Formas de vida de la vegetación en el límite superior de un bosque de alta montaña en México

Abstract

The objective of the present study was to characterize the diversity of life forms and the plant community structure along an altitudinal gradient of the treeline ecotone of Pinus hartwegii Lindl. at Nevado de Toluca, Mexico. Plant species in the treeline ecotone were sampled, identified, and quantified according with the life forms. Diversity of life forms of the ecotone was calculated according to the Shannon diversity Index, and the structure was evaluated based on the density and abundance of plant species. A total of 43 plant species belonging to 30 genera and 18 botanical families were identified. Chamaephytes were the most abundant life form (>50 %), with increasing altitude, the diversity of life forms increased, while the abundance of life forms decreased. Species diversity was proportionally and significantly related accordingly to one-way ANOVA, with increasing altitude along the treeline ecotone. Pinus hartwegii treeline ecotone was diffuse in form and characterized by greater abiotic stress conditions at higher altitudes which was not observed in this case, due to the altitudinal range sampled, and to the fact that this ecotone represents the forest species distribution limit and the beginning of grassland distribution. At high altitudes life forms experiment greater selective pressures and must be adapt to extreme environmental conditions, which increase with the altitude. Also, distinct life forms present at the treeline ecotone of P. hartwegii may modify environmental conditions or processes and therefore regulate the response of other associated species to climate change.