This data set contains measurements of the concentration and stable carbon (13C / 12C) and nitrogen (15N / 14N) isotope ratios of plant (leaves, roots and fungi) and soil samples from southern Africa. The study sites in Zambia, Botswana, Namibia, and South Africa are located along the Kalahari Transect precipitation gradient. Some of the sites were relatively undisturbed while others had different intensities of cultivation, domestic grazing, and fires. The data were collected to detect patterns of N cycling along precipitation and grazing gradients, including N2 fixation by legumes.
Data from multiple projects are included. The plants and soils were sampled mainly in the wet season of years 1995, 1999, and 2000, with most of the data collected during the SAFARI 2000 Kalahari Wet Season Field Campaign in February and March of 2000. Some grass samples were collected in the dry season of year 2000 (from Mongu-dambo and Sua Pan grassland sites).
Soil and plant samples were analyzed in a laboratory for %C, %N, d13C, and d15N with an Optima isotope ratio mass spectrometer coupled to an elemental analyzer. The stable isotope ratios are expressed using standard delta notation in units per mil. The isotope ratios are expressed relative to the international standard PDB (Pee Dee Belemnite) for carbon and atmospheric N2 for nitrogen samples. The carbon and nitrogen contents are expressed in percentage weight of the dry sample.
The data files contain numerical and character fields of varying length separated by commas (.csv format).
Cite this data set as follows:
Aranibar, J. N., and S. A. Macko. 2005. SAFARI 2000 Plant and Soil C and N Isotopes, Southern Africa, 1995-2000. 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/783.
Aranibar J. N., L. Otter, S. A. Macko, C. J. W. Feral, H. E. Epstein, P. R. Dowty, F. Eckardt, H. H. Shugart, and R. J. Swap. 2004. Nitrogen cycling in the soil-plant system along a precipitation gradient in the Kalahari sands. Global Change Biology, 10(3): 359-373.
Aranibar J. N., S. A. Macko, I. C. Anderson, A. Potgieter, R. Sowry, and H. H. Shugart. 2003. Nutrient cycling responses to fire frequency in the Kruger National Park (South Africa) indicated by stable isotopes. Isotopes in Environmental and Health Studies, 39: 141-158.
Aranibar, J. N., I. C. Anderson, S. Ringrose, and S. A. Macko. 2003. Importance of cyanobacterial crusts as a source of nitrogen of Southern African arid ecosystems, as indicated by acetylene reduction and stable isotopes. Journal of Arid Environments, 54: 345-358.
The data files contain numerical and character fields of varying length separated by commas. There are no spaces between the fields. The value 999 is a missing value code for this data set.
Plants: Description of the file plants_C_N_iso.csv
|DATE||Sampling month and year (days are not included unless otherwise available or relevant)||mon-yy|
|DISTURBANCE*||The letters C, G and F indicate cultivation, grazing and fires respectively. Increasing numbers indicate increasing disturbance intensity for each land-use gradient. Additional information on disturbance code.||none|
|TAXONOMY||Taxonomic classification of the samples. Identified to the species and subspecies level if possible, otherwise to genus or plant family. Fungi were only identified to division or order.||none|
|PLANT PART||Part of the plant that was analyzed: L=leaves; LI=soil litter; R=roots; F=fruit; S=sporocarp; W=whole plant||none|
|NOTES*||Any other characteristic observed in the field||none|
|C||Percent Carbon. Organic carbon content in the soils, expressed as percent weight of the dry sample.||%|
|N||Bulk nitrogen content in the soils, expressed as percent weight of the dry sample.||%|
|d13C||Carbon isotope composition of the soil organic matter, expressed in the 'delta' notation, relative to the standard Pee Dee Belemnite (PDB).||per mil|
|d15N||Nitrogen isotope composition of soil bulk nitrogen, expressed in the 'delta' notation, relative to the standard atmospheric N2.||per mil|
Soils: Description of the file soils_C_N_iso.csv
|DATE||Usually only sampling months, days were not always recorded because they were not considered relevant. For some samples when day is available, it is expressed as dd-mon-yy.||mon-yy|
|DISTURBANCE*||The letters C, G and F indicate cultivation, grazing and fires respectively. Increasing numbers indicate increasing disturbance intensity for each land-use gradient.||none|
|START DEPTH||starting depth of the soil sample||cm|
|END DEPTH||ending depth of the soil sample||cm|
|CHARACTERISTICS*||characteristics of the surface cover or vegetation type where the soil was collected||none|
|C||Percent carbon. Organic carbon content in the soils, expressed as percent weight of the dry sample. Organic carbon content of the soil sample||%|
|N||Percent Nitrogen. Bulk nitrogen content of the soil sample||%|
|d13C||carbon isotope composition of the soil organic matter, expressed in the 'delta' notation, relative to the standard Pee Dee Belemnite||per mil|
|d15N||nitrogen isotope composition of soil bulk nitrogen, expressed in the 'delta' notation, relative to the standard atmospheric N2.||per mil|
Note: Additional details and descriptions are available for columns indicated with a '*' in the associated files soils_CNiso_1995-2000_def.txt and plants_CNiso_1995-2000_def.txt for soil and plant data, respectively.
Additional information about the study sites, the precipitation, land use, and fire intensity gradients in the Kalahari, and the field and laboratory methodologies, sample processing, and data quality is found in the companion file: ftp://daac.ornl.gov/data/safari2k/field_campaign/plant_soil_c_n/comp/plant_soil_c_n_readme.pdf.