The nature of soil organic carbon stocks in a tree-based intercropping system in southwestern Ontario

This thesis provides an update on the nature of the soil organic carbon pools in a tree-based intercropping system 25 years after establishment. Soil samples were collected in Summer 2012, Fall 2012 and Spring 2013 to quantify soil organic carbon stocks within soils planted with hybrid poplar (Populus spp.), red oak (Quercus rubra), black walnut (Juglans nigra) and Norway spruce (Picea abies). Results showed that spatial distribution of dissolved organic carbon was associated with litterfall distribution of each tree species. Cores were collected in Summer 2012 to investigate the spatial orientation of soil organic carbon content (SOC) of soils planted with white cedar (Thuja occidentalis), black walnut and Norway spruce. SOC content of soils surrounding walnut, cedar and spruce were 1.62%, 1.73% and 1.58%, respectively. Higher SOC content could be attributed to the higher density tree spacing of cedar (1 m). Soils contained 2.06% SOC within the conventional cropping system.