Diverging Composition of Natural Temperate Grasslands in Response to Land Use Provides Complementary Conservation Opportunities

Abstract

Natural temperate grasslands in south-eastern Australia are threatened ecological communities that have been massively reduced across their range. Relatively intact examples, however, remain on both public land (e.g., roadsides) and private land (e.g., farmland). In western Victoria, natural temperate grasslands have typically been managed by livestock grazing on farmland and by frequent burning on roadsides. Little attention has been given to how grasslands on farmland and roadsides may each contribute to regional or landscape-scale conservation objectives. Our aim was to compare the plant composition of natural temperate grasslands that have been long-managed with fire with those long-managed primarily by sheep grazing, to explore how land-use history influences plant community structure and its potential implications for conservation planning. We sampled 17 sites in frequently burnt grasslands on roadsides, and 10 sites in historically grazed grasslands on farmland. We used non-metric multidimensional scaling ordination techniques to compare plant community composition between grasslands under these different tenures, and to determine how species richness, cover of different species groups and substrate cover were associated with tenure. We also assessed taxonomic beta diversity to quantify species turnover to enable a detailed comparison of species turnover and compositional consistency between roadside and farmland grasslands. There were marked differences in plant community composition between grasslands on roadsides and farmland. Some grazing-tolerant native forbs and C3 grasses were associated with farmland. High native species richness, grazing-sensitive and taller (> 5 cm tall) forbs, native geophytes, and bare ground cover were associated with roadsides. Taxonomic diversity partitioning showed only slight differences in species turnover between farmland and roadside grasslands. Differences in community composition between natural temperate grasslands on roadsides and farmland are consistent with differences in long-term management practices that drive the vegetation in different directions. We argue that long-grazed grasslands on farmland and long-burnt grasslands on roadsides have complementary values for conservation. Both should be targeted for management, which should recognise their differences in size, shape and connectivity. Future funding and incentives for grassland conservation in south-eastern Australia will require careful balance to ensure investments consider the complementary roles of different types of grassland sites at the landscape scale.