Carbon Sequestration Potentials in Temperate Tree-Based Intercropping Systems, Southern Ontario, Canada

Abstract

Carbon (C) sequestration was quantified in two tree-based intercropping and in conventional agricultural systems in southern Ontario, Canada. In the intercropping systems, 13-year-old hybrid poplar (Populus deltoides × Populus nigra clone DN-177) and Norway spruce (Picea abies L.) were intercropped with barley (Hordeum vulgare L. cv. OAC Kippen). In the conventional agricultural system, barley was grown as a sole crop. Above- and below-ground carbon in trees, soil C, soil respiration and C leaching from each system were determined in situ. These data coupled with complementary data obtained from the literature were compiled and used to construct C cycle models, C pools and fluxes for each system. The total mean above- and below-ground C sequestered in permanent tree components was 15.1 and 6.4 t C ha−1 for poplar and spruce trees, respectively at 111 stems ha−1. Soil C pools were 78.5, 66 and 65 t C ha−1 in poplar, spruce intercropping and in barley sole cropping systems, respectively. Soil respiration rates were 3.7, 4.5 and 2.8 t C ha−1 y−1 in poplar, spruce intercropping and barley sole cropping systems, respectively. Carbon leaching within the intercropping systems was greater below the tree row compared to the middle of the alley, but average values differed little from the sole cropping system. Total C pools (including an assumed barley C pool of 3.4 and 2.9 t C ha−1 within the sole cropping and the intercropping systems respectively) were 96.5, 75.3, and 68.5 t C ha−1 within poplar, spruce intercropping and in barley sole cropping systems, respectively. Estimated net C fluxes for the poplar and spruce intercropping systems and for the barley sole cropping system in 2002 were +13.2, +1.1, and −2.9 t C ha−1 y−1, respectively. These results suggest that intercropping systems have a greater potential in reducing the atmospheric carbon dioxide concentration compared to sole cropping systems.