Carbon sequestration of forest soils is reflected by changes in physicochemical soil indicators ─ A comprehensive discussion of a long-term experiment on a detritus manipulation

The interactions of climatic and geochemical factors control soil organic carbon storage capacity and turnover. The comprehensive evaluation of the effect of long-term detritus manipulation on the soil organic carbon, soil-forming processes and the soil physical and chemical properties will help us better understand the carbon sequestration of forest soils. The long-term (19 years) effect of detrital input and removal treatments (DIRT) on physicochemical soil properties were investigated at a Central-European forest site (Síkfőkút, Hungary). In contrast to the results of similar experiments in other parts of the world, the detritus input treatments affected the soil organic carbon and almost all of the soil physicochemical indicators for the upper 15 cm layer. Soil pH, potential acidity and base saturation decreased in the litter removal plots and increased in the detritus doubling treatments. A decrease in organic matter content in the litter removal plots explained the changes in bulk density, as the stability of aggregates also decreased with the decrease of exchangeable bases and organic colloids. In this respect, compared to the other DIRT sites and other similar experiments in the world, our experimental site is considered unique, as it has the highest clay content and the driest climate. We conclude that potential cation exchange capacity and base saturation (exch. Ca) play a fundamental role in predicting the occurrence of the carbon sequestration mechanisms. We suggest to include these parameters into current SOC models.