Measuring Plant Cover in Sagebrush Steppe Rangelands: A Comparison of Methods |
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Authors: | Steven S Seefeldt D Terrance Booth |
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Institution: | (1) Agricultural Research Service United States Sheep Experiment Station, United States Department of Agriculture, Dubois, Idaho 83423, USA;(2) Agricultural Research Service High Plains Grasslands Research Station, United States Department of Agriculture, Cheyenne, Wyoming 82009, USA;(3) United States Department of Agriculture, Agricultural Research Service, Subarctic Agricultural Research UnitRoom 355 O’Neill Building, University of Alaska Fairbanks, Fairbanks, AK 99775, USA |
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Abstract: | Methods that are more cost-effective and objective are needed to detect important vegetation change within acceptable error
rates. The objective of this research was to compare visual estimation to three new methods for determining vegetation cover
in the sagebrush steppe. Fourteen management units at the US Sheep Experiment Station were identified for study. In each unit,
20 data collection points were selected for measuring plant cover using visual estimation, laser-point frame (LPF), 2 m above-ground-level
(AGL) digital imagery, and 100-m AGL digital imagery. In 11 of 14 management units, determinations of vegetation cover differed
(P < 0.05). However, when combined, overall determinations of vegetation cover did not differ. Standard deviation, corrected
sums of squares, coefficient of variation, and standard error for the 100 m AGL method were half as large as for the LPF and
less than the 2-m AGL and visual estimate. For the purpose of measuring plant cover, all three new methods are as good as
or better than visual estimation for speed, standard deviation, and cost. The acquisition of a permanent image of a location
is an important advantage of the 2 and 100 m AGL methods because vegetation can be reanalyzed using improved software or to
answer different questions, and changes in vegetation over time can be more accurately determined. The reduction in cost per
sample, the increased speed of sampling, and the smaller standard deviation associated with the 100-m AGL digital imagery
are compelling arguments for adopting this vegetation sampling method. |
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Keywords: | Image analysis Digital imagery Vegetation measurement Sagebrush steppe |
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