Territorial Heterogeneity of the Earthworm Population (Opisthopora, Lumbricidae) of Omsk Oblast and Environmental Factors: A Quantitative Assessment of the Relationship

Abstract

According to the results of 9 years of earthworm collections in soil in Omsk oblast from 2009 to 2018, their population has been analyzed in order to identify the main environmental factors associated with the territorial heterogeneity of species richness and group density. Five types of Lumbricidae populations have been identified, two of which are divided into two subtypes, where ten species and two subspecies of earthworms are found. It has been established that environmental factors such as zonality and subzonality; the depth of the soil layer; and, to a lesser extent, the topography characteristics have the greatest influence on the distribution of worms: 9, 7, and 0.7% of the considered variance of the density similarity matrix, respectively. In general, all environmental factors and their combinations (modes) explain 38% of the considered variance; the multiple correlation coefficient is 0.62. Dendrobaena octaedra (7–52%) and Aporrectodea caliginosa (15–74%), alien species of European origin, and the native Eisenia n. nordenskioldi (6–28%) took over in terms of the share of the population density in most taxa of the classification, as well as Eisenia ventripapillata (42%) and E. nana (16%) of Asian origin, for the territories of the southern forest steppe and steppe. Such changes in earthworm populations, namely the replacement of native species of the Eisenia nordenskioldi complex with alien species, can significantly affect soil characteristics and ecosystem services determined by earthworms.

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