Much more broadleaves according to nature
Altogether, 71 tree species (only 10 conifers and 61 deciduous trees) have a natural geographical distribution in Slovenia. The major reason why human influence has been less detrimental to forests than in most Central European countries is attributable to the mountainous character of the country, the difficult of access Karst region, and hence a high proportion of poorly accessible forests. The forests have consequently been relatively well preserved, which is particularly true of the diversity of natural tree species composition and the structure (vertical and horizontal) of the stands. There are only 15% of forests in which the share of spruce has strongly increased. However, it has been established that the actual tree composition deviates greatly from the potential vegetation. The ratio between coniferous and deciduous trees is 48:52 (2000), while the potential ratio appropriate for the site conditions is 20:80.
The slash and burn method used to be fairly important in the history of Slovenian forests. In the initial period of colonisation, forests were cleared by means of the slash and burn method and hoe cultivation in the lowlands and on hillsides. These areas are still the basis of agricultural production. In the present, primarily forest regions, traces of the last colonisation, between the 12th and 15th centuries, are still clearly visible.
The high deviation in terms of the actual spruce share compared to the potential is primarily the result of spruce planting in the distant past (following the model of the German forest management school), especially in Štajerska and Koroška. Spruce was extensively introduced into deciduous sites (primarily beech). Especially in the 18th and 19th century, the species structure of Slovenian forests was greatly changed due to extensive felling and the planting of spruce. It was also highly influenced by mulching, which was practised for two centuries and caused a deterioration of soil conditions in forests in the vicinity of settlements and in agricultural regions. Less demanding tree species consequently took hold (spruce and pine).
Pine has also become a characteristic tree species of the Slovenian Karst, where it was planted in the second half of the 19th century in order to alleviate the effects of the strong "bora" wind and to make the barren rocky karstic landscape green again. The discrepancy between the actual and potential proportion of pine is thus an effect of the planting of Pinus nigra and its further spread by means of natural propagation in the Karst, a region that was completely bare a century ago.