Functional Efficiency of the Woody Vegetation Species Composition in Urban Green Spaces

The article discusses the results of a comprehensive analysis of the ecological state and environment-stabilizing functions of woody vegetation species composition in the urban green space. The work is based on a large amount of factual material obtained during the course of a long-term monitoring of Vladivostok's urban vegetation. A methodological substantiation for a comprehensive qualitative-quantitative assessment of species has been developed using the applied qualimetry techniques. An integral indicator, termed the species functional efficiency coefficient (SFEC) has been proposed as the main evaluation unit. It is a relative-quantitative characteristic of plant quality that is based on the vegetation's functional efficiency and significance in urban ecosystems: prevalence in greenery planting, vitality, ability for accumulation of the pollutant metals in the urban environments, their concentration relative to the local environment background, and the capability for accumulating metals from the soil. Comparative analysis of the functional efficiency of 80 species of trees and shrubs of the urban vegetation of Vladivostok has been carried out on the basis of the proposed coefficient. Among the compared sample of plants, the SFEC decreases from 3.70 (Crataegus pinnatifida) to 1.13 (Malus mandshurica (Maxim.) Kom.). These values correspond to 74 and 23% of the conventional quality standard (QS) of the species. The groups of species with different functional significance in the urban green space structure have been identified. The best efficiency in creating the comfortable environmental conditions in the city has been demonstrated by the widespread species: Fraxinus mandshurica, Ulmus japonica, Betulaplatyphylla, Physocarpusopulifolia, etc. They are of the maximum level of participation in the formation of the urban vegetation structure and a high ability to absorb the main pollutants of the urban environments. The SFEC values for these species are within 3.26-2.61, which corresponds to 65-52% of the QS. Also, some suggestions on a rational use of species for the formation of a comfortable urban environment and the introduction of the results into the practice of managing the urban green fund have been proposed.