Searching for Climate and Soil Carbon Feedbacks Using the Oklahoma Mesonet.

Carbon stored in the soil is a larger reservoir than the carbon dioxide in the Earth’s atmosphere, so understanding feedbacks between climate and soil carbon is an important focus in carbon cycle modeling. The objective of this project was to document the relationships between soil carbon, soil physical properties, and climate, in order to better understand the carbon storage capacity of Oklahoma soils under grassland vegetation. From 2009 to 2011, 1093 soil samples were taken at depths of 3-10 cm, 20-30 cm, 40-50 cm, 55-65 cm, and 70-80 cm at 118 Mesonet weather-monitoring sites across Oklahoma. The physical properties of these samples were previously analyzed and climate data from 1994 to 2013 was readily available through the Mesonet network. Total soil carbon was measured by dry combustion. The average total soil carbon from the 118 sites across all depths was 0.85% with a standard deviation of 0.75%. The highest total carbon for the 3-10 cm depth range was 4.03% at Bessie, Oklahoma and the lowest was 0.09% at Antlers, Oklahoma. There was no significant correlation of 3-10 cm soil carbon with the climate variables considered; mean annual precipitation and mean annual air temperature. However, there was a significant positive correlation between effective saturation and soil carbon for the 3-10 cm depth range. The results of this project can be used as a baseline of quantitative carbon data in Oklahoma grasslands but more research is needed to identify possible climate and soil carbon feedbacks.