Time and climate as driving factors of SOM pools dynamics

This study aims at investigating the effect of climate and time on the dynamics of two natural soil organic matter (SOM) pools, i.e., the particulate and the mineral-associated organic matter (POM and MAOM, respectively). Two chronosequences characterized by different climates were investigated; the drier chronosequence (ADI) consisted of fluvial terraces whereas the wetter one (LED) of fluvio-glacial terraces. The age of the ADI soils (ADI125, ADI10, ADI8 and ADI3) ranged from about 125,000 (ADI125) to 3,000 years BP (ADI3), whereas that of the LED soils (LED16, LED14, and LED10) from about 16,000 (LED16) to 10,000 years BP (LED10). All sites were grasslands. Soil samples (1 profile and 2 cores per site) were collected by horizon, and sub-sampled by depth (each 5 cm). From each sample, POM and MAOM were isolated and characterized by elemental and thermal analyses. Overall, LED soils are characterized by a higher organic carbon (OC) content respect to the ADI ones. In particular, the concentration of OC in the mineral (MAOC) and the particulate pool (POC) along the whole profiles is ca. 2x and 3x higher, respectively, in LED compared to ADI. The MAOC concentration in drier climate follows the rank of ADI3 [...]