Changes in soil organic carbon and climate change - Application of the RothC model in agro-silvo-pastoral Mediterranean systems

Due to the complexity of soil organic carbon (SOC), models have proved very useful in helping to improve our understanding of the soil–plant–atmosphere system. In this study we used the Rothamsted carbon model (RothC), which considers the effect of climate (temperature, rainfall and evaporation), soil texture (clay content) and crop management on the decomposition processes, to predict changes in SOC under different land uses and the different climate that may occur in the future. SOC turnover was evaluated in land uses under different levels of agricultural intensification. The agriculture of the study-area is mainly extensive and markedly agro-silvo-pastoral, and is typical of north-eastern Sardinia (Italy) and similar areas of the Mediterranean basin. The following land uses were considered: vineyards, hay crops, pastures, semi-natural systems (formerly vineyards) and cork oak forests. Since the study-area is characterized by the same soil type (Haplic Endoleptic Cambisols, Dystric) derived from granitic rocks and potential native vegetation (Quercus suber L.), this was considered as the model baseline to study soil organic carbon dynamics. Climate change scenarios for 90 yr were generated from the baseline climate with two Global Climate Models: GISS (Goddard Institute of Space Studies, USA), and HadCM3 (Met Office, Hadley Centre, UK), for two of the Intergovernmental Panel on Climate Change (IPCC) emission scenarios (SRES A2 and B2). Land uses at low cropping intensity were more efficient than intensive agricultural systems in terms of SOC storage in the order: hay crop > pasture > cork oak forest > semi-natural systems. Land use change to vineyards decreased the carbon balance significantly between 0.09 and 0.15 t C ha−1 yr−1. However, former vineyards have almost recovered from soil disturbance following the establishment of the vineyards.