Structure of the Ground Vegetation and Natural Regeneration of Tree Species in a 12–15-Year-Old Bilberry Pine Forest–Clear-Cut Ecotone Complex in the Middle Taiga Subzone

Abstract—Logging in mature stands, where part of the forest is harvested in one or several cuts and part is retained (clear-cutting and alternate strip cutting) results in the formation of an ecotone complex: forest (F), transition from forest to clear-cut under the canopy (forest edge – FE), transition from forest to clear-cut outside of the canopy (clear-cut edge – CE), and the clear-cut itself (C). Strips 8 m wide on each side of the mature forest/clear-cut site border form the transitional zone. We studied the ground vegetation composition and structure, and the natural regeneration of woody species (Pinus sylvestris L., Picea abies (L.) H. Karst., Betula sp., Populus tremula L., Sorbus aucuparia L., Juniperus communis L.) in the bilberry pine forest – clear-cut ecotone complex 12–15 years after the stand removal. The studies demonstrate that each of the four zones of the ecotone complex formed after logging of the mature forest has its own structural features of ground vegetation and undergrowth (including tree regeneration). The typical forest (F) habitat is characterized by the minimum number of young regeneration of Pinus sylvestris, Picea abies, Betula sp., Populus tremula, and Sorbus aucuparia and, on the contrary, by the highest abundance of lingonberry V. vitis-idaea L. and bilberry Vaccinium myrtillus L., and the maximum height of bilberry plants and their yield. The amount of tree regeneration in the FE is almost the same as in the F zone. The projective cover, maximum shoot height and yield of bilberry, and maximum shoot height of lingonberry in the FE zone are reliably lower than in the F zone. The transitional zone on the clear-cut side (CE) and the clear-cut itself (C) are distinguished from the forest sections of the ecotone complex (F and FE zones) by a greater number of deciduous and pine regeneration and the low abundance of dwarf shrubs. The clear-cut itself (C) differs from the CE by the higher abundance of grasses and forbs and an established tree regeneration layer composed of pine, birch, and aspen.