Data comprise soil profile (soil texture and pit description during fieldwork) and soil chemistry (bulk density, carbon content, carbon stock and organic carbon content obtained with 13 carbon isotope analysis) from samples taken in the Ankeniheny Zahamena forest corridor, Madagascar.
Data were collected as part of a project funded by the Ecosystem Services for Poverty Alleviation (ESPA) programme under work package 4 P4GES project, grant references: NE/K008692/1, NE/K010115/1, and NE/K010220-1.
Publication date: 2017-03-03
This dataset is part of the following
Two methods were applied for the soil sampling. One for bulk density samples and the other for soil carbon sampling.
Soil sampling by auger for soil carbon determination. It is done in the 4 subplots every 10 cm depth for 0 to 100 cm. That means 0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm, 40-50 cm, 50-60 cm, 60-70 cm, 70-80 cm, 80-90 cm and 90-100 cm depth.
Soil sampling by cylinder for bulk density sampling. The metallic cylinder used for this sampling has a diameter of 8.1cm. It was performed in the soil pits located in the 3 subplots (subplot n°1, n°2 and n°3), according to the depths: 0-10 cm, 10-20 cm, 20-30 cm, 50-60 cm and 80-90 cm. These samples are used for the bulk density measurement. Some samples, to estimate the moisture were also taken in addition to these samples to the cylinder.
Soil profile description. This activity was conducted in the subplot 1 soil pit located in the center of each plot, with a depth of 1.30 m. Its objectives was to determine and describe the different soil horizons, know their colors (by using the soil color of Munsell), their textures and structures and root depth. The abundance of roots and porosity were also observed and recorded.
Soil sample were labelled and sent to the sample preparation room, where they undergo the following preparations:
- air drying at least 3 days
- sieving through a sieve with 2 mm size
- sieved sample collected in a plastic bag and weighed again
- coarse soil (rocks) and coarse root fraction > 2 mm were also recovered in another bag and weighed
- for classic soil analysis were done on the soil sample, it was ground to 200 microns
Different type of analysis is used for the quantification of the soil organic carbon.
Soil drying to determine the moisture. To determine the moisture of the soil samples, they are dried in stoves at 105°C during 48 hours. After, they are weighted and the moisture is obtained by the difference between the weight before and after the drying.
Walkley & Black method. The Walkley-Black titration method is one of the classical methods for rapid analysis of soil organic carbon. The organic material is oxidized without external heating by a sulfuric potassium dichromate solution. It is considered that the heat of solution of H2SO4 (120° C) is sufficient to oxidize 77% of carbon. The excess dichromate is determined by Mohr's salt (NH4) 2 Fe (SO4) 2, 6 H2O. The data obtained using these chemical analysis served as calibration reference for further soil analysis using spectrometry.
Mid Infra Red Spectroscopy (MIRS) soil analysis. The MIRS approach appeared to be a relatively recent soil analysis method. The principle is based on the absorption of infrared radiation by the organic matter. This absorption is related to the chemical composition of the samples. The measure of the light intensity absorbed at each wavelength leads to a characteristic spectrum of the studied product. Subsequently, it predicts the carbon organic contents by interpretation of the spectra.
Carbon stable isotope analysis using 13C. A few soil samples were collected according their land use and carbon stock along the soil profile. These samples were sent to the Laboratoire de Biochimie et Physiologie MolÃ©culaire des Plantes (LBMP montpelier) for stable isotope analysis.