Regional Specificity of Urban Greening at the Residential Areas of the Southern Arid Steppe Zone

Abstract

The study of the current state of urban greening at the towns and development of the basic directions of its improvement, taking into account climatic and soil conditions, is of great scientific and practical importance in the sparsely forested aridity regions. Studies were conducted in the Volgograd region in 2012-2018. The climatic resources of the region (southern dry steppe zone) are characterized by dry, hot summer, lack of precipitation, a wide range of temperatures up to 80 degrees C. The soil cover of light chestnut soils in combination with salt licks has a low humus content (1.61-1.89 %), active moisture and total porosity. The objects of research are the green plantings at the urbanized territories of the towns of Kotel'nikovo, Kalach-on-Don and the Oktyabrskiy urban-type settlement. An inventory was carried out, the destructive factors of horticulture, the current state of the vegetation and the characteristics of greenery in conditions of high aridity of the climate were revealed. It has been established that along with the creation of new landscape plantings and green areas at the present stage, it is necessary to reconstruct and restore 65-70 % of the existing plantings. These are green spaces of general, special, limited use, including the green ring, which was created in the postwar years and reached the age limit (51-60 years). The planting operation is difficult because of the dry top and the death of a significant (45.7 %) number of trees. The natural aging of Ulmus pumila L., Robinia pseudoacacia L., hybrids and plantings of Populus Pinus sylvestris L. (green ring) is aggravated by the lack of care and the pressure of negative natural and anthropogenic factors. A small percentage (from 1.6 to 3.2) of the area in landscaping is occupied by winter-hardy, resistant to external influences and salt-tolerant plantings involving: Acer ginnala, Acer tataricum, Acer semenovii, Sophora japonica, Fraxinus excelsior. It has been established that modern green zones of small cities in the southern dry-steppe zone are characterized by anthropogenically-cultivated urbanozems. The studied urban areas with greenery (Kotelnikovo) are characterized by low total porosity (45-55 %), the lowest moisture capacity (20-24 %) and active humidity (7-14 %). In horizon A, soils are characterized by a low content of hydrolyzable nitrogen (115-125 mg/kg) and mobile phosphorus (13-17 mg/kg); high (443-454 mg/kg) potassium, low gypsum content (0.08-0.09%) in the upper half-meter thicker, higher degree of salinity (1.5-2.0 %) at a depth of more than 1 m. In artificial landscaping systems of represented objects, the resource of shrubs is represented slightly: five percent of species compared to regional recommendations. As a result, architectural and artistic qualities were significantly reduced, sanitary and hygienic functions were lost. The largest percentage (32-38) of plantings of the studied objects of small cities of the southern dry-steppe zone belongs to the third class of resistance. The main directions for the improvement of green spaces, depending on their age group, are substantiated. Proved the need to improve sustainability by expanding the biodiversity of adapted trees (2 times) and shrubs (10 times). The stages of updating and enrichment of the range include: 1. The choice of an adapted range in accordance with the biological requirements of climatic, edaphic and orographic factors; 2. Increase the decorative attractiveness in view of the developed principles and approaches to optimizing the composition, vertical tier, types of plantings and their placement in urban environments. A prerequisite for gardening is watering plantations. The results are recommended for use in planting plants, environmental services in the planning, development and implementation of measures for the reconstruction of green spaces of small cities.