Xiaohong Zhang

Rapid warming in the Arctic is profoundly affecting boreal forests, making the study of tree adaptation essential for predicting ecosystem responses to climate change.    This study aims to compare the Blue Intensity (BI) of digital treering images from Larix cajanderi and Pinus sylvestris and to evaluate the drought response of both species using the Standardized Precipitation-Evapotranspiration Index (SPEI) in relation to temperature and precipitation. Specifically, three BI parameters were derived from tree-ring samples collected at 13 sites in Central Yakutia: earlywood BI (BI-EW), latewood BI (BI-LW), and their difference (BI-D). Using correlation analysis, we examined the responses of these parameters to seasonal temperature, precipitation, and multiscalar SPEI (at 3, 6, and 12 month intervals). The study revealed two distinct drought survival strategies. Cajander larch, a deciduous conifer, exhibited higher vulnerability to elevated summer temperatures and a strong dependence on moisture stored in the winter snowpack. Furthermore, its xylogenesis was particularly sensitive to drought at both medium and short timescales. In contrast, Scots pine growth depended more on precipitation during the current growing season. Notably, the key adaptive mechanism for pine involved modulating the contrast in annual ring structure (BI-D), which conferred physiological resilience and drought resistance across seasonal to interannual timescales. Water-use strategies and drought adaptation in Larix cajanderi and Pinus sylvestris differ according to their life form and water uptake depth. Specifically, larch is more sensitive to rising temperatures and reduced winter precipitation, whereas pine demonstrates greater resilience. In conclusion, these findings are critical for predicting future changes in boreal forests under ongoing climatic shifts.

Climate change, characterized by increased temperature fluctuations and alterations in precipitation and soil moisture conditions, can significantly impact ecosystems that experience both moisture deficits and excesses. Even small changes in precipitation and air temperature can significantly affect tree growth. This paper examines the statistical parameters of the width of annual rings and the results of dendroclimatic analysis of larch (Larix cajanderi Mayr.) and pine (Pinus sylvestris L.) growing in the zone of continuous permafrost. The forest areas where larch and pine samples were collected are located near the village of Magan and the urban-type settlement of Nizhny Bestyakh in the central part of the Republic of Sakha (Yakutia). Woody plants are characterized by a longlife cycle, the annual rings of which are able to store information about their growth. This important resource allows obtaining valuable information about the climate and environmental changes in a given area. To understand how trees respond to climate change, Pearson correlation coefficients were calculated between the width of tree rings and average monthly air temperature, annual precipitation, and the SPEI aridity index using data from the Yakutsk weather station. To identify the response of different tree species to climate change over the past 30 years, each year was considered as a separate period. We assume that air temperature, which tends to increase, is one of the limiting factors that affects precipitation and dry periods. Due to the lack of moisture in the form of rain, tree species experience difficulties. They mainly receive moisture from the active layer of permafrost, which accumulates autumn precipitation of the previous year. Overall, we observe a negative response to the increase in air temperature in the surface layer of the atmosphere. On one hand, this suggests a decline in the radial growth of larch and pine; on the other hand, tree species are adapting to the changing climatic conditions in the central region of Yakutia.

Dendrochronological assessments were conducted on larch samples across three sites within the Tabaga region (central part of Yakutia, Russia), which result

The Hulan River Basin is located in the black soil region of northeast China. This region is an important food-producing area and the susceptibility of black soil to erosion increases the risk of soil erosion, which is a serious environmental problem that affects agricultural productivity, water supply, and other important aspects of the region. In this paper, the changes in LULC (land use and land cover) in the basin between 2001 and 2020 were thoroughly analysed using GIS (geographic information system) and USLE (universal soil loss equation) models. The soil erosion risk in the Hulan River Basin between 2001 and 2020 was also studied and soil erosion hot spots were identified to target those that remained significant even under the implementation of soil conservation measures. Precipitation data were used to obtain the R factor distribution, LULC classification was adopted to assess the C factor distribution, soil data were employed to estimate the K factor distribution, DEM (Digital Elevation Model) data were used to generate an LS factor map, and slope and LULC data were considered to produce a P factor distribution map. These factors were based on the model parameters of the USLE. The findings of LULC change analysis over the last 20 years indicated that, while there have been nonobvious changes, agricultural land has continued to occupy the bulk of the area in the Hulan River Basin. The increase in areas used for human activities was the most notable trend. In 2001, the model-predicted soil erosion rate varied between 0 and 120 t/ha/yr, with an average of 4.63 t/ha/yr. By 2020, the estimated soil erosion rate varied between 0 and 193 t/ha/yr, with an average of 7.34 t/ha/yr. The Hulan River Basin was classified into five soil erosion risk categories. Most categories encompassed extremely low-risk levels and, over the past 20 years, the northeastern hilly regions of the basin have experienced the highest concentration of risk change areas. The northeastern hilly and mountainous regions comprised the risk change area and the regions that are most susceptible to erosion exhibited a high concentration of human production activities. In fact, the combined use of GIS and USLE modelling yielded erosion risk areas for mapping risk classes; these results could further assist local governments in improving soil conservation efforts.

Проведены дендрохронологические исследования лиственницы Каяндера (Larix cajanderi Mayr) на трех участках в районе села Табага (центральная часть Якутии, Россия), и созданы хронологии по ширине годичных колец. Участки охарактеризованы как лиственнично-березовый бруснично-разнотравный тип леса. Собрано более 20 образцов из каждого участка – 73 керна. Применена следующая методика: выбор так называемых «реперных годов», т.е. годов, когда большинство деревьев имеют самые узкие или широкие годичные кольца. Выявлена связь ширины годичных колец лиственниц с гидротермическим коэффициентом Селянинова. С помощью дендроклиматического анализа установлена связь между гидротермическими условиями Центральной Якутии в августе месяце за период 1920–2018 гг. и радиальным приростом лиственниц. Мы полагаем, что в Сибири наблюдается проявление широтной зависимости между гидротермическими условиями и радиальным приростом лиственниц на фоне климатических изменений и иных геофизических факторов.

This study analyzes the monthly and seasonal correlation between the water level in Lake Tyungyulyu and the radial growth of larch across three sites in the Churapcha region of Central Yakutia. The highest Pearson correlation coefficients (r), reaching up to 0.44, have been identified between the water level and the width of the annual rings of larch (Larix cajanderi Mayr) at the third site during the summer-autumn period. These findings suggest the potential of larch in Central Yakutia as an indicator of ecological responses to hydrological conditions and climate changes.