ENVIRONMENT-FORMING ROLE SQUAT ELM ULMUS PUMILA L. IN POSTAGRARIAN SUCCESSIONS ON FALLOW LANDS IN THE SOUTH OF CENTRAL SIBERIA
In 2015-2019 on the old fallow lands of the Ust-Abakansky district of the Republic of Khakassia, a site with 8 field-protective forest belts was surveyed. The purpose of the study is to reveal the environment-forming role of the squat elm (Ulmus pumila L.) in postagrarian successions on fallow lands in the south of Central Siberia. The climate in the region is sharply continental and arid. Linear transects with a width of 1 m were laid on the interstrip fields according to the generally accepted methods of the route method, where the crown density and the height of the squat elm were found, for each interstrip field the weighted average value of overgrowth was found, and the silvicultural qualities of trees in the field-protective forest belts were studied. The indicators of the sanitary condition of trees and the natural regeneration of the squat elm were determined according to the “Sanitary Safety Rules” (2020). The trees in the field-protective forest belts belonged to small forests with low silvicultural indicators and a trunk height of slightly more than 6 m. The sanitary condition of the trees in the plantations was assessed as “very weakened”, “shrinking” or “fresh dead wood”. The squat elm in the dry steppe subzone of the south of Central Siberia is vulnerable in field-protective plantations on highly degraded soils. Fruiting of woody plants worsened over the years of observations and finally stopped at the age of over 40 years. In the absence of a deterrent - animal grazing, by the time the age of the fallow reached 24 years, the squat elm settled in all inter-strip fields and became a dominant in the vegetation cover, performing an environment-forming role in post-agrarian successions. The weighted average value of overgrowth in the interstrip fields varied from 26 to 53%; and at separate points in the northwestern, center, southeastern parts of the field-protective forest belts system - from 17 to 70%. In general, bushing was characterized as medium. Near the forest belts, the undergrowth crown density was 0.7…1.0, in the middle of the fields between the strips it was 0.1-0.3. The sanitary condition of the undergrowth was assessed as "weakened" or "very weakened".