First Short-Term Study of the Relationship between Native and Invasive Earthworms in the Zone of Soil Freezing in Western Siberia—Experiments in Mesocosms

Earthworm invasions often reduce biodiversity and affect the ability of ecosystems to perform ecosystem functions. Over the past few decades, European lumbricid species have spread widely in natural habitats in Western Siberia, without completely displacing the native species. The aim of the present experiment is to study the survival, reproductive potential, vertical distribution, abundance, and biomass of <i>Aporrectodea caliginosa</i> and <i>Lumbricus rubellus</i> invasive species for the region and the native species <i>Eisenia nordenskioldi</i> and their influence on each other. For this purpose, winter and vegetation experiments were conducted in mesocosms simulating the real situation of invasions in the same communities on the same types of soils with the same amount and composition of litter. The authors found that the native species was significantly inferior to <i>A. caliginosa</i> in reproduction rate, number of offspring, and final biomass, but had an advantage over <i>L. rubellus</i>. The native species was positively influenced by the presence of <i>A. caliginosa</i>. In the experiment, there was a significant rejuvenation of the populations of the studied species, as well as an increase in abundance and relative mass under interaction conditions compared to mono variants. The native species had advantages over the invasive species in terms of winter survival. The natural volume of litter used in the experiment was insufficient for <i>L. rubellus</i>. According to the results of the experiment, it can be assumed that the spread of <i>L. rubellus</i> will continue to be limited to non-freezing biotopes rich in organic matter. <i>A. caliginosa</i> will spread in natural communities and agrocenoses of Western Siberia.