Actualmente, el gobierno federal promueve el pago por captura de carbono en los bosques para mitigar el calentamiento global. Por ello, existe la necesidad de estimar la biomasa y tasas de captura de carbono en los bosques de Abies religiosa. En este estudio se generaron modelos para calcular la biomasa de fuste, de madera de ramas y de acículas de árboles completos y de ramas de oyamel en rodales del Cerro Tláloc, Texcoco, Estado de México. Para el caso de árboles completos, la biomasa estuvo en función del diámetro normal (DN), mientras que para ramas individuales fue una función del diámetro basal (DB). El uso de los modelos generados a nivel árbol se recomienda para árboles con DN entre 12 y 105 cm, n cambio los modelos a nivel de ramas se recomiendan para diámetros basales entre 1 y 120 mm. El modelo para fustes fue de tipo potencial y los de madera de ramas y follaje de árboles completos de tipo exponencial. Los coeficientes de determinación de los modelos a nivel árbol indican que existe una considerable variabilidad, principalmente, en las biomasas de ramas, lo que puede ser consecuencia del proceso de declinación en la zona de estudio. La biomasa total de los árboles se distribuye en forma atípica entre los compartimentos aéreos: 97 % en los fustes, 3 % en madera de ramas y 0.07 % en follaje. Este patrón de distribución de biomasa refleja el efecto del deterioro de los bosques de A. religiosa.

No abstract

Megapolis such as Mexico City, have atmospheric pollutants that interact with the humidity and solar radiation. The topography of this city promotes air stagnation, generating atmospheric pollutants and episodes of acid rain, a phenomenon well recorded since the end of the 1980s. However, little we know about how urban trees respond to acid rain in the city. Here we present how simulated acid rain causes anatomical and changes in photosynthetic pigments in two of the most abundant urban trees in Mexico City: Liquidambar styraciflua L. and Fraxinus uhdei (Wenz.) Lingelsh. We first described the leaf anatomy of both species. Then, we used one-year-old trees sprayed with sulfuric acid solutions at pH 2.5 and 3.8, and evaluated visible leaf damage, anatomical alterations, and chlorophyll contents. In both species, the pH 2.5 caused cuticle alterations and areas of total tissue destruction. L. styraciflua showed greater sensitivity, but we discuss some of the tolerance mechanisms. Finally, acid rain also reduced the chlorophyll contents. These results contribute toward a catalogue of urban tree species to describe pollution-induced damages, and the identification of tolerant species useful for short- and mid-term detection of environmental crisis, in cities with similar environmental conditions and urban tree composition.

Particle induced X-ray emission (PÏXE) and Rutherford backscattering (RBS) elemental analyses of tree rings and soils from forests around the Mexico City Metropolitan Area (MCMA) were performed. The aim was to estimate the impact of pollution on the forests. Cores from Pinus montezumae and Abies religiosa trees, in four forests around the MCMA (Desierto de los Leones, Iztapopocatépetl, Villa del Carbón and Zoquiapan) and a reference site (El Chico). Differences were observed in samples from the different forests, showing higher values in the areas closest to the MCMA. A correlation of several elements with ring width was found using cluster analysis. Additionally, soil analyses from different depths in the forests were carried out, trying to relate the elemental concentrations measured in the tree rings with cation mobility. In this case, samples taken in 1993 and 1999 were analyzed, showing elemental mobility to the various depths.