Main features of the Samara-Ulyanovsk Volga Region flora adventive fraction family spectrum

Abstract

The study of the adventive fraction of flora is a separate area of floristic research. General patterns of adventive species introduction consequences as well as their distribution throughout the territory are studied. Often, when studying the adventive fraction, the family spectrum is analyzed. In the paper we consider the adventive fraction of the flora on the territory of Samara-Ulyanovsk Volga Region, which is located within two natural zones: forest-steppe and steppe, four physical-geographical provinces and 15 districts. Each physical-geographical unit is characterized by its peculiarities of relief, geological structure, soils, vegetation and local climatic conditions. In the family spectrum of the adventive faction of Samara-Ulyanovsk Volga Region, it is possible to single out families that play a leading role in the formation of its composition. Based on the data on the adventive fractions of the floras of the physiographic regions and areas identified in the study area, it can be noted that the first four places in the spectrum are occupied by the following families Asteraceae, Poaceae, Brassicaceae and Chenopodiaceae. The list of these four leading families of the adventive fraction of the flora remains unchanged, but their order may be different. Probably, the differences in the natural conditions of the studied territories are reflected precisely in the order of the location of the leading families, since their composition does not change. The change in the composition of the leading four of the family spectrum can be observed on the scales of large areas: comparing the spectra of the adventive fractions of Ivanovo, Tver, Astrakhan Region, and other administrative divisions. Flora of various physical and geographical subdivisions of Samara-Ulyanovsk Volga Region, despite belonging to different natural zones, have similar family spectra of adventive fractions. They differ only in the presence of one or two families. For example, among the leading adventive families Rosaceae, Onagraceae and Rubiaceae were not in all cases.