LAUSR

The paper summarises main ideas concerning the structure of natural forest ecosystems at middle altitudes and documents the changes of humus forms and their chemistry in the natural forest of Žákova hora National Nature Reserve, in typical selected parts with different tree species composition: European beech – Norway spruce. The species composition, age and spatial structure are discussed and analysis of the uppermost soil layer is done in particular parts of the natural forest regeneration cycle, of different stages respectively. We compared the amount and layer composition of surface humus and basic pedochemical characteristics of holorganic and upper mineral horizons. The results document changes in the character of humus forms as a consequence of the tree species change. On the contrary, a high portion of uncertainty as for the species, age and spatial structure follows from discussion about the structure of natural forests at middle altitudes.