Qualitative and quantitative changes in soil organic compounds in Central European oak forests with different annual average precipitation

In Hungary the different climate scenarios predict the warming of the forests and their simultaneous drier. Soils play a significant role in the long-term sequestration of atmospheric CO2, while in other cases they can also become net carbon emitters. Therefore, it is important to know what can be expected regarding future changes in the carbon storage capacity of the soils of forest areas. We used precipitation-gradient studies to solve this problem, using a kind of "space-time" substitution. In this research, we primarily examined the quality parameters of SOC in order to find out how climate change transforms the ratio of the main SOC compound groups in soils. For our studies, we applied elemental and the 13C and 15N isotopic ratio analysis, NMR analysis, FT-IR spectra analysis, Thermogravimetric and differential thermal analyses. Our results showed that the amount of SOC increased in drier forests due to slower decomposition, but the increase was not limited to easily degradable compounds, the amount of recalcitrant SOC also increased moving towards areas with lower average annual precipitation. The main conclusion of our study is that SOC can increase in forests that become drier, which can permanently ensure the storage of carbon in the soil of these ecosystems.