The effects upon shrubby and herbaceous vegetation of two low-intensity fires and/or grazing by feral rabbits and wombats were studied in a subalpine environment between 1977 and 1984. Fire reduced shrub cover and biomass to low levels and their recovery was slow. When unburnt, tall shrubs increased, then decreased as a result of extreme frost and drought and subsequently continued to decrease. The recovery of the herb cover and biomass after fire was complete within a year except when delayed by drought andlor disturbance by rabbits. Bare ground was less than 2% in the absence of fire and rabbit grazing but increased to nearly 20% after fire in the presence of rabbits. Rabbits reduced the cover and biomass of 39 species of forb, in some cases to zero. Feral rabbit populations survived and multiplied on burnt areas but decreased on areas left unburnt. The implications of this research for the management of similar environments are discussed.

The effects of rabbits and kangaroos, and rabbits alone, on the biomass and species composition of a native grassland dominated by Stipa nitida/nodosa, Danthonia caespitosa and Aristida contorta, and a grassland dominated by the exotic species Hordeum glaucum, Vulpia spp., Medicago laciniata and the native Erodium crinitum growing at Yathong Nature Reserve in central New South Wales was monitored between 1979 and 1985. Rabbits generally favoured the grassy component; kangaroos also favoured grasses but less so. Changes in non-grass species composition due to grazing was generally insignificant. Changes in species composition due to seasonal differences in rainfall was highly significant. No new species appeared on plots exclosed from grazing for 10 years, suggesting that the grazing by livestock, rabbits, and kangaroos in the past has determined the present species composition. The annual biomass consumption by rabbits averaged over 6 years was 100-200 kg ha-1, which is equivalent to reducing the carrying capacity by one sheep for every 2-4 ha rabbit-infested area. In the native grassland the spatial pattern of rabbit grazing, as indicated by faecal pellet distribution, biomass removal, and percentage of 'unpalatable' species in the pasture, shows greatest grazing pressure to be within 50 m of the warren, grazing intensity dropping off from there to 300 m the greatest distance studied. From the start of the study 'palatable' species, especially grasses, were at their lowest density within 50 m of the warren; this appeared to be a historical effect of grazing. No patterns were discernible in the pasture dominated by introduced species. Little change in species composition of these grasslands can be expected under a wide range of grazing pressure, except close to rabbit warrens.

The effects of simulated grazing and burning on biomass production, forage quality (CP and DM digestibility), plant mortality and flowering of 4 native perennial grasses (Poa phillipsiana, P. sieberana, Danthonia pilosa and Festuca asperula) and four perennial forbs (Aciphylla simplicifolia, Arthropodium milleflorum, Bulbine bulbosa and Hypochoeris radicata) growing in Kosciusko National Park were studied over a 16-month period. Cutting at 8-week intervals reduced the amount of regrowth at successive harvests as well as the survival of individuals. The season in which a single cut was made generally had a greater effect on the amount of regrowth than length of the regrowth period. Burning promoted flowering and improved the forage quality of the grasses. Rabbits bred only when they were able to obtain forage with a minimum protein content of 14%, provided mainly by the forb species. The management implications resulting from the interaction of fire and grazing, particularly by rabbits and domestic stock, for ecosystem quality are discussed.

In a series of five trials, three conducted in the field and two in seed-flats in the nursery, it was shown that mulched residues from Phalaris aquatica and Triticum aestivum reduced the germination and production of Trifolium subterraneum. The deleterious effects observed with the mulched residues were not evident when the residues were incorporated into the upper soil layer. It is suggested that a reduction of the residues in pastures before the opening rains in autumn would be an essential requirement to ensure good germination and early seedling vigour from the annual legume component in mixed legume/grass pastures, especially those based on P. aquatica.

Sheep exhibited a high degree of species selection when grazed at different seasons on three contrasting pastures typical of the mosaic of communities occurring over the Shoalhaven Valley. They were 1 . a Themeda australis grassland-typical of native grasslands, 2, a Phalaris tuberosa-Poa labillardieri- Trifolium repens pasture-typical of semi-improved pastures, and 3. a P. labillardieri grassland-typical of degenerate pastures resulting from ineffective attempts to establish improved pasture. Under light stocking, associated minor pasture constituents such as Hypochoeris radicata, Trifolium repens, or both were selected avidly and made a major contribution to a diet of adequately high quality. However when these minor species had been consumed, sheep were forced to eat the dominant grasses and diet quality fell appreciably. The T, australis grassland was substantially inferior to both the P. tuberosa- P. labillardieri-T. repens and P. labillardieri pastures. Cutting or burning P. labillardieri improved its quality and intensive grazing is recommended for areas in which this species predominates.