1. Carbon losses from all soils across England and Wales 1978-2003 Pat Bellamy, Peter Loveland, Ian Bradley, Murray Lark (Rothamsted), Guy Kirk g.kirk@cranfield.ac.uk Nature 437, 245-248 (2005)

2. 1:250,000 scale 1:50,000 scale Availability of Soil Surveys in Europe, 2000

3. The National Soil Inventory Unbiased inventory of soil resources across England & Wales at intersects of 5 km x 5 km grid  Whole of E&W sampled in 1979-83 (5,662 sites)  Approx. 40% of sites re- sampled: agricultural 1994-96, non-agricultural 2002-03  Organic carbon content of 0- 15 cm soil (C org ) measured  Sampling scheme designed to detect changes of ± 2 g kg -1

4. Checks on methods – accuracy of relocation  Six surveyors instructed to revisit 10 sites following original protocols  Accuracy better than 20 m on enclosed land, 50 m on open land  Locations recorded with GPS; distance from target measured subsequently  Given the variability of C org at this scale, this is adequate

5. Checks on methods – consistency of lab. analyses  Approx. 10% of archived soils from original sampling re-analysed in 2003  Good agreement between original and re-analysed values with no systematic deviation (slope of reduced major axis correlation = 1.05, concordance correlation = 0.93)

6. Original soil organic carbon contents (1978/83)

7. Original soil organic carbon contents (1978/83) and rates of change

8. Rates of change - grouped by (a) soil type, (b) land use

9. Rates of change - grouped by original C org

11. Estimated changes in carbon stocks across England & Wales (and UK) Net rate of change in England & Wales = - 4.4 Mt yr -1 Net rate of change in UK ≈ - 4.4 x UK / E&W topsoil OC stock ≈ -13 Mt yr -1

12. Changes in carbon stocks across E&W – grouped by land use

13. Dynamics of soil organic carbon (SOC) CO 2, CH 4 Carbon immobilization Plant debris (high temperature, rainfall, land use) Leached OC Carbon accumulation > < Carbon loss SOC ‘pools’ fast intermediate slow Carbon mobilization (Fe, Al, clay association) input + immobilizationmobilization + output After Schultze, E.D. & Freibauer A. Nature 437, 205-206 (2005)

14. Modelling soil carbon dynamics CO 2 Fast POC Slow POC Fast SOC (C 1 ) Intermediate SOC (C 2 ) Slow SOC (C 3 ) CO 2 decomp. rate = k 1 C 1 decomp. rate = k 2 C 2 decomp. rate = k 3 C 3 SOIL POOLS PLANT DEBRIS Rate constants (k i ) vary with soil temperature (T), moisture (θ), texture (t): k i = f(T) f(θ) f(t) k i 0

15. Changes in carbon stocks across E&W – grouped by soil type

16. Most important soil types Surface water gleys Slowly permeable, seasonally wet Podzolic soils Acid sands or loams with leached organic matter & sesquioxides, wet or dry Ah Ea Bs Bh BC&Bs BC&Ea Peat soils Permanently or seasonally wet

17. Modelling soil carbon dynamics CO 2 Fast plant OC Slow plant OC Fast SOC (C 1 ) decomp. rate = k 1 C 1 Intermediate SOC (C 2 ) decomp. rate = k 2 C 2 Slow SOC (C 3 ) decomp. rate = k 3 C 3 CO 2 Rate constants (k i ) vary with soil temperature (T), moisture (θ), texture (t): k i = f(T) f(θ) f(t) k i 0 SOIL POOLS PLANT DEBRIS

18. Soil carbon map of Europe Data sources Soil type Land cover Temperature Rasterization Spatial layers derived by rasterization of a Triangulated Irregular Network (TIN) model with weighted distance interpolation Soil type Temperature

19. Future research  Third sampling of NSI -plus carbon fluxes (to air and water) -plus additional data  Modelling -statistical -semi-empirical -predictive  Similar studies elsewhere