Species diversity across the successional gradient of managed Scots pine stands in oligotrophic sites (SW Poland)

The Scots pine communities are common forest types in Central Europe, however, the general model of changes resulting from cyclical management practices is still unclear. The aim of this paper is to present the changes in species diversity during the development of managed Scots pine stands and to distinguish main stages of vegetation succession. The examined stands were divided into six age classes: ≤ 10 years old, 11-20, 21-40, 41-60, 61-80, 81-120 years old. Data from our study suggest a division of the stands into three main stages of succession on oligotrophic (low nutrient) sites. The first stage is associated with the youngest stands before the canopy formation (< 10 years), the second stage with young closed-canopy stands (11-40 years) and the third stage with the maturing, pre-mature and mature stands (> 40 years). The first stage was characterised by the highest value of the Shannon index, the highest number of vascular plant species, the highest cover of lichens but the lowest cover of bryophytes. There was a group of non-forest cryptogams, exclusive for that stage. In the second stage, there was a significant decline in the Shannon index, the cover of bryophytes increased and the cover of lichens decreased. Cladonia species were characteristic of that succession stage. The third stage was characterised by the lowest species richness, moreover, the cover of bryophytes was highest and the cover of lichens was lowest. Common coniferous forest species were characteristic of the final stage before clear-cutting. Generally, after stand removal the communities indicated higher species diversity than previous forest communities. The final forest plant associations were not determined solely by late-successional species.Forest management appeared to substantially influence changes in diversity and the course of succession.