A Proto-type Laser/Optical System for Measurement of Vegetation Height and Cover in Quadrats

Society for Range Management ConferenceSociety for Range Management Conference, Spokane, WA, 28 January to 03 February 2012

Joseph M. Kleinhenz, Sara C. Norman*, Patrick E. Clark, Mounir Louhaichi, Robert M. Johnson, Norman R. Harris, and Douglas E. Johnson

“Vegetation monitoring is essential if scientists and managers are to effectively evaluate and direct ecosystem dynamics. Two important variables measured are cover and height of both vegetation and litter because of their relationship to phytomass, growth, forage utilization, soil protection from raindrop impact, soil erosion, water infiltration, and moderation of the thermal micro-environment. Unfortunately, many commonly employed measurement techniques are expensive and time consuming or are subjective. In an attempt to automate and quantify the monitoring process, we constructed and evaluated a proto-type system based on laser and optical digital technologies. The height profile of two plants each of 6 species was measured using a Leica Disto® A6 distance meter in the laboratory by measuring distance from a fixed plane above the specimen. Two passes at right angles to one another were done with measurements taken at 1 cm intervals along each pass. Distance from the meter to the plant or ground was calculated and converted to plant height. The Leica Disto® A6 is generally accurate within 1.5 mm up to 200 m on solid objects but plant leaves often only partially intercept the beam. Plants were also sampled by photographing from two sides and directly downward with a Canon® XSi Digital Camera set at a fixed distance from the subject. Images were scaled using a ruler in the image and converted to spatially explicit format. After laser and photographic sampling plants were harvested and above-ground phytomass calculated. Laser and photographic methods of determining cover and phytomass were compared.”