Greek National Map of Soil Organic Carbon

Soil organic carbon (SOC) is the carbon that remains in the soil after the partial decomposition of any material produced by living organisms. It is an essential parameter for agricultural production, the potential sequestration of CO₂ in soil and a vital soil function for global carbon cycle. However, a vast potential of soil carbon is removed from agricultural soils due to non-sustainable soil management practices. Mapping SOC and its changes over time and space is highly valuable for estimating the CO₂ emissions and effects of climate change to the environment. In the present work, the Greek National Map of SOC is presented calculating the SOC stock in 30 arc-seconds spatial resolution using the Global Soil Partnership and Food and Agriculture Organization of the United Nations (FAO) guidelines for SOC mapping. The presented methodology considers the reference framework of the SCORPAN model for digital soil mapping, which can predict SOC stocks in correspondence with soil forming factors. Among the key variables used for estimating SOC stocks are environmental covariates such as climate and meteorological data, thematic maps, digital terrain data, geomorphometry and soil data. Data mining and geostatistical techniques (random forests, support vector machines, regression-kriging) are used to estimate the SOC stocks. Internal and external map accuracy is used to evaluate the performance of the Greek National SOC map. Accuracy of FAO’s methodology was examined herein using different modelling approaches. As indicated in the results, the most accurate map was produced by the random forest technique and an accuracy of FAC2=0.968, RMSE=0.322 and r=0.756. The main findings are also discussed herein covering aspects relevant to the method implementation, validation and feasibility of operational implementation.

Keywords: soil organic carbon, climate change, soil management practices, Greek National Map