95th ESA Annual Meeting (August 1 -- 6, 2010)

PS 33-80 - Soil type determines response of soil microbial activity to an atmospheric CO2 gradient

Tuesday, August 3, 2010
Exhibit Hall A, David L Lawrence Convention Center
Andrew C. Procter1, Philip A. Fay2, Richard A. Gill3, H. Wayne Polley2 and Rob Jackson4, (1)Duke University, Durham, NC, (2)Grassland, Soil & Water Research Laboratory, USDA, Agricultural Research Service, Temple, TX, (3)Department of Biology, Brigham Young University, Provo, UT, (4)School of Earth Sciences, Stanford and Duke universities, Stanford, CA

Rising atmospheric CO2 will have direct effects on ecosystems in addition to consequences for climate.  We investigated belowground response of a prairie ecosystem to a preindustrial-to-future (250-500ppm) gradient of CO2.  Three soil types are represented throughout the gradient, allowing us to ask how soil type influences microbial activity and soil carbon storage response to CO2 treatment.  A long-term (up to 1 year) laboratory soil incubation is conducted to study both microbial activity and the allocation of soil carbon in fast versus slow-cycling pools.


Preliminary results indicate that soil type is a strong determinant of microbial response to CO2 treatment.  Both substrate-induced respiration (SIR) and potential carbon mineralization (Cmin) assays indicate a linear increase in microbial activity with CO2 concentration, but this trend is present only in the clay-rich Austin and Houston soils, not the sandy Bastrop soil.  The Austin soil responded most strongly to CO2 treatment, with SIR increasing 30% and Cmin increasing 50% along the gradient.  This increasing microbial activity may be due to greater root growth and carbon input under elevated CO2.  Soil respiration data suggests that the soil type effects on microbial activity occur in the field; average soil respiration rates in 2009 increased linearly with CO2 treatment in the Austin and Houston soils (both rates increased 30% along the gradient) but no significant trend occurred in the Bastrop soil.  Understanding soil type may improve predictions of how grasslands store carbon in a future high-CO2 world.