Assessing the carbon stock changes in forest soils in Bulgaria

Forest soils are a key element of the forest ecosystems which could contribute to carbon storage and climate change mitigation. The carbon sequestration and storage potential of the forest soils, however, depends to a great extent on the forestry operations and forest management activities carried out in the forest. There is a widely accepted assumption that under a set of climate and management conditions the carbon content in the forest soils is at equilibrium. However, different factors like management activities, productivity, decay rates and/or natural disturbances could alter the carbon dynamics of forest soils. The aim of the current study was to assess the carbon stock and the carbon stock changes in mineral forest soils in Bulgaria based on the forest soil monitoring information gathered under the ICP Forest Programme. For that purpose, a dataset from the programme on mineral forest soils from 1998 was processed and analysed. The carbon stock for each sample plot was estimated for the 0-30 cm layer. The carbon stock change was calculated for all the sample plots with repeated measurements over the study period. The results were further analysed with parametric and non-parametric statistical tests to assess whether the carbon stock changes are significant. However, the lack of other relevant observations within the monitoring implementation such as litter decomposition, turnover rates, climatic conditions, etc., hinder the application of dynamic soil carbon models in assessing and predicting the current and the future rate of the soil carbon in forests in Bulgaria.