Projected climate change implications for the South Australian flora

South Australia has warmed since 1950 and further temperature increases are forecast this century. We explore the implications of climatic warming for individual plant species and the State’s plant biodiversity, which is significant and includes 418 endemic taxa. Environmental constraints and interspecific interactions operate on species to determine which survive in which environment, with resulting compositional signatures. Climate change influences such ‘filtering’ processes via mechanisms such as altered mortality or recruitment rates and indirectly through fire regimes. While modest environmental changes can be absorbed within a given ecological community, significant change will eventually drive species turnover. We use the Hopbush, Dodonaea viscosa subsp. angustissima (DC.) J.G.West as a case study that shows morphological adaptations to arid conditions (narrower leaves and higher stomatal densities), observed in more northern populations in South Australia. Leaves of this species have narrowed through time in conjunction with climatic warming, matching predictions from the spatial cline. Genomic sequencing has also revealed genetic correlations with temperature and aridity, suggesting key climate change variables are impacting the selection of functional genes including those linked to leaf characters. Despite such adaptations in individual species, plant community composition is sensitive to small changes in climate. As a result, predicted climatic changes may ultimately drive complete species turnover, if the more severe scenarios are realised. Spatial analysis highlights a climatic transition zone, between desert and Mediterranean South Australia, where community composition changes more rapidly with climate and this area is therefore likely to be more vulnerable to climate change. Notwithstanding potential evolutionary adaptation, significant climate change will influence ecophysiology, leading to changes in primary productivity and water stress and is predicted to ultimately lead to lower species richness, altered species composition and more uneven abundances. Although we have an empirical understanding of climate sensitivity for South Australian plant communities, we need sophisticated ecological forecasting that considers complex interactions with fire, habitat configuration and evolutionary adaptation.G.R. Guerin, M.J. Christmas, B. Sparrow, A.J. Low

Plant families exhibit unique geographic trends in C4 richness and cover in Australia

Numerous studies have analysed the relationship between C4 plant cover and climate. However, few have examined how different C4 taxa vary in their response to climate, or how environmental factors alter C4:C3 abundance. Here we investigate (a) how proportional C4 plant cover and richness (relative to C3) responds to changes in climate and local environmental factors, and (b) if this response is consistent among families. Proportional cover and richness of C4 species were determined at 541 one-hectare plots across Australia for 14 families. C4 cover and richness of the most common and abundant families were regressed against climate and local parameters. C4 richness and cover in the monocot families Poaceae and Cyperaceae increased with latitude and were strongly positively correlated with January temperatures, however C4 Cyperaceae occupied a more restricted temperature range. Seasonal rainfall, soil pH, soil texture, and tree cover modified proportional C4 cover in both families. Eudicot families displayed considerable variation in C4 distribution patterns. Proportional C4 Euphorbiaceae richness and cover were negatively correlated with increased moisture availability (i.e. high rainfall and low aridity), indicating they were more common in dry environments. Proportional C4 Chenopodiaceae richness and cover were weakly correlated with climate and local environmental factors, including soil texture. However, the explanatory power of C4 Chenopodiaceae models were poor, suggesting none of the factors considered in this study strongly influenced Chenopodiaceae distribution. Proportional C4 richness and cover in Aizoaceae, Amaranthaceae, and Portulacaceae increased with latitude, suggesting C4 cover and richness in these families increased with temperature and summer rainfall, but sample size was insufficient for regression analysis. Results demonstrate the unique relationships between different C4 taxa and climate, and the significant modifying effects of environmental factors on C4 distribution. Our work also revealed C4 families will not exhibit similar responses to local perturbations or climate.Samantha E. M. MunroeID, Francesca A. McInerney, Greg R. Guerin, Jake W. Andrae, Nina WeltiID, Stefan Caddy-Retalic, Rachel Atkins, Ben Sparro

A vegetation and soil survey method for surveillance monitoring of rangeland environments

Published: 16 June 2020Ecosystem surveillance monitoring is critical to managing natural resources and especially so under changing environments. Despite this importance, the design and implementation of monitoring programs across large temporal and spatial scales has been hampered by the lack of appropriately standardized methods and data streams. To address this gap, we outline a surveillance monitoring method based on permanent plots and voucher samples suited to rangeland environments around the world that is repeatable, cost-effective, appropriate for large-scale comparisons, and adaptable to other global biomes. The method provides comprehensive data on vegetation composition and structure along with soil attributes relevant to plant growth, delivered as a combination of modules that can be targeted for different purposes or available resources. Plots are located in a stratified design across vegetation units, landforms, and climates to enhance continental and global comparisons. Changes are investigated through revisits. Vegetation is measured to inform on composition, cover, and structure. Samples of vegetation and soils are collected and tracked by barcode labels and stored long-term for subsequent analysis. Technology is used to enhance the accuracy of field methods, including differential GPS plot locations, instrument-based Leaf Area Index (LAI) measures, and three dimensional photo-panoramas for advanced analysis. A key feature of the method is the use of electronic field data collection to enhance data delivery into a publicly accessible database. Our method is pragmatic, whilst still providing consistent data, information, and samples on key vegetation and soil attributes. The method is operational and has been applied at more than 704 field locations across the Australian rangelands as part of the Ecosystem Surveillance program of the Terrestrial Ecosystem Research Network (TERN). The methodology enables continental analyses and has been tested in communities broadly representative of rangelands globally, with components being applicable to other biomes. Here we also recommend the consultative process and guiding principles that drove the development of this method as an approach for development of the method into other biomes. The consistent, standardized and objective method enables continental, and potentially global analyses than were not previously possible with disparate programs and datasets.Ben D. Sparrow, Jeff N. Foulkes, Glenda M. Wardle, Emrys J. Leitch, Stefan Caddy-Retalic, Stephen J. van Leeuwen ... et al