DOI: 10.5285/c3b400ea-f603-4bc2-9225-5f1abfa9fe65
title: Mean and variability of topsoil organic carbon concentrations across Great Britain at 1km resolution from an ensemble of eight digital soil maps

description: This dataset presents the mean topsoil (0-15 cm) organic carbon concentration (g kg-1) and measures of its variability at 1 km resolution across Great Britain. The mean and variability metrics were calculated from an ensemble of eight previously published digital soil maps applied to all 1 km grid cells across GB where data were available from all eight maps. Four of the maps were generated from the 2007 UKCEH Countryside Survey topsoil data, two of which are available online to use. Two maps are from the International Soil Reference and Information Centre, ISRIC: SoilGrids250m v.1 (2017) and v.2 (2020) which are free to download. Two maps are from the EU’s Joint Research Centre (JRC): the OCTOP map of 2004 and LUCAS map of 2014 which are both free to download.
The dataset comes in the form of a seven-band raster tiff file, with each band representing the following:
1.	Mean predicted soil organic carbon concentration (g kg-1) of all eight maps at each 1 km grid cell
2.	Standard deviation (g kg-1) of all eight maps at each 1 km grid cell
3.	Coefficient of variation (unitless; the standard deviation divided by the mean) at each 1 km grid cell
4.	Signal to noise ratio (unitless; the mean divided by the standard deviation) at each 1 km grid cell
5.	Name of the map that deviates the most from the ensemble mean at each 1 km grid cell
6.	Relative size (%) of the largest difference from the ensemble mean at each 1 km grid cell
7.	Relative size of the largest difference from the ensemble mean expressed as the number of standard deviations exceeded at each 1 km grid cell
This work was supported by the Natural Environment Research Council award number NE/R016429/1 as part of the UK-SCAPE programme delivering National Capability.
description: Topsoil organic carbon concentrations were summarised at every 1 km grid cell where predictions exist from all eight of the compared digital soil maps. Most of the maps used to generate our dataset reflect the topsoil conditions of approximately the year, 2007 at a spatial resolution of 1 km; however, two maps at 250 m resolution were derived from a global soils database, and one map (1 km) from a European database, that include much older topsoil samples. A second map (500 m resolution) developed for Europe covers soil samples taken in 2009.

The first step before comparing the eight maps was to harmonise them to the same coordinate reference system (EPSG: 27700 / British National Grid) and grid resolution (1 km). Reprojection to British National Grid was done using tools in ArcMap, with all eight maps aligned to the Ordnance Survey (OS) 1 km grid system. Resampling to 1 km grids was undertaken on the two ISRIC maps and two JRC maps (see “Description”) by taking the means of all grid cells that occurred within each 1 km grid represented by the OS 1 km grid system.

All layers have been checked to ensure they conform to the same spatial extent, resolution, and coordinate reference system. The mean and standard deviation layers contain only positive values up to a maximum value of 550 g kg-1 (the theoretical upper limit of soil organic carbon concentration).