The Sierra Nevada looms above the Owens Valley in eastern California.
Water flowing from the peaks create oases in the otherwise parched land.
Here, cottonwoods dot the valley where waters run or spring to the surface. Introduction Mountain Life Zones Merriam s life-zone concept Species distribution along elevational gradients Environmental gradients Island Biogeography Theory Desert mountain tops as islands Riparian Corridors Mountains as a source of rivers Riparian habitat Web Resources Life Zone Concept of C. Hart Merriam summarizes the communities on Southwest mountains. C. Hart Merriam is a short biography of this biogeographer. From the Merriam-Powell Center for Environmental Research at Northern Arizona University. Southwestern Sky Island Ecosystems describes the scattered desert mountains that extend from southern Arizona and New Mexico into Mexico.