Dissolved organic carbon in precipitation, throughfall, stemflow, soil solution, and stream water at the Guandaushi subtropical forest in Taiwan

The concentration and flux of dissolved organic carbon (DOC) were measured in precipitation, throughfall, stemflow, soil solution, and stream water for three types of subtropical forest stands, a Chinese fir (Cunninghamia lanceolata) plantation, a secondary hardwood, and a natural hardwood stand in Guandaushi forest in central Taiwan from January 1998 to December 1998. The mean DOC concentration in precipitation was 4.7 mg l(-1). However, in the rain passing through the tree canopies and barks as throughfall and stemflow, the mean concentrations were 7.0 and 30.8, 9.9 and 10.0, and 8.3 and 7.2 mg l(-1) in the Chinese fir plantation, the secondary hardwood, and the natural hardwood, respectively. Mean DOC concentrations in soil solution were lower in the Chinese fir plantation than both hardwoods, and decreased with depth of soil profiles. Stemflow DOC flux (132.4 kg ha(-1)) in the Chinese fir plantation was much higher than the other hardwood stands (15.3 and 6.7 kg ha(-1) in secondary and natural hardwood, respectively). The monthly variations of DOC concentrations were very similar in throughfall and stemflow at the three stands, showing an increase in the beginning of the growing season in April. No clear monthly variations in soil solution DOC concentrations (mean from 3.2 to 21.3 mg l(-1) in different stands and for different depths) were found in our study. DOC concentrations (mean 2.7 mg l(-1)) in the stream draining the watershed were higher in spring and in winter. (C) 2002 Elsevier Science B.V. All rights reserved.