Modeling regional soil C stocks and CO2 emissions under Mediterranean cropping systems and soil types

Abstract

To assess the spatial and temporal dynamics of carbon (C) at regional scale induced by land use and soil type, we performed a simulation study, based on a bio-physical model (RothC10N) combined with a spatially explicit database including soil, land use and climate. RothC10N was linked to GIS and outputs were interpolated using Empirical Bayesian Kriging (EBK) to estimate the C stocks and CO2 emissions in the Mediterranean area of Foggia province in Southern Italy. The typical cropping systems of the area, i.e. arable rainfed (ACR) and irrigated crops (ACI) (cereals in rotation with irrigated tomato), vines (VIN), olives (OLI), and grasslands (GL) were considered. RothC10N simulations showed that OLI and VIN were able to store a considerable amount of C. Conversely, arable crops led to a reduction which was higher when the rotation included the irrigated tomato. The transition from arable to permanent crops (A2P) showed higher SOC stock increases than that from permanent to arable (P2A). The CO2-C released to the atmosphere was higher in ACI, P2A, and VIN, and lower in OLI and GL. Overall, in the year 2013 the total soil C stock in agricultural land across the province of Foggia was 19 Tg C, while the total GHG emission was 16.9 Tg CO2-C. The proposed methodology has proved to be effective to estimate the C stocks and emissions in the Mediterranean area and can be applied to assess the effect of specific land uses and land use change. Main land management recommendations to prevent soil organic C decline in the study area are: conservation tillage of arable lands, improvement of crop rotations, e.g. from continuous wheat to cropping systems including alfalfa or other legume crops, retention of crop residues into the field, rational use of irrigation for the summer crop, use of cover crops during the winter season to replace fallow periods, and supply of organic fertilizers (compost or manure).