TY - JOUR
T1 - Paleoreconstruction of Organic Carbon Inputs to an Oxbow Lake in the Mississippi River Watershed: Effects of Dam Construction and Land use Change on Regional Inputs
AU - Bianchi, Thomas S.
AU - Galy, Valier
AU - Rosenheim, Brad E.
AU - Shields, Michael
AU - Cui, Xingqian
AU - Van Metre, Peter
PY - 2015/1/1
Y1 - 2015/1/1
N2 - We use a dated sediment core from Lake Whittington (USA) in the lower Mississippi River to reconstruct linkages in the carbon cycling and fluvial sediment dynamics over the past 80 years. Organic carbon (OC) sources were characterized using bulk (δ 13 C, ramped pyrolysis-oxidation (PyrOx) 14 C, δ 15 N, and TN:OC ratios) and compound-specific (lignin phenols and fatty acids, including δ 13 C and 14 C of the fatty acids) analyses. Damming of the Missouri River in the 1950s, other hydrological modifications to the river, and soil conservation measures resulted in reduced net OC export, in spite of increasing OC concentrations. Decreasing δ 13 C values coincided with increases in δ 15 N, TN:OC ratios, long-chain fatty acids, and lignin-phenol concentrations, suggesting increased inputs of soil-derived OC dominated by C 3 vegetation, mainly resulting from changes in farming practices and crop distribution. However, ramped PyrOx 14 C showed no discernible differences downcore in thermochemical stability, indicating a limited impact on soil OC turnover.
AB - We use a dated sediment core from Lake Whittington (USA) in the lower Mississippi River to reconstruct linkages in the carbon cycling and fluvial sediment dynamics over the past 80 years. Organic carbon (OC) sources were characterized using bulk (δ 13 C, ramped pyrolysis-oxidation (PyrOx) 14 C, δ 15 N, and TN:OC ratios) and compound-specific (lignin phenols and fatty acids, including δ 13 C and 14 C of the fatty acids) analyses. Damming of the Missouri River in the 1950s, other hydrological modifications to the river, and soil conservation measures resulted in reduced net OC export, in spite of increasing OC concentrations. Decreasing δ 13 C values coincided with increases in δ 15 N, TN:OC ratios, long-chain fatty acids, and lignin-phenol concentrations, suggesting increased inputs of soil-derived OC dominated by C 3 vegetation, mainly resulting from changes in farming practices and crop distribution. However, ramped PyrOx 14 C showed no discernible differences downcore in thermochemical stability, indicating a limited impact on soil OC turnover.
KW - organic carbon cycling
KW - paleoreconstruction
KW - dam reservoirs
KW - biomarker proxies
UR - https://digitalcommons.usf.edu/msc_facpub/2432
U2 - 10.1002/2015GL065595
DO - 10.1002/2015GL065595
M3 - Article
VL - 42
JO - Geophysical Research Letters
JF - Geophysical Research Letters
ER -