Upward Treeline Shifts in Two Regions of Subarctic Russia Are Governed by Summer Thermal and Winter Snow Conditions

Abstract

Climate warming impacts on alpine treeline dynamics. However, we still lack robust assessments of the long-term impacts of climate on tree recruitment at the treeline, particularly in remote areas such as the subarctic regions of Russia subjected to different climate influences. We expected that the treelines in two regions may have different features and dynamics patterns. We analyzed climate variables and assessed treeline dynamics by quantifying recruitment using the tree rings of ca. 7000 trees of four species (Betula pubescens Ehrh. ssp. tortuosa, Pinus sylvestris L., Picea abies Ledeb. ssp. obovata, Larix gmelinii Rupr.) along 14 altitudinal transects (series of study plots). We compared the Khibiny Massif (Kola Peninsula) and the western Putorana Plateau, subjected to oceanic and continental influences, respectively. In both regions, summers became warmer, and winters became snowier during the past century. At the low part of the treeline ecotone, tree recruitment has slowly increased since the mid-18th century at the Putorana Plateau and the mid-19th century at the Khibiny but accelerated in the early 20th century at both regions and reached a maximum peak in the second half of the past century. Treeline encroachment intensified in the 1930s at the Khibiny and the 1950s at the Putorana Plateau. Trees encroached in the tundra leading to upward treeline shifts in the late 20th century. The slope exposure affected the rates of treeline shift with higher upward advances on southern-oriented slopes. Tree recruitment and early-winter precipitation were positively correlated. The differences in species composition, treeline altitude and influences of slope orientation on treeline dynamics can be explained primarily by differences in the degree of continentality. The abundance of saplings in both regions allows the future encroachment of trees into tundra and further treeline upward shifts to be forecast.

Regeneration of Pinus sibirica Du Tour in the Mountain Tundra of the Northern Urals against the Background of Climate Warming

“…The results of our research have shown that the survival and, consequently, further growth and development of Pinus sibirica, are due to climate warming. This conclusion is in good agreement with the results of research (including other tree species) on the Polar Urals [16,48], the Khibiny Massif (Kola Peninsula) [49], the western Putorana Plateau [48,49] in the Southern Rockies (region of northern New Mexico and southern Colorado) [50], in the Himalayas [51], and in the southern European range (the Pyrenees) [52]. The obtained results complement the meta-analysis of annual tree line shift rates at 143 sites from 38 published studies [53] and clarify the impact temperature and precipitation have on Pinus sibirica regeneration.…”

“…This is a certain combination of thermal and hydrological factors that drives treeline shift rates across the Northern Hemisphere [53]. The combination may include temperatures in early summer and precipitation in early winter [48,49], temperature-moisture correlations throughout the year [50], winter precipitation only (high snow depth) [14], and winter temperatures [54]. Our research shows the greatest correlation between Pinus sibirica regeneration and the maximum temperatures in May and June of the previous year.…”

Stand Biomass at Treeline Ecotone in Russian Subarctic Mountains Is Primarily Related to Species Composition but Its Dynamics Driven by Improvement of Climatic Conditions

“…Consequently, the snow cover depth at the beginning of the cold period also increased significantly by +3.3 cm per decade -1 and by +5.2 cm per decade -1 , respectively. For the Khibiny Mountains, we observed a high positive correlation between tree recruitment (birch and pine) and precipitation in July and during the beginning of the cold period (November-December), as well as with the snow depth at the beginning of the cold period [44]. Correlation analysis also showed that on the Putorana Plateau there were positive relations between the number of larches recruiting between 1910 and 2010 and the temperature indicators for the warm period, total precipitation at the beginning of the cold period (October-December), and snow depth at the end of December [44].…”

Temperature data in ecological monitoring of the Kola Subarctic mountain soils

“…Для Хибин факт повышенного биологического разнообразия был установлен почти 100 лет назад сотрудниками первой научной горной станции «Тиетта» [Фридолин, 1934] и неоднократно подтвержден последующими исследованиями [Зенкова, 2020]. При-мером ответной реакции горных экосистем на воздействие глобальных и региональных факторов является высотное продвижение границы леса на фоне повышения среднегодовых температур воздуха, фиксируемое в последние десятилетия от Алтае-Саянской горной провинции на юге Сибири до гор Европейского Северо-Востока России, Скандинавских гор и Хибин [Крючков, 1958а, б;Kullman, 2007;Шиятов, 2009;Моисеев и др., 2010, 2016Петров и др., 2021;Тютькова и др., 2021;Каверин, 2022;Grigoriev et al, 2022].…”