Soil methane (CH4) fluxes in cropland with permanent pasture and riparian buffer strips with different vegetation

Methane (CH₄) has a global warming potential (GWP) 28-times that of carbon dioxide (CO₂) over a 100-year horizon. Riparian buffers strips are widely implemented for their water quality protection functions along agricultural land, but conditions prevailing within them may increase the emissions of greenhouse gases (GHGs), including CH₄. However,  only small amount of information is available regarding the dynamics of unintended emissions of soil CH₄ in these commonplace features of agroecosystems and how the dynamics compare to those for agricultural land not containing buffer strips. To understand the dynamics of soil CH₄ fluxes from a permanent upslope pasture and contiguous riparian buffer strips with different (grass, willow, and woodland) vegetation as well as controls with no buffer vegetation, field measurements were carried out using the static chamber technique on a replicated plot-scale facility. Gas fluxes were measured periodically with soil and environmental variables between June 2018 and February 2019 at Rothamsted Research, North Wyke, United Kingdom. Soils under all treatments were sinks of soil CH₄ with the willow riparian buffer (-2555 ± 318.7 g CH₄ ha^-1) having the lowest soil CH₄ flux followed by the grass riparian buffer (-2532 ± 318.7 g CH₄ ha^-1), woodland riparian buffer (-2318.0 ± 246.4 g CH₄ ha^-1), no-buffer control (-1938.0 ± 374.4 g CH₄ ha^-1), and lastly, the upslope pasture (-1328.0 ± 89.0 g CH₄ ha^-1) which had a higher flux. The three vegetated riparian buffers were more substantial soil CH₄ sinks, suggesting that they may help reduce soil CH₄ fluxes into the atmosphere in similar agroecosystems.