Scientific and Research Projects

• At the pulse of trees: High-resolution measurement and analysis of secondary growth and water balance of beech, spruce, fir and pine trees
  Description of the project:

  European beech (Fagus sylvatica), Norway spruce (Picea abies), silver fir (Abies alba) and Scots pine (Pinus sylvestris) are of high importance in European forest ecosystems and in the European forest and wood sector. It is therefore of great interest, how environmental changes and especially climatic extreme events (e.g. heat and drought) affect growth and productivity of these tree species. We measure the response of trees to environmental conditions with electronic point dendrometers. Point-dendrometers are high-precision measurement devices, which can measure and record changes in the radial dimension of tree stems. These changes are caused by the process of tree-ring formation as well as by a daily cycle of swelling and shrinking of non-lignified tissues within the stem. These measurements not only provide information about the seasonal dynamics of secondary growth, but also reveal information about the stem internal water regime of the trees. Since 1990 the Chair of Forest Growth maintains dendroecological field stations, which are equipped with dendrometers and additional sensors for meteorological and pedological parameters. In the vicinity of Freiburg, four measurement stations are operating along an altitudinal gradient from the Rhine Valley up to the high elevations of the Black Forest. The analysis of this unique long time series contributes to elucidate the complex interactions of various site factors with the short-, medium-and long-term growth dynamics of the studied species in the field. The analysis of the dendrometer data is complemented by the investigation of additional growth parameters such as tree ring width, cell characteristics and high-resolution density profiles on stem cross sections. Special focus is laid on the analysis of the tree species response to the dry and warm summers of the years 2003 and 2006. The results provide an improved assessment of the potential impact of anticipated climate change on the seasonal dynamics of tree growth and give insight into the resilience of trees after stress situations.
  
  contact person: Dr. Hans-Peter Kahle
  Phone: +49 761 203-3739
  Email: Hans-Peter.Kahle@iww.uni-freiburg.de

  Runtime:

  Start of project: 1992
  End of project: (unlimited)

  Project Management:

  Albert-Ludwigs-University Freiburg
  Dr. Hans-Peter Kahle, Prof. Dr. Dr. h.c. Heinrich Spiecker, Dominik Stangler
  

  Financing:
  • diverse Quellen, Sonstiges
• Comparison of inter- and intra-annual growth dynamics and drought response of European beech and Norway spruce along an altitudinal gradient
  Description of the project:

  The impact of anticipated global changes on growth and productivity of Norway spruce and European beech is discussed controversially. The analysis of inter- and intra-annual growth dynamics under different environmental conditions will provide detailed insight into the resilience and adaption potential of stem radial growth to climatic extremes and environmental changes. This study is be based on the exploitation of already existing unique long dendrometer time series collected at three dendroecological field sites of the Chair of Forest Growth along an altitudinal gradient in south-western Germany. At the three field sites, stem radial displacement of beech and spruce sample trees has been recorded by automatic precision point dendrometers in high temporal resolution (every 15 minutes) since 1990 at an altitude of 1250 m and since 1997 in addition at 450 m and 750 m. At these sites meteorological and pedological parameters have been measured in parallel. Complementary environmental data, including high resolution time series of tropospheric CO2 concentrations from the nearby environmental monitoring station ‘Schauinsland’ of the German Federal Environmental Agency (Umweltbundesamt) will be included in the analyses. For extension of the retrospective analyses, stem discs and increment cores of dendrometer trees and neighboring trees will be sampled at each of the three sites. The innovative approach of combining long-term dendrometer data with tree ring features such as ring width, cell structure, intra-annual density profiles and results from detailed studies on cambial activity and wood formation, provide a great opportunity to deepen our understanding and knowledge about the interactions of different environmental factors with the short-, medium- and long-term growth dynamics of the two most important forest tree species in Germany.
  
  contact person: Dr. Hans-Peter Kahle
  Phone: +49 761 203-3739
  Email: Hans-Peter.Kahle@iww.uni-freiburg.de

  Runtime:

  Start of project: 1990
  End of project: (unlimited)

  Project Management:

  Albert-Ludwigs-University Freiburg
  Dr. Hans-Peter Kahle, Prof. Dr. Dr. h.c. Heinrich Spiecker, Dominik Stangler
  

  Financing:
  • diverse Quellen, Sonstiges