Soil properties and carbon stocks

The integrated biodiversity survey compared a range of land-use practices in the Bungo-Tebo district in the lowland peneplain of Jambi. The landscape consists of an undulating plain, formed as marine sediment in the tertiary period (Van Noordwijk et al., 1995, 1997b). Most of the land in the interfluves is covered by highly leached oxisols/ultisols, with more recent sediment and generally higher fertility near the rivers where inceptisols and entisols dominate. The survey was intended to highlight the effects of land use on biodiversity, so variation in soil types would be minimized in the selection of sample points. As older human settlements, and hence an important land use type in the form of extensive rubber agroforest, are usually found close to the streams and rivers, not all sampling points could be located in the oxisol/ultisol complex. Data on conservative soil properties such as texture, pH and exchangeable cations were collected to check the extent to which all variation in biodiversity can be attributed to land use and management, rather than to a priori differences in soil and vegetation. Soil organic matter content and bulk density are likely to be influenced by land use, and may themselves become factors influencing development of vegetation and ecosystem function. The above-ground biodiversity sampling protocol (Gillison et al., this volume) includes an estimate of woody plant basal area. For the full characterization of terrestrial carbon stocks the ASB project has developed a protocol quantifying biomass in trees, understorey vegetation, surface litter and dead wood, and soil carbon in the top 30 cm of the profile. Data were collected with this protocol to help calibrate the simpler assessment of woody plant basal area.

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