Juha-Pekka Hotanen

The structure of forest stands in virgin and managed peatlands: a comparison between Finnish and Russian Karelia

Abstract This study investigated the changes caused by management, including drainage and thinnings, in peatland forest stand structure. Drained peatland sites in Finnish North Karelia were compared within the same type groups and nutrient status levels of virgin peatlands in the Republic of Karelia, the Russian Federation. The variables studied, which depict stand structure variation, included: (1) the diameter of the median tree; (2) the range of sampled diameters; (3) the basal area of the stand; (4) the estimated number of tree storeys; and (5) the number of the tree species. The number of tree storeys was determined through non-parametric Kernel estimation. Over a long duration, management smooths the natural multi-modal structure of virgin peatland stocking by decreasing the variation in size-distribution. Management also changes the natural tree species dynamics on peatland sites by providing a competitive advantage to the tree species, which adjust best to the changed growing conditions. These species begin to dominate the habitat and reduce the species diversity. The effect of recent thinnings and cleaning cuttings on the forest structure is dependent upon fertility of the site and the stage of the forest stock at the moment of silvicultural operation. Cleaning cuttings may have also an increasing effect on the structural diversity of peatland forest stand.