Estimating carbon credits variations supplied from agricultural andforest soils of Italy between 1979 and 2008.

Soils contain approximately three times the world amount of organic carbon in vegetation andapproximately the double of that present in the atmosphere. However, soil organic carbon(SOC) has been found lowering in many areas, while atmospheric CO2 was on increase. It is wellknown that there is a marked inter-dependence between SOC and climate, nevertheless, recentresearches have demonstrated that changes of land use and management can cause gains orlosses of SOC greater than climatic changes. Italy, which has joined the Kyoto Protocol, hasdecided to consider only forest management within the additional activities contemplated forthe count of carbon credits, and to launch a monitoring campaign of SOC only in forests. Thescope of this research work was to demonstrate that it is possible to estimate carbon creditsvariations supplied from both agricultural and forest soils of Italy during last the 3 decades(from 1979 to 2008), taking into account changes due to climate change. The soil database ofItaly was the main source of information. SOC content was expressed as percentage by weight(dag kg-1) analysed by the Walkley-Black procedure and converted to ISO standard. The CRA -CMA (Research Unit for Climatology and Meteorology Applied to Agriculture) database was thesource of information for climatic data. We considered the mean annual temperature and meanvalue of total annual precipitations of the two periods 1961-1990 and 1991-2006, and wemapped them by regression kriging with elevation and latitude as predictors. The soil organiccarbon stock (CS) was calculated referring to the first 50 cm, obtaining a single value for everyobservation. A series of geographic attributes were used in order to spatialize site information. Alinear multiple regression was used to interpolate the values, using the variable CS as target andthe geographic attributes as predictive variables. The model also considered the interactionbetween decade, land use, and climate, to take into account the effect of climatic variables on theSOC content in the different land uses. The SOC variations due to climate change were thensubtracted from the total, for the calculation of carbon credits that may be attributed toagricultural and forest management. Carbon credits were calculated following the EmissionTrading System (EU-ETS, EU Directive 2003/87/EC), and the exchange rate given by the CarbonDioxide Emission Allowances Electronic Trading System (SENDECO2) at September 2010.Ourresults indicate that CS highly correlates with the main groups of land use (forests, pastures,crop lands), as well as with soil humidity and temperature regimes, lithologies, andmorphological classes. CS diminished remarkably in the second decade, while slightly recoveredbetween the second and third decade. Climate change influence on SOC content was limited, as awhole, but relatively more pronounced in meadows. The Italian CS passed from 3,32 Pg in 1979-1988, to 2,74 Pg in 1989-1998, and 2,93 Pg in 1999-2008. The equivalent lost of carbon creditsoccurred from the first to the second decade totalled some 24,260 M€, while in the followingdecade carbon credits recovered about 6,921 M€, mainly because of the SOC increase obtainedin the arable lands. This study demonstrates the possibility to consider carbon credits fromagricultural soils, in addition to forest. Therefore, Italy should extend also to agricultural soils(crop lands and meadows) the current monitoring of SOC for the time of engagement of theKyoto Protocol.