Throughfall- and freeland deposition in Central Sulawesi

Supra-regional deposition of nutrients in tropical rainforests represents an important source of nutrients for these ecosystems. Increasing loads of anthropogenic emitted material into the sensitive nutrient cycles of tropical rainforests lead to a shift in the nutrient balance connected with a loss of richness off species. Measuring of nutrient deposition in tropical areas is mostly difficult because of a lack of infrastructure in remote areas, and in mesoscalic areas it is even impossible. Both the transport of samples to the laboratory and the determination of low-concentrated nutrients in rainwater samples are difficult. Based on ion exchange resin, a passive Ion Exchange Resin-collector (IER-collector) has been developed. The sampler allows collecting bulk deposition samples integrated over a period of approximately one month at field sites. Laboratory tests showed that the IER-collectors are able to absorb 80-99% of solute ion loads, depending on element specific properties and different concentrations. Correction factors for the calculation of the all-in-all nutrient deposit load were necessary because in the extraction only 49 100% of the loaded mass were found depending on element specific characteristics. The comparison different sampler types revealed a correlation between percolation speed and fixation rate on the IER surface. Tests with simulated hard-rain-events of more than 300 mm h-1 and the detection of extremely low nutrient concentrations showed that IER-collectors are suitable for use in field sites. Nearly identical deposited loads between the two sampling systems (conventional bulk water collectors (BWS-collector) versus IER-collectors) were found for the elements calcium (Ca), iron (Fe), magnesium (Mg), manganese (Mn), sodium (Na) and phosphorus (P). Results of the two measuring systems differed between 80% 132%, depending on the element. For aluminium (Al) and nitrate (NO3-N) higher results with more than 400% were found in the IER-collectors. This could be explained with low concentrations in rainwater samples. The deposition of potassium (K) was underestimated in IER-collectors (65%). Generally higher deposition loads were found in IER-collectors compared to BWS-collectors. IER-collectors deliver more precise result because a higher concentration of elements in extraction solutions were better detectable at analyse instruments. In the framework of the Sonderforschungsbereich (SFB) 552, at 13 sites of the 2310 k