Long-term changes in vegetation and site conditions in beech and spruce forests of lower mountain ranges of Central Europe

In the study of vegetation changes in European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst.) forests in the Orlické hory Mts. (the Sudetes range, Czech Republic), 34 research plots were surveyed in 1951-2011 using the seven-point Braun-Blanquet scale. The long-term research was motivated by studying the effects of the pollution disturbance in the mountains of the Sudetes system in the 1980s, but also by the understanding of autonomous development of vegetation differing in human interventions. On the studied plots, soil samples were collected periodically from particular soil horizons for physical and chemical analyses. The results document the fact that beech forests showed a slow and almost one-way succession change in 1951-2011 while in spruce stands more pronounced tendencies of cyclic development and much varied dynamics were evident at the level of particular sites. In recent 20 years, the populations of younger tree species have augmented both in beech and spruce forests. Especially during the air-pollution disturbance, the species diversity decreased moderately and almost returned to the original values at the end of observations. Moderately increasing continentality of the vegetation composition and retreat of warmth-requiring species are typical of beech forests while an increase in nutrient-demanding species and retreat of light-requiring and moisture-demanding species are characteristic of spruce forests. Undergrowth in beech forests is rather more conservative from the aspect of developmental stages than undergrowth in spruce forests. The effect of forest origin on the temporal development of vegetation and species diversity was not statistically significant in either of the forest types. The test of the effect of chemical properties of soil showed the most important role of available potassium and calcium content in humus horizon and magnesium content in B horizon in beech forests and the crucial role of nitrogen content and soil reaction in A horizon in spruce forests.