Changes in the composition of phytocenoses on post-agrogenic lands over an 18 year period

Materials on the dynamics of vegetation on post-agrogenic lands over an 18-year period are presented. The object of the study is abandoned agricultural land in the Plyussky district of the Pskov region. In order to determine the long-term dynamics of the species composition of herbaceous vegetation and upper soil horizons on post-agrogenic lands, a comparative analysis of data obtained in 2005 and 2023 was carried out. There is an intensive change of species in the composition of the herb-shrub layer. Photophilous species dominate. There is a decrease in the projective cover of cereals in most experimental plots. Over 18 years, the share of cereals decreased from 54.4 to 27.9 %. It has been established that the species diversity of vegetation in the experimental plots levels out over time. The similarity of species in experimental plots with a minimum amount of woody vegetation was revealed. When the tree canopy closes, the species composition of the vegetation of the lower tiers changes dramatically, and the dominance of forest species is noted. The coefficient of species commonality in experimental plots ranges from 0.15 to 0.75. Minimal changes in the species composition of living ground cover from 2005 to 2023 were observed in the area initially sown with lupine, and maximum changes were recorded in the area overgrown with birch. The dynamics of soil horizons show an increase in the thickness of the litter and a decrease in the degree of its decomposition. In areas with minimal participation of tree species, an increase in the degree of sod is observed. In areas with a closed tree canopy, there is no turf; forest litter accumulates here. Over the course of an 18-year period, a compacted soil layer below 25 cm (plow base) is maintained at all sites. In the leaching horizon (illuvial horizon), humus leaks increase.