Biomass and floristic patterns in the ground layer vegetation of box-gum grassy eucalypt woodland in Goorooyarroo and Mulligans Flat Nature Reserves, Australian Capital Territory

摘要

We establish a methodology and present baseline data for a long-term grassy woodland restoration study that commenced in 2007 in two nature reserves (Mulligans Flat, Goorooyarroo (35 degrees 9-13' S; 149 degrees 9-12' E)) totalling 1386 ha on the northern boundary of Canberra, in the Australian Capital Territory in south eastern Australia. The experimental infrastructure comprises 96 x 1 ha sites established in Eucalyptus blakelyi / Eucalyptus melliodora dominated woodland. These are being subjected to varying kangaroo grazing pressure and augmentation with logs, while burning treatments are planned. One reserve (Mulligans Flat) has been fenced for feral predator control and contains half the sites, forming a companion experiment to Goorooyarroo. Our baseline floristic study comprised estimates, at the site level, of ground layer biomass, species biomass, ground cover types and soil (0-10 cm) properties. From these data we conclude that the groundlayer vegetation is dominated by Joycea Pallida, Austrodanthonia spp., Themeda australis and Aristida ramosa. These grasses varied in abundance according to differences in soil pH, phosphorus and to a lesser extent nitrates. Forb frequencies were highly sensitive to nitrate levels with annual exotic forbs dominating at high nitrate sites. More generally, soil nutrient levels and exotic species in some sites indicated areas of previous pasture improvement activities. Biomass estimates indicated extremely high grazing pressure, sufficient to negatively affect the habitat quality for ground-dependent fauna and some soil processes. These data will provide an important basis for examining rates of ecosystem recovery under different restoration strategies.