Soil respiration and carbon cycling in hybrid poplar plantations in northern Alberta, Canada

The use of fast-growing poplars to sequester C in biomass and soil organic matter has been proposed as a way to mitigate greenhouse gas emissions. This study examined two aspects of C cycling in hybrid poplar plantations: (1) how land-use systems affect soil respiration rates; and (2) the contributions of root (Rr) and heterotrophic (R h) respiration to soil respiration (Rs). No differences were found in respiration rates between barley and poplar plots in the first year after land-use conversion and both were net sources of C. Net primary productivity was higher in the barley plots and was the primary factor determining the C source size. The mean contribution of Rh to Rs was 63 +/- 2.6% along a chronosequence of hybrid poplar stands. No relationship existed between plantation age and Rh, Rr or R s; possibly resulting from too few replications, restricted plantation ages and heterogeneity of soils in the region.