Time series of wood characters - a new proxy to determine changing environments through the Holocene and to evaluate the impact of future climate change

What is the natural variation in climatic factors throughout the Holocene? How will future climate change affect trees and forests in Europe? These are important questions that can be studied using tree rings as natural archives.

Project description

Tree-ring width is an important proxy in terms past climate and environment reconstruction. However, to date it was impossible to use the full potential of the longest tree-ring chronologies, the Central European oak chronologies, for climate research. The climate signal is too complex to be captured by tree-ring width which integrates all causal factors of annual tree growth throughout in one value. However, high-resolution wood anatomical characters have found to be sensitive indicators of climate and environmental changes. A new approach is presented whereby sets of wood anatomical variables (WAVs) are assessed by using newly developed image-analysis software. A network of WAV chronologies will be developed from oaks growing under both inundated and dry conditions in the Netherlands, Germany and France. This database will be supplemented by results from controlled (flooding) experiments on young oaks. Climate-growth relationships (response functions) will be calculated for oaks in modern floodplain environments and projected on sub-fossil oaks from ancient floodplain forests to reconstruct natural hydrological, climate and environmental changes in the past. Moreover, WAVs will be incorporated in a physiologically based mechanistic tree model to gain insight in the physiological response of oak to (future) climate-induced environmental change.


  • Sass-Klaasen, U.; Sabajo, C.R.; Ouden, J. den (2011) Vessel formation in relation to leaf phenology in pedunculate oak and European ash. Dendrochronologia (Online first) doi:10.1016/j.dendro.2011.01.002
  • Sass-Klaassen, U.; Chowdhury, Md. Q.; Sterck, F. J.; Zweifel, R. Effects of water availability on the growth and tree morphology of Quercus pubescens Willd. and Pinus sylvestris L. in the Valais, Switzerland. TRACE 2006 (in press).
  • Werf, G.W. van der; Sass-Klaassen, U.; Mohren, G.M.J. (2006). The impact of the 2003 summer drought on the intra-annual growth pattern of beech (Fagus sylvatica L.) and oak (Quercus robur L.) on a dry site in the Netherlands. Dendrochronologia (in press)
  • Sass-Klaassen, U.; Poole, I.; Wils, T.; Helle, G.; Schleser, G.H.; Bergen, P. van (2005). The use of stable isotope dendrochronology for environmental interpretations from growth-ring patterns in sub-fossil bog oaks, IAWA J. 26 (1): 121-136.

MSc theses

  • Developmental trajectories of pubescent oak (Quercus pubescens) and Scots pine (Pinus sylvestris) in drought-stressed environments in the Wallis Valley (Alfred Chitiki, completed 2005)
  • The pipe model theory tested for pines and oaks dry versus wet forests in the Wallis valley, Switzerland. (Simone de Brock, completed 2006)
  • Effects of water availability on hydraulic architecture of Quercus pubescens Willd. and Pinus sylvestris L. in the Wallis Valley, Switzerland. (Chowdhury, Q., completed 2006)
  • Exploring the origination of oak clusters. Wood anatomy, dendrochronology and three-dimensional growth of oak shrubs. (Yanguas-Fernandez, E., completed 2010)
  • Dendrogeomorphological analysis of an oak cluster (Quercus robur.L.) from a drift sand area in The Netherlands. (Zyadin, A., completed 2007)
  • Spring floods reduse earlywood vessel area of oak (Quercus robur). (Belien, E., completed 2008) 
  • Early wood vessel formation in pedunculate oak (Quercus robur L.) and common ash (Fraxinus excelsior L.). (Sabajo, C., completed 2009)              
Sub-fossile wood
Tree rings in oak (EW=early wood, LW=late wood)
Experimental flooding of young oaks
Oak shrubs at De Braak, NL
Coring an old  pine
Dendro team