the largest remnants of Cumberland Plain Woodlands located at Holsworthy Military Area in southeastern Sydney. This area has been part of the army training area for the last 100 years and forms the boundary of two geographical regions, the Cumberland Plain and the Woronora Plateau. Past management practises have involved the presence of frequent fires with the ability to contain these fires hampered by the presence of unexploded ordnances. There was little shrub or eucalypt regeneration occurring in the study area and it was believed that this was a result of the interaction between these fires and herbivores on the range. The site provided an ideal area to study the interaction between disturbances such as fire, trampling by humans and grazmg on the regeneration of species in a remnant of Cumberland Plain Woodlands.

An exclosure experiment found that after 18 months there was no effect of grazing or trampling on the ability of species to regenerate following fire. There was strong evidence to suggest that fire was important in the regeneration of shrub and eucalypt species with greater richness and abundance measured following fire. The inclusion of a wildfire in the experiment provided an opportunity to study the effect of fire season on the regeneration of species in the understorey. The season of fire was only found to be important for the regeneration of eucalypt species, with an indication that the timing of seed release by the eucalypt species had more of an effect than simply the fire season alone.

A dramatic change in the species composition was measured over the study period. However, this was not due to the interaction between the disturbances and was believed to be a result of favourable rainfall that occurred in the second year of the study. Changes in the percentage cover of grasses versus non-grass species were measured after 18 months and grazing was found to be more influential than the other disturbance factors. More evidence is required to determine whether grass species affects the diversity of non-grass species at Holsworthy in absence of disturbances.

Rabbits, swamp wallabies, wallaroos and eastern grey kangaroos were the four main herbivore species identified foraging in the woodland at Holsworthy. The abundance of scats was used to indicate the number of herbivores in the woodland. Low scat abundances indicated that grazing pressure was low during the study. The location of scats also indicated that herbivores did not favour the unburned areas and suggested that the movement of animals was influenced more by a particular season rather than whether an area was burnt or not.

Investigation of the soil seedbank found it to be dominated by native perennial herbs, which supports other seedbank studies of remnants of Cumberland Plain Woodlands. Heating the soil seedbank to stimulate germination of species was found to be favourable, with greater richness and abundance of species recorded at a temperature of 80°C compared with 40°C. This was found to be important for the regeneration of shrub species, especially the legumes, whose seed dormancy was broken by the heat.

The research in this study found that fire is important for the regeneration of shrub and eucalypt species in the understorey. Therefore, fire must form an important part of the management of this area at Holsworthy. This project forms the basis of the experimental and monitoring component of the Plan of Management for the area at Holsworthy and provides worthwhile data that opens up a whole range of new research projects.

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.