THE NUMBER OF SHREWS AND STRUCTURE OF THEIR COMMUNITIES IN THE INFLUENCE ZONE OF THE NIZHNEBUREYSKOYE RESERVOIR

Abstract

The construction of hydroelectric power plants is accompanied by a large-scale landscape transformation and environmental changes, caused by the fact that the dynamics of the natural processes in the vicinity of the reservoirs is determined by regime of artificial maintaining of the water level. In order to clarify the impact of anthropogenic habitat disturbance on small mammals, in August 2015-2018, studies were conducted in the vicinity of the newly formed Nizhnebureyskoye reservoir located on the Bureya River in the Amur Region. At the previous stage of flooding, monitoring stations were set at two sites in the zone of direct and indirect impact of the reservoir on the right and left banks and one site below the dam. Six shrew species were caught, of which common ones are Laxmann’s shrew S. caecutiens, flat-skulled shrew S. roboratus, largetoothed shrew S. daphaenodon and even-toothed shrew S. isodon, and secondary ones are Eurasian least shrew S. minutissimus and tundra shrew S. tundrensis. It was found and confirmed by a comparative analysis of diversity indices that at each monitoring site the entire population of shrews forms a unified community represented by a continuum of local groups related to the gradient of the habitat type. Before the reservoir was filled, all shrew communities were characterized by a monodominant type of structure with absolute predomination of S. caecutiens with participation in samplings more than 50% and maximum abundance of 14.5 ind./100 cone-days. Shrew communities consist of representatives of different faunal groups that differently react to environmental change. As a result not only participation of different species change but it is also possible the transition of secondary species to the rank of subdominants and even replacement of dominant species. As an indicator of the changes taking place, it is proposed to use the dominance structure in shrew community with the identification of trends in its dynamics.