Changes in understorey plant species richness following logging and prescribed burning in shrubby dry sclerophyll forests of south-eastern Australia

The impacts of prescribed burning and timber harvesting on species diversity have been the subject of considerable debate. The temporal and spatial scale of these disturbances often presents major limitations to many studies. Here we present the medium-term results of a planned long-term study examining the impacts of logging and prescribed burning on the understorey floristic richness in shrubby dry sclerophyll forest in the south-east of New South Wales, Australia. Generalized estimating equations were used to model the effect of environmental factors and disturbance variables on species richness at the coupe (similar to 30 ha) and plot (similar to 0.01 ha) scale. At the plot scale, fire effects on separate components of the vegetation were broadly consistent with other studies, with frequent fire resulting in a relative increase of species richness for species less than 1 m in height and a decline of larger species taller than this height. At the coupe scale, there was no decline in richness of larger shrub species, possibly owing to the spatial heterogeneity of fire frequency at this scale. Logging resulted in significantly greater species richness in the shrub layer, but had no significant effect on species richness in the ground layer. During the study period, there was a general decline in plant species richness at both coupe and plot scales which occurred independently of imposed management regimes. This is thought to be related to a natural succession following wildfire, and may be due to the absence of high-intensity fire in the study area since 1973, or to an effect related to season of burning.