Tree structure and composition in an altitude gradient of the Metzabok Protected Natural Area, Chiapas, Mexico

Abstract

Introduction: The forests are home to more than half of the planet's species, despite of their biodiversity, they are the ecosystems most threatened mainly by anthropic activities, but their complexity in relation to altitude has information gaps despite of the values it represents. Objective: Describe the structure and diversity of trees on an altitudinal gradient. Methods: In five altitudinal strata (EA) 21 sampling plots (UM) of 20 x 50 m were established: six in EA1, five in EA2, four in EA3, three in EA4 and 5. The structure was characterized by the categories diametric and height, and the importance value indexes (IVI) and forestry (IVF). Diversity was analyzed with the Shannon-Wiener (H´) and Simpson (S) indices, while the floristic similarity with the Sørensen coefficient (IS). Results: It was registered 209 tree species, eight are listed in the Official Mexican Standard-059-Secretariat of the Environment and Natural Resources-2010 (NOM-059-SEMARNAT-2019) as vulnerable species. The species with the highest IVI and IVF were Haematoxylum campechianum and Manilkara zapota in EA1; Rinorea guatemalensis and Pouteria reticulata in EA2; M. zapota and Brosimum alicastrum at EA3; Guatteria anomala and Pseudolmedia spuria in EA4; and Terminalia amazonia and Pouteria durlandii at EA5. In the five EAs, three ranges of height and six of diameter were identified, the largest number of individuals was found in the first diametric range. Species diversity was lower at higher altitudes. In EA 2 and 3 the greatest similarity was presented (IS= 58.7 %). Conclusion: The structure and diversity of the tree species present greater changes in wider altitude ranges, related to the environmental need of each species.

It was registered 209 species, eight are listed in the Official Mexican Standard-059-SEMARNAT-2010 as vulnerable species. The species with the highest importance value index and forest importance value index were Haematoxylum campechianum L., Manilkara zapota (L.) Royen in the altitudinal strip 1; Rinorea guatemalensis (S. Watson) Bartlett, Pouteria reticulata (Engl.) Eyma in the altitudinal strip 2; M. zapota, Brosimun alicastrum Sw in the strip 3; Guatteria anomala R.E. Fr, Pseudolmedia spuria (Sw.) Griseb in strip 4; y finally Terminalia amazonia (J. F. Gmel.) Ecell, P. durlandii in altitudinal strip 5. In the five strata, three height ranges and diametric categories were identified. The largest number of individual was registered in the first diametric category (< 10 cm).  The species diversity of the species was lower alt higher altitude. In stripes 2 and 3 the greatest similarity was present (IS = 58.7%). Conclusion The diversity of species was influenced by altitude. In some places population of almost the same species are constituted as an adaptation to the effect of height

Key Words: tropics, Perennifolia, basal area, wealth, jungle.