Читать книгу The Amphibians and Reptiles of Michoacán, México - William Edward Duellman - Страница 9

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For the purposes of this report I have adopted the classification of types of vegetation that seem to me most significant in terms of ecological distribution of reptiles and amphibians in Michoacán. These types are as follows:

Temperate (1000–4000 meters)

Fir Forest (2400–4000 meters)

Pine-oak Forest (1000–4000 meters)

Mesquite-grassland (1500–2100 meters)

Tropical (0–1000 meters)

Arid Tropical Scrub Forest (0–1000 meters)

Tropical Semi-deciduous Forest (150–600 meters)

The vegetation of the Pacific Coastal Plain and the Balsas-Tepalcatepec Basin consists of arid tropical scrub forest, composed of deciduous trees, which in many places are stunted and widely spaced. In the dry season there is little cover provided by this forest. In the rainy season there is a sparse growth of grasses and some shade provided by the small leaves of the thorny trees.

In Michoacán the rainfall is heaviest on the southern slopes of the Sierra de Coalcomán and somewhat less so on the southwestern slopes of the Cordillera Volcánica. At these relatively low elevations (150 to 600 meters) there is tropical semi-deciduous forest, characterized by relatively dense shade throughout the year and by a leaf mulch on the ground. This type of forest forms the gallery forest along the larger streams in the Balsas-Tepalcatepec Basin and on the Pacific Coastal Plain.

Rainfall also is heavy on the high mountain ridges, where temperatures are low. On these ridges, fir forest, often mixed with pine and oaks, is found. This habitat is characterized by a cool, moist climate, many rotting logs, and a moist ground cover of leaves and needles.

Most of the mountains are covered with pine-oak forest, which in most places is decidedly subhumid, but where this forest occurs on the windward sides of high ridges, it sometimes is noticeably humid. In this forest the important animal habitats include the needle- and leaf-litter, and in some areas, bromeliads.

The rolling terrain of the Mexican Plateau supports cacti, small leguminous trees, and grasses. Like the arid tropical scrub forest, this type of vegetation, the Mesquite-grassland association, is deciduous and thus provides little shelter in the dry season. Unlike the areas in which arid tropical scrub forest is developed, the Mesquite-grassland is found in areas having warm days and cool nights.