Habitat distributions of 12 co-occurring wallaby grasses (Rytidosperma spp., Poaceae) and their response to a transition from pastoral to conservation land use

The extent and abundance of Rytidosperma Steud. species in mixed woodland, forest and derived grassland was examined over a 15-year period following removal of long-term sheep grazing. Ground-layer vegetation in 73 permanent plots was surveyed five times between 2005 and 2020 in a 50-ha paddock on the southern tablelands of New South Wales. Sites were stratified over the slope positions and micro-habitats represented at the site. Of the 12 Rytidosperma species recorded, only R. pallidum was morphologically and ecologically distinct in the field. The remaining 11 species, termed `cryptic Rytidosperma', were assessed using a novel sampling method developed for this group. Rytidosperma pallida was the only species strongly associated with sclerophyll forest habitat. The 11 other species varied in their habitat preferences but, as a group, were most dominant and persistent on upper slopes. Over the 15 years, the relative abundance of R. pilosum, R. erianthum, R. monticola, R. carphoides and R. caespitosum declined as annual exotics, native sub-shrubs and low-palatability graminoids became more dominant. But only one species (R. pilosum) significantly declined in overall frequency of presence (constancy) in the plots. The changes observed suggest that when pastoral land is converted to conservation management, reduced grazing pressure could affect the abundance of Rytidosperma species important to other species, such as the threatened moth Synemon plana.