Introduced species in new ecosystems: concerning possible distortions of local biogeochemical cycles

The higher plants species during introduction demonstrate their properties, sometimes going beyond their traits in the natural areas. The most striking example may be given in this case is Acer nugundo L. (ash-leaved maple from the North America, a common component of forests in river valleys). In the forest-steppe –steppe landscapes of the Middle Volga region, it became a tree weed that exhibits exceptional resistance to abiotic stress conditions, including droughts.

Being introduced to alien territories, tree species generate different sorts of  “distortions” into local biogeochemical cycles in natural ecosystems and anthropogenically transformed environment. We would like to list briefly some kinds of such influence expressed in the conditions of the forest-steppe-and steppe ecosystems of our region.

The direct or indirect effects on water cycle may be connected with:

- The changes in water balance due to additional transpiration during the overgrowth of previously treeless localities with the transition from grassy to pseudo-forest communities (Ulmus foliaceae L., Acer negundo L., Elaeagnus angustifolia L.).

- The emission of additional amount of terpenes and other aeroions into the air (various types of coniferous and deciduous trees and shrubs), which can act as centers of water vapor condensation.

The direct or indirect effects on carbon cycle (as well as nitrogen and phosphorus) may be connected with:

- The formation of leaf mass not eaten by local phytophages, replenishing the fund of leaf litter (Acer negundo L., Aesculus hyppocastanum L., species of Juglans genera.).

- The influence on the soil biological activity by stimulating or inhibiting the development of soil microbiota members (different tree species including Juglans cinerea L., J. mandshurica Maxim. , J. nigra L. and others).

- The changes in the soil nitrogen balance, especially pronounced for species with "symbiotic support" (Elaeagnus angustifolia L., Hyppophae ramnoides L.).

The above effects were detected by us for the few species including named above using various field and laboratory methods. Now we can consider them at the level of their identification as such Their scale assessment at the ecosystem level may become a next stage.

An analysis of the possibilities of identifying new pseudo-forest communities developing on the grassy deposits was carried out in local conditions by integrating ground-based survey data and remote sensing. This aspect seems to be valuable for our region with highly mosaic combination of natural, cultivated, anthropogenically transformed and other territories.