Soil organic carbon sequestration: scoping study

A report evaluating the ability of existing datasets to answer questions regarding the status of organic carbon in Scottish soils.

Appendix 1. Soil datasets with measurements of soil organic carbon of Scottish soils

(* denotes datasets that are component parts of the ‘Scottish Soils Database’ held by the James Hutton Institute)

Datasets Number of sites Extent Land Use Specific Strengths Weaknesses
1 Representative Soil Profiles of Scotland * ~14000 National No
Extensive dataset covering most of Scotland especially cultivated land. Collected over a long period of time with bulk of samples taken 1970s and 80s but still being added to. Sampled by horizon to 100cm and Has measurements of SOC and LoI for topsoils and subsoils. Data can be linked to soil maps to show spatial distribution of SOC.

Collected over a long period of time from 1940s with bulk of samples taken 1970s and 80s. Different methods used to determine SOC concentrations during this period. Soils subjectively sampled to characterise soil map units. Very few measurements of bulk density to calculate stocks.
2 National Soil Inventory of Scotland (1978-88) * 721 National No Extensive dataset covering all of Scotland at 10km intervals. Objectively sampled Inventory. Soil horizons sampled to 100cm. SOC and LoI measured Slight weakness is the time frame taken to complete the survey (10 years). No direct measurements of bulk density to calculate stocks.
3 National Soil Inventory of Scotland (2007-9) * 183 National No A subset of the National Soil Inventory of Scotland (1978-88) resampled in 2007-9 on a 20km grid. Soils sampled by horizon to 100cm. SOC and Loi both measured as well as bulk density. Was used to assess change over time. Less extensive than the first Inventory, 25% of those sites revisited.
4 Countryside survey 195 National No Based on classification of 1km squares into ‘ITE’ land classes that represent major environmental gradients and habitats in the UK. Soils sampled 3 times (1978, 1998 and 2007 at a depth of 0 -15cm. LoI measurements. Only sampled 0-15cm and bulk density data only available for 2007. The samples are taken from different locations within the 1km square each time.
5 Geochemical Baseline Survey of the Environment ~40,000 Regional No Composite soil sampled every 2 km2 at depths 0-20 and 35-50cm. Greater density in Urban areas. Only Loss on Ignition for limited parts of Scotland
6 Scottish Soil Fertility database ~180,000 Regional
Cultivated soils
Data from 1996. Composite field-scale sample 0-20cm for arable and 0-10 for grasslands. LoI measured primarily for Liming requirements. Data also available for James Hutton Inst. farms. Spatial reference is to postcode of the submitter, not the field. Data ‘owned’ by the submitter.
7 LUCAS _2009 190 Regional Primarily cultivated soils Composite topsoil samples taken 0-20cm on a predetermined sample frame. SOC measured. Topsoil only. Mainly cultivated land with a small sample of other land uses. No measured bulk density or topsoil thickness.
8 LUCAS _2015 234 Regional Primarily cultivated soils Composite topsoil samples taken 0-20cm on a predetermined sample frame. SOC measured. 150 of the original sites resampled. Topsoil only. Mainly cultivated land with a small sample of other land uses. No measured bulk density or topsoil thickness.
9 SoilBio 5152 Regional Cultivated soils Recent topsoil LoI data with a subset of soils with bulk density and water retention. Also has management data. Topsoils only mainly from arable soils. Limited distribution of sites.
10 NE experimental Farm 37 Regional Cultivated soils Samples of former (mainly 1950s) experimental plots taken resampled in 2017 at 0-15cm to assess change in SOC concentration. Bulk density measurements and topsoil depth also taken so stocks can be calculated. Limited to North-east Scotland and small dataset.
11 Scottish soil map unit transect study * 6 transects (64-138 sites Local Cultivated soils Soils sampled in 1988 at 0-15 and 40-50cm (unless cuts across horizons) on a transect with regular intervals of 5 and 10m to assess soil variability in extensive soil types. Useful for assessing variability in SOC for designing sampling schemes Soils sampled in 1988. Only one had topsoil bulk density measurements.
12 ‘Woodlands’ long-term rotational experiment at Craibstone ? Local Cultivated soils Arable fertiliser treatment experiment started in 1922, occasional measurements of soil organic matter Only occasional measurements of SOM are available.
13 Water stable aggregates 203 Local Cultivated soils 150 of the samples taken 0-5cm in 2009-10 have SOC measurements from the Lunan catchment and 50 have SOC from the Tarland catchment taken in 2012 Limited to 2 Catchments
14 Rainton Farm 214 Local Cultivated soils Derived SOM values from a number of fields starting in 1996 to present. Farmer has made data publicly available. Limited to 1 farm
15 East of Scotland Farm Survey 105 Regional Arable land Triplicate 0-15cm taken in 2007 and SOC measured, bulk density core taken adjacent to the sample. No indication that topsoil thickness was measured
16 Barley Soils 50 Local Arable land Soils sampled in Spring/autumn 2016 at 0-15cm Limited to only 5 fields
17 Balruddery Farm Grid survey * 124 Local Arable land Soils sampled in 2008 and some later in 2014 on Berryhill Farm at 0-15 and 40-50cm on a 100m grid. SOC and LoI measured at both depths. Limited to Balruddery Farm.
18 Mylnefield Farm Grid Survey * 325 Local Arable land Soils sampled in 1987at 0-15 and 40-50cm on a 25 and 100m grid. SOC and LoI measured at both depths. Limited to Mylnefield Farm. Some land no longer available.
19 Centre for Sustainable Cropping Balruddery Farm 350 (6 fields) Local Arable land Soils sampled annually beginning in 2010 on a 18m grid at 0-20cm depth. SOC data available and limited bulk densities, Main focus is on arable production systems and limited to 6 fields.
20 Glensaugh agroforestry plots * 190 Local Pasture to agroforestry Soils sampled in 1987at 0-15 and 35-45cm on a 10 and 50m grid prior to establishing agroforestry experimental plots. SOC and LoI measured at both depths. Partial resampling in 2012 with bulk density measurements made. Underwent a land use change from pasture to agroforestry. Some trees removed.
21 Grid Surveys in Scotland *
8 grid surveys (19-1214)
Local No Various dates. Some soils sampled by horizon to 1m and some fixed depth. Grid intervals from15-400m. One site (Hartwood) has topsoil SOC and bulk densities Only 3 have SOC measurements, one upland and two lowland. Limited number of samples in each, between 10 and 90.
22 UK Soil and Herbage Survey 56 Regional No Three 0- 5cm soil cores taken at 3 locations within a 20 x 20 m square in 2001/2 and bulked providing 3 samples 6 x 5cm samples taken from each site for bulk density and SOC. Includes urban areas 50 km grid
23 Environmental Change Network – soil * 3 Local No Started in 1993 and repeated on 5- and 20-year cycles. Complex sampling protocols including auger borings and full profile pits. SOC measured every 5 years and bulk density every 20 years. 2013 profile pit sampling was not done.
24 Afforested soils * 39 National Afforested soils Soils sampled in 2013 by horizon to 100cm and by fixed depths. Resampling of soils that underwent afforestation. SOC, LoI and bulk densities available so stocks can be calculated Only includes sites that were moorland before trees were planted.
25 SNH woodland exclosures * 12 Regional Woodland 6 paired sites inside and outside of exclosed woodland. Sampled in 2014. Mineral subsoil sampled by horizon and whole thickness of organic layers sampled. LoI, C and bulk density measured Only Brown earth soils samples and limited sample size
26 ITE/NCC ‘Bunce 1971’ woodland survey 103 (across GB) National Woodland Started in 1971 and repeated in 2000-3. 0-15cm sample from a 200m2 plot. SOC measured. Litter layer not sampled.
27 Level I Forest Conditions survey 67 (across UK) National (UK) Woodland Started in 1994, composite soil samples at 0-5, 5-10, 10-20cm. Scheme replaced by BioSoil.
28 Level II Intensive Monitoring of Forest Ecosystems 10 (across GB) National (UK) Woodland Baseline soil sampling in 1995 including SOC Mainly aimed at solute chemistry.
29 BioSoil 69 in Scotland National Woodland Started in 2006 with soils sampled at fixed depths of 0-5, 5-10, 10-20, 20-40 and 40-80cm. Organic layers sampled separately. SOC, bulk density and depths recorded so stocks can be calculated. Woodland sites only and fixed depth samples can mean that horizons are mixed perhaps diluting SOC concentrations.
30 Birse and Robertson Survey soils * 660 National Woodland, grassland, montane Soils initially sampled as part of Soil Survey of Scotland sampling programme between 1945 and 1985. Resampled in 2011-2013 for grasslands, 2007 for woodlands, 2004-2006 for montane. Sample depths variable depending on habitat. SOC and bulk density available from all habitats/ Samples were purposively selected.
31 Trends in pollution of Scottish Soils 30 National Moorland First sample in 1990, repeated 1990 and National Inventory 2007-9 data used for repeat in 2010. Soils sampled 0-5cm on three transects across Scotland at roughly 20km intervals. SOC and LoI measured. Restricted to soils under heather moorland. Primarily organic horizons.
32 MOORCO (Moorland Colonisation) 10 Local Moorland One set of experimental plots establish in 1975 and has SOC, bulk density and horizon thickness data. Others established 2005 with bilk density and surface layer SOC measurements Mixture of treatments on relatively small plots.
33 Alpine Mosaics * 99 (35 soil profiles) Local Montane Soil profiles sampled in 2018/9 by horizon to 100cm where possible. Horizon thickness, bulk density and Soc data available to calculate stocks. Only upland, montane soils.
34 Racomitrium Heath Survey 17 Local Racomtrium heath Composite soils samples at 0-4cm taken in 2006 and 0-15cm core samples in 2011. Both have SOC measurements. Very restricted habitat.
35 Scottish Peat survey 140 sites (number of sample points not recoded) National Peat deposits Earliest samples 1956. Multiple depths up to 1100cm. Peat volumes calculated for each site along with carbon concentrations. Grid survey at intervals between 25 and 100m. Samples taken at depths of approx. 50cm intervals. Originally the surveys were to identify exploitable peat resources for power stations.
36 Glensaugh Peat depth survey 96 Local Peatland Soils sampled in 2005 on a 200m grid at fixed depths of 0-15, 15-30 and 50-65cm. SOC and bulk density data available. Peat depths recorded. Bulk density from sample cut from Russian auger.
37 Forsinard 40 Local Peatland Composite surface organic layer 0-5cm sampled in 2011 and 2017. FTIR analyses may give C concentrations Limited sampling of specific habitat. Protocols changed.



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