Riparian vegetation data used for comparing sampling methods along the Colorado River, Grand Canyon, Arizona

These data were collected as part of a methodological comparison for collecting riparian vegetation data. Two common methods for collecting vegetation data were used: line-point intercept and 1m2 ocular quadrats (visual cover estimates). At each site and transect, both methods were used to collect cover and composition data by four different observers. The same transects and quadrats were utilized for both methods and all observers. Field data collected included percent cover for total living foliar cover, each plant species encountered, litter, dead plant material that is still standing, and ground cover features (biological soil crust, rock, sand, and fine soil particles). Line-point intercept data were collected at 25 cm intervals along each transect and at four points along the edge of each 1m2 quadrat. Since transects varied in length, the number of data points collected along each transect also varied. A pin flag was dropped vertically to the ground at 25 cm intervals and every plant species and ground cover element that touched the pin flag was recorded in the order it touched the pin flag from top to bottom, including any species that would touch the pin flag if it continued upward indefinitely. Each species was only recorded once at each point. Ocular quadrat data were collected at each of the 1 m2 quadrats. Cover estimates were recorded to the nearest 5% other than those estimates under 5% which were recorded as either 1% or “trace”. Observers calibrated their ocular estimates at the beginning of sampling and when a new observer started sampling. Observers were given reference cards illustrating multiple levels of percent cover (1 – 95%), which were used during calibration and throughout data collection. Five observers with three levels of experience participated in this study. Two observers had extensive experience with identification of plant species in the study area, as well as with the methods used. One observer was familiar with the methods as well as riparian plant identification, but had not previously worked in this study area. Two observers had not worked in this system or with these methods before, but had experience conducting vegetation surveys. All observers received on-site training. At each site, four observers sampled the entire site using both field methods.