Impact of earthworm iLumbricus terrestris/i living sites on the greenhouse gas balance of no-till arable soil

摘要

We studied the effect of the deep-burrowing earthworm Lumbricusterrestris on the greenhouse gas (GHG) fluxes and global warming potential(GWP) of arable no-till soil using both field measurements and a controlled15-week laboratory experiment. In the field, the emissions of nitrous oxide(N₂O) and carbon dioxide (CO₂) were on average 43 and 32 %higher in areas occupied by L. terrestris (the presence judged bythe surface midden) than in adjacent, unoccupied areas (with no midden). Thefluxes of methane (CH₄) were variable and had no consistent differencebetween the midden and non-midden areas. Removing the midden did not affectsoil N₂O and CO₂ emissions. The laboratory results were consistentwith the field observations in that the emissions of N₂O and CO₂were on average 27 and 13 % higher in mesocosms with than withoutL. terrestris. Higher emissions of N₂O were most likely due tothe higher content of mineral nitrogen and soil moisture under the middens,whereas L. terrestris respiration fully explained the observedincrease in CO₂ emissions in the laboratory. In the field, thesignificantly elevated macrofaunal densities in the vicinity of middenslikely contributed to the higher emissions from areas occupied by L.terrestris. The activity of L. terrestris increased the GWP offield and laboratory soil by 50 and 18 %, but only 6 and 2 % of thisincrease was due to the enhanced N₂O emission. Our results suggest thathigh N₂O emissions commonly observed in no-till soils can partly beexplained by the abundance of L. terrestris under no-till managementand that L. terrestris can markedly regulate the climatic effects ofdifferent cultivation practises.