Resumo

QUINONES-VERA, Jesús José et al. Variables que definen los grados de condición en una sabana de Prosopis-Sporobolus al Noreste del estado de Durango, México: (con 4 cuadros y 6 figuras). Phyton (B. Aires) [online]. 2004, vol.73, pp.301-318. ISSN 1851-5657.

By using a direct gradient analysis, a relationship between the variability in abundance of species and the variability in the physical and chemical properties of soils, as well as its surface, was established in a savanna site; in the analysis, also the distance to the closest permanent drinking reservoir was considered. Based upon these parameters, it was determined that the variables more related to the vegetal distribution in the study area were: fine particle density of soils, aerial standing biomass of gramineous, bare ground rate, and aerial canopy of the vegetation. However, the magnitude of the canonical eigenvalues for the four main ordination axis showed no clear differentiation among the niches of species. Species such as Bouteloua curtipendula, Sporobolus airoides, Setaria macrostachia, Chloris gayana, Aristida pansa, Bouteloua gracilis, and the shrub Atriplex canescens were identified in the units portraying the higher production. On the other hand, Larrea tridentata, Flourensia cernua, Opuntia leptocaulis, and Condalia ericoides were more frequently found in the units showing lower production. Mesquite (Prosopis laevigata) was the specie with highest ecological extent on the study site.

Palavras-chave : Canonical correspondence analysis; desert shrubland; niches of species.

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