Paliza Shrestha1, John Seiler2, Brian Strahm3, Eric Sucre4 and Zakiya Leggett4, (1)Forest Resources & Environmental Conservation, Virginia Tech, Blacksburg, VA (2)Forestry and Environmental Conservation, Virginia Tech University, Blacksburg, VA (3)Department of Forest Resources and Environmental Conservation, Virginia Tech, Blacksburg, VA (4)Southern Timberlands Technology, Weyerhaeuser NR Company, Vanceboro, NC
Soil respiration (RS) recycles CO2 fixed by terrestrial plants to the atmosphere and is an important and large part of the global carbon cycle. RS is the result of root respiration (RA) and microbial decomposition of organic matter (RH) releasing CO2 as a by-product. Accurate estimates of the two components are required as they vary greatly spatially and temporally with species composition, temperature, moisture, NPP, soil type and management activities. Therefore, we measured soil CO2 efflux every six weeks in 2012 from an intercropped system of loblolly pine (Pinustaeda L.) and switchgrass (Panicum virgatum L.), both of which are promising feedstock for bioenergy production, in the Lower Coastal Plain in North Carolina. We quantified RA and RH components of soil respiration by using root exclusion cores. The technique is based on root carbohydrate depletion ideally eliminating root respiration within the cores over time. We separated roots into species and analyzed root length (cm), area (cm2) and biomass (kg/ha). As trace greenhouse gases (CH4 and N2O) have a higher warming potential than CO2, fluxes of CH4 and N2O were monitored quarterly using static chambers. Since pine (C3 plant) and switchgrass (C4 plant) have varying photosynthetic pathways, we analyzed the stable isotopic composition of soil CO2 efflux (δ13CO2) to predict the role of switchgrass and pine in driving RS. The relationship between CO2 and trace gas fluxes and root biomass were determined. We predict that switchgrass by way of competition for water and nutrients and their additional organic matter inputs will significantly influence RS of intercropped plots.