Ökoinformatik, Biometrie und Waldwachstum

Thema (M12)

Comparison of virtual trees, generated by two different simulation models


Motivation:


There exist several simulation models for creating virtual, 3-dimensional trees. To identify the strengths and weaknesses of these systems, which use different assumptions regarding physiological processes, carbon allocation, mechanisms of competition and plasticity of morphological development (just to mention some main issues), it is desirable to compare them at identical "benchmark" tree species.
Comparison of different models is seldom done, but is a necessary step towards a well-founded evaluation of models and can generate ideas for their improvement.


Description:


The two plant models LIGNUM and GreenLab, which are able to produce virtual, 3-d branching structures based on physiological principles, shall be compared. Both are implemented on the open-source platform GroIMP (developed at the Ecoinformatics department), which ensures that differences in model behaviour are really due to conceptual differences between the models, not to technical issues of their implementation. Practically, no programming work concerning the simulation system itself is necessary. (The supervisors will help to adapt some functions.) Both models have to be parameterized for 2 tree species which will be used for the comparison. Morphological rules of shoot development have to be adapted. Parameters will be provided by the teams which have developed the models (the Ecoinformatics team has contacts to both groups) or will be taken from the literature. The simulation runs and their results have to be documented rigorously. Aggregated values like total biomass, leaf area index, dbh, height and crown dimensions, but also the branching habit and realism of the crown morphology will be used for the evaluation of the simulation results. A list of proposals for improvements to both models will be part of the conclusion at the end of the thesis.




Literature:


  • Cournède, P.-H.; Mathieu, A.; Houllier, F.; Barthélémy, D.; de Reffye, Ph. (2008): Computing competition for light in the GreenLab model of plant growth: A contribution to the study of the effects of densitiy on resource acquisition and architectural development. Annals of Botany 101 (8), 1207-1219. GreenLab: http://liama.ia.ac.cn/gl_research.htm
  • GroIMP: http://sourceforge.net/projects/groimp/
  • LIGNUM: http://www.metla.fi/metinfo/kasvu/lignum/index-en.htm
  • Perttunen, J.; Sievänen, R.; Nikinmaa, E.; Salminen, H.; Saarenmaa, H.; Väkevä, J. (1996): LIGNUM: a tree model based on simple structural units. Annals of Botany 77, 87-98.
  • Perttunen, J.; Nikinmaa, E.; Lechowicz, M. J.; Sievänen, R.; Messier, C. (2001): Application of the functional-structural tree model LIGNUM to sugar maple saplings (Acer saccharum Marsh) growing in forest gaps. Annals of Botany 88, 471-481.








Supervision:




M.Sc. thesis for 1 candidate (Forest science and forest ecology)