Projected changes in mineral soil carbon of European croplands and grasslands, 1990–2080

Abstract

We present the most comprehensive pan-European assessment of future changes in cropland and grassland soil organic carbon (SOC) stocks to date, using a dedicated process-based SOC model and state-of-the-art databases of soil, climate change, land-use change and technology change. Soil carbon change was calculated using the Rothamsted carbon model on a European 10 Â 10 0 grid using climate data from four global climate models implementing four Intergovernmental Panel on Climate Change (IPCC) emissions scenarios (SRES). Changes in net primary production (NPP) were calculated by the Lund-Potsdam-Jena model. Land-use change scenarios, interpreted from the narratives of the IPCC SRES story lines, were used to project changes in cropland and grassland areas. Projections for 1990-2080 are presented for mineral soil only.Climate effects (soil temperature and moisture) will tend to speed decomposition and cause soil carbon stocks to decrease, whereas increases in carbon input because of increasing NPP will slow the loss. Technological improvement may further increase carbon inputs to the soil. Changes in cropland and grassland areas will further affect the total soil carbon stock of European croplands and grasslands. While climate change will be a key driver of change in soil carbon over the 21st Century, changes in technology and land-use change are estimated to have very significant effects.When incorporating all factors, cropland and grassland soils show a small increase in soil carbon on a per area basis under future climate (1-7 t C ha À1 for cropland and 3-6 t C ha À1 for grassland), but when the greatly decreasing area of cropland and grassland are accounted for, total European cropland stocks decline in all scenarios, and grassland stocks decline in all but one scenario. Different trends are seen in different regions. For Europe (the EU25 plus Norway and Switzerland), the cropland SOC stock decreases from 11 Pg in 1990 by 4-6 Pg (39-54%) by 2080, and the grassland SOC stock increases from 6 Pg in 1990 to 1.5 Pg (25%) under the B1 scenario, but decreases to 1-3 Pg (20-44%) under the other scenarios. Uncertainty associated with the land-use and technology scenarios remains unquantified, but worst-case quantified uncertainties are 22.5% for croplands and 16% for grasslands, equivalent to potential errors of 2.5 and 1 Pg SOC, respectively. This is equivalent to 42-63% of the predicted SOC stock change for croplands and 33-100% of the predicted SOC stock change for grasslands. Implications for accounting for SOC changes under the Kyoto Protocol are discussed.

Carbon management in dryland agricultural systems. A review

“…In turn, global warming and drought in grasslands will change the physiology of grassland species and, consequently, the SOC balance (Sanaullah et al 2014). In Europe (the EU25 plus Norway and Switzerland), some predictions suggest that cropland SOC stocks from 1990 to 2080 would decrease by 39 to 54 %, and grassland SOC stock could increase up to 25 % under the baseline scenario, but could decrease by 20-44 % under other scenarios (Smith et al 2005).…”

Winter cover crops as green manure in a temperate region: the effect on nitrogen budget and yield of silage maize

“…Source: Smith et al, 2005. Conversely, the warmer and more humid conditions in Fennoscandinavia could lead to more vegetation growth, higher levels of soil biodiversity and an enhancement of SOC stocks. Figure 29 illustrates how local conditions and climate will determine the carbon fluxes for peatlands.…”

Potential carbon sequestration of European arable soils estimated by modelling a comprehensive set of management practices

“…In their simulation, the conversion of arable to grassland yielded a sequestration of 1.44 t C ha À1 yr À1 , while incorporation of straw and reduced tillage yielded a gain of 0.15 and 0.25 t C ha À1 yr À1 in the first Kyoto commitment period (2008)(2009)(2010)(2011)(2012). Smith et al (2005) estimated SOC changes in grassland and arable soils using RothC and IPCC climatic scenarios at European level; however, their projection was made for a BAU and a generic high soil carbon returns scenario. Other studies were more recently published using agroecosystem models (e.g., Century, DNDC etc.)…”