UK land-use change and its impact on SOC: 1925-2007

Abstract

The contribution of soil organic carbon (SOC) to atmospheric greenhouse gas (GHG) concentrations could increase due to rising temperatures, agricultural land‐management, and land‐use change. Here the results of a modeling study are presented, which reviews the changing patterns of UK land‐use from 1925 to 2007, and estimates the contribution that these changes have had toward UK GHG emissions. The study uses a large database of SOC concentrations from which SOC stocks are estimated for land‐uses typical of the UK, and combines this with literature values of transition times for SOC to adjust to a new concentration following land‐use change. The model was designed to be used with limited input data, allowing the impacts of historical land‐use change, lacking in site specific soil and vegetation change data to be assessed. This study suggests that from 1925 to 2007 the UK's soils have acted as a net carbon sink as a result of land‐use change, sequestering a total of 102 Tg C. This represents a 5% net gain in total SOC stocks, and an average increase of 1.9 Tg C/year (inter‐quartile range: 0.19–3.12 Tg C/yr). When the reported losses of SOC due to climate change are compared to the gains resulting from land‐use change the UK's soils are a sink of carbon, with the gains from land‐use change offsetting those due to climate change. This overall sink is the result of an increase in the area of woodland, and conversion of arable land to permanent grassland. The greatest sequestration in any one year occurred in 1993 and coincides with the introduction of set‐aside. The largest SOC flux to the atmosphere occurred in 1942 following arable expansion, emitting 12.3 Tg C in one year. This flux is equivalent to almost 10% of the UK's current total GHG emissions, indicating that such land‐use change should be avoided in the future if targets to reduce GHG emissions are to be met.

Carbon stock and its responses to climate change inCentralAsia

“…This study also considered the built-up land (Table 1), where VEGC and SOC were calculated by assuming the built-up areas to be covered by 25% grass, 25% forest, and 50% impervious surface (Zhang, 2004;Sun, 2007). The impervious surface was assumed to have zero C stock (Bell et al, 2011). Finally, the VEGC and SOC of each vegetation type were multiplied by its area to estimate the total C stocks.…”

“…†The carbon densities of the built-up lands were calculated by assuming the built-up areas to be covered by 25% grass, 25% forest, and 50% impervious surface (Zhang, 2004;Sun, 2007). The impervious surface was assumed to have zero C stock (Bell et al, 2011).…”

Human impact on long‐term organic carbon export to rivers

“…Here we investigate the main drivers for the increase in fluvial DOC (Figure ) in the temperate, lowland, mineral soil‐dominated Thames basin, which has a significant urban population, and estimate their relative contributions. We develop a model linking basin properties and DOC release to the river by adapting a UK nation‐scale DOC export model [ Worrall et al , ] and combine it with a model of the effects of land use and land use change (LU and LUC) on soil organic carbon (SOC) release [ Bell et al , ] to estimate the relative influence of drivers of land use, climate, and population on DOC dynamics for the Thames basin since 1884.…”

Long‐term management changes topsoil and subsoil organic carbon and nitrogen dynamics in a temperate agricultural system

“…Furthermore, Poeplau et al (), in a review of grass‐to‐arable changes under temperate climates more generally, reported a loss of 36% of SOC over the same period, which suggests continuous loss from cultivation. It is widely reported that it is easier to lose SOC than to gain it (Don et al , ; Bell et al , ). Johnston et al () demonstrated precisely this in their comparison of the effects on SOC of grass‐to‐arable and arable‐to‐grass experiments at Rothamsted.…”