Greenhouse gas emissions along a shelterbelt-cropped field transect

Abstract

The influence of shelterbelts on soil properties and crop yield at various distances from the shelterbelt have been studied; however, there are no available data detailing the spatial effects from shelterbelts into adjacent cropped fields on soil-derived greenhouse gas (GHG) emissions. The objective of this study was to quantify, for the first time, changes in soil CO2, CH4 and N2O fluxes along replicate (n=5) transects extending from the center of the shelterbelt to the center of the adjacent agricultural field. The shelterbelt was a 31-year-old, two-row hybrid poplar-caragana shelterbelt located in the parkland region of Saskatchewan Canada. Soil-derived GHG fluxes were measured using non-steady-state vented chambers placed along parallel transects situated within the shelterbelt strip (0H), at the shelterbelt edge (0.2H), at the edge of the adjacent cropped field (0.5H), and in the cropped field at distances of 40m (1.5H) and 125m (5H) from the shelterbelt. Summed over the entire study period, cumulative CO2 emissions were greatest at 0H (8032±502kg CO2-C ha−1) and lowest at 5H (3348±329kg CO2-C ha−1); however, the decrease in CO2 emissions at increasing distances away from the shelterbelt was irregular, with soil temperature and organic carbon distribution being the dominant controls. Soil CH4 oxidation was greatest at 0H (−1447±216g CH4-C ha−1), but decreased as distance from the shelterbelt increased. Conversely, soil N2O emissions were lowest at 0H (345±15gN2O-Nha−1) but increased with increasing distance from the shelterbelt. Patterns of soil CH4 uptake and N2O emissions were strongly correlated with root biomass, and soil temperature and moisture in the upper 30cm of the soil profile. Tree root distribution may be a key factor in determining the spatial range of shelterbelt effect on GHG emissions in adjacent fields