The only land cover type to show an increase in soil organic carbon stocks was woodland, while the soils under arable, improved grassland, semi-natural grassland, moorland and bog showed no statistically significant change. The carbon stocks over the top 100cm of soil were calculated at each location were grouped by land cover. The national scale resampling programme in 2007-9 sampled soils at around 180 locations that had been sampled between 20 and 30 years previously. How has Scotland’s soil carbon content changed over time? Peatlands have the greatest stocks followed by moorland soils, woodland and then semi-natural grasslands. Coupling the Integrated Administration and Control System ( IACS) land use data with recent soil organic carbon data could help improve our understanding of some of these factors such as the effect on soil organic carbon contents by including grassland in an arable rotation.Ī national scale resampling programme in 2007-9 sampled soils at around 180 locations throughout Scotland and showed that upland or semi-natural soils store more soil organic carbon per hectare than lowland soils. Therefore, only in some cases can soil organic carbon contents be related to land use histories such as the length of time since last ploughed or since the last application of organic fertilisers or since sown to grass. Often the land use at the time of sampling is recorded but land management or land use history are rarely recoded in the datasets. The same soil types occur in each of these three land use categories suggesting that land use is a key driver of the difference but factors that predispose an area to a particular land use may have a role. How much carbon is stored in soils under different land uses (specifically arable, rotational grassland, permanent grassland and upland semi-natural land)?Įvidence from several datasets shows the least soil organic carbon concentrations in cultivated land are in arable land, followed by land under rotational grassland and then land under permanent or long ley pasture. Some of these maps can also be viewed online ( ) where they can be queried in more detail, however, the maps are produced at fixed scales and zooming-in does not change the resolution of the map. ![]() The lowest SOC concentrations and stocks are found mainly in the eastern lowlands while the greatest concentrations and stocks are in uplands. The maps give an overview of where the high and low soil organic carbon contents are. The distribution of soil organic carbon concentrations and stocks have been mapped with examples shown below. ![]() However, previous analytical methods may have over-estimated soil organic carbon concentrations. The total stock of soil organic carbon to 100 cm depth in Scottish soils is estimated to be around 3000 Mt C. How much carbon is stored in Scottish soils and where is it? Few of these datasets were specifically designed to quantify soil organic carbon concentrations, stocks or changes over time. Many have data on soil organic carbon concentrations, but few have data on the quantity (stock) of soil organic carbon. Thirty-seven datasets with organic carbon measurements in Scottish soils have been identified. Loss on ignition ( LoI), where a soil sample is burnt in a furnace, is often used as a surrogate of SOM but the loss on ignition value can vary depending on furnace temperature. It is usual to measure SOC and convert the value to SOM using a conversion factor that assumes that SOC comprises around 58% of SOM. Soil organic carbon ( SOC) is a component of SOM along with other elements such as nitrogen, phosphorous, potassium and calcium. However, when decomposition rates exceed the accumulation rate, then greenhouse gases such as carbon dioxide and methane are released and the amount of soil carbon declines. If the rate of accumulation is greater than the rate of decomposition, then the amount of SOM in the soil increases. Soil organic matter ( SOM) is derived from the breakdown of leaf litter, dead roots, plant material and animal waste. This report sets out to critically evaluate the ability of existing datasets to answer a series of questions regarding the status of organic carbon in Scottish soils how much is there and where, how it is affected by specific land uses, has it changed over time and what is the potential for Scotland’s soils to gain or lose carbon.
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