Composition and diversity of the vegetation in four sites of Mexico's Northeast

During the summer of 2007, a study of the status of trees and woody vegetation was performed at four sites, in the state of Nuevo Leon, Mexico. Site one (S1, Bosque Escuela) was located at 1600 m elevation in Iturbide county. Sites S2 (Crucitas, 550 m), S3 (Campus, 350 m) and S4 (Cascajoso, 300 m) were located in Linares county. In each site, 10 random plots (10 m x 10 m) were laid out, and relative abundance, relative dominance and relative frequency were estimated. In addition, dasometric parameters such as height and crown diameter were determined. Plant diversity was estimated by the Shannon-Wiener index, and similarity between sites was calculated using the Jaccard index. A total of 13710 individual plants belonging to 28 families were registered. Leguminosae had the highest number of species (10) followed by Fagaceae (4), Rutaceae (4), Euphorbiaceae (3), Oleaceae (3), Cupressaceae (3), Rhamnaceae (2) and Verbenaceae (2). Eighteen families included only one species. The site with higher and lower Shannon index was Cascajoso (2,08) and Bosque Escuela (1,64), respectively. The Jaccard index showed similarity among species only among S2, S3 and S4 sites. The plant species more frequent were: in S1 Quercus canbyi, Pinus pseudostrobus and Rhus pachyrranchys (11,9%); in S2 Havardia pallens (9,9%); in S3 Havardia pallens and Forestiera angustifolia (9,8%) and in S4 Acacia rigidula, Cordia boissieri and Karwinskia humboldtiana (9,8%). S2 and S3 were the sites with the greatest species diversity, perhaps as a result of higher rainfall.