This data set contains leaf area index (LAI), leaf inclination angle, and canopy dimension data from study sites along the Kalahari Transect in southwest Botswana. The data were collected during the 2001 wet season field campaign of the SAFARI 2000 at a total of seven plots of 200 x 150 meter dimensions: two plots each at Tshane and Mabuasehube and three plots at Tsabong. The data set consists of measurements of leaf angle for plot-dominant woody species, LAI calculated from overstory and understory photosynthetically active radiation (PAR) measurements, and canopy dimension data (i. e., crown height, crown width, and height to crown) for grass and woody vegetation for use in the parameterization of plant canopy reflectance models.
Measurements of LAI were made with a plant canopy analyzer, which records direct and diffuse PAR at the top of the canopy using a beam fraction sensor. PAR beneath the canopy was measured simultaneously with a one-meter long probe held horizontally beneath the canopy. Leaf inclination angle measurements were made using a clinometer. Measurements of tree height, crown height, height-to-crown, and crown width were made for 10 to 20 individual trees of the dominant species at each field plot using a tape measure or simple trigonometry and calculations based on these data.
The data files are stored as ASCII table files, in comma-separated-value (.csv) format, with column headers. Photographs (.jpg) are provided of each plot to provide an idea of site conditions. The photographs can be viewed on the S2K Photo Gallery pages.
Cite this data set as follows:
Bowyer, P., N. M. Trodd, and F. M. Danson. 2005. SAFARI 2000 Canopy Structural Measurements, Kalahari Transect, Wet Season 2001. Data set. Available on-line [http://daac.ornl.gov/] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. doi:10.3334/ORNLDAAC/768.
Bowyer, P. 2005. Estimating land surface biophysical variables in savanna ecosystems, using remote sensing and inverse modelling. Ph.D. Thesis, University of Salford, Manchester, UK.
Privette, J. L., R. B. Myneni, Y. Knyazikhin, M. Mukelabei, G. Roberts, Y. Tian, Y. Wang, and S. G. Leblanc. 2002. Early spatial and temporal validation of MODIS LAI product in the Southern Africa Kalahari. Remote Sensing of Environment, 83: 232-243.
Data files contain records of LAI, leaf inclination angle, and canopy dimensions (i.e., crown height, crown width, and height to crown) from three study sites in the Kalahari district. Data availability is summarized in the table below. Additional notes and exceptions can be found in the companion file: http://daac.ornl.gov/daacdata/safari2k/field_campaign/kt_canopy_structure/comp/kt_canopy_structure_readme.pdf.
| Site/Plot | LAI | Canopy Dimensions | ||||
|---|---|---|---|---|---|---|
| Grewia flava | Acacia mellifera | Boschia albitrunca | Acacia erioloba | Acacia leuderitzii | ||
| Tshane | ||||||
| Plot 1 | x | x | x | |||
| Plot 2 | x | x | x | |||
| Mabuasehube | ||||||
| Plot 1 | x | x | x | x | ||
| Plot 2 | x | x | x | x | ||
| Tsabong | ||||||
| Plot 1 | x | x | x | x | ||
| Plot 2 | x | x | x | x | x | |
| Plot 3 | x | x | x | |||
| Site/Plot | Leaf Angle | ||||
|---|---|---|---|---|---|
| Grewia flava | Acacia mellifera | Boschia albitrunca | Acacia erioloba | Acacia leuderitzii | |
| Tshane | |||||
| Plot 1 | x | x | |||
| Plot 2 | |||||
| Mabuasehube | |||||
| Plot 1 | |||||
| Plot 2 | x | x | |||
| Tsabong | |||||
| Plot 1 | |||||
| Plot 2 | x | x | |||
| Plot 3 | x | x | |||
The LAI data files contain header information at the top, followed by the main body of 10 data columns, defined below.
Variables in LAI Data Records Table
| Column | Definition | Units/format |
|---|---|---|
| Time | Time of data collection (local time) | hh:mm:ss |
| Plot Code | Site indicator | ASCII |
| Sample Number | The sample number of the measurement. If the measurements are made along a 200 m transect at 10 m intervals, the sample numbers will be 1-21. | numeric |
| Transmitted | The amount of photosynthetically active radiation (PAR) transmitted through the canopy. | µmol m-2 s-1 |
| Spread | PAR is measured at 64 photodiodes located along the length of the SunScan 1 m probe. A single value of LAI is calculated from an average of all 64. The spread is the coefficient of variation of the PAR levels recorded at each of the 64 photodiodes. | dimensionless |
| Incident | The amount of PAR incident on the top of the canopy. | µmol m-2 s-1 |
| Beam Fraction | The fraction of direct radiation in the total incident radiation. | dimensionless |
| Zenith Angle | The solar zenith angle, calculated from the SunScan software. | degrees |
| LAI | The leaf area index, defined as the one-sided green leaf area per unit ground area. The LAI is calculated from an average of all 64 PAR values. | dimensionless |
| Notes | Overstory measurement indicator. A cell with an 'o' indicates a measurement of the overstory LAI. A cell that is empty indicates the measurement is of the understory LAI. | NA |
Data File Naming Convention
The file naming convention for LAI data files is site_datatype_plotdimension_transect_plotid.csv, such that LAI data collected in Tshane, Plot 1 (200 x 150 m), along the "A" transect, is named tshane_lai_200_a_p1.csv. Straight line measurement transects were established within the field plots.
There is just one canopy dimension file per plot, containing measurements of 10-20 individual trees for each of the dominant species at the site. The data columns are as follows: species, tree height, crown height, height-to-crown, and crown width. All canopy dimension measurements are in meters.
The leaf inclination angle distribution files contain a few header lines at the top, followed by the data records, two columns, species and leaf angle. Because of the time consuming nature of the leaf angle data collection, these data are not available at all plots. See the first table above for availability.
Additional information about the data format, site conditions, instrumentation, and parameters measured is found in the companion file: http://daac.ornl.gov/daacdata/safari2k/field_campaign/kt_canopy_structure/comp/kt_canopy_structure_readme.pdf.
2004/10/25
2004/10/25
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