patron George Engelmann, a St. Louis area physician and botanist, then described the plant. This tree was first collected in California by William Lobb on his expedition to California of 1849–1853, after it was overlooked by David Douglas in his 1825–27 expedition to the Pacific coast region. The specific epithet concolor means "all one color". Distribution This tree is native to the mountains of western North America from the southern Cascade Range in Oregon, south throughout California and into the Sierra de San Pedro Mártir in northern Baja California, and south throughout the Colorado Plateau and southern Rocky Mountains in Utah and Colorado, and into the isolated mountain ranges of southern Arizona, New Mexico, and Northern Mexico. It naturally occurs between above sea level. Ecology White fir is very closely related to grand fir (Abies grandis), with subspecies lowiana being particularly similar to the interior variety of grand fir, A. grandis var. idahoensis, intergrading with it where they meet in the Cascades of Central Oregon. White fir occupies a broader range, including dryer and colder sites, being more drought tolerant and having thicker, fire-resistant bark. In Mexico, it is replaced by further close relatives, Durango fir (A. durangensis) and Mexican fir (A. mexicana). Like grand fir, white fir is more shade tolerant than Douglas fir, but less so than western hemlock and western redcedar. White fir is a climax species, which means the forest has reached complex maturity in forest succession in western coniferous forests of the U.S. White fir and yellow pine (ponderosa pine/Jeffrey pine) have co-existed for millennia in old growth forests throughout their range. In the presence of logging of large diameter trees and exclusion of cleansing wildfires, young trees have become abundant over the past two centuries. White fir had been regarded as a pest in the past by those in the lumber industry, but this opinion has changed. White fir is now one of the most important of all commercial softwoods according to the Western Wood Products Association. The white fir trait of retaining lower limbs creates an escape route for medium-to-small forest birds (such as spotted owl) from larger flying predators and provides a drip zone around the roots for collecting moisture. The retained limbs can become a fuel ladder that allows flames to climb up to the canopy. Limbing-up white fir, instead of removing medium to large diameter trees, in areas where the