In the American Southwest, and across the continent, vegetation is a key component of vertebrate and invertebrate habitat. The photosynthetic process is fundamental to all ecosystems and provides the material base for energetic flow in the system. In addition, above-ground structures of vascular plants protect soil resources from erosion by water and wind. Roots stabilize soils, conduct and redistribute resources, and provide organic matter to soil food webs. Plants also modify the physical environment by shading and litter deposition. Changes to the structure and composition of vegetation can disrupt an ecosystem’s function and make it unsuitable for associated biota. Monitoring of vegetation communities is a critical component of monitoring in the parks of the American Southwest.