Pine-oak Forests, Puebla
The Pine–oak Forest of Puebla covers the mass of pine and oak forests in the Mexican state of Puebla.
Preamble
Due to the geographical location of Mexico, the middle part of the country runs through the Tropic of Cancer; as such, it is located in an area of contact between boreal and tropical floras. Because of its shape, climate, topography, geology and soil, it contains a great floristic diversity and a diversity in types of vegetation. The diversity of these ecological factors explains why in Mexico there are nearly all of the plant formations observed worldwide.The diversity of plant communities is not only due to ecological characteristics, but also from historical and evolutionary aspects. The fact that the country is in the contact area of the boreal and tropical floras allows for the development of communities where both floras fight to excel, having developed indigenous communities. Generally, it can be considered that the distribution of vegetation in Mexico is conditioned, in the first instance, by climate factors. Although frequently, geological, edaphic or topographic nature plays a very important role.
The pine–oak forest is a biome characterized by the abundance of certain species of pine and oak, of the genus Pinus and Quercus respectively.
Characteristics
The pine-oak forest develops at altitudes between 1600 and 3000 meters, where the climate is temperate and humid with summer rain, with temperatures ranging between 16 and 20 degrees Celsius, and with rainfall that varies between 700 and 1500mm.In this type of forest, many different types of rock can be found: igneous, metamorphic, and sedimentary. The soil in which they are located is thin and poorly developed, being principally litosol, regosol, and cambisol. Though, they are also located on soil originating from volcanic ash, such as andosol. Pines and firs are characteristic of the pine-oak forest.
Flora
In Sierra de Pahuatlán y Tetela de Ocampo, this type of forest is dispersed as isolated spots and is formed, in the tree layer, by species like red ocote, Chinese ocote, ocote, and broadleaf oak. The middle layer is made up of species like cile and the strawberry tree. In the lower layer, there is broom or tepopote and Pteridium sp. The distribution of species in this type of forest varies from factors such as exposure, moisture, temperature, and wind. In the east/northeast, where the humidity and temperature are high, pinus patula predominates the top tier. In contrast, at lower altitude and with the same exposure, you can find Cornus disciflora, Garrya laurifolia, Mexican Clethra, and ferns in the lowest layer. In this exposition, where humidity is low and temperature is high, the Chinese ocote dominates.In the foothills of the Sierra Nevada, in the Malintzin and Citlaltépetl volcanoes, between 2500 and 3000 meters above sea level, the arboreal layer above 32m is dominated by the red torch pine, fir, ocote brush and ayacahuite ; in the 10m layer you can find laurelillo, milkweed and madrone ; in the 4.5m layer you can find Salix paradoxa, brush, wild cherry, alder, and strawberry trees ; in the 0.5m layer you find Baccharis conferta, sage, topozán, grass and fern.
In the southeast, from the western slopes of Sierra de Zongolica until the municipality of Nicolas Bravo, an area of pine-oak forest is located more than 2500 meters above sea level. In it can be found species such as Pinus patula, teocote, white oak and black oak.