Soils are the biggest carbon store in theworld (1500 Gt, e.g. 1.5×1021 g). The European Commission indicates theaccounting of soil organic carbon (SOC) variations in space and time as the first step in the strategy for soilprotection. It is indeed necessary in evaluating the risk of soil organicmatter decline and soil biodiversity decline,andwhen evaluating the role played by soils in global CO2 accounting. Previousmaps of SOC variations in Italy didnot consider the direct effect of climate. There is a marked inter-dependence between SOC and climate. SOCincreaseswith the increase in precipitations and decreaseswith a rise in temperatures. It is also known that landuse and management have a bigger impact on SOC than climate. The aim of this work is to understand to whatextent the SOC variations occurring in Italy from 1961 to 2008 could be explained by climate change. The soildatabase of Italy was the source of information for SOC content: 17,817 observations (3082 before and 14,735after 31 Dec 1990). SOC contentwas referred to the first 50 cmof soil depth, one single data obtained byweightedhorizon thickness. SOC content was expressed as percentage by weight (dag kg−1) analyzed by the Walkley–Black procedure and converted to ISO standard. The CRA–CMA (Research Unit for Climatology andMeteorologyApplied to Agriculture) databasewas the source of information for climatic data.Weconsidered themean annualtemperature (MAT) andmeanvalue of total annual precipitation(MAP) of the two periods 1961–1990 and 1991–2006, and we mapped them by regression kriging with elevation and latitude as predictors. The climate changebetween the two periodswas characterized by a generalMAT increase,whichwas greater at lower altitudes andhigher latitudes. The precipitation generally decreased, with some local exceptions. Some linear regressionanalyseswere used to investigate the relationship between SOC content and climate/land use. Temperatures hadmost relevant impact on SOCwith an inverse correlation. SOC contentwas directly correlatedwith precipitationson arable lands and inversely inforests andmeadows. Two generalmultiple linear regression analyses consideredall the pedogenesis factors and: either by time periods (1979–1990; 1991–2009), model 1; or byMAT andMAP,model 2. The twomodels both had lowprecision(multipleR-squared=0.26–0.27; RMSE=1.42; IoA=0.61), butvery different accuracies. Model 1 correctly predicted the mean SOC values for the 3 land uses in the 2 periods,detecting a significative decrease in all three land uses. Model 2 was not accurate every time. SOC decreasesestimated with model 2 were always significatively lower than the observed ones. Model 2 did not estimate asignificative SOC decrease in forests. Climate change had a general lowinfluence on SOC variations. The relativelyhigher climatic influence occurred inmeadows and in agricultural areas with a moderate or highMAP decrease(b−100 mm/y) and a moderate to high MAT increase (N0.62 °C). Other changes, probably linked to landmanagement, need to be investigated to explain SOC variations.
|Numero di pagine||9|
|Volume||Geomorphology 135 (2011)|
|Stato di pubblicazione||Published - 2011|
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