Madrean pine-oak woodlands

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The Madrean pine-oak woodlands are subtropical woodlands found in the mountains of Mexico and the southwestern United States.

Pine Forest on the road between San Isidro Llano Grande and San Miguel Cajonos, in the Sierra Madre de Oaxaca

The Madrean pine-oak woodlands are found at higher elevations in Mexico's major mountain ranges, the Sierra Madre Occidental, the Sierra Madre Oriental, the Trans-Mexican volcanic belt, the Sierra Madre del Sur, the Sierra Madre de Oaxaca, the Peninsular Ranges of the Baja California Peninsula, and there are also approximately 27 enclaves in southern Arizona and New Mexico and in western Texas, where they are known as the "Madrean sky islands". The major Madrean "sky island" ranges in Arizona are the Dragoon Mountains, Chiricahua Mountains, Pinaleño Mountains, Santa Catalina Mountains, Rincon Mountains, Santa Rita Mountains and Tumacacori Highlands. In New Mexico the Sacramento Mountains and Guadalupe Mountains, which extend into Texas, as well as the Davis Mountains and Chisos Mountains, are also forested sky islands.

Conservation International estimates the woodlands' original area at 461,265 km². The woodlands are surrounded at lower elevations by other ecoregions, mostly tropical and subtropical deserts and xeric shrublands, forests, and grasslands. Woodland areas were isolated from one another and from the pine-oak woodlands of the Sierra Madre Occidental to the south by the warming and drying of the climate since the ice ages.

The pine-oak woodlands are composed of stands of oak (Quercus), pine (Pinus), douglas-fir (Pseudotsuga) and fir (Abies). The trees generally occur in mixed stands, though monospecific stands are sometimes found. The pine-oak woodlands are home to one-quarter of Mexico's plant species, and Mexico is home to 44 of the 110 species of pine and over 135 species of oak, over 30 percent of the world's oak species. Plant species derived from Madrean ancestors, known as the Madro-Tertiary flora, are an important element of the California chaparral and woodlands ecoregion.

The World Wildlife Fund recognizes several distinct pine-oak woodlands ecoregions, based on geographic distribution and species mix.

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