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In many agricultural landscapes, roadside (or road verge) environments provide important refuge for threatened native species and ecosystems, and are often selected as benchmark sites to guide restoration activities. However few studies have investigated potential temporal variability in roadside vegetation conditions. In this paper we used archived cadastral maps to determine road age and examine potential variability in roadside vegetation structures in a typical rural landscape in south-eastern Australia. We found significant differences in the density of mature trees for road segments in different road-age categories. The oldest roads (<1870s) were characterized by having the greatest density of large hollow-bearing Eucalyptus trees, but few native conifer trees or shrubs. Roads surveyed when broad-scale clearing commenced (1870–1879), and not the oldest roads, were found to be more intact in terms of the density of large pre-settlement trees, range of tree stem-size classes and overall shrub diversity. By contrast, the youngest roads (post-1900s) had the greatest number of native conifer trees, but few shrubs or large Eucalyptus trees. As a result, roads of different ages had different densities of hollow-bearing trees, which is discussed in terms of past land-use legacies. These results have important implications for selecting roadsides as benchmark sites for restoration activities, and highlight the critical importance of roadsides to conserving native biota in agricultural landscapes. [Copyright &y& Elsevier]

A survey of cotton ( Gossypium hirsutum) volunteers was conducted along the 1400 km of a cottonseed transport route in north-east Australia to determine the extent of naturalisation from spilt seed. In each year, 1% of the road distance was inspected for volunteer plants. The survey results were juxtaposed with the eco-climatic suitability predictions from inferential modelling. Over 3 years, 22 cotton plants were found at eight sites. Within the cotton production region, volunteers averaged 2.28 plants km−1 of road; their most likely source was seed cotton spilt during the previous harvest. Further north, three plants were found over 3 years, at an average density of 0.089 plants km−1 of road; all three plants were found in locations with a positive Ecoclimatic Index. No secondary spread was detected. Roadside slashing reduced plant survival and the potential to produce seed. In the wet tropics, weed competition and slashing prevented volunteers establishing. The surveys indicate that roadsides in north-east Australia are a hostile environment for the establishment of cotton plants, with no evidence of naturalisation or secondary spread. Current transport practices utilizing fully covered loads present negligible risk of producing naturalised populations of cotton (either transgenic or non-transgenic) on roadsides in north-east Australia. [ABSTRACT FROM AUTHOR]

Management of plant invaders causes disturbance and the compounding effects of both invasion and management on biodiversity merit rigorous assessment. We explored the impacts of both plant invasion and management disturbance in coastal dune communities of Australia invaded by the introduced shrub bitou bush (Chrysanthemoides monilifera ssp. Rotundata). We compared the effects of intensive, manually based invader control with those of extensive control (mainly herbicide spraying from aircraft) across fore dune communities. We examined one management regime, which was typically intensive, in hind dune communities. Our main aim was to test the prediction that intensive methods would achieve better biodiversity outcomes than extensive approaches in fore dune communities. We found that extensive management created native species complements that diverged from non-invaded sites while intensive management approached non-invaded site conditions. However, intensively managed sites were also richer in other exotic species than extensively managed sites. Thus, while biodiversity outcomes were better under intensive management, the risk profile of such sites was increased by the greater array of exotics that could potentially replace the original invader. The positive effects of management evident on some fore dunes were not found in hind dunes, where managed sites had the highest exotic species richness and similar bitou bush seedling abundance as both non-invaded and bitou-invaded sites. Hind dune managed sites were also compositionally distinct from non-invaded sites. Thus fore and hind dune communities exhibited different responses to bitou management regimes. [Copyright &y& Elsevier]

Fires are integral to the healthy functioning of most ecosystems and are often poorly understood in policy and management, however, the relationship between floristic composition and habitat structure is intrinsically linked, particularly after fire. The aim of this study was to test whether the variability of habitat structure or floristic composition and abundance in forests at a regional scale can be explained in terms of fire frequency using historical data and experimental prescribed burns. We tested this hypothesis in open eucalypt forests of Fraser Island off the east coast of Australia. Fraser Island dunes show progressive stages in plant succession as access to nutrients decreases across the Island. We found that fire frequency was not a good predictor of floristic composition or abundance across dune systems; rather, its affects were dune specific. In contrast, habitat structure was strongly influenced by fire frequency, independent of dune system. A dense understorey occurred in frequently burnt areas, whereas infrequently burnt areas had a more even distribution of plant heights. Plant communities returned to pre-burn levels of composition and abundances within 6 months of a fire and frequently burnt areas were dominated by early successional species of plant. These ecosystems were characterized by low diversity and frequently burnt areas on the east coast were dominated by Pteridium. Greater midstorey canopy cover in low frequency areas reduces light penetration and allows other species to compete more effectively with Pteridium. Our results strongly indicate that frequent fires on the Island have resulted in a decrease in relative diversity through dominance of several species. Prescribed fire represents a powerful management tool to shape habitat structure and complexity of Fraser Island forests. [ABSTRACT FROM AUTHOR]

Investigates the impact of insect grazing on the establishment of plant populations from seed after bushfires in coastal plain woodland near Perth, Western Australia. Measurement of seedling germination; Observation of individual seedlings to estimate survivorship and causes of mortality; Invasion rates of acridid grasshoppers into both small and large burnt areas; Results discussed in the light of current models of plant succession; Conclusion that fire is not a succession-initiating disturbance in this ecosystem because the long association with fire has allowed the evolution of specific survival and recruitment strategies.