ECOHYDROLOGY IN A COLORADO RIVER RIPARIAN FOREST: IMPLICATIONS FOR THE DECLINE OF POPULUS FREMONTII.

The article focuses on ecohydrology in riparian forests. Riparian ecosystems provide essential habitat for a variety of species in the desert southwest of the United States. In these areas, "Fremont cottonwood" is a common riparian species that becomes established following flooding and depositional events in alluvial plains. Human-caused alterations in hydrology, grazing, and invasive species have had a large impact on riparian areas once dominated by Fremont cottonwood and its co-occurring species. Stands of Fremont cottonwood have been reduced to a small fraction of their former extent, having been replaced by secondary successional species, upland species, and exotic invasives. A number of mechanisms have been ascribed to the decline of Fremont cottonwood, including drought stress, salinity stress, and inter-specific competition. Management and restoration of riparian ecosystems requires an understanding of the importance of potential mechanisms of ecosystem degradation and shifts in community structure.