Bacterial communities associated with the cycling of nitrogen in a tree-based intercropping system

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Graungaard, Karla Celia
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University of Guelph

This research examined the influence of a tree-based intercropping system (TBI) on the abundance of bacterial communities associated with the soil nitrogen cycle. Soil cores were collected along a positional transect around four tree species (Juglans nigra L, Quercus rubra L., Picea abies (L.) H. Karst, and Populus x. canadensis) and into the intercropping row. Quantitative real-time PCR was used to determine the abundance of 16S, nifH, amoA, nosZ, and nirS gene transcripts. Both tree species and proximity to the tree influenced the abundance of nirS, nosZ, and nifH, genes. A modified denitrification enzyme assay comparing poplar and oak soil showed poplar had a greater potential for N2O production than the oak soil in this TBI system. Our work indicates that tree species are associated with unique microbial communities within a tree-based intercropping system, and suggests that this may play a role in ecosystem functioning, such as N2O emissions.

Agroforestry, Intercropping, Denitrification, Nitrogen fixation, Soil, Nitrous oxide, Bacterial gene abundance