Positive trends in organic carbon storage in Swedish agricultural soils due to unexpected socio-economic drivers

[摘要] Soil organic carbon (SOC) plays a crucial role in the global carbon cycle asa potential sink or source. Land management influences SOC storage, so theEuropean Parliament decided in 2013 that changes in carbon stocks within acertain land use type, including arable land, must be reported by all membercountries in their national inventory reports for greenhouse gas emissions.Here we show the temporal dynamics of SOC during the past 2 decades inSwedish agricultural soils, based on soil inventories conducted in 1988–1997(Inventory I), 2001–2007 (Inventory II) and from 2010 onwards (InventoryIII), and link SOC changes with trends in agricultural management. FromInventory I to Inventory II, SOC increased in 16 out of 21 Swedish counties,while from Inventory I to Inventory III it increased in 18 out of 21counties. Mean topsoil (0–20 cm) SOC concentration for the entire countryincreased from 2.48 to 2.67% C (a relative increase of 7.7%, or0.38% yr⁻¹) over the whole period. We attributed this to asubstantial increase in ley as a proportion of total agricultural area inall counties. The horse population in Sweden has more than doubled since1981 and was identified as the main driver for this management change(R² = 0.72). Due to subsidies introduced in the early 1990s,the area of long-term set-aside (mostly old leys) also contributed to theincrease in area of ley. The carbon sink function of Swedish agriculturalsoils demonstrated in this study differs from trends found in neighbouringcountries. This indicates that country-specific or local socio-economicdrivers for land management must be accounted for in larger-scalepredictions.

[学科分类] 地球化学与岩石