Lauria, Cara M听1听;听Haveles, Andrew W听2听;听Snell, Kathryn E听3听;听Hinckley, Eve L听4;听Fox-Dobbs, Kena听5听;听Richardson, Hannah K听6听;听Fox, David L听7
1听乐播传媒 at Boulder
2听Macalester College
3听乐播传媒 at Boulder
4听乐播传媒 at Boulder
5听University of Puget Sound
6听University of Puget Sound
7听University of Minnesota Twin Cities
Carbon isotope (?13C) values of bulk soil organic matter (SOM) from paleosols (fossil soils) are used as proxies for reconstructing paleovegetation and paleoclimate. These proxies have been widely used in the Meade Basin of southwestern Kansas, USA for investigating the expansion of C4 grasslands. During wet parts of the year, it is expected that more SOM will be preserved in the soil profile; while in the drier parts of the year more pedogenic carbonates will precipitate. Drought-like conditions can be expressed isotopically through plant tissues and SOM as more positive ?13C values due to water stress or a shift in vegetation coverage. This potentially biases the paleosol SOM record towards wet growing season conditions. Our study investigates this proxy bias by comparing ?13C values of vegetation collected in the Meade Basin during severe drought conditions of 2012, 2013 and 2014 to 2016鈥檚 moderately wet growing season. We will also compare the ?13C values of vegetative biomass to the ?13C values of SOM at the same locations, to investigate how carbon fixed during wet versus dry growing seasons is incorporated into the soil profile. Aboveground vegetative biomass samples were taken at 16 sites throughout the Meade Basin, each of the selected sites has isotopic data of soil and vegetation from previous drought years. Our preliminary data shows an increase in aboveground biomass in this year鈥檚 relatively wetter growing season. We predict to see more positive ?13C plant values during the drought years and more negative ?13C values in this year鈥檚 wetter growing season, as consistent with prior studies. We also expect the ?13C values of SOM to reflect similar ?13C values as vegetation during the wetter growing season conditions, as a factor of more biomass produced and preserved as SOM in the soil. Understanding the isotope dynamics of carbon in plant tissue and soil organic matter during these wet and dry growing seasons will improve our interpretation of carbon isotopes as proxies in paleosols.