Assessment of riparian vegetation patterns and change downstream from Glen Canyon Dam from 2014 to 2019

First posted April 13, 2023 For additional information, contact: Southwest Biological Science CenterU.S. Geological Survey2255 N. Gemini DriveFlagstaff, AZ 86001 Changes in riparian vegetation cover and composition occur relation to flow regime, geomorphic template, climate, can have cascading effects on aquatic terrestrial ecosystems. Tracking such changes over time is therefore an important part of monitoring the condition trajectory Maintaining diverse, self-sustaining comprised mostly native species identified Glen Canyon Dam Long-Term Experimental Management Plan as a key resource objective for section Colorado River between Lake Mead. The U.S. Survey Grand Monitoring Research Center implemented annual program 2014 assess status trends along this river, particularly they relate regime. In report, we summarize plant data collected under from 2019, with special consideration given hydrologic position, associated feature class, local climate patterns, nonnative species, floristic region metrics species. We divided study area into four river segments (referred Canyon, Marble eastern western Canyon) basis geography calculated each recorded species’ relative frequency foliar by segment. These were then used evaluate relationships among segments, zones, features, sampling years through ordination analysis. Temporal our focal objectives—species richness, total cover, proportion Tamarix Pluchea sericea Baccharis cover—were assessed using mixed-effects models. Four patterns related emerged: (1) fixed-site sandbars differed that randomly selected sites (including sandbars), (2) other previously regions, (3) across zones dam operations, (4) within did not change years. temporal main findings fixed-sites sites; although few directional observed increased at areas influenced daily water fluctuations; richness greater than all zones; trend here be groups, enabling assessment ecosystem whole. addition these findings, lists are included appendixes. variations presented report baseline against which future compared.