Local populations of Sorbus torminalis (L.) Crantz in forest plantings of natural origin in the South-Podolsk Forest-Steppe of Ukraine

The determination of factors that adversely affect the populations of rare plant species and development of measures to eliminate them are the important conditions for maintaining the rare component of natural flora. The article describes the study of forest phytocoenoses in the eastern territory of South-Podolsk Forest Steppe of Ukraine. The influence of natural conditions, morphological and physiological features of Sorbus torminalis (L.) Crantz on the distribution and population density in the studied region was analysed. The species is found in 80 quarters of different forestry districts with the population densities ranging from single to 300 individuals per hectare. The rare species has little prospect of natural seed restoration. The natural reforestation process of Sorbus torminalis is largely due to the specific conditions of phytocoenosis, age and vital structure of the forest stand. Most local populations have a low lifecycle. Very rare seed reproduction makes this species extremely vulnerable to the effects of any negative factors.

In the oak-hornbeam plantations, the plants of reproductive age prevail, but with the die-back of old individuals, the influx of renewal has almost disappeared. According to the results of the studied region, the oak plantations with Sorbus torminalis are found to have better values of the species distribution in the protected area compared to the recreational and economic ones (Sorbus torminalis remains in any sanitary condition in the plantations and on clean felling). Artificial resettlement should be carried out in places with a small projective cover of the vegetation, and Sorbus torminalis should be introduced into Quercus robur cultures as an associate species. This territory is the northeast boundary of the natural growth of the species.