Biodiversity is important for maintaining of forest ecosystems functioning and in their resistance to anthropo-climatic challenges. Assessment of species diversity and species ecomorphic analysis is the basis for determining their current status, rational use and protection. At the end of the nineteenth century, Belgard A. L. (1950) in his system of ectomorphs using terminology presented by Dekandol (1956) and Warming (1903), had proposed a «trophomorph» category that reflected species relation to soil richness. Analysis of trophomorphs reflects diversity of soil conditions in different biotopes within forest ecosystems. The article gives an analysis on vascular plant trophomorphs distribution in various forest biotopes of Oril river valley. Flora and vegetation surveys in forests of Oril river valley were carried out by A. L. Belgard and T. F. Kirichenko since the 30s of the 20th century. The latest data on forest vegetation state within the Oril river valley were given in the works of Y. Gamulja and V. Manyuk. Generalized bioecological analysis of flora Oril river valley was represented in the monograph of B. Baranovsky, V. Maniuk, I. Ivanko, L. Karmyzova «Flora analysis of the Oril National Park». As is known, edaphic conditions of plant habitats in a first place are determined by soil fertility depending on the plant nutrients availability. Soddy-forest soil on sandy terrace of Oril river valley has a relatively low content of humus and total nitrogen: 2 and 0.04 %. Under these conditions, pine phytocenoses were ocсurred that represented exclusively by artificial plantings. Soils in the depressed area of Oril river floodplain are much richer in humus and nitrogen content (10 and 0.37 %). Here, arboreal and shrubby vegetation is represented by communities with common oak. On the second terrace of Oril river valley, forest vegetation is represented by artificial pine forests. Microcenoses with black locust, amorpha and willow occurred on elevated areas of sandy terrace (arena). In the depressed area of the arena, microcenoses with aspen and birch, aspen, Tatarian maple, amorpha, black locust were occurred additionally to pine communities. In the Oril floodplain, native arboreal and shrubby vegetation is represented mainly by communities with common oak. In depressed areas of the floodplain, microcenoses with white poplar, black poplar, aspen, Tatarian maple, amorpha, willow (Salix alba, S. fragilis), osiery (Salix cinerea, S. triandra), and alder are fragmentarily occurred. In conditions of elevated areas of the floodplain, 196 vascular plants species were found, and 105 species in depressed areas. On the second terrace, 38 plant species grow on the elevated areas, and 54 species on the depressed ones. Flora includes 45 adventive plant species. In depressed floodplain areas, oligotrophs are represented by 7 species, mesotrophs by 126 species, megatrophs by 50 species, and in elevated areas: 7, 126 and 25 species, respectively. In depressed areas of arena oligotrophs are represented by 4 species, mesotrophs by 29 species, and megatrophs by 11, elevated areas: 7 and 21 species respectively, and megatrophs were absent.
Plant species richness in riparian forests: Comparison to other forest ecosystems, longitudinal patterns, role of rare species and topographic factors
