SS3.04 Biogeochemistry of DOC/DON in a Watershed Context
Date: Wednesday, June 12, 2002
Time: 11:00:00 AM
Location: Carson B
 
KaiserK, Univ. Bayreuth, Inst. of Soil Sci., D-95440 Bayreuth, Germany, klaus.kaiser@uni-bayreuth.de
Moeller, A, , Univ. Bayreuth, Inst. of Soil Sci., D-95440 Bayreuth, Germany, 
 
SOURCES OF DISSOLVED ORGANIC MATTER IN STREAMS IN THE TROPICAL HIGHLAND OF NORTHERN THAILAND
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Streams draining three sloping catchments under different land use (native-secondary forest, reforestation, cabbage cultivation) were investigated for concentrations and composition dissolved and particulate OC and ON and compared with those in bulk precipitation, throughfall, and soil water. Largest concentrations of both elements occurred in the stream from the cultivated catchment and the smallest were found in the stream of the catchment under native-secondary forest. With exception to the stream from the cabbage cultivation, the concentrations of DOC and DON corresponded to those of soil water at 90 cm depth. Also the similar composition of dissolved organic matter (DOC and DON in hydrophilic and hydrophobic fractions, DOC/DON ratio, delta13C) suggested a close linkage between the streams and the subsoils in the forested catchments. The composition of dissolved organic matter in the stream draining the cabbage cultivation differed clearly from that in precipitation and soil water. However, it compared well to water-extractable organic matter from the topsoil. Thus dissolved organic matter in this stream may derive from leaching of eroded topsoil material.