The processes of depletion of zonal vegetation are closely related to the settlement of invasive species. Within the forest ecosystems of the urban district of Voronezh, 31 invasive species from 30 genera and 19 families were recorded. The method of ecological scales revealed the ecological-coenotic aspects of phytoinvasions.
The sample involved geobotanical descriptions (grouped by formational feature) of native phytocenoses without an alien component in the flora and phytocenoses replacing them with the active participation of invasive species within the same research object.
Infestations of these species are accompanied by the development of allogeneic successions, which are characterized by a decrease in the species diversity of communities and the role of native taxa in them. The processes of infestations are typical for the region and are observed in communities of floodplain forests and meadows, native and derived forests and sub-forests, broad-leaved and mixed forests, slope meadow and steppes.
Plant invasions in the coniferous and deciduous forests of the district are characterized by the expansion of 3 species of woody (Acer negundo, Fraxinus pennsylvanica, Robinia pseudoacacia), 5 species of shrub (Sambucus racemosa, Caragana arborescens Lam., Viburnum lantana, Amelanchier spicata, Parthenocissus quinquefolia) and 4 species of herbaceous plants (Bidens frondosa, Impatiens parviflora, Galinsoga parviflora, Solidago canadensis).
Phytoindication of pine forests shows the transformation of all 10 environmental indicators for communities with invasive species. For broad-leaved forests, the introduction of biomorphologically close taxa to native species does not lead to a sharp transformation of the ecological parameters of forest biotopes.
The introduction of alien species into alder forests leads to a change in the ecological parameters of their biotopes towards mesophilization. This speeds up the process of the emergence of new alien species from the number of mesophytic taxa and an increase in the role of already settled ones. From 2007 to 2017, the invasive flora of the alder forests of the Voronezh increased from one species to four. According to the degree of invasiveness, the ecosystems of the southern upland, southwest oak forest, northern upland oak forests and pine forests have average values of 6.4 %, 6.1 %, 5.1 %, 5.7 %, respectively. Alder forests are minimally invasive, the share of invasive species is 1.3 %, which does not exceed 5 % of the threshold.
Minor changes cover indicators: climate thermal mode (TM), continental climate (KN), climate aridity / humidity (OM), cryoclimatic (CR), soil trophicity (TR), soil acidity (RC), moisture variability (FH).
Communities with a high level of participation of invasive species are actively developing in ecotonic conditions: forest edges and alder areas of terraces.
As a result of the settlement of alien species in the Alder forests, a decrease in the price activity of the following native species is observed: Impatiens noli-tangere, Humulus lupulus, Solanum dulcamara, Thelypteris palustris, Paris quadrifolia, Maianthemum bifolium. To warn of the possible expansion of Acer negundo, Parthenocissus quinquefolia and Galinsoga parviflora, a high water cut regime for alder forests is required. Under the conditions of global and climatic changes, this is a rather complicated task, requiring constant monitoring of the abiotic and biotic components of the forest, as well as the regulation of nature management regimes in the floodplains of small rivers.
The implementation of ecological and cenotic strategies for invasive species in forest communities is accompanied by a restructuring of the ecology of biotopes, which is expressed in the transformation of the ecological parameters of pine forests, mesophilization of alder biotopes, increasing the moisture content and richness of oak forests, the emergence of new alien species and reducing the cenotic activity of some native taxa. The most significant changes are subject to parameters: soil moisture (HD), soil nitrogen richness (NT), illumination/shading (LC).
Ailanthus altissima Forests Determine a Shift in Herbaceous Layer Richness: A Paired Comparison with Hardwood Native Forests in Sub-Mediterranean Europe
