Field measurement of shrubland ecological properties is important for both site monitoring and validation of remote-sensing information. During the NASA Earth Observing System Prototype Validation Exercise (PROVE) at the Jornada Experimental Range, New Mexico, on May 20-30, 1997, we calculated plot-level plant area index, leaf area index, total fractional cover, and green fractional cover with data from four instruments: (1) a Dycam Agricultural Digital Camera (ADC), (2) a LI-COR LAI-2000 plant canopy analyzer, (3) a Decagon sunfleck ceptometer, and (4) a laser altimeter.
Estimates from the LAI-2000 and ceptometer were very similar (plant area index 0.3, leaf area index 0.22, total fractional cover 0.19, green fractional cover 0.14), but the ADC produced values 5 to 10% higher. Laser altimeter values, depending on the height cutoff used to establish total fractional cover, were either higher or lower than the other instruments' values: a 10-cm cutoff produced values approximately 80% higher, whereas a 20-cm cutoff produced values approximately 30% lower.
The LAI-2000 and ceptometer are designed to operate in homogenous canopies, not the sparse and irregular vegetation found at the Jornada Experimental Range. Thus these instruments were primarily useful for relative within-site plant area index monitoring. Calculation of some parameters required destructive sampling, a relatively slow and labor-intensive activity that limits spatial and temporal applicability. Validation/monitoring campaigns therefore should be guided by consideration of the amount of time and resources required to obtain measurements of the desired variables. Our results suggest the ADC is both efficient and accurate for long-term or large-scale monitoring of arid ecosystems.
More information about the experiment at the Jornada Experimental Range site can be found at http://modarch.gsfc.nasa.gov/MODIS/LAND/VAL/prove/grass/prove.html.
In addition, information about PROVE and links to related Web sites can be found at http://www.daac.ornl.gov/PROVE/prove.html.
Cite this data set as follows:
White, M. A., G. P. Asner, R. R. Nemani, J. L. Privette, and S. W. Running. 2003. PROVE Land Cover and Leaf Area of Jornada Experimental Range, New Mexico, 1997. ORNL DAAC, Oak Ridge, Tennessee, USA. http://dx.doi.org/10.3334/ORNLDAAC/665.
Havstad, K. M., W. P. Kustas, A. Rango, J. C. Ritchie, and T. J. Schmugge. 2000. Jornada Experimental Range: A unique arid land location for experiments to validate satellite systems. Remote Sensing of the Environment 74(1):13-25.
Privette, J. L., G. P. Asner, J. Conel, K. F. Huemmrich, R. Olson, A. Rango, A. F. Rahman, K. Thome, and E. A. Walter-Shea. 2000. The EOS prototype validation exercise (PROVE) at Jornada: Overview and lessons learned. Remote Sensing of the Environment 74(1):1-12.
White, M. A., G. P. Asner, R. R. Nemani, J. L. Privette, and S. W. Running. 2000. Measuring fractional cover and leaf area index in arid ecosystems: Digital camera, radiation transmittance, and laser altimetry methods. Remote Sensing of the Environment 74(1):45-57.
Data files of the measurements taken with the various instruments are available in self-documenting .csv format files listed below. Comparison and synthesis results are in files intercomparison.csv and k_estimate.csv.
The individual measurement files and intercomparison summary spreadsheets have also been compiled into a single .xls workbook format file (lai_land_cover_intercomparison.xls).
|Dycam Agricultural Digital Camera (ADC)||land_cover_by_adc.csv|
|LI-COR LAI-2000 plant canopy analyzer||asner_lai_by__lai2000.csv, lai_by_cept_lai2000.csv|
|Decagon sunfleck ceptometer||lai_by_cept_lai2000.csv, destructive_samp_fipar.csv|
April 29, 2003
April 29, 2003