Conseils pour l’échantillonnage des arbres en peuplements purs et réguliers en vue de l’estimation de leur sensibilité au climat par analyse dendroécologique

Dendroecology consists in estimating the sensitivity to climate of a forest stand by building an mean treering chronology using a sample of trees. Choice of samples may have significant consequences on the estimation of climate signal derived from chronologies of ring widths, and therefore on the growth-climate relationships. A smaller sample reduces the quality of climate signal estimation, which in turn decreases the correlation between mean tree-ring chronology and the climate series. This bias and its correction are described in the article. There is also a risk of misestimating the significance of those correlations. The bias associated with the size of the sample is not constant from one species to another and between growth environments for sampled stands. Indeed, the effects of reducing sample size are greater on sciophilous species than heliophilic ones in environments with few limitations for growth, and potentially for uneven stands in terms of structure, age and composition. All in all, to be sure of the validity of the results of dendroecological studies, the sampling strategy should be designed on the basis of the target species and the ecological characteristics of the site investigated and of the stand.