Tuesday, November 14, 2006

Surface and Depth Distribution of Soil CO2 Efflux and Concentrations in a Young Hybrid Poplar Plantation in Northern Alberta, Canada.

Carmela Arevalo1, David T. Price2, Jagtar S. Bhatti2, Alberto L. Orchansky2, and Scott X. Chang1. (1) Dept of Renewable Resources, Univ of Alberta, Edmonton, AB T6G 2E3, Canada, (2) Canadian Forest Service, Northern Forestry Centre, 5320-122 St., Edmonton, AB T6H 3S5, Canada

Temporal and spatial variability of soil surface and profile respiration were measured in the first growing season of a newly established hybrid poplar (Populus deltoides x P. petrowskyana var. Walker) plantation established by Alberta-Pacific Industries Ltd. at Ashmont, Alberta, Canada. Soil surface CO2 efflux was measured using a LICOR 6400-09 soil respiration system from a total of 55 collars placed along transects north, east, south, and west of an eddy covariance tower established at the site. Profile CO2 concentrations at 0.02, 0.10, 0.25, and 0.50 m were measured continuously using Vaisala GMM 221 solid-state infrared CO2 sensors. For the period July 27 November 6, 2005, C lost via soil surface respiration was 0.62 Mg C ha-1 (102 days). Soil C efflux decreased from 1.33 g C m-2 day-1 in July to 0.20 g C m-2 day-1 in November ranging from 0.47 4.95 g C m-2 day‑1 (July) and from 0.04 to 0.52 g C m-2 day‑1 (November). Soil CO2 concentrations along the soil profile were closely related to soil temperature and moisture, and responded positively to rain events. Soil CO2 concentration close to the surface was about 4 times higher than ambient CO2, increasing to 10 times ambient at 0.5 m depth. Temporal and spatial variability of soil respiration may be attributed primarily to the influence of biophysical factors on organic material decay derived from previous land-use (hay production).