Estimating changes in Scottish soil carbon stocks using ECOSSE. I. Model description and uncertainties

Smith, Joanne Ursula; Gottschalk, Pia; Bellarby, Jessica; Chapman, Stephen J.; Lilly, Allan; Towers, Willie; Bell, John; Coleman, Kevin; Nayak, Dali Rani; Richards, Mark; Hillier, Jonathan; Flynn, Helen; Wattenbach, Martin; Aitkenhead, Matthew; Yeluripati, Jagadeesh; Farmer, Jenny; Milne, R.; Thomson, Amanda; Evans, C. D.; Whitmore, A. P.; Falloon, Pete; Smith, Peter L.

doi:10.3354/cr00899

Cited by 111 publications

(105 citation statements)

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“…Future model development should ensure a dynamic coupling of soil organic carbon content and soil thermal and hydraulic properties (Falloon et al, 2011), as well as allowing for sub-grid variability and uncertainty in soil properties. A separate peat module for JULES is already under development in order to study peatland carbon dynamics in the boreal zone, and work is underway to couple JULES to a more advanced model of carbon and nitrogen turnover in both mineral and organic soils (Smith et al, 2010).…”

Section: Discussionmentioning

confidence: 99%

Simulation of permafrost and seasonal thaw depth in the JULES land surface scheme

2011

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Abstract. Land surface models (LSMs) need to be able to simulate realistically the dynamics of permafrost and frozen ground. In this paper we evaluate the performance of the LSM JULES (Joint UK Land Environment Simulator), the stand-alone version of the land surface scheme used in Hadley Centre climate models, in simulating the largescale distribution of surface permafrost. In particular we look at how well the model is able to simulate the seasonal thaw depth or active layer thickness (ALT). We performed a number of experiments driven by observation-based climate datasets. Visually there is a very good agreement between areas with permafrost in JULES and known permafrost distribution in the Northern Hemisphere, and the model captures 97 % of the area where the spatial coverage of the permafrost is at least 50 %. However, the model overestimates the total extent as it also simulates permafrost where it occurs sporadically or only in isolated patches. Consistent with this we find a cold bias in the simulated soil temperatures, especially in winter. However, when compared with observations on end-of-season thaw depth from around the Arctic, the ALT in JULES is generally too deep. Additional runs at three sites in Alaska demonstrate how uncertainties in the precipitation input affect the simulation of soil temperatures by affecting the thickness of the snowpack and therefore the thermal insulation in winter. In addition, changes in soil moisture content influence the thermodynamics of soil layers close to freezing. We also present results from three experiments in which the standard model setup was modified to improve physical realism of the simulations in permafrost regions. Extending the soil column to a depth of 60 m and adjusting the soil parameters for organic content had relatively little effect on the Correspondence to: R. Dankers (rutger.dankers@metoffice.gov.uk) simulation of permafrost and ALT. A higher vertical resolution improves the simulation of ALT, although a considerable bias still remains. Future model development in JULES should focus on a dynamic coupling of soil organic carbon content and soil thermal and hydraulic properties, as well as allowing for sub-grid variability in soil types.

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Section: Discussionmentioning

confidence: 99%

Simulation of permafrost and seasonal thaw depth in the JULES land surface scheme

2011

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“…There is, therefore, considerable research activity in predicting changes in soil carbon in response to land-use change (e.g. ECOSSE; Smith et al, 2007c), but this knowledge is not yet at a stage at which it can be incorporated into the national inventory for the UK. The potential advantages in decreasing net carbon emissions of changing land use from arable to grass are thus challenging to estimate at the farm level, and cannot yet be captured in the metrics used by policy-makers.…”

Section: Gill Smith and Wilkinsonmentioning

confidence: 99%

Mitigating climate change: the role of domestic livestock

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2010

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Livestock contribute directly (i.e. as methane and nitrous oxide (N 2 O)) to about 9% of global anthropogenic greenhouse gas (GHG) emissions and around 3% of UK emissions. If all parts of the livestock production lifecycle are included (fossil fuels used to produce mineral fertilizers used in feed production and N 2 O emissions from fertilizer use; methane release from the breakdown of fertilizers and from animal manure; land-use changes for feed production and for grazing; land degradation; fossil fuel use during feed and animal production; fossil fuel use in production and transport of processed and refrigerated animal products), livestock are estimated to account for 18% of global anthropogenic emissions, but less than 8% in the UK. In terms of GHG emissions per unit of livestock product, monogastric livestock are more efficient than ruminants; thus in the UK, while sheep and cattle accounted for 32% of meat production in 2006, they accounted for , 48% of GHG emissions associated with meat production. More efficient management of grazing lands and of manure can have a direct impact in decreasing emissions. Improving efficiency of livestock production through better breeding, health interventions or improving fertility can also decrease GHG emissions through decreasing the number of livestock required per unit product. Increasing the energy density of the diet has a dual effect, decreasing both direct emissions and the numbers of livestock per unit product, but, as the demands for food increase in response to increasing human population and a better diet in some developing countries, there is increasing competition for land for food v. energy-dense feed crops. Recalculating efficiencies of energy and protein production on the basis of human-edible food produced per unit of human-edible feed consumed gave higher efficiencies for ruminants than for monogastric animals. The policy community thus have difficult decisions to make in balancing the negative contribution of livestock to the environment against the positive benefit in terms of food security. The animal science community have a responsibility to provide an evidence base which is objective and holistic with respect to these two competing challenges.

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“…There were only small differences in the organic C contents of organic layers under forestry compared to semi-natural soils, with some horizons having greater organic C contents in afforested compared with semi-natural soils, and other horizons showing the opposite trend (Smith et al 2010b). Therefore, no adjustment was made to the C contents of the soil horizons of uncultivated soils to distinguish between afforested soils and those under semi-natural vegetation.…”

Section: Input Data Used To Drive the Simulationsmentioning

confidence: 99%

“…Because it is able to function at both field and national scales, if the model is driven by appropriate input data, field-scale evaluations can be used to determine uncertainty in national simulations. In an evaluation of uncertainty in simulations driven only by the limited data available at a national scale, Smith et al (2010b) concluded that simulated values show a high degree of association with the measurements in both total C and change in C content of the soil. Over all sites where land-use change occurred, the average deviation between the simulated and the measured values of percentage change in soil C was less than the experimental error (11% simulation error, 53% measurement error), suggesting that the uncertainty in the national-scale simulations is ~11%.…”

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confidence: 99%