Structural Features of Pine Catena Stands: from Forest to Oligotrophic Bog

The article presents the results of studies of the pine catena’s stands structure, conducted in the Zapadnodvinsky forestry of the Tver region (Zapadnodvinsky forest-swamp station of the Institute of Forest Science of the RAS, IFS RAS), linking the biogeocenosis of the forest and swamp parts of the oligotrophic bog. The purpose of the research is to study the forestry characteristics, morphometric indices, origin, age structure, dynamic processes and volume indicators of pine stands during the transition of the forest part of the catena to the oligotrophic bog. The pine catena includes four sections with a total length of 110 m and a width of 40 m: the upper forest automorphous zone (PP 1), the slope transit zone (PP 2 and 3) and accumulative zone (PP 4) with forest types changing from cranberry-blueberry pine woods of II quality class to shrub-sphagnum meso-oligotrophic pine woods on 6 m of peat (V quality class), underlain by organic lake sediments. The age structure of stands varies from the conditional evenly-aged restorative dynamics in the forest part to the highly-unevenly-aged dynamics found closer to the climax phase of the meso-oligotrophic sphagnum swamp. The forest part is characterized by the better condition indicators’ values, while the oligotrophic bog’s stands have the worst ones. The pine biogeocenosis of an oligotrophic sphagnum bog is close in dynamic characteristics to sustainable climax forest communities with a maximum age of the first generations trees of approximately 240–280 years. The stands condition along the catena profile varies from healthy in the forest part to the weakened with the degradation development dynamics in the accumulative part of the sphagnum bog.