Research of the vegetation species composition dynamics in the Nadezhdinskaya drainage system (Jewish Autonomous region) different age fallows

This paper contains research results for the vegetation composition dynamics on fallow lands of the Nadezhdinskaya land reclamation system in the Jewish Autonomous region. It was determined that on lands that were withdrawn from agricultural circulation more than 5 years ago, a grassy cover is formed, belonging to the wormwood-grain-mixed-grass association. In such areas, perennial and annual weedy-ruderal plants predominate. As the fallow age increases, the proportion of weedy-ruderal vegetation decreases and overgrowth occurs with woody and shrub species, among which the Salicaceae family species are represented as pioneer ones. They grow separately in young and middle–aged fallows, and form separate groupings in older fallows. The maximum species richness is observed in the middle–aged deposit (15 years) – 35 species, the minimum – in the 10–year deposit – 13 species. The Asteraceae family dominates in the fallow areas species composition, but with an increase in the age of the deposit the proportion of other families – Fabaceae, Poaceae and Rosaceae – is also significantly increasing. In addition, the geobotanical analysis revealed the fallow lands stages of overgrowth: weedy – rhizomatous – woody-shrubby.