Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

To assess daily relationships between xylem development and the environment, precise knowledge of tree-ring development is required. This includes accurate estimations of the rate and duration of the cell enlargement and wall thickening phases. This paper presents an application where the Gompertz equation is used to calculate cell number increase and to estimate both the rates and periods of the differentiation phases on a daily scale during the growing season. Tests were performed on two coniferous species, Abies balsamea (L.) Mill. and Pinus cembra L., growing in the Canadian boreal forest and on the Italian Alpine treeline respectively. Wood micro-cores, including the most recent tree-rings, were collected during the growing season of 2001. Cross-sections were cut with a microtome and stained with cresyl fast violet to differentiate xylem cells of the growing tree-ring. The number of cells within the zones of radial cell enlargement, secondary wall thickening and mature xylem were counted. The normalised cell number increases were fitted into a Gompertz function [y=f(t)]. The results showed that the function provided suitable descriptions of the cell increase for both Abies balsamea and Pinus cembra with R2 ranging between 0.60 and 0.90. Subsequently, to assess the development phases in time, the Gompertz equation was expressed in function of the independent variable [t=f(y)]. The use of only one equation for the estimation of both cell division and differentiation throughout the vegetative season has demonstrated to be an important improvement.