Biogeochemical Fluxes in Soils of Boreal Forest Ecosystems

The second characteristic feature of Forest Ecosystem soils is the accumulation of macro-nutrients in the litter with sharp decreasing to the download horizon. However, the trace elements show the opposite trend and the concentration of micro-nutrients is gradually increasing up to the soil forming rocks. 

Various forms of macro- and microelements differ in their ability to migrate and redistribute among the soil profile. The elements contained in clastic minerals are practically immobile. The elements bound to finely dispersed clay minerals are either co-transported with clay particles, or are involved in sorption-desorption processes. Part of the elements are found in concretions and also in very thin coating films of hydrated iron oxides some elements make a part of specially edaphic organic compounds. 

The determination of distribution pattern of various forms of both macroelements and trace metals in soil profile is a very complicated task. We have to know the distribution of organic matter, mineral particle, and microbes, the existence of different barriers, redox conditions etc (Box 3) 

Distribution of various forms of trace metals in Podzols of Boreal Forest ecosystems (after Dobrovolsky, 1994) 

In the Mixed Eorest ecosystems a soil fraction less than 1 /rm contains most of the elements previously confined in the forest litter and gradually involved in the biogeochemical cycle. In this fraction Cu and Mo forms account for 60-70% of the total soil content. The metals, poorly absorbable by plants, for example, Cr and V, occur in finely dispersed soil fraction in smaller amounts, about 20-30%. 

---