Conducted jointly by Cirad and INRA, this research analyzes structure-function relationships in teak in Togo.
The Essentials: Conducted jointly by Cirad and INRA, this research analyzes structure-function relationships in teak in Togo.
Kodjo Tondjo, researcher at UMR AMAP (Université de Lomé [Togo]).
Thesis defended in 2016.
This research is the product of an international joint supervision between several partner institutions.
Context and Research Problem
Tectona grandis, commonly known as teak, is a tree species widely cultivated for the quality of its wood, particularly in plantations in Togo. The country has implemented an intensive plantation policy aimed at supporting forestry production and meeting growing demand for high-quality timber. Teak is favored for its rapid growth and the commercial value of its wood, making it a key species in Togo's silvicultural development.
Teak plantations in Togo raise questions about the interaction between tree architecture and the physical and mechanical properties of their wood. Understanding these relationships is essential for optimizing silvicultural practices and maximizing the quality of the wood produced. This thesis focuses on these interactions, analyzing how the development of teak architecture influences wood properties depending on provenance and the silvicultural treatments applied.
Methodology
The study was conducted at a private forest station in Agbavé, near Avétonou, in the Agou prefecture in southwestern Togo. Two methodological approaches were adopted to explore structure-function relationships in teak. The first consists of an experimental analysis, integrating a retrospective analysis of tree growth and the assessment of wood properties using near-infrared spectroscopy. The architectural characteristics studied include growth, ontogeny, flowering, and immediate reiteration, notably the establishment of the first fork in the tree crown. The key properties measured include wood basic density and the modulus of elasticity.
The second approach relies on a functional-structural modelling framework, the GreenLab model. This method made it possible to estimate sink and source strength parameters of the plant that cannot be measured directly. Model inversion was used to obtain values for these parameters, providing essential information for improving wood quality. The modelling also shed light on the supply relationships (carbon sources) and demand relationships (construction and maintenance costs of organs) between the plant's different organs, thereby determining the tree's overall development.
Key Findings
The study results reveal several significant interactions between teak architecture and its wood properties. The stabilization of radial growth was correlated with a decrease in height growth, observed with a certain delay in development. This relationship has implications for forest management practices, as it suggests that growth strategies must account for these dynamics to optimize wood production.
Another major finding concerns teak flowering, which showed a significant correlation with the physical properties of the wood. This suggests that flowering cycles could influence harvesting and planting strategies, taking into account the variations in wood quality associated with this developmental phase.
Near-infrared spectroscopy analyses made it possible to quantify physico-mechanical properties of the wood, which are crucial for furniture and construction markets. These results highlight the importance of assessing wood properties in relation to silvicultural practices in order to improve the quality and durability of teak-derived products.
Discussion and Outlook
The application of the GreenLab model in this research shows significant potential for optimizing silvicultural practices. The results obtained provide a better understanding of how different cultural practices affect tree development and the quality of the wood produced. The modelling capacity of the GreenLab model offers a way to further explore the complex interactions between plant organs and their environment.
The knowledge gained could also be extrapolated to other tree species, broadening the prospects for innovation in forest management. Integrating these findings into current forestry policies can contribute to sustainable management of forest resources in Togo, maximizing wood quality while preserving biodiversity.
The results of this thesis open avenues for future research, particularly on adapting silvicultural practices to different environments and market requirements. The practical implications of this research could transform silviculture in Togo, positioning the country as a key player in quality timber production in West Africa.
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Sources and Access
Kodjo Tondjo. Analyse et Modélisation des relations structure-fonctions chez le Teck (Tectona grandis) de plantation au Togo. Systématique, phylogénie et taxonomie. Université de Lomé (Togo), 2016. Français. ⟨NNT : ⟩. ⟨tel-02489455⟩