Submitted to: Environmental Management
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/14/2007
Publication Date: 6/12/2008
Publication URL: http://dx.doi.org/10.1007/s00267-008-9110-x
Citation: Booth, D.T., Cox, S.E., Meikle, T., Zuuring, H.R. 2008. Ground-cover measurements: Assessing correlation among aerial and ground-based methods. Environmental Management DOI 10.1007/s00267-008-9110-x. Interpretive Summary: Conventional monitoring methods commonly used by Federal land-management agencies are inadequate for the vast areas encompassed in many public-land management units. This study compared 2 conventional ground-based monitoring methods with 2 image-measurement methods in which photographs were made from 6.5 ft and from about 330 ft above ground level using a camera stand and a light airplane. The photographs were evaluated using SamplePoint and VegMeasure software. We found good agreement between aerial and most ground methods. We conclude that ground with aerial data-set associations can be equal to, or better than those among ground-based data sets; also, that bare ground is a more consistent ecological indicator than is vegetation cover when using current conventional or innovative image-analysis techniques for ground-cover measurements. Aerial methods and analysis were less expensive and allowed data to be collected from many more locations than could be obtained with conventional ground methods.
Technical Abstract: Wyoming’s Green Mountain Common Allotment is public land providing livestock forage, wildlife habitat and unfenced solitude, amid other ecological services, and is the center of ongoing debate over the adjudication of land uses by the USDI Bureau of Land Management (BLM). BLM land-management responsibilities include monitoring the appropriateness of resource use; however, conventional monitoring methods are inadequate for the vast areas encompassed in this, and other public-land management units. New methods must be developed and tested. This study compared 2 conventional methods with 2 image-measurement methods in which images were captured from 2 and 100 m above ground level using a camera stand and a light airplane. Image analysis used either SamplePoint or VegMeasure software. Aerial methods allowed for greatly increased sampling intensity at low cost relative to the time and travel required by ground methods. Costs to acquire the aerial imagery and measure ground cover on 162 aerial samples representing 9,000-ha was less than $4,000. The 4 highest correlations for bare ground—the ground-cover characteristic yielding the highest correlations--ranged from 0.76 to 0.85 and included ground with ground (1), ground with aerial (2), and aerial with aerial (1) data-set associations. Among the 15 data-set pairs there were 5 nonsignificant associations for bare ground and 12 for vegetation. We conclude that ground with aerial data-set associations can be equal to, or better than those among ground-based data sets, and that bare ground is a more consistent ecological indicator than is vegetation cover when using current conventional or innovative image-analysis techniques for ground-cover measurements.