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An evaluation of overhead laser scanning to estimate herbage removals in pasture quadrats

Radtke, Philip J., Boland, Holly T., Scaglia, Guillermo
Agricultural and forest meteorology 2010 v.150 no.12 pp. 1523-1528
Medicago sativa, Festuca arundinacea, alfalfa, forage grasses, pastures, lidar, dry matter accumulation, spatial variation, grazing, physical models, volume, spatial distribution, accuracy, reliability, new methods, methodology
The goal of this study was to test the utility of terrestrial laser scanning (lidar) as a means to estimate the dry weight and spatial distributions of herbage removals from small pasture plots. High resolution measurements of sward surface heights (SSH) were generated from lidar data acquired at close range over alfalfa (Medicado sativa subsp. sativa L.) and tall fescue (Festuca arundinacea Schreb. or Lolium arundinaceum (Schreb.) S.J. Darbyshire) pasture quadrats, before and after the collection of hand-plucked samples designed to mimic grazing by livestock. Removed herbage dry weights ranged from 3 to 65g for n =32 samples collected on 1m² quadrats, half in each pasture type. Volume change was calculated based on differences in SSH before and after plucking. Strong relationships were observed between volume change and dry weights of removals for both species (alfalfa r ² =0.970, tall fescue r ² =0.957). Contour maps gave detailed information on SSH before and after plucking, and the spatial distributions of herbage removed from field plots. Subject to further testing, lidar-based estimates could prove both reliable and non-invasive to livestock in grazing or herbage studies.