291-11 Black C Effects On Soil CO2 Emissions: A Methodological Study.



Tuesday, October 18, 2011: 3:50 PM
Henry Gonzalez Convention Center, Room 210B, Concourse Level

Thea Whitman and Johannes Lehmann, Crop and Soil Science, Cornell University, Ithaca, NY
The impact of black carbon (BC) addition to soils on soil CO2 emissions is poorly understood. Furthermore, in the field setting, partitioning of soil CO2 emissions from non-BC soil organic carbon (SOC) and BC is confounded by the added effects of changes in root respiration due to BC additions. This pot trial takes a step toward clarifying these issues and examines the effects of BC additions to soil on total soil CO2 emissions while exploring the relative contributions of CO2 from plant roots, SOC, and BC. Differences in 13C stable isotopes from a C3-derived soil and C4 plant roots (maize, Zea mays L.) are used to differentiate between SOC- versus root-derived CO­­2. Differences between BC- and SOC-derived CO2 are determined by using BC produced from 13C-labelled sugar maple wood (Acer saccharum) pyrolysed at 350°C for 2 hours. The results of using different proxies for the isotope signature of the CO­2 sources are also compared. For SOC-derived emissions, the proxies that are used are DOC, total SOC, microbial biomass, and soil without BC additions or plants. For BC-derived emissions, bulk BC, BC volatiles, and soil CO­2 emissions from a pot with BC in soil that has been combusted to remove SOC are compared as proxies. For root respiration, bulk roots, fine roots, root sugars, and soil CO­2 emissions from a plant grown in soil combusted to remove SOC  are contrasted. Plants are grown over 2 months, with CO2 emission rates measured every two weeks. Results are expected to: a) determine optimal proxies for 13C signatures of each component when using isotope partitioning techniques b) indicate whether soil CO2 emissions in plant systems with BC application are additive or if there are other interactions between the components.
See more from this Division: S11 Soils & Environmental Quality
See more from this Session: Environmental Functions of Biochar: I