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Title: Effects of elevated atmospheric CO2 enrichment on soil CO2 efflux in a young longleaf pine system

item Runion, George
item Prior, Stephen - Steve
item Rogers Jr, Hugo

Submitted to: International Journal of Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2012
Publication Date: 5/21/2012
Citation: Runion, G.B., Butnor, J.R., Prior, S.A., Mitchell, R.J., Rogers Jr, H.H. 2012. Effects of elevated atmospheric CO2 enrichment on soil CO2 efflux in a young longleaf pine system. International Journal of Agronomy. doi:10.1155/2012/549745. 9p.

Interpretive Summary: Examining how the rise in global atmospheric CO2 impacts the structure and function of forest ecosystems is important due to their economic and ecological value. This is particularly true for Longleaf pine savannahs which once occupied 37.2 million ha of the southeastern United States; however, timber harvesting, fire suppression, and conversion of forests to farmland has reduced the land area of this system to 4% of its original range. A model regenerating Longleaf pine community exposed to two levels of atmospheric CO2 (ambient or elevated) was monitored for soil CO2 losses. Our results suggest that soil CO2 losses were higher under elevated atmospheric CO2, but this forest system could still be a net sink for atmospheric CO2 due to more biomass being added.

Technical Abstract: Elevated atmospheric CO2 can affect both the quantity and quality of plant tissues, which will impact the cycling and storage of carbon (C) within plant/soil systems and thus the rate of CO2 released back to the atmosphere. Research is needed to more accurately quantify the effects of elevated CO2 and associated feedbacks on soil respiration in order to predict the potential of terrestrial ecosystems to sequester C. We investigated the effects of three years of exposure to ambient and twice ambient levels of atmospheric CO2 on soil respiration in a model regenerating longleaf pine community using a novel, continuous, soil CO2 efflux monitoring system. A significant increase (26.5 %) in soil CO2 efflux, across a 90 day measurement period, was observed for plant communities exposed to elevated CO2; this effect was significant for all weekly and daily average soil respiration rates during this period with the exception of the two days when soil temperatures were lowest. Soil CO2 efflux showed a strong positive relationship with soil temperature and a trend towards increased soil respiration response to temperature under elevated CO2. Soil CO2 efflux showed a strong negative relationship with soil moisture; however, CO2 efflux was not strongly correlated with root biomass. Our data indicate that, while increasing levels of CO2 will increase the feedback of CO2 to the atmosphere via soil respiration, terrestrial ecosystems remain potential sinks for atmospheric CO2 due to greater biomass production. [GRACEnet Publication]