Soil Organic carbon and Land Use Mapping

The impact of land use and land use change and forestry (LULUCF) on soil organic carbon (SOC) stocks and greenhouse gas (GHG) emissions is important both in terms of national GHG inventory reporting, and as a strategy to offset GHG emissions. Globally, the loss of SOC due to LULUCF has been estimated to be ~156 Pg of carbon to the atmosphere between 1850 and 2000, comprising 18% of global emissions (Houghton, 2003). This is mainly due to the conversion of forested areas to agriculture, and the conversion of grassland to cropland. Land use change can however, also enhance the carbon (C) sink strength of particular systems, due to increases in above and below ground biomass.

Conversions from arable ecosystems to grasslands, as well as afforestation can lead to significant carbon sinks (Guo and Gifford, 2002). Additional to gross changes in land use, recent research has shown strong underlying patterns of agricultural land use change in Ireland (Zimmermann et al., 2016), with constant shifts between cropland and grassland. While, these short-term changes may significantly influence SOC stocks and GHG emissions, there is a lack of information on the impact of these short term transitions. Conversely, grassland and arable management may offer significant potential to increase SOC stocks through optimal nutrient and tillage management and reductions in fallow periods (Soussana et al., 2004, Ceschia et al., 2010).

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Soil disturbance has been shown to trigger SOC loss due to the disruption of soil aggregates which protect SOC, and increased aeration which enhances mineralisation rates (Roberts and Chan, 1990). The carbon emissions and potential sequestration linked to LULUCF are acknowledged in the United Nations Framework Convention on Climate Change (UNFCCC) and need to be reported in national GHG budgets (Höhne et al., 2007; Schlamadinger et al., 2007).

Currently, LULUCF reporting for national inventory purposes relies on Tier 1 reporting methodologies (Duffy et al., 2015) with the main limiting factors being the lack of availability of soil property and agricultural activity data at an adequate spatial resolution. The recent development of new high resolution data products, including the Land Parcel Identification System (LPIS), and the Teagasc Soils Identification System (SIS) have the potential to address this knowledge gap, and, together with recent advances in earth observation sciences these data will provide a new foundation for the development of Tier 2 LULUCF GHG reporting methodologies in Ireland. Re-interpreting the Eurostat LUCAS 2015 points against SIS using geospatial techniques and remote sensing data will generate the Land-use and Soils Inventory for Ireland - LUSII.