Species diversity of vegetation on former lands agricultural purposes

The results of a geobotanical survey of abandoned agricultural lands on three experimental sites with a total area of more than 15 hectares are presented. Geographically, the research objects are located in the Sebezhsky district of the Pskov region. The objects of study are former fields, gradually overgrown with woody and herbaceous vegetation. The composition, occurrence and projective cover by species were determined using the method of circular counting plots with a radius of 1.785 m. The number of counting plots at each study site is at least 30. Woody vegetation is represented by single trees of silver birch, aspen, gray alder, and several species of willow. Among the undergrowth species found at the study sites are common mountain ash (66-320 ind./ha), brittle buckthorn (132-280 ind./ha), and common viburnum (52-432 ind./ha). 66 species were identified as part of the herb-shrub layer. More often than other species, mouse peas, cereals, meadow clover, wormwood, and tripartite succession are found. In terms of projective cover, ground reed grass dominates - 17.2%, meadow clover - 11.4%, meadow foxtail - 11.2%, soddy meadow grass - 9.1%, tortuous meadow grass - 9.0%, meadow bluegrass - 6.5%, meadow fescue - 3.2%. The density of species growth ranges from 1 to 14 species on an accounting area of 10 m2. The coefficient of species commonality according to Jaccard indicates that the composition of vegetation in the herb-shrub layer varies slightly among the experimental plots. The range of variation in the value of this coefficient is from 0.79 to 0.91, i.e. the number of common species is 79-91%.