Effect of Carbonate Rocks on the Dissolved Organic Matter Leaching from Soil in Mountainous Forests Affected by Windthrow

An increase in the number of windthrow events has been observed in mountainous areas of central Europe. In such areas, rock fragments are transported from the subsoil to the soil surface, which in the case of carbonate rocks leads to the incorporation of Ca²⁺ into acid soils. These processes can alter the quality and quantity of dissolved organic matter (DOM). The study aimed to determine the role of carb onate rocks as a factor determining the quality and quantity of DOM released by gravity leaching under laboratory conditions in a long-term experiment using soil in its natural state. The soil was collected from the Tatra Mts. Three organic O-horizons and two A-horizons were selected. Relatively pure limestone collected in the study area was used. During the 20-week experiment, the soils with and without limestone were leached with deionised water. The chemical composition of the collected filtrate was measured at regular intervals, including the amount of dissolved organic carbon (DOC). The qualitative composition of the filtrate was determined by FTIR-ATR spectroscopy. The addition of limestone caused an increase in DOC leaching from the acidic O-horizons. In the A-horizons, the DOC leaching rate was reduced in the first stage of the experiment, demonstrating adsorption processes occurring in these horizons. The presence of limestone changed the quality of the leached DOM. Immobilisation of carbohydrates and aliphatic compounds occurred in the A-horizons. DOM was leached from both the O- and A-horizons mainly in the form of Ca-DOC complexes.