Comparison of soil greenhouse gas fluxes from extensive and intensive grazing in a temperate maritime climate

摘要

Greenhouse gas (GHG) fluxes from a seminatural, extensively sheep-grazeddrained moorland and intensively sheep-grazed fertilised grassland inSouth East (SE) Scotland were compared over 4 yr (2007–2010). Nitrousoxide (N₂O) and methane (CH₄) fluxes were measured by staticchambers, respiration from soil plus ground vegetation by a flow-throughchamber, and the net ecosystem exchange (NEE) of carbon dioxide (CO₂)by eddy-covariance. All GHG fluxes displayed high temporal and interannualvariability. Temperature, radiation, water table height and precipitationcould explain a significant percentage of seasonal and interannualvariations. Greenhouse gas fluxes were dominated by the net ecosystemexchange of CO₂ at both sites. Net ecosystem exchange of CO₂ andrespiration was much larger on the productive fertilised grassland (?1567and 7157 g CO_2eq m?2 yr?1, respectively) than on the seminaturalmoorland (?267 and 2554 g CO_2eq m?2 yr?1, respectively). Largeruminant CH₄ (147 g CO_2eq m?2 yr?1) and soil N₂O(384 g CO_2eq m?2 yr−1) losses from the grazed grasslandcounteracted the CO₂ uptake by 34%, whereas the small N₂O (0.8 g CO_2eq m?2 yr−1) and CH₄(7 g CO_2eq m?2 yr?1) emissions from the moorland only impacted the NEE flux by3%. 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 forthe moorland.