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 Research Report for 2020

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
  • KonKlim : Adaptive capacity, growth plasticity and productivity of Norway spruce, silver fir and douglas fir in the context of predicted climatic changes in the Black Forest
      Description of the project:
      Global warming and other changes in the physical and chemical environment have diverse impacts on forest ecosystems with different effects, depending on the forest composition and site conditions. It is expected that atmospheric greenhouse gas concentrations will continue to rise in the upcoming decades and as a consequence the intensity, duration and frequency of heat waves and summer droughts in Central Europe will increase. The aim of the KonKlim research project is to assess the suitability of the economically important coniferous tree species Norway spruce, silver fir and Douglas fir regarding their growth responses to predicted climatic changes and extreme events and their CO2 sink capacities. Due to the long production cycles in forestry and the ecological and economical risks associated with climate change, it is advisable to minimize the uncertainties regarding the admixture of conifers into close-to-nature forest ecosystems, which is seen as an important forest management measure in the context of sustainable development and climate change mitigation policy. The three selected tree species are of great interest to the forest and wood sector. They share a considerably higher volume productivity compared to the deciduous tree species and their favorable stem and wood properties make them particularly suitable for the utilization as construction timber. In the context of Green Economy, a continuously high future demand is expected for the sustainable provision of timber of these tree species. The joint research project is conducted in close cooperation between the Department of Soil and Environment of the Forest Research Institute Baden-Württemberg (FVA) and the Chair of Forest Growth of Albert-Ludwigs-University Freiburg (ALU). The research design is based on a space-for-time substitution approach to study the effects of changing conditions in climate, weather and soil water availability on growth, hydraulic architecture, woody biomass production and carbon sequestration. These parameters will be investigated at various spatial and temporal scales in different site conditions along six altitudinal transects in the Black Forest. For this pur-pose, the project tasks will be carried out by three complementary work packages with the following aims. Work package 1 ("Water availability and growth plasticity", FVA) uses wood anatomical analyzes to identify drought stress indicators, to assess the plasticity and adaptive capacity of the water conducting system in the studied trees, and to evaluate the trade-offs between hydraulic efficiency and safety. In work package 2 ("Tree-ring phenology and prediction of seasonal growth dynamics", ALU), the onset, cessation and duration of secondary growth and xylogenetic processes will be assessed with the support of the weekly sampling of microcores togeth-er with dendrometer measurements. Based on the functional relationships between tree growth phenology and environmental conditions, climate-growth models will be developed to prospectively assess for different climate scenarios the short-, medium- and long-term effects of changes in the length of the growing season and in soil water availability on the growth performance of the studied tree species. Work Package 3 ("Woody biomass production and carbon sequestration", ALU) will contribute an integrated analysis of above-ground woody bio-mass production and carbon sequestration at the scales of the cell, tissue, tree-ring, stem, tree and forest stand to quantify and compare the short-, medium- and long-term CO2 sink potential of the studied tree species within the context of climatic changes. The joint synthesis of the results of the work packages will contribute to a better understanding of the adaptive capacity and phenotypic plasticity of growth and productivity of Norway spruce, silver fir and Douglas fir in perspective of the anticipated climatic changes and extreme climatic events. The project therefore aims to provide the scientific basis for a sustainable woody biomass production in climate stable forest ecosystems with high CO2 sink capacity and simultaneously high substitution potential of the pro-duced wood raw material.

      contact person: Stangler D.
      Phone: +49 761 203 8543
      Email: Dominik.Stangler@iww.uni-freiburg.de
      Runtime:
      Start of project: 01.10.2018
      End of project: 30.09.2021
      Project Management:
      Albert-Ludwigs-University Freiburg
      Kahle H.-P., Stangler D.

      Contributors:
      • Linne R.
      • Larysch E
      • Miller T
      • Honer H
  • 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