No 1 (2024)

The paper presents new paleobotanical data in combination with the results of radiocarbon dating obtained from organomineral deposits of the northern shore of Lake. Pechevalavato (70°13’22.3” N, 71°50’57.6” E) in the Seyakha river basin and characterizing the dynamics of vegetation in the northern part of Central Yamal in the Holocene. It has been established that in the Early Holocene (10.2–8.7 thousand years ago) in Yamal, tree-shaped birch (Betula sect. Betula) grew no less than 400 km north of the modern northern limit of distribution of Betula pubescens ssp. tortuosa. Favorable conditions for the existence of birch woodlands at this time were due to the higher temperature of the growing season, exceeding by approximately 3–4 °C the modern parameters of the warmest month of the summer season. At the end of the Early Holocene (after 8.5 thousand cal BP), forest vegetation began to degrade, and open landscapes with diverse plant communities of the subarctic tundra and single trees in the river valley spread. About 6.5 thousand cal BP the northern subarctic tundra began to form the zonal appearance of the study area in climatic conditions close to modern ones.

The features of the horizontal spatial structure of multi-aged open forests of Gmelin larch (Larix gmelinii (Rupr.) Rupr.), forming the northern limit of tree vegetation in the forest-tundra ecotone in the eastern part of the Taimyr Peninsula, are considered. It was found that all studied tree stands are characterized by a mosaic structure, in which areas occupied by woody vegetation alternate with open spaces, the area of which ranges from 37 to 50%. In all cases, the composition of the tree layer includes both single trees and their aggregations (biogroups), share of which varies from 17 to 32%. Pair aggregation of trees predominates in biogroups, amounting to 83%. The predominance of the random nature of the location of trees in the formation of the horizontal pattern has been snown, but the specific type of spatial distribution is also determined by the stage of ontogenesis in which the cenopopulation is located.

The generation abundance of peled has been assessed at the lower reaches of the Ob’ River. Based on data on the number of larvae migrated downstream from spawning grounds, obtained in 1981–2021 on the main spawning rivers, current population structure of peled at the lower reaches of the Ob’ River is described, the influence of anthropogenic factors and of the water content of the Ob’ River floodplain on peled reproduction is analyzed. The Severnaya Sos’va River definitely plays a decisive role in the reproduction of peled. In recent years, there has been an increase in the contribution of the Voikar and Sob’ rivers. Seven-year cycles have been identified (between the peaks in the larvae number); their maximums coincide with the peaks of water content at the lower reaches of the Ob’ River with a 1-year lag, which supports the world’s largest river peled population abundance. The presence of such cycles makes it possible to predict phases of high fish abundance. An equation describing the dependence of the generation size of peled at the lower reaches of the Ob’ River on the average water level of Ob’ River in June–August at the Salekhard gauging level in the previous year is proposed.