The bait-lamina test (BLT) is a widely used method for assessing the feeding activity of soil detritivores. However, one of its limitations is the ambiguity in the interpretation of results, as it is difficult to determine which taxa or size groups consumed the bait. To address this issue, we propose a modification of the BLT called the differential BLT, which allows for the estimation of the contribution of macrofauna to the total feeding activity of soil detritivores. In the differential BLT, the size of the holes is reduced to prevent bait ingestion by macrofauna. The values obtained from the large holes represent the bait consumption by all groups, while the difference between values obtained from large and small holes is attributed to macrofauna alone. Through a laboratory experiment with defaunated soil subsequently inoculated with earthworms and using the strips with various hole sizes, we identified the threshold aperture size of 0.2-0.3 mm that excludes earthworms from the bait. In an experiment with laboratory-cultured enchytraeids, we demonstrate that these aperture sizes do not prevent bait consumption by mesofauna. We also conducted a field experiment in the southern taiga coniferous forests, where we verified the applicability of the differential BLT in situ and estimated that macrofauna contributes two-thirds to the total feeding activity. The partitioning of the total feeding activity of soil detritivores using the differential BLT can be a valuable tool for soil ecologists to assess the functioning of below-ground animal communities.

The bait-lamina test (BLT) is widely adopted for assessing the feeding activity of soil detritivores. The downside of the BLT is that it leads to ambiguity in the interpretation of results; it is unclear which taxa or, at least, which size groups consumed the bait. We propose a novel differential BLT to partition the individual contribution of macro-detritivores (earthworms, dipteran larvae, millipedes, woodlice, and mollusks) and meso-detritivores (enchytraeids, collembolans, and oribatids) to the total feeding activity. The main idea of the differential BLT is alternating large and small apertures within the same strip. The miniaturization of the holes mechanically prevents bait ingestion by macrofauna. Thus, the bait losses from small holes estimate only the mesofauna feeding activity, while the values in large ones represent the bait consumption by both groups. The effects of competition between macrofauna and mesofauna were negligible, therefore, the difference between values for large and small holes is attributed to macrofauna alone. In the laboratory experiment with defaunated soil subsequently inoculated with earthworms, and using the strips with various hole sizes, we identified the threshold aperture size (<0.4 mm) to exclude earthworms from the bait. In the experiment with laboratory cultured enchytraeids, we show these aperture sizes did not prevent bait consumption by meso-detritivores. In the field experiment in the southern taiga coniferous forests, we verified the applicability of the novel differential BLT in situ and estimated the contribution of macrofauna to the total feeding activity as two-thirds. After testing many variants, we propose the following modifications to strips: add three 0.3 mm width rectangle apertures to the left, right, and top of each standard round hole. Differential BLT allows researchers to partition the macro- and mesofauna contributions to the total feeding activity of soil detritivores, providing a valuable tool for soil ecologists performing assays of below-ground invertebrate communities.

Since the mid-2000s, long-term monitoring of various components of natural ecosystems under conditions of industrial pollution has been carried out in the Southern Urals. As a part of these monitoring programmes, the data on various components of biota in different biotopes, collected with different methods and in different time intervals, continue to be gathered. In addition, data collected through these monitoring programmes can also be used to study the local biodiversity of non-polluted areas.In 2012, in the vicinity of the Karabash Copper Smelter, a study of communities of small mammals was carried out, considering the heterogeneity of their habitats. Within the framework of this project, we presented a detailed description of the state of woody vegetation in the study area.The dataset (available from the GBIF network at https://www.gbif.org/dataset/61384edd-2d0a-437b-8cf0-ff4d2dfcc0da) includes the results of an assessment of the woody vegetation biomass at seven habitats (pine, birch and floodplain forests, reed swamp, sparse birch stand, marshy meadow and dump of household waste) of areas with different levels of industrial pollution in the vicinities of the Karabash, the Southern Urals. Karabash Copper Smelter (KCS) is one of Russia's most significant point polluters; the main components of its emissions are heavy metals, dust and sulphur dioxide. Parameters of woody vegetation (diameter at breast height, diameter at root collar level and biomass) were estimated for seven forest elements (forest stand, subcanopy (undergrowth and underwood), half-dead tree of a forest stand and four types of coarse woody debris (downed bole, fragment of downed bole, standing dead tree and stump)) at 41 sampling plots (20 at unpolluted and 21 at polluted areas) and 165 subplots (81 and 84, respectively). The dataset includes 411 sampling events (estimation events of the forest elements at sampling plots and subplots), corresponding to 5786 occurrences (estimations of the woody vegetation components) observed during July 2012. For most woody vegetation components (72%), an estimate of the above-ground phytomass is given. For each sampling event, information on the presence or absence of woody vegetation species at the considered habitats is provided (a total of 1479 occurrences with status "absent"). The dataset can be used for environmental monitoring, sustainable forest management, modelling forest productivity considering global changes, studying the structure and biodiversity of forest cover and assessing forests' carbon-sequestration capacity. In addition, the dataset provides information about different forest ecosystems under the influence of strong industrial pollution.

The bait-lamina test is one of the few available methods for measuring the functional activity of soil animals, which was standardized for soil health assessment by ISO 18311. The bait consumption is measured visually on discrete scales. A two-point scale (0 or 1) is used more often, but the threshold for bait consumption scores varies from study to study: 1 point is assigned either to a hole that has been perforated to any extent, or to a hole that has been at least half perforated, or to a fully empty hole. Less often, a three-point scale (0, 0.5, and 1) or a five-point scale (0, 0.25, 0.5, 0.75, and 1) can be used. We investigated how much the use of different scales can influence statistical inferences. We have established that a point on a five-point scale is directly proportional to the proportion of the mass consumption of bait, so in this scale the value of feeding activity is an acceptable surrogate for the bait consumption rate. We analyzed outcomes of the bait-lamina test for 7 measurement rounds at the control area and an area highly polluted with metals near the copper smelter. We assumed the most accurate five-point scale to be the reference and compared it to six less precise scales with fewer points (two three-point and four two-point scales). The difference between the reference and such rough scales depends on the percentage of intermediate points (0.25, 0.5, and 0.75). It turned out that intermediate values are by no means rare (from 11% to 100% of all non-zero values), and in the polluted area they are almost twice as common as in the control area (66% and 28%, respectively). Because of this, the relative difference between the reference scale and rough scales is 2–4 times greater at the polluted site than at the control site. This can lead to a bias in the effect size index: for the rough scales, the log Response Ratio can either double or decrease by one-third relative to the reference scale. This increases the probability of type I and II errors in statistical hypothesis testing. Thus, the outcomes of the bait-lamina test are not invariant relative to the measuring procedure. The three-point scale and ISO 18311 two-point scale are the least biased relative to the reference scale. The use of other rough scales carries a risk of artifacts and should be avoided.

Coarse woody debris (CWD) provides food and shelter to a large proportion of forest biota and is considered vital for biodiversity during periods of harsh weather. However, its importance in long-term stressed ecosystems remains largely unknown. In this work, we explored the contribution of CWD to fungal diversity along the gradient of boreal forest degradation caused by 77 years of heavy industrial emissions. We analyzed the diversity and composition of fungi in 270 samples of well-decayed Picea abies and Abies sibirica logs, as well as forest litter both adjacent to and distant from the logs. Compared with forest litter, the wood had higher water content and possessed substantially lower concentrations of heavy metals, which suggests its potential favorability for biota in polluted areas. The pollution-induced loss of fungal diversity in forest litter reached 34% and was stronger in the microhabitats not influenced by CWD. Meanwhile, wood fungal communities lost less than 10% of their total richness and even increased in alpha diversity. These processes led to the diversity and compositional convergence of fungal communities from different microhabitats and substrates in polluted areas. Despite this, the importance of wood and CWD-influenced microhabitats for fungal diversity maintenance was low. Apart from wood-associated fungi, the taxa whose diversity increased in the wood of polluted areas were ectomycorrhizal fungi and eurytopic soil saprotrophs (Mucoromycota, Mortierellomycota, Eurotiomycetes, and Helotiales) that easily tolerate highly toxic litter. Within the majority of pollution-sensitive soil saprotrophic groups, only terricolous Tricholomataceae benefit from CWD as microrefugia. Upon considering the ecological variability within low-rank taxa, the importance of decayed logs as safe sites can be high for certain soil-inhabiting fungal groups in polluted areas.

The fertility and viability of pollen grains of two morphological forms of Taraxacum officinale Wigg. s.l. were estimated. These forms compose common coenopopulations growing in various coenotic and edaphic conditions. The forms studied possess developed gynoecia-a large number of fertile pollen grains capable of germinating under certain temperature conditions. This fact points to the amphimictic properties of the plants. Comparison of the data on the fraction of fertile pollen grains and seed productivity allows assuming that some seeds develop without fertilization. This can be considered as evidence of the apomictic properties of plants. Therefore, the presence of facultative apomixis in the species considered was confirmed indirectly in our work. The fertility of pollen grains was shown to be a characteristic of the male gametophyte that was more environmentally dependent than its viability. Under favorable conditions, the share of fertile pollen grains in f. dahlstedtii and f. pectinatiforme differ insignificantly. Under stress, the differences between the dandelion forms by this index increase. This can be considered as a mechanism of adaptation to adverse environmental factors. The revealed differentiation of the morphological forms of dandelions by the index of pollen grain fertility suggests that edaphic and coenotic stresses increase the differences between them in the degree of apomictic and amphimictic properties. The morphological forms of dandelions, by realizing two reproductive strategies under stress, ensure both the abundance and the genetic heterogeneity of the coenopopulations. The morphological forms studied do not differ in the proportion of viable pollen grains. This index increases in the gradient of coenotic competition only to a certain extent, which can be considered as a manifestation of the properties of the facultative apomict.

Measurement of feeding activity of soil saprophages by the consumption of bait made of plant material—the bait-lamina test—is used for solving many problems of functional ecology. It is important to choose the correct exposure duration of bait to obtain unbiased data. This requires the analysis of time dependence of bait consumption, however, it has not been performed for technogenically polluted soils. We have compared two study sites of spruce–fir forest in the area affected by long-term emissions of the Middle Ural Copper Smelter: background (30 km away from the plant) and strongly polluted by heavy metals (1 km away). The feeding activity was evaluated on days 3, 6, 9, 12, and 15. The dependence of the consumed bait portion on the exposure duration sharply differs at the background and polluted sites: it is clear linear in the period from the third till the twelfth day on the former and is absent on the latter. This is related to the difference not only in the abundance, but also in the species composition of saprophages. The pollution effect is the most pronounced on the ninth day of exposure, and deviations from this period for more than two days both to the higher and smaller sides are undesirable. The recalculations of the original values should be carefully applied: the linear interpolation may be used to recalculate the activity in the background area to adjust it to the exposure duration in the polluted site, but not vice versa.

Boreal forests store a large portion of the planet's terrestrial carbon. A significant portion of this carbon is stored in coarse woody debris (CWD). Industrial pollution greatly inhibits organic matter decomposition and thus enhances carbon sequestration in the soil. However, lithe is known about the decomposition of CWD in polluted areas. In this work, by means of dendrochronological cross-dating, we determined the death dates of 90 downed Siberian spruce (Picea obovata Ledeb.) and Siberian fir (Abies sibirica Ledeb.) logs in the latest stages of decay in an undisturbed boreal forest and in two industrially polluted forests with 10-fold and more than 100-fold higher copper content in the soil. We found that, in the unpolluted area, the mean halftime of fir and spruce decomposition was 26 years and 23 years, respectively. In polluted areas, this time increased by approximately 16 years for fir and 5 years for spruce. Based on an exponential decay model, pollution caused a 16-60% decrease in the wood decomposition rate constant. Copper concentrations in CWD were similar between tree species and were about 10-20 times lower than in the surrounding soil. These values are comparable with the concentrations tolerated by fungi in laboratory tests, indicating that heavy metal excess cannot be considered a primary inhibitor of wood decomposer activity. The greater pollution-induced delay in the decomposition of fir trees, which are lighter and smaller in size than spruce trees, suggests that dead tree leaning is an important factor in the wood decomposition slowdown in polluted areas where stand density increases due to intensive forest regeneration because of the reduced competition of tree seedlings with toxically inhibited herbaceous vegetation. We also evaluated dynamic probing as a rapid, low-cost, and nondestructive surrogate of wood density measuring. Dynamic probing performed in the field on heavily decayed CWD explained about 40% of wood density variability and about 70% of variability when taking into account the gravimetrically measured wood moisture content. With negligible modifications, this method can be applied in the field monitoring of wood density loss. For the purpose of between-study comparisons, we recommend transforming the widely used measure of penetration depth to specific resistance to penetration and encourage the elaboration of reference tables that relate specific resistance to penetration and wood density for different tree species across distinct ecological zones.

This paper is concerned with the phytomass of herbaceous phytocenoses growing in anthropogenically impacted areas in the Middle Urals at different stages of succession along the heavy-metal pollution gradient. Cenoses of young soils of dumps have less resistance and higher sensitivity to changes in weather factors, in contrast to the phytocenoses of the deposits. It is shown by general regression models that the epiterranean and subterranean biomass of cenoses on technozems depends on Selyaninov’s hydrothermic coefficient for September and the amount of precipitation in October–November of the previous year and in January–May of the current year. The degree of this dependence for cenoses under research is determined by edaphic conditions that affect the species diversity and dominance structure.

The feeding activity of soil saprophages was assessed by the bait-lamina test in pine forests of native origin within the city of Yekaterinburg and its suburbs in 2011–2013. Four areas, drastically different in terms of manifestation of two main factors—urbanization and recreation loads—were compared. The effect of urbanization on the feeding activity of soil saprophages was both positive and negative. Recreation loads, as a rule, adversely affected the feeding activity. Probable mechanisms responsible for the influence of a large city environment on the feeding activity of soil saprophages are discussed.

We have studied the share of coarse woody debris (CWD) reserves at different decay classes in the spruce and fir woodland within the impact area of aerial pollution from the Middle Ural Copper Smelter (Revda, Sverdlovsk oblast). Control and impact areas slightly differ in total reserves and number of trunks of CWD (sum of standing and fallen dead wood). However, the number of CWD tends to grow in proximity to the plant. The mechanisms involved in CWD-reserve formation differ between impact and control sites. A larger number of relatively thin trunks prevail in CWD reserves of impact sites when compared to the lower number of thick trunks at control sites. The CWD share of 30% in the total number of dead and living trees did not differ across pollution loads. However, the share of CWD reserves in total stock is 1.9 times higher near the plant than at the control site. The share of logs at the initial stages of decomposition (first and second decay classes) is 3.2 times higher in terms of CWD number and 4.2 times higher in terms of CWD reserves than at the control sites. This points to the strong inhibition of CWD decomposition. The pattern of decay classes of all sizes of fallen trees significantly differs in volume across pollution zones.

The influence of industrial pollution on mortality values (dead fallen wood and dead standing trees) and its distribution by degrees of decomposition were investigated in spruce-fir forest stands in the vicinity of the Middle Ural copper smelter (the city of Revda, Sverdlovsk region). The total mortality and mortality in each size category did not depend on the distance to the source of pollution. At the same time, the amount of dead fallen wood was significantly greater (1.9 times) in the polluted area (2 and 4 km from the smelter) as compared with the background territory (30 km from the smelter). Mortality proportion out of the total number of the trees (both live and dead) did not differ significantly between the sites, although this parameter tended to increase nearer the smelter. The distribution of mortality by size categories revealed significant differences between background territory and site with average level of contamination, as well as background territory and highly contaminated site. Observed differences are associated with an increased proportion of lesser mortality near the smelter (by 15 % and 12 % as compared with areas of background and middle levels of contamination, respectively), as well as because of double-declining of medium- and large-sized mortality near the smelter. The distribution of the living tree stands by size categories also has a connection with level of contamination. The average diameters of the living tree stand and the elements of coarse woody debris (dead fallen wood and dead standing trees) do not differ significantly between sites with different levels of contamination. For the small-sized dead fallen wood, the proportion of weakly decomposed stems increased with the level of pollution, while proportion of strongly decomposed stems decreased. The distribution of medium- and large-sized dead fallen wood on the stages of decomposition does not vary between sites with different levels of pollution.

Boreal coniferous forests act as an important sink for atmospheric carbon dioxide. The overall tree carbon (C) sink in the forests of Europe has increased during the past decades, especially due to management and elevated nitrogen (N) deposition; however, industrial atmospheric pollution, primarily sulphur dioxide and heavy metals, still negatively affect forest biomass production at different spatial scales. We report local and regional changes in forest aboveground biomass, C and N concentrations in plant tissues, and C and N pools caused by long-term atmospheric emissions from a large point source, the nickel–copper smelter in Monchegorsk, in north-western Russia. An increase in pollution load (assessed as Cu concentration in forest litter) caused C to increase in foliage but C remained unchanged in wood, while N decreased in foliage and increased in wood, demonstrating strong effects of pollution on resource translocation between green and woody tissues. The aboveground C and N pools were primarily governed by plant biomass, which strongly decreased with an increase in pollution load. In our study sites (located 1.6–39.7km from the smelter) living aboveground plant biomass was 76 to 4888gm−2, and C and N pools ranged 35–2333gCm−2 and 0.5–35.1gNm−2, respectively. We estimate that the aboveground plant biomass is reduced due to chronic exposure to industrial air pollution over an area of about 107,200km2, and the total (aboveground and belowground) loss of phytomass C stock amounts to 4.24×1013gC. Our results emphasize the need to account for the overall impact of industrial polluters on ecosystem C and N pools when assessing the C and N dynamics in northern boreal forests because of the marked long-term negative effects of their emissions on structure and productivity of plant communities.

The state of tree and ground vegetation layers in spruce-fir forests around the Middle Ural Copper Smelter (Revda, Sverdlovsk oblast) has been repeatedly evaluated in 25 permanent sampling plots at 5- to 10-year intervals (1989–2013). The results have been used to characterize the dynamics of plant communities in the period of reduction of emissions from the smelter. Although the annual amount of emissions has decreased from 150–225 × 103 t in the 1980s to less than 5 × 103 t after 2010, the vegetation in the impact zone (1 and 2 km from the smelter) remains severely suppressed: the trees continue to die off, and the diversity of ground vegetation layer is very low. In zones with low and moderate levels of industrial pollution (30 and 4–7 km from the smelter), natural factors associated with windfall disturbance after the 1995 windstorm with snow have played a more important role in the dynamics of forest communities than the reduction of emissions itself.