Social and ecological dimensions of urban conservation grasslands and their management through prescribed burning and woody vegetation removal

Natural grasslands are threatened globally. In south-eastern Australia, remnants of critically endangered natural grasslands are increasingly being isolated in urban areas. Urbanisation has led to reduced fire frequency and woody plant encroachment in some patches. Grasslands are currently being managed under the assumption that desirable management actions to address these threats (prescribed burning and removing woody vegetation) (1) lead to improved conservation outcomes and (2) are restricted by negative public attitudes. In this study, we tested these two assumptions in the context of native grassland conservation reserves in Melbourne, Australia. Firstly, we investigated differences in species and functional trait composition between patches that had been recently burnt, patches that were unburnt and patches subject to woody vegetation encroachment. We found that the functional traits of species converged in areas subject to woody plant encroachment and areas frequently disturbed by fire. Burning promoted native species, and patches of woody plants supressed the dominant grass, providing a wider range of habitat conditions. Secondly, we surveyed 477 residents living adjacent to these grassland conservation reserves to measure values, beliefs and attitudes and the acceptance of prescribed burning and removing woody vegetation. We found conflict in people's attitudes to grasslands, with both strongly positive and strongly negative attitudes expressed. The majority of residents found prescribed burning an acceptable management practice (contrary to expectations) and removing trees and shrubs from grasslands to be unacceptable. Both cognitive factors (values and beliefs) and landscape features were important in influencing these opinions. This research provides some guidance for managing urban grassland reserves as a social-ecological system, showing that ecological management, community education and engagement and landscape design features can be integrated to influence social and ecological outcomes

Biotic homogenization in an increasingly urbanized temperate grassland ecosystem

Question: How does urbanization and associated declines in fire frequency alter the floristic composition of native temperate grasslands? Does it lead to: (1) biotic homogenization, i.e. compositional similarity between remnants increases; (2) biotic differentiation, whereby similarity between remnants declines, or; (3) clustered differentiation, where similarity between remnants remainsunchanged, but composition shifts from the historical state?Location: Victoria, Australia.Methods: Using site-level surveys, we examined changes in the floristic similarity of 29 urban grasslands from 1992 to 2013 and compared these changes to those of 63 rural grasslands from 1989 to 2014. Community-level changes in the representation of key functional traits were also examined in urban grasslands, with traits advantaged following disturbance regime change and urbanfragmentation predicted to increase in frequency. Results: Our results supported the biotic homogenization hypothesis in urban grasslands. Compositional similarity between grasslands increased principally because of an increase in commonly shared non-native species, with change in native composition comparatively minor. However, no evidence of biotic homogenization was found in rural grasslands, with no significant change in overall composition identified. The most urbanized sites had the highest number of non-native species in both the current and historical data sets, yet non-native composition over the past two decades changed the most in sites on the urban fringe, becoming more similar to sites closer to the urban core. As expected, following declines in fire frequency and increased urbanization, the overall composition of urban grasslands shifted to taller plant species, while native speciescapable of vegetative reproduction and exotic species with an annual life spanincreased in frequency.Conclusion: Urbanization was an important driver of biodiversity change in the investigated system, with increasing competition intensity in response to disturbance regime change a likely cause of biotic homogenization. Our results demonstrate that non-native species are a key driver of biotic homogenization,emphasizing the importance of managing non-native immigration and maintaininghistorical disturbance processes once native ecosystems become urbanized