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Background: Although the mesquite (mesquital or mezquital in Spanish) is one of the representative ecosystems of the landscapes in the north of Mexico, it is also one of the least studied. This study evaluated the structure (horizontal and vertical) and diversity of a plant community of mesquite in Northeastern Mexico. Three plots of 1,600 m(2) each were established. All trees and shrubs with a basal diameter (d(0.10)) >= 0.5 cm were recorded, and total height (h) and crown diameter (d(crown)) were measured.

Results: There were 8 families, 12 genera and 14 species. The genus presenting the most species was Acacia (three species). The most representative family was Fabaceae with seven species. The evaluated community presents a density of 375 N/ha and a crown area of 6,600 m(2)/ha. The species with the highest values on the Importance Value Index (IVI) were Prosopis glandulosa (15.95%), Acacia amentacea (14.50%), Havardia pallens (14.27%) and Acacia farnesiana (11.22%). These four species account for 55.94% of IVI. The value obtained from the Vertical Species Profile Index (A) was 3.03, with an A(max) of 3.74 and an A(rel) of 81.15%, indicating high structural diversity in the high strata. The evaluated plant community had a Margalef Diversity Index value of D-Mg = 2.50 and a Shannon Index value of H’ = 2.28, values which are intermediate and considered to be common in the scrublands of Northeastern Mexico.

Conclusions: 1) The studied community presents intermediate values that are considered as common in comparison to other arid and semi-arid vegetation associations of Northeastern Mexico. 2) The abundance curve of the species was well adjusted to the geometric model, and the distribution is associated with adverse environments such as semi-arid. 3) The family with greater importance for its contribution to the community is Fabaceae, while the genus with more species was Acacia. The research generated quantitative information of the plant community of a mesquite which is in a phase of mature ecological succession.