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

Abstract

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.

Resilience of a eucalypt forest woody understorey to long-term (34 - 55 years) repeated burning in subtropical Australia

“…Plot burn coverage had a significant negative influence on the richness of taxa 3-7.5 m in height, densities of other woody taxa 1-7.5 m in height and densities of eucalypts ,1 m in height. This supports the idea that patchiness allows individuals to escape the effects of repeated fire, as individuals that would normally be killed or suppressed by fire are able to survive and grow in unburnt patches (Penman et al 2008). If understorey plants are able to avoid the effects of fire for 1 or more years, they may be more likely to survive the next fire, because fire resistance increases with age and height in many woody plant species (Fensham and Fairfax 2006;Gignoux et al 2009).…”

“…Persistence of most plant taxa in the frequently burnt areas may be partly attributed to the patchiness of the fire treatments (Ooi et al 2006;Penman et al 2008). Fires in the annually burnt treatment were patchier in nature than those in the triennially burnt treatment owing to low fuel loads.…”

“…Lemon 1946;Hodgkinson et al 1990). Frequent fire may also reduce long-term fuel accumulation (Birk and Bridges 1989), minimising the potential wildfire effects to human life, properties and other assets, such as timber resources (Sneeuwjagt 2008; although see Penman et al 2011a for a discussion on the effectiveness of prescribed burning programs).…”

“…Debate continues in Australia and internationally regarding the benefits and ecological costs associated with frequent prescribed burning (Fernandes and Botelho 2003;Sneeuwjagt 2008;Penman et al 2011a). Published management recommendations for dry sclerophyll eucalypt forests and woodlands with shrubby understories usually suggest interfire intervals greater than 6 years, based on ecological considerations (e.g.…”

The influence of prescribed fire on the extent of wildfire in savanna landscapes of western Arnhem Land, Australia

“…This analysis was conducted as a Generalised Linear Model. To account for spatial autocorrelation, we added a Spatially-Lagged Response Variable (Haining 2003;Penman, Binns et al 2008) to the model. This was the mean LDS fire frequency in the neighbouring blocks (mean of eight values for those blocks not on an edge).…”