Transformations of the Vegetation Cover on the Southern Kuril Islands under the Impact of Natural and Anthropogenic Factors

Abstract

The modern typological structure of vegetation inhabiting the southern Kuril Islands has been identified on the basis of computed Bravais correlation coefficients. This structure is represented by eight pleiades: fir forests with Abies sachalinensis; spruce forests with Picea ajanensis; Sasa senanensis thickets (Shikotan Island); elm–maple forests with Acer ukurunduense and Acer mayrii (Kunashir Island); maple–oak forests with Acer mayrii and Quercus crispula (Iturup Island); Juniperus sargentii thickets (Shikotan Island) and communities with Pinus pumila (Iturup and Kunashir Islands); and alder–birch phytocoenoses, reed–tall-grass and coastal meadows, and ruderal vegetation. The species diversity of plants is determined by local species of East Asian origin. The amphipacific group manifested along the coastline demonstrates the affinity of local species and the North American flora. The proportion of foreign species increases on disturbed sites. Indigenous phytocoenoses are represented by fir and spruce forests, as well as Pinus pumila and Juniperus sargentii thickets in the mountains and on the rocks. Under the impact of unfavorable factors, indigenous groups are replaced by birch forests with Betula ermanii and secondary meadows, including ruderal–forb–gramineous coenoses; felling and fire sites are overgrowing with bamboo thickets with Sasa senanensis. Preliminary estimates indicate that the share of disturbed lands on Shikotan reaches 40%, including 30% disturbed by anthropogenic impacts and 10% due to natural factors. On Kunashir, proportions of these lands amount to 16 and 17%, respectively, and, on Iturup, 23 and 16%. It is shown that Sasa senanensis thickets, despite their secondary nature, play a key role in preventing the further degradation of natural complexes, soil erosion, and exogenous geological processes.