干旱区生态环境知识资源中心

The main objective of this study is to prove the contribution of GIS in the multisource data integration for pastoral activities management in a semi-arid area and to look for the degradation causes. The study concerns a steppic area situated in the north of the city of Laghouat (Algeria) (1degrees20'20" less than or equal to 1 less than or equal to 2degrees21'55", 33degrees51'10" less than or equal to phi less than or equal to 34degrees41'53").

First of all, we started by the introduction on a GIS of all the necessary layers of the study area. These data were served to the development of pastoral data base of kind (GIS) which required a modelisation of the different data.

The use of this data base was considered to several levels. In a given plan: 1) estimation of pasture rates and densities over the total surface; 2) evaluation of the charge index of each township; 3) computation of the distribution of the livestock possessed by each inhabitant. In a combined plan: overlay of the vegetation covert layer where are presented the different grazing with the pasture area distribution layer.

The result of the charge index have shown its considerable increase through the three dates 87-91-1994 (superior to the norm which is 0.25 ovine heads per hectare). This is explained by the reduction of grazing surface and by the increase of livestock number. The advantage of the index computation is the identification of the grazing which risks degrading (index superior to 0.25). This is probably due to the highly demographic and to the livestock evolution in the region. These first results show the considerable contribution of the GIS in the integration process of the multisource data in the aim of production maps and answers to complex interrogations in order to fond out the grazing degradation causes and to propose the best plans for the suitable grazing management.