Stand structural dynamics on drained peatlands dominated by Scots pine

The structural unevenness of the stands, indicated by positive skewness of the DBH distributions, initially increased after drainage. Ingrowth of new trees was enhanced more on sparsely forested composite peatland sites (Group II sites) than on more fully stocked sites (Group I sites). Structural heterogeneity started to decrease 20-30 years after drainage, depending on the site type. DBH distributions continued to develop towards normality and then to negative skewness. This trend reflected inherent stand dynamics mediated by increased inter-tree competition, which resulted in mortality of small trees. Thinnings hastened the change in DBH distributions. Highly uneven-sized understories of Norway spruce (Picea abies L. (Karst.)) and pubescent birch (Betula pubescens Ehrh.) became established beneath the dominant canopy layer of Group II sites.