Effect of Simulated Alluvial Burial On Soil Carbon.

Floodplain stratigraphy commonly contains buried soils that are used as indicators of paleoclimatic conditions (landscape stability, ecology, etc.). This study was conducted to evaluate the effects of rapid sedimentation on soil organic carbon; both in relative storage value/stability and discrimination of carbon isotope values (δ13C) currently used in paleoclimatic reconstruction. In spring of 2005, plots were set up on a Teller fine sandy loam (fine-loamy, mixed, active, thermic, Udic Argiustoll) located south of Stillwater, OK. Experiment consisted of 4 treatments of simulated alluvial burial (0, 8, 16, 24 cm in depth) by a fine sandy loam deposit. Native vegetation of the plots was dominated by tall prairie grasses. After six years of burial, both the surface and buried A horizons were evaluated for changes in SOC and carbon isotopic values. All buried horizons significantly decreased in SOC compared to the control. Control (unburied) averaged 1.6 % SOC while the buried horizons averaged 0.83 %; almost a 50 % drop in SOC. Significant changes in δ13C values were observed between the control, buried, and new soil surface. Buried A horizons δ13C values were significantly more positive compared to the control, while the newly formed soil was more negative than the control.  Burial/discontinuation of organic matter additions results in significant reductions in SOC and the alteration of δ13C values reaffirming the loss of easily oxidizable carbon.