An analysis of the daily radial activity of 7 boreal tree species, northwestern Quebec

In the 'Des Vieux Arbres' ecological reserve situated within northwestern Q uebec, 40 band dendrometers were installed on 7 of the major boreal tree sp ecies. The late Spring-early Summer daily radial activity registered in 199 7 was related to daily weather variables. For each tree species, the daily mean i) cumulative radial increment and ii) radial activity indexed series obtained by first-difference standardization were analyzed. The results ind icate the existence of strong similarities among the 7 species. All showed strong synchronous fluctuations in radius during late winter and early spri ng. This period ended with a short but sharp increase in radial increments that marked the passage of water into the stem. This initial swelling, less obvious in Pinus species was followed by a prolonged period of little chan ge in radial activity. Meteorological data indicated that air temperature w as positively related to stem swelling during the late winter-early spring period. Both air and soil temperatures became negatively related to radial expansion once the passage of water has occurred in the stem. Starting in e arly June, all species registered a sustained increase in radial increments possibly associated with active cell division. After this, radial expansio n was negatively related to air temperature and positively to rainfall.