Dendroarchaeology Potential in Various Natural Areas in West Siberia

Scientists face with many limitations that affect the success of dendrochronological dating working with archaeological (architectural) sites in Western Siberia. Here we analysed 134 sites and carried out the existing limitations of the method in different natural areas. As a result, a connection between the efficiency of dendrochronological dating and the physical and geographical conditions of sites was found. Created algorithm allowed to assess the potential of dendrochronology for the forest-steppe, taiga and forest-tundra areas of Western Siberia. The scientific results presented in the article can be used to solve the problems of chronology and periodization of archaeological and architectural sites of Western Siberia, as well as to increase the overall efficiency of the application of the dendrochronological method.

Изменение сукцессионных систем палеофитоценозов на границе межледниковья и ледниковья позднего эоплейстоцена в пыльцевой записи оз. Эльгыгытгын (Центральная Чукотка)

Lake El'gygytgyn is located beyond the Arctic Circle in Chukotka at 67°30' N, 172°05' E and formed following a meteorite impact that occurred 3.6 million years ago (core interval 45.79-43.65 m). In its sediments, 5 palinologic zones are distinguished; they reflect changes in paleosuccessional systems and are consistent with MIS 33, 32, and 31 (1.114-1.062 mya). During warmings, thickets of birch trees and alder were widely spread. Cliseries, caused by macroclimate changes in cold substages, are characterized by a significant reduction in tree and shrub vegetation as well as by expansion of the arctic and subarctic tundras. Grass tundras dominated and were replaced by forest tundra communities in the valleys of the Anadyr Plateau surrounding the lake. The most abrupt change of phytocenosis succession systems is observed at the border of 32 and 31 isotopic stages. The succession processes are primarily expressed in a sharp increase of birch-shrub communities in the vegetation cover and in the appearance of late succession edificators (Carpinus, Corylus, Myrica, Quercus) forming forest climax associations.

Laser Scanning and Aerial Photography with UAV in Studying the Structure of Forest-Tundra Stands in the Khibiny Mountains

Studying the structure of stands is a key point in assessing the role of trees in carbon deposition. Information on the spatial structure of ground vegetation at the upper treeline is still insufficiently presented in modern studies. High resolution remote sensing can provide important data to understand the properties and dynamics of vegetation in these conditions. We test the applicability of ground-based mobile laser scanning of the terrain and aerial photography for the rapid and high-precision assessment of the characteristics of tree stands in the forest-tundra ecotone. We obtained canopy height models (CHMs) of the forest and supplemented them with aerial photographs of the research area on the southeastern slope of the Khibiny Mountains. Using CHMs we have delineated boundaries of tree crowns. The height and projection area were determined for each tree. The first characteristic obtained by laser scanning was compared to the heights of the same trees estimated by field measurements. This was done for the purposes of verification. The comparison revealed that laser scanning data allow to set heights closest to field measurements in case the heights are determined by the maximum values of brightness of pixels of CHMs with manual correction of values when outliers are detected (R2 = 0.84). Since manual correction of outliers is time-consuming, we proposed a way to automate the measurements by determining tree heights using the sum of the average value of pixel brightness and the standard deviation multiplied by 2.5 (R2 = = 0.79). We compared the area characteristics of the stands obtained by laser scanning and the unmanned aerial vehicle (UAV) photography. Thus, we obtained detailed information on the spatial location and size of 4424 trees in an area of about 10 ha and compared the results of measuring tree characteristics obtained by different methods. It was also found that with increasing height from 290 to 425 m above sea level on the studied slope, the average height of stands decreases gradually from 4.5–5.0 to 1.1–1.6 m with small fluctuations (0.2–0.4 m), while the density of stands changes from 4620–5860 to 145 m2/ha in a non-linear way.

Zonal aspects of the influence of forest cover change on runoff in northern river basins of Central Siberia

Background Assessment of the reasons for the ambiguous influence of forests on the structure of the water balance is the subject of heated debate among forest hydrologists. Influencing the components of total evaporation, forest vegetation makes a significant contribution to the process of runoff formation, but this process has specific features in different geographical zones. The issues of the influence of forest vegetation on river runoff in the zonal aspect have not been sufficiently studied. Results Based on the analysis of the dependence of river runoff on forest cover, using the example of nine catchments located in the forest-tundra, northern and middle taiga of Northern Eurasia, it is shown that the share of forest cover in the total catchment area (percentage of forest cover, FCP) has different effects on runoff formation. Numerical experiments with the developed empirical models have shown that an increase in forest cover in the catchment area in northern latitudes contributes to an increase in runoff, while in the southern direction (in the middle taiga) extensive woody cover of catchments “works” to reduce runoff. The effectiveness of geographical zonality in regards to the influence of forests on runoff is more pronounced in the forest-tundra zone than in the zones of northern and middle taiga. Conclusion The study of this problem allowed us to analyze various aspects of the hydrological role of forests, and to show that forest ecosystems, depending on environmental conditions and the spatial distribution of forest cover, can transform water regimes in different ways. Despite the fact that the process of river runoff formation is controlled by many factors, such as temperature conditions, precipitation regime, geomorphology and the presence of permafrost, the models obtained allow us to reveal general trends in the dependence of the annual river runoff on the percentage of forest cover, at the level of catchments. The results obtained are consistent with the concept of geographic determinism, which explains the contradictions that exist in assessing the hydrological role of forests in various geographical and climatic conditions. The results of the study may serve as the basis for regulation of the forest cover of northern Eurasian river basins in order to obtain the desired hydrological effect depending on environmental and economic conditions.

Remotely-sensed trends in vegetation productivity and phenology during population decline of the Bathurst caribou herd

The Bathurst caribou herd declined from ~349,000 animals in 1996 to ~8,200 in 2018. Climate-driven changes to tundra and boreal vegetation is one hypothesis for the decline. We modeled and mapped annual productivity and phenology across the herd’s range using enhanced vegetation index (EVI) data derived from a MODIS time series spanning 2000-2017. Maximum annual EVI, growing season length, and time-integrated EVI increased significantly on 16%, 18%, and 49% of the core annual range, respectively. Trends towards longer growing seasons were driven entirely by earlier spring green-up and, along with time-integrated EVI, were most prevalent in tundra regions. Trends in forested regions were overwhelmingly related to the influence of forest fires, which burned more than half of the range below the forest-tundra ecotone since 1965. These trends suggest that climate-driven changes in production and phenology have occurred in the tundra and forest-tundra portions of the range and could have contributed to the recent herd decline. However, the trends may also be a result of herd decline itself, given the loss of this large herbivore from the landscape. Elucidating cause and effect will require explicit analysis of interactions between climatic variables, herd dynamics, and vegetation change, complemented by comprehensive field investigations.