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Knot extractives: a model for analysing the eco-physiological factors that control the within and between-tree variability

05 October 2017

kebbi-benkeder, z. ; Manso, R. ; Gérardin, P. ; Dumarçay, S. ; Chopard, B. ; Colin, F.
Trees, 2017, 31 (5) : 1619-1633.
Abies alba knot extractive concentration increase from tree tip to living crown base and from tight to loose knot parts. The fitted model is proposed for further eco-physiological studies. The physiological and ecological mechanisms controlling the knot richness in extractives require further investigations. We aim to design a model of the vertical distribution of the knot extractive concentrations as a prerequisite for further studies on the eco-physiological studies. At a first attempt, we use this model to test the effect of different competition situations. Fifteen Silver fir trees were sampled according to their social status within three thinning treatments. Discs containing knots were sampled according to their position in reference to the lowest living branch of each tree. Extractions were carried out with hexane and acetone successively. Extractive concentrations in both solvents as well as branch diameters were simultaneously modelled through the seemingly unrelated regression method. For all trees, knot extractive concentrations increase from the tree tip to the living crown base. According to the model, trees with the longest crowns, dominant or/and growing in the thinned stands, exhibited the largest knot extractive concentrations. The model depicted a vertical trend that strongly suggested inducing physiological factors such as protection zone, branch heartwood formation combined with compression wood formation. A strategy was proposed for the quantification of the effect of the ecological factors on the extractive concentrations of knots when these factors act either directly or indirectly via physiological factors. The model is thus an efficient tool to quantify the eco-physiological control on knot extractives.