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Title: Comparison of point intercept and image analysis for monitoring rangeland transects

Author
item CAGNEY, JAMES - Bureau Of Land Management
item Cox, Samuel
item Booth, D

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2010
Publication Date: 5/1/2011
Citation: Cagney, J., Cox, S.E., Booth, D.T. 2011. Comparison of point intercept and image analysis for monitoring rangeland transects. Rangeland Ecology and Management. 64(3):309-315.

Interpretive Summary: Professional land managers (government and private) need to improve the quality and verifiability of data used to support land management decisions. We conducted a field test at the Red Rim area of Wyoming’s Red Desert, to compare data collected with the widely-used point-intercept method (PI), and with digital images analyzed with freely-available software from USDA-ARS. We found that precision (repeatability) across users was about the same between methods, cover measurements were often different, and the image analysis technique took only a third as long to complete. We conclude that image analysis has several advantages over the PI method: images are a permanent record of the resource that can be reanalyzed if data are questioned, if software improves, or if management objectives change; and, image analysis is quicker and less subject to biases.

Technical Abstract: Amidst increasing workloads and static or declining budgets, both public and private land management agencies face the need to adapt resource-monitoring techniques or risk falling behind on resource monitoring volume and quality with old techniques. Image analysis of nadir plot images, acquired with common digital cameras, can be manually analyzed for cover using free software. In a comparison between the point intercept (PI) and image-analysis techniques, we found that precision (repeatability) across users was about the same, cover measurements were often different and the image analysis technique took only a third as long to complete. We conclude that image analysis has several advantages over the PI method: images are a permanent record of the resource that can be reanalyzed if data are questioned, if software improves, or if management objectives change; image analysis is quicker and less subject to biases from moving vegetation, moving pointer devices, and bright vegetation color.