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1 March 2012 Indirect Measurement of Leaf Area Index in Sagebrush-Steppe Rangelands
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Leaf area index (LAI) is defined as the one-sided area of leaves above a unit area of ground. It is a fundamental ecosystem parameter that is a required input of process-based plant growth and biogeochemical models. Direct measurement of LAI is the most accurate method, but is destructive, time-consuming, and labor-intensive. LAI is highly variable in time and space on sagebrush-steppe rangelands, and a rapid, nondestructive method is desirable to understand ecosystem processes. The point-intercept method is nondestructive and has been demonstrated to provide accurate LAI estimates, but the method is time-consuming. LAI measurement with the Accupar ceptometer (Decagon Devices, Pullman, WA) is nondestructive and faster than the point-intercept method, but has not been evaluated on sagebrush-steppe rangelands. The objective of this study was to evaluate the ceptometer for measurement of LAI in sagebrush-steppe rangelands. Ceptometer and point-intercept LAI data were collected at six sites in sagebrush-steppe rangelands and the values were compared. We found that 1) ceptometer LAI data were consistently greater than point-intercept LAI data, 2) ceptometer data were much more variable than the point-intercept data based on standard deviations, and 3) the overall correlation between the two methods was very weak (r2  =  0.15). The much greater ceptometer LAI values were, at least partly, due to the large woody component of the vegetative cover. We attribute the high variability of ceptometer-measured LAI to high instrument sensitivity of the angle of the instrument relative to the sun.

Society for Range Management
Julie A. Finzel, Mark S. Seyfried, Mark A. Weltz, James R. Kiniry, Mari-Vaughn V. Johnson, and Karen L. Launchbaugh "Indirect Measurement of Leaf Area Index in Sagebrush-Steppe Rangelands," Rangeland Ecology and Management 65(2), 208-212, (1 March 2012).
Received: 14 April 2011; Accepted: 1 November 2011; Published: 1 March 2012

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