Project Tree Stability

Forests - a protective shelter against natural hazards?

Contact:

• Axel Volkwein
  

The public accounts of swiss forests as protective shelter against natural hazards amounts to milliards of swiss francs per annum. What is actually the mechanical resistance of forest stands against natural hazards? At SLF the tree stability team sees into these questions.

In an interdisciplinary project "Tree Stability" we investigate how the interconnected biological and mechanical tree characteristics influence the tree structure stability when exposed to dynamic actions, such as avalanches, rock falls and strong winds. The results will be translated into adapted guidelines for forest management, how to optimise the forest's protective function on the long term.

Our aims are...

• to describe and evaluate the mechanical stability of forests against multiple natural hazards, such as winds, rock falls and avalanches.
• to describe the most important links between biological, physiological and mechanical tree variables.
• to optimise a forest stand against natural hazards from a mechanical, economical and ecological point of view.

Methods

The main objective of the project is to investigate the tree and the forest stand protection function under nature-like conditions, by direct methods, giving direct answers. These examination methods, applied to a single tree or a forest stand, lead to an ever increasing knowledge of the interaction between natural hazards and forests. Successional investigations in a natural environment is the project's red line.

Practically, a certain number of trees in their natural environment have been selected, where the same tree is exposed to a sequence of examinations and tests, at times until failure. The results are put in a tree and forest stand database. A FEM single tree model is under development which is to be implemented in a forest stand model, linking physiological and biological properties to mechanical ones for tree and stand. With biomechanical models carefully accompanied with tests we are able to reproduce nature-like conditions for the interaction between natural hazards and a forest.
In sensibility analyses of the natural hazard - forest interaction in-situ, this approach illuminates the weaknesses and the strengths of a forest stand in relation to its function as a protective shelter, its limits and its all-over economical potential.

Project elements

Local impacts in laboratory
In situ impacts
Material properties tests
Tree dynamics / Interaction wind - tree
Root soil stiffness and strength
Numerical modelling

Staff

Tor Lundström
Andrea Fötzki
Holger Simon
Matthias Kalberer
Martin Jonsson

Publications

• Lundström T, Jonas T, Volkwein A. 2008. Analysing the mechanical performance and growth adaptation of Norway spruce using a nonlinear finite-element model and experimental data. J. Exp. Bot. 59, 2513-2528.
  http://jxb.oxfordjournals.org/cgi/reprint/59/9/2513
• Lundström, T., M. Stoffel and V. Stöckli. 2008 Fresh-stem bending of silver fir and Norway spruce. Tree Physiol. 28: 355–366. Published online January 2, 2008;
  http://heronpublishing.com/tree/contents/volume28.3.html.
  
• Lundström T, Jonsson MJ, Kalberer M. 2007. The root-soil system of Norway spruce subjected to turning moment: resistance as a function of rotation. Plant and Soil 300: 35-49.
  http://www.springerlink.com/content/2vw5r6858213x3u3/
• Lundström, T., U. Heiz, M. Stoffel and V. Stöckli. 2007. Fresh-wood bending: linking the mechanical and growth properties of a Norway spruce stem. Tree Physiol. 27:1229-1241.
  http://heronpublishing.com/tree/contents/volume27.9.html.
  
• Lundström, T., T. Jonas, V. Stöckli and W. Ammann. 2007. Anchorage of mature conifers: resistive turning moment, root-soil plate geometry, and orientation of root growth. Tree Physiol. 27:1217-1227.
  http://heronpublishing.com/tree/contents/volume27.9.html.
  
• Jonsson, M.J., A. Foetzki, M. Kalberer, T. Lundström, W. Ammann and V. Stöckli. 2006. Root-soil rotation stiffness of Norway spruce (Picea abies L. Karst) growing on subalpine forested slopes. Plant Soil 285:267-277.
• Jonsson, M.J., A. Foetzki, M. Kalberer, T. Lundström, W. Ammann and V. Stöckli. accepted. Modal properties of Norway spruce (Picea abies (L.) Karst) in subalpine forest. Trees.
• Jonsson, M.J., in prep. Energy absorption of trees and forest due to rockfall. Monogr. ETH, Zürich, xx pp.
• Kalberer, M., 2007. Quantifizierung und Optimierung der Schutzwaldleistung gegenüber Steinschlag. Monography. Albert-Ludwigs-Universität, Freiburg i. Brsg., 229 pp.
• Jonas, T. and T. Lundström. 2005. STEMTRACK - digital image analysis as tool to detect the stem deflection in tree stability experiments, SLF, Davos
• Jonas, T. and T. Lundström. 2005. STEMTRACK - digital image analysis as tool to detect the stem deflection in tree stability experiments, SLF, Davos
  

Interesting links to other projects and partners:

	Financially supported by:Federal Office for Education and Science
	ROCKFOR EC project
	Forestry utility Davos
	Rockfall protection systems Test site for type tests of rockfall protection system