Dynamics of Species Diversity in Small Mammal Communities in Slope Larch Forests on the Northern Coast of the Sea of Okhotsk

In 2010-2023, the dynamics of the population abundance and changes in the proportion of species in the community of small mammals (insectivores and rodents) inhabiting a slope larch forest in the vicinity of the city of Magadan (northern coast of the Sea of Okhotsk) was traced. The census of animals was carried out using Gero traps and cone traps (trap-line methods). In total, we analyzed 4700 trap-nights and 15 720 cone-nights. Altogether, 3384 individuals of 9 species belonging to the families of shrews (Soricidae), squirrels (Sciuridae), mice (Muridae), and hamsters (Cricetidae) were trapped. During the considered period, the relative abundance and the amplitude of its interannual fluctuations decreased in the populations of even-toothed shrews (Sorex isodon) and grey red-backed voles (Craseomys rufocanus). The proportion of Laxmann's shrews (S. caecutiens) and Korean field mice (Apodemus peninsulae) in the community increased 2.6 and 2.5 times, respectively, while the proportion of even-toothed shrew and grey red-backed vole decreased 2.8 times and 3 times, respectively. As a result, about 50% of the individuals in the samples were Laxmann's shrews and about 30% were northern red-backed voles (Clethrionomys rutilus). This, in turn, led to an increase in the dominance (the Simpson index increased from 0.21 to 0.34), a decrease in evenness (the Pielou index decreased from 0.87 to 0.61), and a significant decrease in the species diversity of the small mammal community (the Shannon index decreased from 1.7 to 1.3; t = 10.90, p < 0.001).