Methods

Field surveys and data analysis are conducted in the selected forests to address the following issues:

1) Flux determination of sulphur and nitrogen
2) Analysis of sulphur isotope ratio of rainwater and stream water
3) Speciation of sulphur compounds in soil layerb
4) Trial application of biogeochemical simulation model

The data obtained from the topics 1) to 3) will be utilized for a trial application of a biogeochemical simulation model. The outcomes from the project will be informative for evaluating possible impacts of sulphur deposition on the forests. Since nitrogen deposition is also quite high in the region, its relation to acidification/eutrophication would also be determined. As for 1) flux determination of sulphur and nitrogen, the fluxes by rainfall outside forest canopy (RF), throughfall (TF), soil solution (SS) and stream water (SW) have been measured by previous projects in Kajikawa, Sakaerat and Danum Valley sites. The existing data are utilized to summarize the fluxes in these sites, while RF, TF and SW are still measured in Kajikawa and Sakaerat sites. The data obtained from the resin samplers (Figures) for sulphur isotope analysis will also be used for this purpose. In the case of Bintulu site, the fluxes from SW may not be able to be estimated, since the stream is flowed not continuously but just seasonally.