Climate and landscape drivers of tree decline in a Mediterranean ecoregion

Niels C. Brouwers,Pieter Poot,Giles Hardy,Erik Veneklaas,Tom Lyons,Jack Mercer

doi:10.1002/ece3.437

Niels C. Brouwers, Pieter Poot + Show 4 more

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https://doi.org/10.1002/ece3.437

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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.

Highlights

Climate change, habitat loss and fragmentation are important drivers of biodiversity decline around the world (Mantyka-Pringle et al 2012)
Many dominant tree species have shown distinct periods of dieback and mortality linked to frequent short-term extreme weather events (Phillips et al 2009; Allen et al 2010; Huang and Anderegg 2012; Matusick et al 2012), or shown gradual increases in mortality rates and/or reduced growth rates linked to the long-term global increases in temperature and changes in rainfall (Jump et al 2006; van Mantgem and Stephenson 2007; Sarris et al 2007, 2011; van Mantgem et al 2009; Dulamsuren et al 2010; Carnicer et al 2011; Peng et al 2011; Vila-Cabrera et al 2011)
This study investigates the role of climate and landscape variables on changes in tree health, and provides a first test of how the range of a southwest of Western Australia (SWWA) tree species might shift with climate change as suggested in modeling studies (Hughes et al 1996; Klausmeyer and Shaw 2009)

Summary

Introduction

Habitat loss and fragmentation are important drivers of biodiversity decline around the world (Mantyka-Pringle et al 2012). Forest and woodland ecosystems are increasingly showing the effects of these change processes (van Mantgem and Stephenson 2007; van Mantgem et al 2009; Phillips et al 2009; Allen et al 2010; Barbeta et al 2011; Carnicer et al 2011; Peng et al 2011; Huang and Anderegg 2012).

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