Vegetation and climate of the iset-tobol interfluve from the eneolithic to the early iron age: new palaeoecological data on the oskino-09 swamp

The article analyses new data, which provides the opportunity to reconstruct the natural environment of peo-ple in the Tobol area (forest-steppe zone of Western Siberia) in the 3rd–1st millennia BC. The authors consider the issue associated with the consistency between off-site pollen data and on-site palynological data, as well as how correctly they reflect natural conditions defining the living environment of the ancient population. Materials for the study were obtained from the Oskino-09 swamp-lake located near the confluence of the Iset and Tobol Rivers in the immediate vicinity of a multilayer settlement (Oskino Boloto). The age of swamp-lake sediments was de-termined using an age-depth model developed on the basis of AMS dates. In this study, the authors analysed pollen and plant macro-remains, as well as the indicators of economic activity (non-pollen palynomorphs, weed pollen). The analysis of stratigraphy, the composition of plant macro-remains and local pollen revealed that up to 1.2 cal ka BC the water body in question was developing as a fresh lake, which allowed the inhabitants of the Oskino Boloto settlement to use it for fishing and as a source of water in the Eneolithic and in the Bronze Age. Its transformation into a swamp occurred in 1.1–0.8 cal ka BC, which coincided with the transition period from the Bronze Age to the Iron Age. During the study period, the swamp-lake and the settlement were surrounded by forests confined to the terraces of the Iset River; starting from the middle of the Eneolithic, birch-pine forests ap-peared in the vicinity. However, pine forests were actively replaced with birch forests at the beginning of the Bronze Age; evidently, warmer temperatures and higher humidity resulted in the appearance of deciduous trees. Most of the Bronze Age is associated with a gradual decrease in humidity, with the signs of an increase in the water table level and the active expansion of birch forests being observed only at the turn of the Bronze and Iron Ages. A new stage of coniferous forest expansion in the Early Iron Age (ca 0.8 cal ka BС) is probably associated with a low level of the water table, as well as with a general fall in the temperature. The natural environment at the beginning of the Early Iron Age is very similar to that at the end of the Eneolithic. New data indicate that there were no completely treeless areas in the studied interval; forests always grew along river terraces. However, most of the settlements located nearby in the Ingala Valley were confined to open meadow-steppe areas forming an inhabited landscape. Despite the differences in the off-site pollen data obtained from the swamp and the on-site data, these data reveal similar trends in climatic changes in the 3rd–1st millennia BC.