Climate and landscape drivers of tree decline in a Mediterranean ecoregion

Authors

  • Niels C. Brouwers,

    Corresponding author
    • State Centre of Excellence for Climate Change, Woodland and Forest Health, School of Environmental Science, Murdoch University, Murdoch, Western Australia, Australia
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  • Jack Mercer,

    1. Marlak Environmental Services, Albany, Western Australia, Australia
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  • Tom Lyons,

    1. State Centre of Excellence for Climate Change, Woodland and Forest Health, School of Environmental Science, Murdoch University, Murdoch, Western Australia, Australia
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  • Pieter Poot,

    1. State Centre of Excellence for Climate Change, Woodland and Forest Health, School of Plant Biology, University of Western Australia (M084), Crawley, Western Australia, Australia
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  • Erik Veneklaas,

    1. State Centre of Excellence for Climate Change, Woodland and Forest Health, School of Plant Biology, University of Western Australia (M084), Crawley, Western Australia, Australia
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  • Giles Hardy

    1. State Centre of Excellence for Climate Change, Woodland and Forest Health, School of Biological Sciences and Biotechnology, Murdoch University, Murdoch, Western Australia, Australia
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Correspondence

Niels C. Brouwers, State Centre of Excellence for Climate Change, Woodland and Forest Health, School of Environmental Science, Murdoch University, 90 South Street, Murdoch, Western Australia, 6150, Australia. Tel: +61 (0) 8 9360 2737; E-mail: n.brouwers@murdoch.edu.au

Abstract

Climate change and anthropogenic land use are increasingly affecting the resilience of natural ecosystems. In Mediterranean ecoregions, forests and woodlands have shown progressive declines in health. This study focuses on the decline of an endemic woodland tree species, Eucalyptus wandoo (wandoo), occurring in the biodiversity hotspot of southwest Western Australia. We determined the change in health of wandoo stands between 2002 and 2008 across its geographic and climatic range, and associated this change in health with non-biotic variables focusing on: (1) fragment metrics; (2) topography; (3) soil characteristics; and (4) climate. Only fragment metrics and climate variables were found to be significantly related to the observed change in health. Stands that were small with high perimeter/area ratios were found to be most sensitive to health declines. Recent increases in autumn temperatures and decreases in annual rainfall were negatively affecting health of wandoo most prominently in the low rainfall zone of its climatic range. Together, these results suggest the onset of range contraction for this ecologically important species, which is likely to be exacerbated by projected future changes in climate. Our results emphasize the importance of establishing monitoring programs to identify changes in health and decline trends early to inform management strategies, particularly in the sensitive Mediterranean ecoregions.

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