Contrasting 20-year trends in NDVI at two Siberian larch forests with and without multiyear waterlogging-induced disturbances

The fate of a boreal forest may depend on the trend in its normalized difference vegetation index (NDVI), such as whether the NDVI has been increasing significantly over the past few decades. In this study, we analyzed the responses of two Siberian larch forests at Spasskaya Pad and Elgeeii in eastern Siberia to various waterlogging-induced disturbances, using satellite-based NDVI and meteorological data for the 2000–2019 period. The forest at Spasskaya Pad experienced waterlogging (i.e., flooding events caused by abnormal precipitation) during 2005–2008 that damaged canopy-forming larch trees and increased the abundance of water-resistant understory vegetation. By contrast, the forest at Elgeeii did not experience any remarkable disturbance, such as tree dieback or changes in the vegetation community. Significant increasing NDVI trends were found in May and June–August at Elgeeii (p < 0.05), whereas no significant trends were found at Spasskaya Pad (p > 0.05). NDVI anomalies in May and June–August at Elgeeii were significantly associated with precipitation or temperature depending on the season (p < 0.05), whereas no significant relationships were found at Spasskaya Pad (p > 0.05). Thus, the 20-year NDVI trend and NDVI–temperature–precipitation relationship differed between the two larch forests, although no significant trends in temperature or precipitation were observed. These findings indicate that nonsignificant NDVI trends for Siberian larch forests may reflect waterlogging-induced dieback of larch trees, with a concomitant increase in water-resistant understory vegetation.

The impact of fires on the landscapes of the Baikal-Dzhugdzhur type underclimate fluctuations

In light coniferous forests of the Baikal-Dzhugdzhur type fires are considered as factors and processes inseparable from the forest landscapes and their dynamics. The study period of 1998–2015 is highlighted as extremely arid. In 2008, 2013–2014, 2018 conducted ground studies of the state of vegetation after fires in the area of Vitim Plateau. The conditions of arid period with high frequency, duration and intensity of fires were the main factors in the dynamics of transformation of the structure of mountain-taiga larch forests. Analysis of cruising materials and expedition research showed that from 1996 to 2015 the area of larch forests with canopy density of 5–7% decreased by 45–50%. The area of burned forests and thin forests increased by 45-48%, and the area of shrubs – by 17.0%. The main part of forests is disturbed at the foot of the mountains and in intermountain depressions, at altitudes of 942 -1100 m. Strong desiccation of the ground cover and consistent ground fires with complete loss of trees and undergrowth activated natural processes of bush formation and prairiefication. The duration and degree of fluctuations in climatic parameters determine the nature of the impact of fires on Baikal-Dzhugdzhur larch forests and the degree of their transformation.

Genome Analysis of an Alphabaculovirus Isolated from the Larch Looper, Erannis ankeraria

The larch looper, Erannis ankeraria Staudinger (Lepidoptera: Geometridae), is one of the major insect pests of larch forests, widely distributed from southeastern Europe to East Asia. A naturally occurring baculovirus, Erannis ankeraria nucleopolyhedrovirus (EranNPV), was isolated from E. ankeraria larvae. This virus was characterized by electron microscopy and by sequencing the whole viral genome. The occlusion bodies (OBs) of EranNPV exhibited irregular polyhedral shapes containing multiple enveloped rod-shaped virions with a single nucleocapsid per virion. The EranNPV genome was 125,247 bp in length with a nucleotide distribution of 34.9% G+C. A total of 131 hypothetical open reading frames (ORFs) were identified, including the 38 baculovirus core genes and five multi-copy genes. Five homologous regions (hrs) were found in the EranNPV genome. Phylogeny and pairwise kimura 2-parameter analysis indicated that EranNPV was a novel group II alphabaculovirus and was most closely related to Apocheima cinerarium NPV (ApciNPV). Field trials showed that EranNPV was effective in controlling E. ankeraria in larch forests. The above results will be relevant to the functional research on EranNPV and promote the use of this virus as a biocontrol agent.

Structure of forest litter in larch forests of Middle and Southern Siberia

Forest litter plays a significant role in the functioning of forest ecosystems. As a product of forest and soil interaction, forest litter participates actively in the processes of soil formation and plant nutrition. We measured the total stock and analyzed difference in structure of forest litter formed in permafrost larch forests growing in the different climatic zones: in northern taiga of Central Siberia and in the mountain taiga of the Eastern Baikal region. The forest-forming species in both regions is Gmelin larch (Larix gmelinii (Rupr.) Rupr.), but climatic conditions and soil cover in these regions differ. It was found that average stock of forest litter is higher in mountain larch forests of the Eastern Baikal region in comparison with northern boreal forests. The litter composition in these larch forests is characterized by a relatively larger contribution of soft fractions (needles and leaves) in contrast to the larch forests in the northern taiga, where a higher contribution of hardly decomposable components (branches, cones, bark, semi-decomposed wood, thick roots, and moss residues) was observed. Higher stock of fermented plant residues in comparison with humified ones indicated the accumulation of incompletely decomposed plant residues on the soil surface of these northern forests.

The larch forest of the “Bastak” State Nature Reserve (Jewish autonomous region)

The article presents the information about the current state of the larch forests of the “Bastak”. State Nature Reserve The area, ecological and cenotic conditions of growth are determined, the classification of the studied plant communities is presented, a brief description of the forest structure is given. The current state of the larch forests of the “Bastak” State Nature Reserve can be assessed as fairly stable. Currently, larch forests occupy within 25 % of the forested area. The most widespread area is occupied by lowland larch forests (94 %). Mountain larch forests are derived plant communities formed after forest cutting in fir-spruce forests.

Stock of standing dead trees in boreal forests of Central Siberia

A significant part of carbon assimilated by forest is deposited in tree trunks. Growth and development of tree stands is accompanied by accumulation of standing dead trees (snags) due to natural tree mortality and as a result of the impact of exogenous factors. Carbon accumulated in these dead trunks is excluded from the fast turnover due to low rate of wood decomposition, so that snags can be considered as a pool of organic carbon with a slow rate of its return to the atmosphere. We estimated stock of snags on 54 sample plots, which represent the main types of forest ecosystems in the northern and middle taiga of Central Siberia. In the middle taiga, stock of snags varied from up to 7 m3 ha-1 in Siberian spruce forests to 20-42 m3 ha-1 in Scots pine forests. Larch forests in the northern taiga had the similar stock of snags as larch forests in the middle taiga despite significantly higher growing stock in the later. Snags contributed from 4 to 19% to the total stock of woody biomass in studied forests. This study indicated the significance of snags and can be used to estimate carbon budget of forest ecosystems of the region.

Evaluating the Differenced Normalized Burn Ratio for Assessing Fire Severity Using Sentinel-2 Imagery in Northeast Siberian Larch Forests

Fire severity is a key fire regime characteristic with high ecological and carbon cycle relevance. Prior studies on boreal forest fires primarily focused on mapping severity in North American boreal forests. However, the dominant tree species and their impacts on fire regimes are different between North American and Siberian boreal forests. Here, we used Sentinel-2 satellite imagery to test the potential for using the most common spectral index for assessing fire severity, the differenced Normalized Burn Ratio (dNBR), over two fire scars and 37 field plots in Northeast Siberian larch-dominated (Larix cajanderi) forests. These field plots were sampled into two different forest types: (1) dense young stands and (2) open mature stands. For this evaluation, the dNBR was compared to field measurements of the Geometrically structured Composite Burn Index (GeoCBI) and burn depth. We found a linear relationship between dNBR and GeoCBI using data from all forest types (R2 = 0.42, p < 0.001). The dNBR performed better to predict GeoCBI in open mature larch plots (R2 = 0.56, p < 0.001). The GeoCBI provides a holistic field assessment of fire severity yet is dominated by the effect of fire on vegetation. No significant relationships were found between GeoCBI components (overall and substrate stratum) and burn depth within our fires (p > 0.05 in all cases). However, the dNBR showed some potential as a predictor for burn depth, especially in the dense larch forests (R2 = 0.63, p < 0.001). In line with previous studies in boreal North America, the dNBR correlated reasonably well with field data of aboveground fire severity and showed some skills as a predictor of burn depth. More research is needed to refine spaceborne fire severity assessments in the larch forests of Northeast Siberia, including assessments of additional fire scars and integration of dNBR with other geospatial proxies of fire severity.

FEATURES OF THE CONTENT OF CHEMICAL ELEMENTS IN THE CONIFEROUS LARCH GMELINA IN THE AR-EA OF THE UDOKAN COPPER DEPOSIT

The article presents materials for the study of the content of chemical elements in the coniferous larch Gmelina (Larix gmelinii (Rupr.) Rupr.) family Pinaceae (syn.: Larix dahurica Turcz. ex Trautv., Larix amurensis Beissn.), growing in the high-altitude region of the North of the TRANS-Baikal territory, near the Udokan copper Deposit. The purpose of the research is to assess the concentration of a number of chemical elements in high-altitude and permafrost soils, while preparing the territory of the copper Deposit for exploitation. Selection of larch plant samples was carried out in the types of larch forests widely distributed in the research area, in June 2011. The analysis of pine needles samples was performed according to approved methods using modern instruments and equipment in the laboratory of Institute of Natural Resources, Ecology and Cryology SB RAS. It was found that in General L. Gmelin needles have a low concentration of chemical elements, which are arranged in the following sequence: Mg> Sr> Al> Ba> Fe > Ti> Ni> Cu> Mn> Hg> Zn> V> Ag> Cr> Pb> Cd> Sb> Co> Se> As. At the same time, mercury is the only element whose concentration in larch conifers is much higher, 3.8 times, than that of land plants. The article presents a correlation table of the interaction of chemical elements. The table shows that titanium, aluminum, zinc, and silver have a greater effect on the content of chemical elements in conifers. The results presented in the article were obtained in the studied area for the first time. It is important to use the results of this work to monitor environmental pollution, to take into account when using larch to obtain medicinal substances, and to increase the productivity of forest plantations. Further research in this area may be related to other areas of distribution of larch forests, geochemical assessment of the region.