PARENT SESSION
Monday, August 7, 8:00-11:30 am
COS 9 - Grassland ecology I
Mississippi, Mezzanine Level, Cook Convention Center
Presiders: S Baez and B Molano
Temperature sensitivity of soil organic matter: results from two experiments.
Steinweg, Jessica*,1, Haddix, Michelle1, Conant, Richard1, Paul, Eldor1, Greenwood, Rebecca1, Carlson, Jenny1, 1 Colorado State University, Fort Collins, CO
ABSTRACT- Currently there is debate surrounding the effects of increased global temperature on soil respiration. Understanding how different soil fractions react to changes in temperature will help determine their relationship to CO2 as a sink or source. The purpose of this work was to investigate temperature sensitivities of labile versus resistant soil carbon. For our first experiment, we initially incubated soils from two sites, each with a native vegetation and a cultivated treatment, at three temperatures: 5, 15, and 25°C. After 60 ,150 , 300, 450, or 600 days at one temperature, the incubation temperature was increased 10°C. Respiration was measured for 60 days following the temperature increase to determine the effects of increased temperature using Q10 temperature coefficients. The results from the increased temperature after 60 days demonstrate an increase in respiration for all three temperatures, with the largest difference for the ten degree shift from 5 to 15°C. For our second experiment, we used three acid hydrolysis treatments to isolate successively more resistant soil carbon for native soils from Akron, Colorado. After the restoring the soils to neutral pH and inoculating we incubated the soils at three temperatures: 15, 25, 35°C, with the respiration measured for eight weeks. Results from this experiment indicate that the more biochemically protected soil organic matter was more temperature sensitive to increases in temperature. Taken together, results from these experiments suggest that increased global temperature will have a greater effect on recalcitrant soil carbon decomposition.
Key words: temperate grassland and cropped systems, soil ecology, acid hydrolysis and soil incubations