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Caractérisation de la structure spatiale des individus ligneux dans une brousse tachetée au sud-ouest du Niger

par Diouf, Abdoulaye ;Barbier, Nicolas Serge ;Mahamane, Ali A. M.;Lejoly, Jean ;Saadouc, Mahamane;Bogaerta, Jan
Référence Canadian journal of forest research, 40, 4, page (827-835)
Publication Publié, 2010-04

Article révisé par les pairs

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Résumé :

In arid regions, according to self-organization models, the spatial structure of periodic vegetations depends on local processes (facilitation or competition). The current study verified the importance of these processes and the role of Combretum micranthum G. Don through a detailed description of the spatial distribution of ligneous species in gapped bush vegetation of southwest Niger, using Ripley's K function. Spatial organization of shrubs reveals a two-scale structure: (i) aggregative (average radius, 9-15 m) and (ii) repulsive (at about 35 m), corresponding to the general periodic pattern. Only C.micranthum presents a similar distribution, which suggests that it could be the "keystone species", determining the vegetation structure. A local aggregation of secondary species around C.micranthum strongly suggests facilitation at a short distance (1-3 m), proportional to the crown's average radius of mature shrubs, in accordance with model predictions and empirical studies of soil hydrodynamics. The absence of spatial relations between C. micranthum and the other species of the family Combretaceae, which tend to cluster together, suggests the existence of a three-component structure. These elements open up new perspectives for field research and for the improvement of models, which are essential for the management of Sahelian vegetations against the exploitation and aridity constraints.