Landscape response to the Medieval Warm Period in the South Russian Far East

摘要

The landscape changes during the Medieval Warm Period were discussed for the Kuril and Sakhalin Islands, Primorye and the Amur River Basin. Some paleoclimatic parameters and shifts in landscape boundaries were estimated. The environmental changes on the Kuril Islands were manifested mostly in changes of areas occupied by the same plant communities that we see now in modern landscapes. The paleoenvironmental changes in the North and Central Kurils have been partly hidden due to volcanic ashfalls. On Simushir Island birch forests expanded at the expense of diminished tundra landscapes. On the South Kurils, the warming led to the increasing importance of broadleaf trees. In dark coniferous forests, the fir proportion increased. On small islands devoid of forests, the changes in the shrub and herb composition indicated warmer and less humid conditions. On Sakhalin, there were certain distinctions in the changes in the paleolandscape between the north, which was devoid of thermophilic elements in the forests and the south, which belonged to the zone of dark coniferous forests with an admixture of broadleaf trees. In Primorye, the warming caused an increase in the proportion of Korean pine and broadleaf species in the forests, as well as fir prevalence in dark coniferous forests. In the Amur River region, the warming involved considerable changes in the forests, which were expressed by an increase in the role of thermophilic species in the reduction of the proportion of dark coniferous species. The spread of broadleaf trees on the continental and island coasts could be influenced by warm currents amplifying the warming effect. In all regions, the warming was accompanied by a minor transgression. The sea level was higher than at present by similar to 1 m, which resulted in the formation of low marine and lagoon terraces, the attenuation of eolian processes on the coasts, and the fixation of coastal dunes with the development of a thick soil.