Soil Organic Carbon Depletion in Managed Temperate Forests: Two Case Studies from the Apennine Chain in the Emilia-Romagna Region (Northern Italy)

Forest soils contain a large amount of organic carbon (OC); therefore, small changes in these ecosystems have effects on climate. In this study, variation in the quantity of C pools that occurred in one year in the soil of temperate forests managed by two farms in the Apennine chain (Emilia-Romagna Region) was investigated using elemental and isotopic C analyses of soil samples collected in 2020 and 2021. In one year, soil from the Branchicciolo (BRA) farm lost organic matter as shown by the decrease in C contents and the less negative C isotopic signatures (13C/12C), whereas the C contents and C isotopic signatures remained almost stable during time in the soil from the Beghelli (BEG) farm. This cannot be related to thinning interventions, as much more forest material was removed from the BEG forest than from the BRA forest (60% and 25%, respectively). Therefore, other causes should be considered. The BRA forest was at a lower altitude than the BEG forest; thus, it was more affected by C depletion due to the warmer temperature. Moreover, the sandy soil in the BRA forest was less prone to sequestering organic matter than the soil in the BEG forest, which was characterized by phyllosilicates (including vermiculite) and zeolites (clinoptinolite) having high C sequestration capacity. This work showed the different impacts of the pedo-climatic conditions in two nearby farms, which should be considered in planning appropriate silvicultural management for OC sequestration.