Forest plantation productivity - soil interactions within Western Forest-Steppe of Ukraine: effects of pH and cations

Dark grey podzolized soils on the loess like loams, which are represented in the soil cover within fresh and humidity gradients in the Western Forest Steppe of Ukraine, are characterized by high forest vegetation potential, which ensure the formation of mostly pure and mixed larch and spruce stands with high level of the productivity. Despite the fact that both species are coniferous, their effect on the soil, in particular, on its acid-base indicators (actual and potential forms of acidity, sum of absorbed bases, degree of saturation of bases, content of mobile aluminium), which are important components of soil fertility, are specific. Due to the fact that there is a close interaction between forest plantations and soil properties, changing the participation of species in the stand, it is possible to adjust the actual soil fertility. The soils under both pure and mixed spruce and larch stands are characterized by a high level of potential acidity that reaches the high acidic values in the upper horizons. A similar reaction of soil solution under coniferous forests is caused by acid hydrolysis of aluminosilicates and accumulation of mobile Al in the rhizosphere zone. Simultaneously, the same acidic characteristics, including the presence of movable aluminium, are also found in soils under broadleaved plantations. In general, acid-exchange properties of soils (high potential acidity, unsaturation of bases and availability of movable aluminium) traditionally are considered as unfavourable for vegetation. However, our researches refute it and prove that within certain values, these indicators do not limit the productivity of pure and mixed spruce and larch stands.