This paper examines the linkages between the carbon cycle and sedimentary
processes on land. Available data suggest that sedimentation on land
can bury vast quantities of organic carbon, roughly 1015 g C yr&8722;1.
To evaluate the relative roles of various classes of processes in
the burial of carbon on land, terrestrial sedimentation was modeled
as a series of 864 scenarios. Each scenario represents a unique choice
of intensities for seven classes of processes and two different global
wetland distributions. Comparison was made with presumed preagricultural
conditions. The classes of processes were divided into two major
component parts: clastic sedimentation of soil-derived carbon and
organic sedimentation of autochthonous carbon. For clastic sedimentation,
masses of sediment were considered for burial as reservoir sediment,
lake sediment, and combined colluvium, alluvium, and aeolian deposits.
When the ensemble of models is examined, the human-induced burial
of 0.6-1.5·1015 g yr&8722;1 of carbon on land is entirely plausible.
This sink reaches its maximum strength between 30° and 50° N. Paddy
lands stand out as a type of land use that warrants future study,
but the many faces of rice agriculture limit generalization. In an
extreme scenario, paddy lands alone could be made to bury about 1·1015
g C yr&8722;1. Arguing that terrestrial sedimentation processes could
be much of the sink for the so called &8220;missing carbon&8221;
is reasonable. Such a hypothesis, however, requires major redesign
of how the carbon cycle is modeled. Unlike ecosystem processes that
are amenable to satellite monitoring and parallel modeling, many
aspects of terrestrial sedimentation are hidden from space.
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