Factors Affecting Long-Term Soil Organic Carbon Storage in Greek Forests

The recent Glasgow Climate Pact has recognized the contribution of ecosystems as sinks and reservoirs of greenhouse gases and their importance to achieve the objective of a maximum temperature increase of 1.5 degrees C. Thus, the knowledge of the long-term storage capacity of the soil organic carbon (C) in forest soils, and the driving factors, are considered of great importance for the mitigation of global climate changes. A database of published data in a 'grey' Greek bibliography, concerning the long-term storage of soil organic C in soil profiles for Greek forests, was compiled, including 307 full soil profiles, distributed between 21 types of forest ecosystem throughout the country (Greece). The data collected concerned the amount of long-term stored carbon in the full soil profile, per soil horizon, up to the uncracked bedrock. These also contained information on the sampling location, the type of forest ecosystem, the soil depth, the type of land management, the forest origin, the floristic zone, the altitude, and the climate type. According to the results analysis, the average soil organic C stored was 108.19 Mg ha (-1), and ranged greatly between 11.49 and 409.26 Mg ha (-1). The type of forest ecosystem, soil depth, land management practices, forest origin, floristic zone, and climate type played an important role in the carbon sequestration process, greatly influencing the long-term amount of stored carbon. Under the demands for mitigating climate change and reducing the rates of global warming, data evaluation indicates the directions to be followed for increasing the long-term storage of carbon, named systematic forest management, and the exclusion of the drivers responsible for the low carbon storage of soil, such as human pressure and overgrazing. Restoration actions such as reforestation and rehabilitation of the degraded forest ecosystems, which were found to store low carbon amounts, can be also considered as effective tools for increasing the long-term carbon storage in forest ecosystems.