Экологические особенности адвентивной фракции флоры боров на южном пределе развития сосны обыкновенной

Abstract

The investigated burs develop under severe conditions of the subarid climate, where the main limiting factor is the humidification: Usmansky and Khrenovskaya, located in the subzone of the typical forest-steppe of the Oka-Don lowland; Buzuluk and Krasnosamarsky burs of the steppe zone of the Volga region. The ecological structure according to the humidification factor is represented by 4 ecological components: hydato- and hydrophytic, hygrophytic, mesophytic, xerophytic, which consist of ecological groups.It was revealed a significant predominance of mesophytes in the adventive fraction of forests of flora. Despite the fact that the most rich in the adventive fraction of the flora is the mesophyte component with a mesophytic group uniting more than 50 % of the species, the xerophyte group (with the exception of the Krasnosamarskiy forest) of the eponymous component is of greater significance. An important feature in the addition of ecological components of the adventive fraction of flora in relation to the moisturizing factor is the following: in the forest-steppe along with the mesophyte, a high percentage also has a xerophytic component, and in the steppe borons the share of the mesophytic component is more significant. This somewhat confirms the assumptions made earlier by us on the stability of natural cenoses to the penetration of alien elements of the flora.Steppe cenoses populated mainly by species of the xerophytic component (mezoxerophytes, xerophytes) are less stable for adventites in the forest-steppe forests of Usmanskiy and Khrenovskiy and are more stable in the steppe forests of Buzulukiy and Krasnosamarskiy.