Comparison of soil greenhouse gas fluxes from extensive and intensive grazing in a temperate maritime climate
Greenhouse gas (GHG) fluxes from a seminatural, extensively sheep-grazed drained moorland and intensively sheep-grazed fertilised grassland in South East (SE) Scotland were compared over 4 yr (2007–2010). Nitrous oxide (N 2O) and methane (CH 4) fluxes were measured by static chambers, respiration from soil plus ground vegetation by a flow-through chamber, and the net ecosystem exchange (NEE) of carbon dioxide (CO 2) by eddy-covariance. All GHG fluxes displayed high temporal and interannual variability. Temperature, radiation, water table height and precipitation could explain a significant percentage of seasonal and interannual variations. Greenhouse gas fluxes were dominated by the net ecosystem exchange of CO 2 at both sites. Net ecosystem exchange of CO 2 and respiration was much larger on the productive fertilised grassland (−1567 and 7157 g CO 2eq m −2 yr −1, respectively) than on the seminatural moorland (−267 and 2554 g CO 2eq m −2 yr −1, respectively). Large ruminant CH 4 (147 g CO 2eq m −2 yr −1) and soil N 2O (384 g CO 2eq m −2 yr −1) losses from the grazed grassland counteracted the CO 2 uptake by 34%, whereas the small N 2O (0.8 g CO 2eq m −2 yr −1) and CH 4 (7 g CO 2eq m −2 yr −1) emissions from the moorland only impacted the NEE flux by 3%. The 4-yr average GHG budget for the grazed grassland was −1034 g CO 2eq m −2 yr −1 and −260 g CO 2eq m −2 yr −1 for the moorland.