CHANGES IN RIPARIAN VEGETATION ALONG THE COLORADO RIVER AND RIO-GRANDE, COLORADO

Changes in vegetation including area occupied, canopy cover, and maturity class of cottonwoods (Populus spp.) within lower-elevation zones of the Clorado River and Rio Grande in Clorado were monitored over 25- and 37-year intervals, respectively, using photo-interpretative methods. Estimated loss of cottonwoods along the Colorado River was 2 ha/km (- 17.5%), and remaining stands had become more open and older. Cottonwoods along the Rio Grande increased 1.6 ha/km (9.3%) with minor canopy cover and maturity class changes. Area occupied by shrubs and river channel changed little along the Colorado River, but declined along the Rio Grande. Loss of hay meadows occurred along both rivers, whereas developed land increased along the Colorado River and farmland increased along the Rio Grande. Wildlife habitats along the Colorado deteriorated much more rapidly than those along the Rio Grande during monitored intervals.