Carbon stock changes for Italian beech forests under a changing climate

In Italy, beech forests are the most important ecosystem for their carbon stock, but they are also threatened by climate change. In fact, one study showed a considerable reduction of beech extent between 64.5% and 98.8% in different IPCC scenarios along with a reduction in C stock. In further detail, the C stock in the first 5 cm of soil was influenced by temperature seasonality and elevation. On this basis, we carried out an elevation transept in 10 beech forests in Italy, sampling 3 stands at an increasing distance of 200 m from each other. In each of these 30 stands we collected litter and topsoil. A preliminary analysis of the relationship between the organic carbon and temperature seasonality and elevation as predictors showed a much stronger effect of the former, together with spatial autocorrelation. As a consequence, we added uncorrelated bioclimatic variables used as predictors in GLS modelling. Our models have been projected on current, potential and future (2070 RCP6) beech extent. Considering the sum of leaf litter and topsoil, our results showed that, on the one hand, taking into account a stock in the potential conditions of 410 Tg, there can be a change of the organic C stock to 225 Tg in 2070, while under the current extent of beech the estimate is 121 Tg. On the other hand, the concentration of organic C is expected to increase from 80 Mg/ha under current and potential conditions up to 122 Mg/ha for 2070. This increase will be much more evident in the southern Apennines (up to 4 times) than in the Alps (almost no change). These results can be explained by temperature seasonality changes, which is expected to increase from 6.2 to 6.9 ° C for 2070 in beech’s area of occurrence.