In order to evaluate the sources of DOC in a subalpine bog, we compare
the lignin and carbohydrate compositions of aquatic fulvic acid isola
ted from the bog (BogW-FA) with the fulvic acids isolated from water l
eachates of two local plants, sedge (sedgeL-FA) and willow leaves (wil
lowL-FA), and of the peat in the bog (peatL-FA). The bogW-FA and peatL
-FA. have similar biomarker compositions and both differ significantly
from either of the fulvic acids from the water leachate of the plants
. Thus, the biomarker data strongly suggest that the peat, and not fre
sh leaffall, provides most of the aquatic fulvic acid to the bog at th
is lime of year (Fall). However, additional sources of lignin- and car
bohydrate depleted fulvic acid to the bog are also needed to quantitat
ively match the relatively low levels of recognizable biochemicals in
the aquatic fulvic acid from the bog. The unusual lignin compositions
of both plant leachates suggest that nonstructural lignin phenol produ
cing components, such as lignans, are part of the water-extractable co
mponent of plants. These extractable plant products could potentially
contribute to aquatic fulvic acids in other environments or at differe
nt times of the year.