HR: 0800h
AN: B11A-0994    [Abstracts]
TI: In-Situ Measurements of Isotopic Variability in Autotrophic and Heterotrophic Soil Respiration
AU: * Risk, D
EM: drisk@stfx.ca
AF: Environmental Sciences Research Centre, St. Francis Xavier University, PO Box 5000, Antigonish, NS B2G 2W5 Canada
AU: Kellman, L
EM: lisa@stfx.ca
AF: Environmental Sciences Research Centre, St. Francis Xavier University, PO Box 5000, Antigonish, NS B2G 2W5 Canada
AU: Moroni, M
EM: mmoroni@NRCan.gc.ca
AF: Atlantic Forestry Centre, P.O.Box 960, Corner Brook, NF A2H 6J3 Canada
AB: Several in-situ methods can be used to establish the relative contribution of autotrophic and heterotrophic sources to total soil respiration. Trench plots, a physical partitioning tool, are the most popular of these methods and although their use is widespread, they are seldom used for more than simple budgeting. Trench plots are underutilized for biogeochemical applications, and may also be used as a springboard to develop more spatially-extensive partitioning methodologies. In this study, we are performing regular δ¹³C and δ¹⁸O analyses of soil CO₂ surface flux at five research sites in Nova Scotia and Newfoundland, Canada, all of which contain trench plots, but differ in species composition and climate. We are seeking to establish whether isotopic partitioning of autotrophic and heterotrophic soil respiration is possible at these sites, and are also hoping to elucidate information about respiration processes and isotopic signatures. Approximately 800 surface flux samples were collected and analyzed during the summer and early autumn of 2005. Here we present temporal trends and spatial variability in δ¹³CO₂ surface flux for both trenched and untrenched plots at each site. Using a simple mixing model, we are able to establish the contribution and δ¹³C signature of both autotrophic and heterotrophic sources. These results are presented in the context of a thorough aboveground and soil δ¹³C characterization. We observe strongly site-specific patterns, especially in the autotrophic δ¹³CO₂ flux signature which can be estimated in-situ using this coupled physical and chemical approach to soil respiration analysis.
DE: 0400 BIOGEOSCIENCES
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0490 Trace gases
SC: Biogeosciences [B]
MN: Fall Meeting 2005