Dissolved organic matter (DOM) dynamics in spruce forested sites -examinations by analytical DOM fractionation

Dissolved organic matter from two spruce forested sites in the Fichtelgebirge (Germany) was divided into different chemical and functional fractions, and the budgets of the fractions obtained were calculated. For both sites hydrophobic acids (HoS), hydropholic acids (HiS), hydrophobic neutrals (HoN), hydrophilic neutrals (HiN), and hydrophilic bases (HiB) are discriminated concerning their dynamics in the compartments. Most of the HiN and HoN are mobilized by leaching from the forest canopy. Both neutral fractions are netto retained in the forest floor as well as in the mineral soil. In contrast, HoS and HiS are mainly released in the organic layers with a total input of organic acids from the forest floor into the mineral soil of ca. 100 kg C (HoS) ha-1 a-1, and 50 kg C (HiS) ha-1 a-1, respectively. HoS are selectively better retained in the mineral horizons, leading to a mineral soil output of 2.4-4.4 kg C (HoS) ha-1 a-1, and 2.7-6.5 kg C (HiS) ha-1 a-1, respectively. It is concluded that the different mobility of the DOM fractions has implications for the mobilization and transport or organic pollutants and heavy metals. (orig.)