Transport of dissolved organic carbon (DOG) from the forest floor to t
he mineral soil in Spodosols affects many biogeochemical processes. Th
e nature of the C reservoir in organic soil immediately before leachin
g, however, is not clear. Extractable organic C may partition between
dissolved and undissolved phases, or reside in entrained water prior t
o leaching. We used laboratory incubations and extractions to test whi
ch model more accurately describes the reservoir from which DDC is rem
oved. We also measured the rate at which C enters the extractable rese
rvoir, how that rate changes with time, and the partitioning relations
hip between this reservoir and bulk solution. In addition, we tested w
hether the composition of extractable DOC changes with time. Extractab
le organic C was stored in an adsorbed phase. DOC in a solution of hyd
rophobic acids isolated from soil solution reduced dissolution of addi
tional DOC by 41-44%. Furthermore, in each extraction, approximately 1
mg DOC remained in the unextracted phase for every 16-29 mg DOC l(-1)
in the aqueous phase. This partitioning relationship was not consiste
nt with storage of DOC in entrained water alone. Soil produced 48 mu g
g(-1) h(-1) of DOC when extracted repeatedly at 1-h intervals, but on
ly 1 mu g g(-1) h(-1) when extracted at 1-week intervals. Extractable
organic C production is fast (230 mu g g(-1) d(-1)) within 1 day of th
e last extraction, and then declines to a constant rate (15 mu g g(-1)
d(-1)). Hydrophobic acids accounted for 75% of the extracted DOC afte
r a 1-week incubation, but contributed only 50% of the increase in the
extractable pool in subsequent weeks. Laboratory incubations and extr
actions of Oa material provided useful, consistent data for studying t
he dynamics of DOC removal from soil. Copyright (C) 1996 Elsevier Scie
nce Ltd