A Laser Point Frame to Measure Cover

Abstract

The point sample method has been a standard plotless method for measurement of ground cover on ragelands since it was introduced by Levy in 1927. The instrument most commonly used to do point sampling is the point frame. Since its introduction, the point frame has undergone numberous modifications to improve efficiency and ease of use. This article introduces a laser point frame (LPF) that was designed by the Agricultural Research Service for measurement of ground cover and utilizes lasers in place of conventional metal pins. A comparative pilot study was conducted on a shortgrass prairie in northern Colorado to compare data collected using a magnetic point frame (MPF) with data collected using the LPF. Cover by species was measured from identical plots using 100 points per plot for each point frame, and sampling times were recorded for each plot. Correlations between cover data collected using the MPF and the LPF were relatively high (r2 = 0.62-0.81). Total average vegetative cover measured with the MPF was 35%, compared with 40%, using the LPF. Cover of total grasses, C4 grasses, C3 grasses, and litter, were significantly greater with the LPF method. Total sampling time per 100 points was almost half using the LPF compared with the MPF. The LPF was easy to use, efficient for measurement of cover, and is a potential replacement for conventional point frames.