Nitrous oxide emissions from trees planted on a closed landfill site

Trees growing in natural and managed environments have the capacity to act as conduits for the transport of greenhouse gases produced belowground to the atmosphere. Nitrous oxide (N₂O) emissions have been observed from tree stems in natural ecosystems but have not yet been measured in the context of forested former landfill sites. This research gap was addressed by an investigation quantifying stem and soil N₂O emissions from a closed UK landfill and a comparable natural site. Measurements were made by using flux chambers and gas chromatography over a four-month period. Analyses showed that the average N₂O stem fluxes from the landfill and non-landfill sites were 0.63 ± 0.06 μg m^–2 h^–1 and 0.26 ± 0.05 μg m^–2 h^–1, respectively. The former landfill site showed seasonal patterns in N₂O stem emissions and decreasing N₂O fluxes with increased stem sampling position above the forest floor. Tree stem emissions accounted for 1% of the total landfill N₂O surface flux, which is lower than the contribution of stem fluxes to the total surface flux in dry and flooded boreal forests.