Sensitivity of plant functional types to climate change: classification tree analysis of a simulation model Alexandra Esther, Ju¨ rgen Groeneveld, Neal J. Enright, Ben P.Miller, Byron B. Lamont, George L.W. Perry, F. Benjamin Blank & Florian Jeltsch Abstract Question: The majority of studies investigating the impact of climate change on local plant commu- nities ignores changes in regional processes, such as immigration from the regional seed pool. Here we explore: (i) the potential impact of climate change on composition of the regional seed pool, (ii) the influence of changes in climate and in the regional seed pool on local community structure, and (iii) the combinations of life history traits, i.e. plant func- tional types (PFTs), that are most affected by environmental changes. Location: Fire-prone, Mediterranean-type shrub- lands in southwestern Australia. Methods: Spatially explicit simulation experiments were conducted at the population level under different rainfall and fire regime scenarios to determine the effect of environmental change on the regional seed pool for 38 PFTs. The effects of environmental and seed immigration changes on local community dynamics were then derived from community-level experiments. Classification tree analyses were used to investigate PFT-specific vulnerabilities to climate change. Results: The classification tree analyses revealed that responses of PFTs to climate change are determined by specific trait characteristics. PFT-specific seed production and community patterns responded in a complex manner to climate change. For example, an increase in annual rainfall caused an increase in numbers of dispersed seeds for some PFTs, but decreased PFT diversity in the community. Conver- sely, a simulated decrease in rainfall reduced the number of dispersed seeds and diversity of PFTs. Conclusions: PFT interactions and regional processes must be considered when assessing how local commu- nity structure will be affected by environmental change. Keywords: CART; Classification and regression tree analysis; Coexistence; Seed immigration; Spatially explicit model. Nomenclature: Paczkowska & Chapman (2000). Introduction Climate change is receiving widespread scien- tific attention as a major threat to biodiversity, potentially causing species range shifts and losses, population declines and species extinctions (Thomas et al. 2004; De Boeck et al. 2007). While there is clear evidence that climate change has significant ecosys- tem-level impacts (e.g. Hughes 2003), the direction and magnitude of effects on communities is less cer- tain (Chesson 2000; Brooker et al. 2007; Barnard & Thuiller 2008). Long-term monitoring along natural Esther, A. (corresponding author, esther@uni- potsdam.de) & Jeltsch, F. (jeltsch@uni-potsdam.de): Institute of Biochemistry and Biology, Plant Ecology and Nature Conservation, University of Potsdam, Maulbeerallee 2, 14469 Potsdam, Germany Esther, A.: (esther@uni-potsdam.de): Julius Kuehn- Institute (JKI), Federal Research Centre for Cultivated Plants, Vertebrate Research, Toppheideweg 88, 48161 Mu¨ nster,Germany Groeneveld, J. (juergen.groenveld@ufz.de): UFZ Helmholtz Centre for Environmental Research, De- partment of Ecological Modelling, P.O. Box 50 01 36, 04301 Leipzig, Germany Groeneveld, J. (j.groeneveld@auckland.ac.nz) & Perry, G.L.W. (george.perry@auckland.ac.nz): School of En- vironment, University of Auckland, Private Bag 92019, Auckland, New Zealand Enright, N.J. (N.Enright@murdoch.edu.au): School of Environmental Science, Murdoch University, Mur- doch 6150, Australia Miller, B.P. (Ben.Miller@bgpa.wa.gov.au): Botanic Gardens and Parks Authority, West Perth 6005, Aus- tralia Miller, B.P. (Ben.Miller@bgpa.wa.gov.au): School of Plant Biology, University of Western Australia, Craw- ley 6009, Australia Lamont, B.B. (B.Lamont@curtin.edu.au): Centre for Ecosystem Diversity and Dynamics, Department of Environmental and Aquatic Sciences, Curtin Univer- sity, P.O. Box U1987, Perth 6845, Australia Blank, F.B. (benjamin.blank@umwelt.uni-giessen.de): Institute for Landscape Ecology and Resources Management (ILR), University Giessen, Heinrich- Buff-Ring 26, 35392 Giessen, Germany Journal of Vegetation Science 21: 447–461, 2010 DOI: 10.1111/j.1654-1103.2009.01155.x & 2010 International Association for Vegetation Science