Abstract
This paper deals with the evaluation of the effect of afforestation of previously arable land to soil characteristics changes. One of the main aims was to evaluate the effects of each forest species on the soil structure quality after afforestation. Soil samples were taken at two climatically distinct subregions within the Czech Republic. Based on the different site conditions, two study sites were chosen at each locality for a total of four research sites. Detailed soil survey and basic forest stand inventories were conducted at all four sites. The first locality was established in the Rychnov nad Kněžnou district in the Protected Landscape Area of the Orlické mountains (soil type a Haplic Cambisol). The second locality was established in the Prague-East district (soil type a Haplic Cambisol and a Haplic Stagnosol). Afforestation had a positive influence on the soil physical characteristics which are important for the maintenance of soil stability. Forest cover has a major influence on increasing the soil porosity, by decreasing the reduced bulk density and increasing capillary and gravitational pores, which is crucial. Afforestation was also found to be positively related to increases in soil organic matter content in different forms, both stable and unstable, and tendency of considerable soil organic matter accumulation not only in the layer of surface humus but also in the entire soil profiles of the research sites. The main contributor to soil improvement after afforestation is the formation of stable soil aggregates. This is typical also for spruce and pine cover.