Tamaulipan scrubland is a type of shrub vegetation endemic to Northeastern Mexico and Southern Texas in the U.S. The structure of the Tamaulipan scrubland was evaluated in the study, establishing the minimum area with plots of 256 m2 by determining the species-area curve, valuing the composition and diversity of the strata of the plant species (arboreal, shrub, low forest, semi shrubby, herbaceous and epiphytes); three sampling sites of 16×16 m were established. Dasometric information such as height, diameter and cup coverage was recorded to determine the structural variables of coverage, density, relative density, dominance, relative dominance, frequency, relative frequency and Importance Value Index, as well as estimation of the Margalef richness index, Shannon-Wiener diversity index, Menhinick, Simpson and Pielou’s evenness index. The floristic richness was of 33 species distributed in 30 genera and 19 families, leaving the predominance value of the highest species of Leguminosae (Fabaceae). Six strata were recognized for the studied vegetation from which the highest IVI was Helietta parvifolia with 17.68 % for the shrubby stratum with 14 species and within the plant community of the MET the IVI was 8.53 %; for the low forest stratum with 8 species, the one with the highest IVI was Bernardia myricifolia with 39.20 %; and within the vegetal community 7.74 % for the semi shrubby there were 7 species where Lantana canescens has an IVI of 60.38 % and of 13.09 % inside the community. For the herbaceous stratum with 2 species, Wissadula sp. dominates with 54.20 % and 2.06 % for the community. In the arboreal stratum, the species with the highest IVI was Celtis laevigata with 100.00 % and when integrated to the plant community, it presented a value of 1.98 %. For the stratum formed by the epiphytes, the species Adiantum capillus-veneris had an IVI of 100 % and inside the plant community presented an IVI of 1.55 %. For the MET plant community studied, an H' value of 2.42 and a DMg value of 4.34 was obtained.

Keywords: Index value of importance, Montemorelos, Margalef, strata.