Influence of species-transformers invasion on the vegetation dynamics for fallow land Ukrainian Polissya

Abstract

Plant invasion is the reason of plant communities modern evolution. Alien flora elements penetrate indigenous plant communities and effect on their dynamics and stability. These plants change the structure of phytocenoses by redistributing ecosystems and alter the succession vector by breaking the syngenesis. We chose species through their ability to radically change the ecosystem which it penetrates. These species are called species-transformers. This is in accordance with the D. Richardson classification. Invasions of the species-transformers are reasons for changing the processes of dynamics natural plant communities and their species composition. Newly formed communities often have quarantine species that are dangerous to humans and pestiferous weeds. The behavior of these species is often difficult to predict so their study is extremely relevant. The purpose of our study is to establish the presence of species at different stages of fallow overgrowth, determining influence on vectors and rate of succession.

Not all ecosystems are equally vulnerable to invasions. Alien species make it easier for them to penetrate into ecosystems at an earlier stage of succession. The packaging is more compact and the specialization of species is narrowed in the late forest succession stages. It complicates the invasion.

We made 537 standard geobotanical descriptions. We used the B. Yakubenko classification to determine the early stages of successions and traditional distribution of dominant biomorphs for late stages of successions.

We have identified 16 species-transformers: Acer negundo L., Ambrosia artemisiifolia L., Anisantha tectorum (L.) Nevski, Conyza canadensis L., Echinocystis lobata (Michx.) Torr. & A.Gray, Elaeagnus angustifolia L., Grindelia squarrosa (Pursh) Dunal, Impatiens parviflora DC, Heracleum sosnowskyi Manden, Hippopha¸ rhamnoides L., Phalacroloma annuum (L.) Desf., Robinia pseudoacacia L., Rudbeckia laciniata L., Salix fragilis L., Solidago canadensis L., Xanthium albinum (Widd.) Scholz & Sukopp. The rest of the types of transformers that occur on the territory of Polissya were not taken into account in connection with the fact that they inhabited the ecotopes not connected with the fallow land.

All types can be divided by their distribution at different stages of succession into three groups: well distributed (Conyza canadensis (100%), Acer negundo (71% стадій), Echinocystis lobata (57%), Impatiens parviflora (57%), Phalacroloma annuum (100%), Solidago canadensis (71%)); moderately distributed: (Ambrosia artemisiifolia (29%), Anisantha tectorum (29%), Grindelia squarrosa (29%), Heracleum sosnowskyi (33%), Robinia pseudoacacia (33%), Salix fragilis (29%), Xanthium albinum (43%)); limited distribution: (Elaeagnus angustifolia (14%), Hippopha¸ rhamnoides (14%), Rudbeckia laciniata (14%)). The heterogeneous presence of transformer species at different stages indicating their environmental heterogeneity in terms of dynamics.

Most species-transformers are in communities of rhizome stages (69%), shrub-forest stages (69%) and forest stages (68%). The least number of this species on the subshrub stages (19%.). Only three species are recorded here: Conyza canadensis, Phalacroloma annuum, Xanthium albinum. Subshrub stage occurs on the logs formed in unfavorable edaphic conditions. Some species are found on most stages of succession (Conyza canadensis (100%), Acer negundo (71%)), some species are poorly distributed (Elaeagnus angustifolia (14%), Hippopha¸ rhamnoides (14%), Rudbeckia laciniata (14%)).

The species cause three impacts on the vegetation dynamics: change in the pace of dynamics, change the vector of dynamics and the formation of catastrophic climax.

Species-transformers are able to slow down the processes of the vegetation dynamics. Sometimes they can lead to a complete stop, creating a catastrophic climax. Robinia pseudoacacia have high levels of constancy in the fallow land at later stages of succession. It has a projective coating of 5 for Brown Blanket and a constant of 60%. Robinia saturates the soil with nitrates. This leads to the formation of a nitrogenous succession series that ends with a catastrophic climax. Other types of forest succession stages can not compete with active nitrophils. Such communities capture new areas and active invasion of species-transformers poses a major threat to the biodiversity of the region. The largest area of such invasions is observed in the south of Volyn Polissya (for example, the Hoshchansky geobotanical district).

Our results often correspond to the data obtained by other Ukrainian researchers of the synanthropic flora. However, there is a need to study the influence of species-transformers on dynamics in different edaphic conditions.

Key words: species-transformers, invasions, dynamics, fallow land