EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Hotspots of change in major tree species under climate warming

Flurin Babst1,2, Richard L. Peters3, Rafel O. Wüest1, Margaret E.K. Evans4, Ulf Büntgen5, Andrew J. Hacket-Pain6, Christoforos Pappas7, Alexander V. Kirdyanov5, Stefan Klesse1, Volodymyr Trotsiuk8, Jesper Björklund1, Jodi Axelson9, Jill Harvey10, Dan Smith11, Christian Zang12, Dirk N. Karger1, and Niklaus E. Zimmermann1
Flurin Babst et al.
  • 1Swiss Federal Research Institute WSL, Birmensdorf, Switzerland
  • 2W. Szafer Institute of Botany, Polish Academy of Sciences, Krakow, Poland
  • 3Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Belgium
  • 4Laboratory of Tree-Ring Research, University of Arizona, Tucson, USA
  • 5Department of Geography, University of Cambridge, Downing Place, Cambridge, UK
  • 6School of Environmental Sciences, University of Liverpool, Liverpool, UK
  • 7Département de Géographie and Centre d’études nordiques, Université de Montréal, QC, Montreal, Canada
  • 8Department of Environmental Systems Science, ETH Zurich, Zürich, Switzerland
  • 9Department of Environmental Science, Policy and Management, UC Berkeley, USA
  • 10Northern Forestry Center, Canadian Forest Service, Natural Resources Canada, Edmonton, Canada
  • 11Department of Geography, University of Victoria, Victoria, Canada
  • 12Department of Ecology and Ecosystem Management, Technical University of Munich, Germany

Warming alters the variability and trajectories of tree growth around the world by intensifying or alleviating energy and water limitation. This insight from regional to global-scale research emphasizes the susceptibility of forest ecosystems and resources to climate change. However, globally-derived trends are not necessarily meaningful for local nature conservation or management considerations, if they lack specific information on present or prospective tree species. This is particularly the case towards the edge of their distribution, where shifts in growth trajectories may be imminent or already occurring.

Importantly, the geographic and bioclimatic space (or “niche”) occupied by a tree species is not only constrained by climate, but often reflects biotic pressure such as competition for resources with other species. This aspect is underrepresented in many species distribution models that define the niche as a climatic envelope, which is then allowed to shift in response to changes in ambient conditions. Hence, distinguishing climatic from competitive niche boundaries becomes a central challenge to identifying areas where tree species are most susceptible to climate change.

Here we employ a novel concept to characterize each position within a species’ bioclimatic niche based on two criteria: a climate sensitivity index (CSI) and a habitat suitability index (HSI). The CSI is derived from step-wise multiple linear regression models that explain variability in annual radial tree growth as a function of monthly climate anomalies. The HSI is based on an ensemble of five species distribution models calculated from a combination of observed species occurrences and twenty-five bioclimatic variables. We calculated these two indices for 11 major tree species across the Northern Hemisphere.

The combination of climate sensitivity and habitat suitability indicated hotspots of change, where tree growth is mainly limited by competition (low HSI and low CSI), as well as areas that are particularly sensitive to climate variability (low HSI and high CSI). In the former, we expect that forest management geared towards adjusting the competitive balance between several candidate species will be most effective under changing environmental conditions. In the latter areas, selecting particularly drought-tolerant accessions of a given species may reduce forest susceptibility to the predicted warming and drying.

How to cite: Babst, F., Peters, R. L., Wüest, R. O., Evans, M. E. K., Büntgen, U., Hacket-Pain, A. J., Pappas, C., Kirdyanov, A. V., Klesse, S., Trotsiuk, V., Björklund, J., Axelson, J., Harvey, J., Smith, D., Zang, C., Karger, D. N., and Zimmermann, N. E.: Hotspots of change in major tree species under climate warming, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22325,, 2020