Abstract• Effects of thinning on epicormics have rarely been demonstrated especially due to inaccurate surveying methods.• Our objective was to assess the effect of contrasted thinnings on the ontogeny of epicormics on sessile oak. We used the epicormic composition defined as the arrangement of epicormics in different classes (isolated bud, clustered buds, short and long shoots and "picots") and quantified by the total frequency of epicormics and the proportion of each class.• Epicormic composition was recorded in a silvicultural experiment testing highly contrasted thinnings, at 3 different stand stages and on lower (0.5-3 m) and upper (3-6 m) boles. Ageing provoked an accumulation of bud clusters and of picots. After thinning, epicormic shoots emerged mainly from (1) still present short epicormic shoots, (2) buds either isolated or in clusters depending on the stand stage. Upper boles bore epicormic compositions close to those observed on lower boles in the few preceding years. Upper logs were more reactive than lower boles.• To conclude, the epicormic composition was a relevant tool to follow the dynamics of the epicormic ontogeny and to demonstrate the effects of thinning on it.

Among the plants studied, var. purpurea was the most efficient in accumulating Pb and Zn in its shoots, whereas var. rubra was most suitable for phytostabilization of sites contaminated with Cu and Ni.

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The variations of tropospheric ozone levels was assessed for the first time in the Boukornine National Park (N.E. Tunisia) by detection of leaf injury development on Nicotiana tabacum "Bel-W3" exposed to environmental conditions during summer 2004. Two cultivars of tobacco (Nicotiana tabacum), Bel-W3 (sensitive) and Bel-B (resistant to ozone), were used for this biomonitoring study. These cultivars were dispersed in 24 different biostations, according to a square grid mesh, every 2 weeks. Four successive cultures were utilized to follow the ozone levels inside the park during the summer exposure period. Levels of ozone may vary in time and space depending on the local environmental and meteorological conditions. The results showed a positive correlation between ozone concentration and foliar injury index (FII; r=0.958; p<0.05). A significant positive correlation was observed between the FII of Bel-W3 tobacco plant and AOT40 (accumulated over the threshold of 40 ppb). The altitude appeared to be the most important variable explaining the variation of ozone pollution with the highest correlation coefficient (r=0.964; p<0.0001). The altitude was followed by topography for the prediction of ozone concentration levels. Maximal temperature was also an important factor in addition to the others in determining the FII and was negatively correlated with the FII (r=−0.979; p<0.05). Average ambient ozone levels were positively linked to plant leaf damage. The ozone profile characterizing the study area was primarily influenced by wind direction and speed in relation to intercontinental transport, in addition to the local influence of motor vehicles traffic flow in the Tunis region.