Developing models that explain CO2 release during the decomposition of dead stems and woody debris requires an understanding of the hierarchy of factors controlling this process. The aim of this study was to evaluate the main probable drivers of variation in CO2 emission rates during the decomposition of downed spruce and fir stems at a single dark-coniferous forest site in the Middle Urals. CO2 flux was measured by the closed-chamber method on large fragments of woody debris of Picea obovata and Abies sibirica at different decomposition stages. During the 2022–2024 growing seasons, 906 CO2 flux measurements were obtained in 17 measurement campaigns. CO2 emission activity was analyzed in relation to the following factors: (1) air temperature at the time of measurement; (2) year (growing season); (3) calendar month; (4) topographic position of the sample plot; (5) tree species; (6) decomposition stage; and (7) fungal species recorded on the stem, only for stage II deadwood. Significant predictors were selected using the Akaike information criterion. The following components of variation were found to be the most important for explaining CO2 emission activity from woody debris: (1) air-temperature-related variation: emissions increased by 3.9 C–CO2 mg/m2/h for each 10°C increase within the range from 0 to 30°C; (2) temporal variation, including variation among growing seasons, with the mean CO2 flux ranging from 20 to 24 C–CO2 mg/m2/h in different growing seasons, and within-season variation, with values ranging from 16 to 25 C–CO2 mg/m2/h in different months; and (3) variation associated with the stage of deadwood decomposition, with values ranging from 17 to 25 C–CO2 mg/m2/h across decomposition stages. These results emphasize the value of long-term monitoring for understanding the hierarchy of factors that affect CO2 emission activity from woody debris in forest ecosystems.
The response of the bank vole (Clethrionomys glareolus Schreber, 1780) population to differences in the distribution density of coarse woody debris (CWD) in its microhabitats was studied over a ten-year period (2015–2024) in the Visim Nature Reserve (Middle Urals, Sverdlovsk oblast) in biotopes differing in the degree of disturbance caused by natural catastrophic events, namely windfall and fire. The total density of CWD and the distribution density of individual size categories were analyzed in biotopes disturbed by windfall and two fires, by windfall and one fire, and partially by windfall and one fire. These biotopes were compared with a biotope unaffected by natural catastrophic disturbances. It was found that bank vole microhabitats differing in the degree of natural disturbance also differed in the distribution density of coarse woody debris and in the species response to CWD under different biotopic conditions. In the most severely disturbed biotopes, the abundance of Cl. glareolus was not associated with coarse woody debris. In the partially disturbed habitat and in the habitat unaffected by windfall and pyrogenic impacts, the density of coarse woody debris affected the population abundance indices of the bank vole.
Data on the diet of juvenile muksun Coregonus muksun (Pallas, 1814) reared in cages placed in a channel in the lower reaches of the Taz River have been analyzed. It has been established that, in addition to artificial feed, juveniles consume zooplankton and zoobenthic organisms that drift into the cages. Artificial feed is shown to constitute the main component of the food bolus in juvenile muksun, accounting for 74.6
The spatial synchronicity of the abundance dynamics of small mammals from three localities in the Middle Urals and the abundance dynamics of the bank vole from two localities in the European part of Russia were studied. Spatial synchrony of abundance dynamics was revealed both between samples of small mammals and between samples of bank voles. For three samples of small mammals it was established the influence of such an atmospheric circulation index as the June Atlantic Multidecadal Oscillation Index (AMO-VI) on the dynamics of their abundance. For three samples of the bank vole, the influence of such an atmospheric circulation index as the December index of the North Atlantic Oscillation (NAO-XII) on the dynamics of their abundance was revealed. It is known that the AMO and NAO circulation indices can influence the atmospheric circulation in the Atlantic-European sector up to the Southern Urals. We have established that circulation indices, within the limits of their influence, can cause spatial synchronization of abundance dynamics both at the species level and in small mammals.
The morphological diversity of the channel relief of small mountain rivers of Sikhote-Alin was established, caused by the specific impact of dense woody vegetation on the intensity of horizontal and vertical deformations of the channels. The role of large trees in the spatial stability of river beds, the structure of stretches and riffles, and the combination of areas with sediments of different granulometric compositions has been revealed. The causes and mechanism of furcation of the channels of mountain rivers in the region, caused by the formation of small blockages consisting of several large trees, are considered. Based on the analysis of the distribution of current velocities, depths, and composition of bottom sediments on the adjacent elements of the channel relief, the diversity of habitat conditions for river hydrobionts is shown. Small streams in mountain-taiga regions, when the channel flow interacts with trees growing and lying in the river, significantly increase the heterogeneity of the channel, contributing to a sharp differentiation of various ecological niches for aquatic organisms. Thus, trees in the beds of small rivers can be considered as ecosystem engineers that contribute to the formation and stabilization of aquatic habitats.
