An important issue in conservation biology is the extent to which one group of organisms can function as a surrogate for less well-known groups. We explored the extent to which vascular plant species diversity (both ␣ -diversity, or species richness, and ␤ -diversity, or turnover) Diversidad de Plantas Vasculares como Substituto de la Diversidad de Briofitas y Líquenes Resumen: Un asunto importante en biología de la conservación es la magnitud con la cual un grupo de organismos puede funcionar como substituto de grupos menos conocidos. Exploramos la magnitud a la cual la diversidad de plantas vasculares (tanto diversidad ␣ o riqueza de especies y diversidad ␤ o revovación) y los subgrupos sotobosque, dosel y helechos pueden actuar como substitutos de la diversidad de especies de briofitas y líquenes. Muestreamos 35 sitios en un rango de tipos de bosque en las tierras bajas de la costa Este de

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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 (~30 ha) and plot (~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.

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Stock grazing has degraded many riparian ecosystems around the world. However, the potential for ecosystem recovery following the removal of grazing stock is poorly known. We developed a conceptual model to predict the responses of native and exotic herbaceous plants to grazing exclusion, based on site productivity and the degree of initial vegetation degradation. The effects of excluding grazing stock on richness, cover and composition of herbaceous plants were examined over 12 years in the degraded understorey of a riparian forest in Gulpa Island State Forest in south-eastern Australia. We predicted that grazing exclusion would lead to limited changes in vegetation cover, richness and composition, owing to presumed low site productivity and the high degree of understorey degradation. Results showed that the cover, richness and composition of native and exotic species varied significantly among years. Over all plots, regions and years, total cover was slightly but significantly lower in grazed than in ungrazed plots (43.4% vs. 50.8%). While the cover of native plants increased over time in both treatments, the rate of increase was slightly greater in ungrazed plots. Grazing exclusion had no effect on the richness of native or exotic species, but had a significant but minor impact on plant composition, with different common species (mostly exotics) being promoted or diminished in ungrazed plots. The composition of grazed and ungrazed areas did not become more different over time. Overall, the effects that could be attributed to grazing exclusion were relatively minor and transient. Results are consistent with predictions based on site productivity and initial degradation, and should not be extrapolated to other more productive, or less degraded, riparian systems.