Valorisation du Pin pignon (Pinus pinea L.) dans la région de Djebel Ouahch - Constantine
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The Stone pine (Pinus pinea L.) is a forest tree species to be valorized on the economic level by its production of wood and pine nuts. In Algeria, it occupies a total surface of 3506 ha; the largest surface is located on the massif of Djebel Ouahch 2278 ha. The present work aimed mainly at determining on the development and adaptation of this forest species in the zone of Djebel Ouahch for possible reforestations in form of equilateral plantings with a medium age of 40 years. Medium fruit-bearing production is assessed between 3,80 and 523,76 tons of pine nuts in shells. In good conditions, the quantity of harvested is 554,110 cone / hectare in the studied zone. The physicochemical characterization of the study zone reveals a balanced texture, with a low percentage in loam (~ 27 %), a medium pH ranged between 6 - 7.5 and a very low total quantity of limestone. On morphological level, the germinal capacity of seeds is of good quality with a bellow and above-ground live biomass fairly sustained. These morphological parameters showed a statistically significant difference among different treatments and seasons. The seedlings grown in semi controlled conditions suffer from short –term stresses (03 hrs) in a range of temperature varying between-10 °C and 50°C while the biochemical markers (chlorophyll, proline, soluble sugars, proteins and enzymes) are quantified. Under a thermal pressure, the results show an increase of the chlorophyll pigments at 38°C. The seedlings show an adaptation to lower temperatures at 44°C for the proline, the soluble sugars, the catalase and MDA. The intensity of hydric and thermal stress is significant for all analyzed parameters. The Pine Seedlings are capable to accumulate the different osmolytes in the different organs in response to combined stress. The accumulation of soluble sugars is highly marked for the control at 38°C; while the increase of the proline is very significant in roots under thermal pressure at 38°C at level N1 and at 44°C at level N2 (55 %). The Seedlings show clear features of biochemical adaptation in response to combined, hydric and thermal, fluctuations. The phenology analysis was observed on branches of a growth ranging between 15-20 years in the region of Provence-Alpes-Côte d'Azur and in the region of Djebel Ouahch. The exclusion of rainfall diminished the annual number of growth cycles of shoots and their duration and also the speed of needles growth. The quality of the populations of Stone pine is moderately stable with a weak rate of regeneration and a quite high mortality rate due to anthropic action and fires.