Moisture and soil texture effects on soil CO 2 efflux components in southeastern mixed pine forests John J. Dilustro * , Beverly Collins, Lisa Duncan, Chris Crawford Savannah River Ecology Laboratory, University of Georgia, Drawer E, Aiken, SC 29802, USA Received 27 April 2004; received in revised form 8 September 2004; accepted 9 September 2004 Abstract Monitoring soil CO 2 efflux rates and identifying controlling factors, such as forest composition or soil texture, can help guide forest management and will likely gain relevance as atmospheric CO 2 continues to increase. We examined soil CO 2 efflux and potential controlling factors in managed mixed pine forests in southwestern Georgia. Soil CO 2 efflux was monitored periodically in two stands that differed in soil texture in 2001 and 2002, and in six additional stands in 2003. We also monitored controlling factors: soil temperature, moisture, organic layer mass, and A layer depth. Soil moisture and CO 2 efflux varied with soil texture differences among the stands. As expected, soil temperature had a strong influence on soil CO 2 efflux. Soil moisture, organic layer mass, and A layer depth also were correlated with soil CO 2 efflux during periods of water stress, but these relationships differed with soil texture. Forest management activities can alter components of soil CO 2 efflux, including soil carbon pools, temperature, and moisture; understanding the underlying variation of these components and resultant CO 2 efflux over soil types can help guide management toward desired forest carbon balance trends in southeastern mixed pine forests. # 2004 Elsevier B.V. All rights reserved. Keywords: Soil CO 2 efflux; Soil respiration; Mixed pine; Soil temperature; Microbial biomass carbon 1. Introduction Soil is the major carbon pool in terrestrial eco- systems (Schlesinger and Andrews, 2000; Houghton, 2003). Soils contain substantially greater carbon (1500 Pg C) than either terrestrial vegetation (550 Pg C) or the atmosphere (780 Pg C) (Houghton, 2003). With increases in global atmospheric CO 2 concentra- tion, the characterization of soil CO 2 efflux response through time and space is increasingly important. Soil CO 2 efflux, or total soil respiration (R ts ), integrates all components of soil CO 2 production, including respira- tion of soil organisms and plant roots, and organic matter decomposition. To identify dominant sources and sinks of soil CO 2 efflux and parameterize carbon cycling models, the components must be decoupled and their response to varying environmental conditions understood. Laboratory experiments have decoupled the com- ponents of soil CO 2 efflux. Field-based studies have www.elsevier.com/locate/foreco Forest Ecology and Management 204 (2005) 85–95 * Corresponding author. Tel.: +1 706 545 6136; fax: +1 706 545 6140. E-mail address: dilustro@srel.edu (J.J. Dilustro). 0378-1127/$ – see front matter # 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2004.09.001