Last updated: July 17, 2014
Blanketing the upper elevation plateaus and mountains of the Southwest are forests of ponderosa pine (Pinus ponderosa), mixed conifer, spruce-fir, and quaking aspen (Populus tremuloides), collectively known as montane forests. Occurring at elevations of 1,850 to 2,900 meters (approximately 6,000 to 9,500 feet), these forests are adapted to cold winters, and warm to cool summers. While large expanses of ponderosa pine forest occur in northern New Mexico and Arizona, smaller, more discontinuous patches of montane forest, called "sky islands" occur as isolated peaks within the surrounding lowland deserts of southern Arizona, New Mexico and western Texas. Moisture and natural disturbances such as climate variability, fire, and insects are among the key factors influencing the structure and composition of montane forests, as well as human impacts such as livestock grazing, timber harvest, and fire suppression.