Riparian vegetation metrics for the Colorado River between Glen Canyon Dam and Lake Mead, AZ

These data were compiled to assess the status and trends of riparian plant communities along the Colorado River between Glen Canyon Dam and Lake Mead, AZ. Three metrics have been proposed to evaluate the "Riparian Vegetation" goal identified in the Glen Canyon Dam Adaptive Management Program's Long Term Experimental and Management Plan (U.S. Department of Interior, 2016). The three metrics are total living plant cover, the proportion of living cover composed of native species, and native species richness. Current policies for Glen Canyon Dam operations result in three longitudinal bands within the riparian area that are flooded at different frequencies. The band, or hydrologic zone, that is most frequently inundated is referred to here as the “active channel” or “AC.” This includes all areas inundated by releases up to 25,000 cubic feet per second (707 m3/s). The “active floodplain” or “AF” is inundated by high flow experiments and includes areas that are inundated by releases between 25,000 cubic feet per second and 45,000 cubic feet per second (1,274 m3/s). The “inactive floodplain” or “IF” is the area along the river that is inundated by releases over 45,000 cubic feet per second, which is not planned under current policies. The metrics are assessed for each of these hydrologic zones. Data from the Grand Canyon Monitoring and Research Center's riparian vegetation monitoring protocol (Palmquist and others, 2018) can be used to evaluate these metrics, which is what is provided here. In short, 80-100 sample sites are randomly selected each year. These sites include debris fans, eddy sandbars, and channel margins. At each randomly selected sample site, ocular cover estimates of each plant species occurring in 1-m2 quadrats spanning the hydrological zones are recorded, along with an estimate of total living plant cover and associated environmental variables. The first metric, total living plant cover, consists of two pieces of data; plant occurrence (a plant is present in the sample frame) and plant cover (proportion of the sample frame covered with living plants). Cover is represented by both an ordinal cover class (1, 2, 3, 4, 5, 6, etc.) and the midpoint of the cover class value (0.01%, 0.5%, 1%, 5%, 10%, 15%, etc). The proportion of native cover is the sum total of native plant cover divided by the sum total of plant cover (native plus nonnative cover) for a sample frame. Native plant richness is the total number of native species rooted inside a sample frame. The total living plant cover data are available for 2016 through 2023. The native cover and richness data are available for 2014 and 2016 through 2023.