Typologie et adaptation des espaces verts de l'agglomération d'El Khroub (Constantine).

Abstract

The sustainable management of green spaces requires a vast set of arboreal practices both in terms of its design (landscape study, choice of species), as its maintenance, it is intended to find a balance between landscape comfort, ecological requirements and practical and economic constraints. This work aims essentially to draw a typology appropriate to the green spaces of the city of El Khroub with the help of the GIS software, to inventory and evaluate the viability of the diversity of the ligneous of the city, and to integrate the social part in this evaluation, to propose a differentiated management mode, and finally to elucidate the effect of heat stress by biochemical markers (chlorophyll, proline, soluble sugars, proteins, catalase and peroxidase) on the adaptability of seedlings of Acacia heterophylla Willd, Fraxinus angustifolia, Maclura pomifera, Melia azedarach, and Phytolacca americana vis-à-vis high and low temperatures. Our results reveal the existence of 11 types among the 13 proposed by Jancel, the predominant type is the accompaniments of collective dwellings; we note the deficit of green spaces in the city of El Khroub with a ratio of 0.53 m² / ha, a recovery rate of 1.58%, and a total density of about 1.33/ km². The inventoried results on the floral diversity of the city of El Khroub shows the existence of 34 species belonging to 18 families for the tree layer, and 19 species belong to 14 families for the shrub and herbaceous strata, their states varies between good, medium and bad. Alignment trees and plants that constitute green spaces remain dependent on the aesthetic, ornamental, and does not meet the ecological characteristics (adaptation), this is confirmed by the respondents. In fact, the dispersed greening operations, by the responsible management departments, pose problems of sustainability. The results of the chlorophyll (a and b) content assay as a function of the high and low temperatures show a decrease in the synthesis of chlorophyll in comparison with the control in all the species studied, except for Acacia heterophylla Willd and the Maclura pomifera. The accumulation of proline was well marked at the roots at temperatures (-6 ° C and 44 ° C) in all species indicating resistance to thermal stresses, growth rates in the higher are obtained from Phytolacca americana. Sugar levels are generally more concentrated in the leaves than other organs in Acacia heterophylla Willd. However, for the other species the concentration is higher at the root level. Protein assay results in the organs of Melia azedarach, Acacia heterophylla Willd, and Fraxinus angustifolia show a strong accumulation of these at leaf levels relative to other organs; unlike Maclura pomifera and Phytolacca americana where the highest accumulation is observed at the root level. All young plants noted an increase in peroxidase activity as temperatures increased, except for Maclura pomifera, which experienced a decrease in potency. Increasing values of antioxidant activity may suggest tolerance / adaptation. It was found that Acacia heterophylla Willd, Melia azedarach, and Fraxinus angustifolia exhibited the highest specific activities under thermal stress. The present contribution shows that these species can exhibit interesting catalytic properties, as well as thermal resistance.