The influence of land-use and seasons on SOM distribution in headwaters
of a central Ohio watershed
Abstract
Soil organic matter (SOM), the accumulated, decaying debris of biota
living on or in the soil, represents the largest of the active
terrestrial C pools, holding about 1500 Pg C to a depth of 1 m. In
aquatic ecosystems, SOM is a storehouse of inorganic nutrients which,
after mineralization, are released to the stream and used by planktonic
and benthic microorganisms. Here we present the results of a study
designed to elucidate the controls on the spatial and temporal
variations of the SOM distribution along the Clear Fork River, which
drains a mixed urban-agricultural landscape in north-central Ohio.
Fluvial bed sediments were sampled monthly (March to October) in eight
stations along the river. Organic matter (OM) and carbonate content were
determined by loss-on-ignition (LOI). Sediments from all stations were
analyzed in triplicate to account for intrasample variation and to
provide a measure of precision. Textural analysis was also performed in
all samples. Results show OM content varying between 14 and 109 g kg-1,
with highest values observed during spring, and lower values during
summer. Sediments from stations where the stream flow is high generally
presented lower OM concentration. In addition, stations located within
urban landscapes presented the highest OM concentrations.