2. Climate and Pedoclimate of Italy

Climate has a potential strong influence on the soil forming processes of Italy. The elongated shape of the Italian peninsula, stretching along 11 parallels in the middle of the Mediterranean Sea, and the presence of two morphological barriers, the Alps and the Apennines, cause great local climatic variations. Actually, in Italy, authors recognized 14 of the 35 climatic regions occurring in Europe. Average climatic conditions are temperate, in particular, long-term mean annual air temperature (MAT) is 12.6 (°C) and total annual precipitation (MAP) 932.5 mm, but variations are much more important than means, in fact, they span about 30 °C and 1,800 mm. The degree of continentality, that is, the difference between summer and winter temperature is on average more than 15 °C, but it reaches more than 17 °C in the Po Plain. Seasonality of the precipitations, that is, the difference between the amount of long-term rainfall fallen in the most and in the least rainy months, proportioned to the total long-term annual rainfall, is on average 11 % and more pronounced in the southern regions. Mean long-term potential evapotranspiration is 1,002 mm, ranging from around 600 mm in the Alps and the Northern Apennines to more than 1,300 mm in some parts of Apulia, Sicily and Sardinia. As a result, climatic deficit dominates Italy. The ustic soil moisture regime is the relatively most widespread udometric regime, while the udic regime dominates the Alps and the Apennines chains, and xeric and dry xeric are well correlated with lands with the highest aridity. The mesic soil temperature regime dominates most part of the country, but the thermic regime dominates southern Italy. The frigid and cryic regimes are present in large areas of the Alps and the Apennines. A general climatic change occurred in Italy in the period 1961–2000, with a general reduction in mean total annual precipitation (MAP) and number of rainy days, and a general increase in mean air temperature (MAT). The climate change had a general low influence on soil organic carbon variations. Nevertheless, the relatively higher climatic influence occurred in meadows and in arable lands with a moderate or high MAP decrease (<−100 mm/y) and a moderate to high MAT increase (>0.62 °C). The decreasing SOC content of lands with increasing hot and arid climate could be a soil indicator of the consequences of the extension of the Mediterranean subtropical climatic regions in Italy.