Coniferous Forest Ecosystems Research Articles

Dynamics of Water Use Efficiency of Coniferous and Broad-Leaved Mixed Forest in East China

The aim of our study is to understand the patterns of variation in water use efficiency (WUE) in coniferous and broad-leaved mixed forest ecosystems across multiple scales and to identify its main controlling factors. We employ the eddy covariance method to gather data from 2017, 2018, and 2020, which we use to calculate the gross primary productivity and evapotranspiration of these forests in East China and to determine WUE at the ecosystem level. The mean daily variation in WUE ranges from 4.84 to 7.88 gC kg−1 H2O, with a mean value of 6.12 gC kg−1 H2O. We use ridge regression analysis to ascertain the independent effect of environmental factors on WUE variation. We find that WUE responds differently to environmental factors at different time scales. In mixed conifer ecosystems, temperature and relative humidity emerge as the most significant environmental factors influencing WUE variability. Especially at the seasonal scale, temperature and relative humidity can explain more than 51% of the WUE variation. Our results underscore the varied effects of environmental factors on WUE variation across different time scales and aid in predicting the response of WUE to climate change in coniferous and broad-leaved mixed forest ecosystems.

Tracking effects of extreme drought on coniferous forests from space using dynamic habitat indices

Terrestrial ecosystems such as coniferous forests in Central Europe are experiencing changes in health status following extreme droughts compounding with severe heat waves. The increasing temporal resolution and spatial coverage of earth observation data offer new opportunities to assess these dynamics. Dense time-series of optical satellite data allow for computing Dynamic Habitat Indices (DHIs), which have been predominantly used in biodiversity studies. However, DHIs cover three aspects of vegetation changes that could be affected by drought: annual productivity, minimum cover, and seasonality. Here, we evaluate the health status of coniferous forests in the federal state of Hesse in Germany over the period 2017–2020 including the severe drought year of 2018 using DHIs based on the Normalized Difference Vegetation Index (NDVI) for drought assessment. To identify the most important variables affecting coniferous forest die-off, a series of environmental variables together with the three DHIs components were used in a logistic regression (LR) model. Each DHI component changed significantly across non-damaged and damaged sites in all years (p-value 0.05). When comparing 2017 to 2019, DHI-based annual productivity decreased and seasonality increased. Most importantly, none of the DHI components had reached pre-drought conditions, which likely indicates a change in ecosystem functioning. We also identified spatially explicit areas highly affected by drought. The LR model revealed that in addition to common environmental parameters related to temperature, precipitation, and elevation, DHI components were the most important factors explaining the health status. Our analysis demonstrates the potential of DHIs to capture the effect of drought events on Central European coniferous forest ecosystems. Since the spaceborne data are available at the global level, this approach can be applied to track the dynamics of ecosystem conditions in other regions, at larger spatial scales, and for other Land Use/Land Cover types.

Effects of litter and root inputs on soil CH4 uptake rates and associated microbial abundances in natural temperature subalpine forests

Climate change altered the quantities of aboveground plant litter and root inputs, but the effects on soil CH4 uptake rates and underlying mechanisms remain unclear. To investigate these factors, a three-year detritus input and removal treatment (DIRT) study including six treatments (namely, CK, control; NL, litter removal; DL, double litter; NR, root exclusion; NRNL, root exclusion plus litter removal; and NRDL, root exclusion plus double litter) was conducted in broadleaf and coniferous forest subalpine forest ecosystems. The results showed that both the subalpine forest soils acted as sink for atmospheric CH4 across all treatments, while the broadleaf forest had consistently higher CH4 uptake rates than the coniferous forest. Based on the annual mean values, root exclusion (NR, NRNL and NRDL) significantly decreased soil CH4 uptake rates by 35.9 %, 31.0 % and 43.4 % in the broadleaf forest and 36.7 %, 31.9 % and 40.6 % in the coniferous forest compared with CK treatments, respectively. Meanwhile, the mean soil CH4 uptake rates were significantly reduced by 23.6 % and 17.3 % in the broadleaf forest and the coniferous forest under the DL treatments, respectively; nevertheless, the NL treatment significantly increased soil CH4 uptake rates by 19.68 % and 14.4 %, respectively. The results clearly demonstrated that root exclusion exerted a greater influence on soil CH4 uptake rates than plant litter manipulations. Correlation and redundancy analysis (RDA) revealed that the separation of root exclusion treatments from aboveground plant litter manipulations was based on higher soil water content, NH4+-N and NO3−-N concentrations, and lower DOC (dissolved organic carbon) concentrations and methanotroph pmoA gene abundance. The results suggest that future alterations in aboveground plant litter and root input, particularly a reduction in root input, can exert a stronger influence on regulating soil CH4 uptake than aboveground litter manipulations in subalpine forests with cold and humid climatic conditions in response to future climate scenarios.

CENOTIC ROLE OF INFECTIOUS DISEASES IN ABIES SIBIRICA LEDEB. STANDS IN THE SOUTH CENTRAL SIBERIA

Background. Degradation of Abies sibirica Ledeb.-dominated forests in the South Central Siberia is a reflection of the global trend of coniferous forest ecosystems decline. Nevertheless, the role of infectious diseases in coniferous forests degradation and dieback is often underestimated.
 Research aim. To assess the coenotic role of infectious diseases in fir-dominated stands in the South Central Siberia, considering the differentiation in trees.
 Materials and methods. The research was based on a survey of A. sibirica-dominated forest stands growing in Biryusinsky forest management unit of the Krasnoyarsk Krai government-owned publicly funded “Emelyanovskoye forestry”. Research methods included a detailed (instrumental) forest pathological examination, macroscopic diagnostics of tree diseases, graph analytics and statistical analysis of tree diameter distribution series, evaluation of disease manifestation indicators.
 Results. Stem rot and fir broom rust are typical diseases increasing the risk of windsnap and trees weakening. The prevalence of fir broom rust was over 10%. Rust fungus intermediate hosts in the forest floor determine the degree of damage to a stand. Fir broom rust randomly affected trees of different age and diameters. The bacterial blight in fir forests mainly affected trees of I-II Kraft classes causing their gradual dying. The bacterial blight in the study area was of low infection degree (up to 20%). The most dangerous was the root rot caused by Armillaria mellea s.l. that affected trees of different cenotic roles causing their group dieback.
 Conclusion. Dendropathogenic organisms are an important endogenous factor influencing the state of dark coniferous forests with a predominance of A. sibirica in the South Central Siberia. Their cenotic role is unequal. The most significant are pathogens causing necrosis and cancer diseases, and especially the root pathogen A. mellea, which leads to weakening and dying of a large number of trees of different status in the stand structure.

A dataset of carbon and water fluxes of the boreal forest ecosystem in Huzhong (2014 – 2018)

As an important component of the global carbon pool, boreal forests have attracted much attention in the research on climate change and carbon cycle due to their extreme sensitivity to climate warming. Located in the largest cold-temperate coniferous forest ecosystem nature reserve in China, China Boreal Forest Ecosystem Research Station (Huzhong Station) is one of the member stations of Chinese FLUX Observation and Research Network (ChinaFLUX), which has conducted long-term carbon and water flux observations of boreal forest ecosystems based on eddy covariance techniques since 2006. Following the ChinaFLUX data processing protocols, we collected the carbon and water fluxes and auxiliary meteorological environment observations of the boreal forest ecosystem at Huzhong Station from 2014 to 2018. Processing the data in a standard process, we formed a standardized dataset with four time scales, namely half-hourly, daily, monthly and yearly. The dataset is expected to provide data support for the studies on climate change, boreal forest ecosystem carbon, as well as water and energy balance.

Biomass Models and Ecosystem Carbon Density: A Case Study of Two Coniferous Forest in Northern Hunan, China

The carbon sink capacity of forest ecosystem and its function of mitigating climate change have been confirmed. As two common coniferous species, Cunninghamia lanceolata (Lamb.) Hook. (C. lanceolata) and Pinus elliottii Engelmann (P. elliottii) are widely planted in southern China, and their carbon sink capacity has always been concerning. According to their diameter class, we randomly harvested 42 C. lanceolata trees and 38 P. elliottii trees from our entire study area, measured their carbon concentration, and constructed biomass models with DBH and tree height as variables. The biomass of the tree layer was estimated by measuring the DBH of all trees in the plots, and the biomass and carbon concentration of shrubs, herbs, dead wood and litter in the plot were measured by harvesting them. The results showed that the total biomass in C. lanceolata and P. elliottii plantations were 117.1 and 151.8 t·ha−1; the biomass in the tree layer was 94.7 and 122.9 t·ha−1; and in the other parts was 22.4 and 28.9 t·ha−1, respectively. In addition, the total carbon densities in the C. lanceolata and P. elliottii plantation ecosystems were 166.3 and 198.6 t·ha−1; the carbon densities in the soil were 108.1 and 124.6 t·ha−1; and in the other parts, they were 58.2 and 74.0 t·ha−1, respectively. These results indicate that there are significant differences in total biomass or total carbon storage between the two coniferous forest ecosystems, and net productivity and carbon sink capacity are higher in the P. elliottii plantation ecosystem. This study lays the foundation for the biomass estimation and carbon trading of these two coniferous forests in northern Hunan.

Intracenotic patterns in damage of Abies sibirica Ledeb.-dominated stands by infectious diseases in the south of Central Siberia

Abies sibirica Ledeb.-dominated stands degradation is of special concern. Nevertheless, insufficient attention is paid to the role of pathogens in this process. The aim of the present study is to assess the coenotic role of infectious diseases in fir-dominated stands in the south of Central Siberia. The research was based on a forest pathological examination conducted in A. sibirica-dominated forest stands in the Krasnoyarsk Krai. The cenotic role of the identified diseases is unequal. Stem decay and fir broom rust are typical diseases that weaken trees and induce rotten windsnap accumulation. Fir broom rust randomly affects trees of different age and size. The prevalence of fir broom rust in the studied fir stands reached 10% or more. The most hazard diseases in the studied stands are bacterial soft rot and root rot. Bacterial soft rot damages up to 20% of trees and causes their gradual dieback. The main cause of tree mortality in fir-dominated stands is root rot. The root rot-causing fungi lead to rapid dieback of trees of different cenotic status. In synergy with other factors, root rot acts as a significant endogenous factor in the current reorganization of coniferous forest ecosystems in the south of Central Siberia.

Catchment scale spatial distribution of soil enzyme activities in a mountainous German coniferous forest

Topography features within catchments influence soil properties, nutrient status, microbial dynamics and ultimately enzyme activities. Extracellular soil enzymes are essential for the decomposition of organic substrates and play a central role in global biogeochemical cycles. How topography and soil properties drive the spatial expression of enzyme activities at the catchment scale is still underexplored, especially in coniferous forest ecosystems. This study investigated the activity of four extracellular soil enzymes: β-glucosidase (β-glu), β-cellobiosidase (β-cello), acid phosphatase (pho) and leucine-aminopeptidase (l-leu) in Oh and Ah horizons of a (27 ha) mountainous coniferous forest catchment (Wüstebach, Eifel National Park, Germany). Spatial patterns and "hot spots" of activities of these four enzymes (involved in C-,N-, and P- cycling) were examined in connection to catchment units differing in slope, exposure and soil type (Cambisol vs. Gleysol), and multiple soil parameters (i.e., moisture content, pH, C, N, P, K, Fe, Mn content, C:N, C:P and N:P ratio). Catchment enzyme activities were overall, except for β-cello, significantly higher in the Oh than Ah horizon. Lower β-glu, and l-leu activities were found where more anaerobic soil conditions did occur, e.g., the river valleys (RV). Neither enhanced Oh horizon erosion on steeper Eastern (ES) and Northeastern (NES) slopes nor larger spatial soil nutrients heterogeneity on Northern (NS) and Western (WS) slopes, did significantly affect enzyme activity. Landscape topography did lead to a spatial variation of the activity of the four enzymes examined. The site-specific variation in C-cycling enzymes (β-glu and β-cello) was most marked at drier East, Northeast and Northern slopes, for P-cycling (pho) within the central wetter river valley but was for N-cycling (l-leu) enzyme activity more homogeneously distributed over the whole catchment. Overall, enzyme activities were strongly correlated to soil properties (especially soil moisture and organic carbon), but locations NS (Wüstebach source area) and RV (Wüstebach river flow path) showed less site-specific correlations. Further refinement of site-specific soil and external factors driving spatial distribution of enzyme activities at catchment scales and beyond will help to further tool up this research at larger spatial scales.

Contribution of the synergistic interaction between topography and climate variables to pine caterpillar (Dendrolimus spp.) outbreaks in Shandong Province, China

Outbreaks of the pine caterpillar (Dendrolimus spp.) have substantial impacts on coniferous forest ecosystem structure, distribution, and productivity, as well as the economy. Furthermore, there is emerging evidence that increasing frequencies of fires and windstorms driven by climate change are contributing to more severe pine caterpillar outbreaks. Therefore, there is a need to identify areas susceptible to pine caterpillar outbreaks to apply prevention measures efficiently and facilitate sustainable forest management. This study constructed an integrated index for assessing the susceptibility of forest ecosystems in Shandong Province, China to pine caterpillar outbreaks based on the indicators of mainly forest structure, climate, topography, landform, and soil conditions. This index suggests the risk and susceptibility of a forest area to a pine caterpillar outbreak. In addition, a geodetector model was used to identify the synergistic or antagonistic effects of environmental factors on risk of pine caterpillar outbreak. The results showed that: (1) mountain and hilly areas are more susceptible to pine caterpillar outbreaks, whereas surrounding areas show a medium susceptibility in central and southeastern part of Shandong Province; (2) there was an increasing susceptibility of the study area to pine caterpillar outbreak in the 1990s, 2000s and 2010s; (3) synergism between certain topography and climate variables enhanced the susceptibility of the study area to pine caterpillar outbreaks, including the interaction between elevation and sunshine hours and between slope and humidity. The integrated susceptibility index was shown to perform well in indicating the risk and susceptibility of forest ecosystems to pine caterpillar outbreaks. The present study can act as a reference for forest management within the identification of areas with high susceptibility to pine caterpillar outbreak.

The contribution of forest reserves and managed forests to the diversity of macrofungi of different trophic groups in European mixed coniferous forest ecosystem

We report the first robust estimate of macrofungal assemblages in European mixed coniferous forest to better understand species diversity under two management strategies (managed vs. not managed) and to rate the recovery of forest reserves, transformed from formerly managed stands, to their natural state. Following extensive repeated sampling in three regions of Poland, we found 318 fungal species from different trophic groups. The two forest management strategies showed similar cumulative fungal species richness and values for Shannon, evenness, and Simpson’s dominance indices, suggesting that both management strategies did not generate factors stimulating or limiting species richness and biodiversity. In contrast, site as well as forest management strategy affected the composition of all fungal trophic groups, with site being a stronger influencing factor. Different fungal ecological groups responded differently to environmental drivers, with ectomycorrhizal symbionts and parasites being more tightly linked to tree traits than saprotrophs, which were affected mostly by climate and substrate. Indicator species associated mainly with managed forests comprised predominantly wood-inhabiting fungi. Conservation-relevant species (red-listed in Poland) were noted in both forest reserves and managed forests; however, they predominated in the former. The results indicated a rather slow process of transformation of fungal communities in forest reserves originating from previously managed forests. The major conclusion of this study is that managed forests complement forest reserves in fungal diversity conservation.

How do nitrogen-limited alpine coniferous forests acquire nitrogen? A rhizosphere perspective

Alpine coniferous forest ecosystems dominated by ectomycorrhizal (ECM) tree species are generally characterized by low soil nitrogen (N) availability but stabilized plant productivity. Thus, elucidating potential mechanisms by which plants maintain efficient N acquisition is crucial for formulating optimized management practices in these ecosystems. We summarize empirical studies conducted at a long-term field monitoring station in the alpine coniferous forests on the eastern Tibetan Plateau, China. We propose a root-soil interaction-based framework encompassing key components including soil N supply, microbial N transformation, and root N uptake in the rhizosphere. We highlight that, (i) a considerable size of soil dissolved organic N pool mitigates plant dependence on inorganic N supply; (ii) ectomycorrhizal roots regulate soil N transformations through both rhizosphere and hyphosphere effects, providing a driving force for scavenging soil N; (iii) a complementary pattern of plant uptake of different soil N forms via root- and mycorrhizal mycelium-pathways enables efficient N acquisitions in response to changing soil N availability. Multiple rhizosphere processes abovementioned collaboratively contribute to efficient plant N acquisition in alpine coniferous forests. Finally, we identify several research outlooks and directions to improve the understanding and prediction of ecosystem functions in alpine coniferous forests under on-going global changes.

The Contribution of Forest Reserves and Managed Forests to the Diversity of Macrofungi of Different Trophic Groups in European Mixed Coniferous Forest Ecosystem

The Contribution of Forest Reserves and Managed Forests to the Diversity of Macrofungi of Different Trophic Groups in European Mixed Coniferous Forest Ecosystem

Effect of Climate Change on CO2 Flux in Temperate Grassland, Subtropical Artificial Coniferous Forest and Tropical Rain Forest Ecosystems.

The interactions between CO2 flux, an important component of ecosystem carbon flux, and climate change vary significantly among different ecosystems. In this research, the inter-annual variation characteristics of ecosystem respiration (RE), gross ecosystem exchange (GEE), and net ecosystem exchange (NEE) were explored in the temperate grassland (TG) of Xilinhot (2004–2010), the subtropical artificial coniferous forest (SACF) of Qianyanzhou (2003–2010), and the tropical rain forest (TRF) of Xishuangbanna (2003–2010). The main factors of climate change affecting ecosystem CO2 flux were identified by redundancy analysis, and exponential models and temperature indicators were constructed to consider the relationship between climate change and CO2 flux. Every year from 2003 to 2010, RE and GEE first increased and then decreased, and NEE showed no significant change pattern. TG was a carbon source, whereas SACF and TRF were carbon sinks. The influence of air temperature on RE and GEE was greater than that of soil temperature, but the influence of soil moisture on RE and GEE was greater than that of air moisture. Compared with moisture and photosynthetically active radiation, temperature had the greatest impact on CO2 flux and the exponential model had the best fitting effect. In TG and SACF, the average temperature was the most influential factor, and in TRF, the accumulated temperature was the most influential factor. These results provide theoretical support for mitigating and managing climate change and provide references for achieving carbon neutrality.

Differences in the flow of spruce-derived needle leachates and root exudates through a temperate coniferous forest mineral topsoil

Coniferous forest ecosystems are important pools of soil organic carbon (SOC) in the Northern temperate zone. Needle leachates and root exudates represent a significant input of C to these soils and can differently affect soil C cycling because of their differences in chemistry and stoichiometry. This is the first study to investigate the differences in the flow of dissolved organic C (DOC) in the form of needle leachates, root exudates, and their combination through a forest mineral topsoil. We conducted a 5-month microcosm experiment with ecologically relevant additions of 13C-labelled spruce-derived substrates. The proportion of DOC lost from or incorporated into the mineral soil as microbial biomass or soil fractions (free, occluded by or adsorbed onto mineral particles) as well as differences in the priming effect (PE) caused by the two substrates were assessed.Needle leachates (higher in phenolics and C:N ratio) were less utilized by the microbial community than root exudates but caused a higher PE probably because they lacked sufficient N to satisfy microbial N demands. The addition of either substrates failed to change microbial community composition or SOC content in soil fractions. Most of the substrate C in soil fractions was stabilized by adsorption onto mineral particles. On average, 69% of the substrate C was lost via mineralization; only 0.23% via leaching. The most important C pool related to substrate C gain was the C stored in soil fractions (29%); only 1.7% was stored in the microbial biomass. A consideration of all C gains and losses indicates that the addition of spruce-derived substrates resulted in an average net substrate C retention of 31%.

Resilience of terrestrial and aquatic fauna to historical and future wildfire regimes in western North America.

Wildfires in many western North American forests are becoming more frequent, larger, and severe, with changed seasonal patterns. In response, coniferous forest ecosystems will transition toward dominance by fire‐adapted hardwoods, shrubs, meadows, and grasslands, which may benefit some faunal communities, but not others. We describe factors that limit and promote faunal resilience to shifting wildfire regimes for terrestrial and aquatic ecosystems. We highlight the potential value of interspersed nonforest patches to terrestrial wildlife. Similarly, we review watershed thresholds and factors that control the resilience of aquatic ecosystems to wildfire, mediated by thermal changes and chemical, debris, and sediment loadings. We present a 2‐dimensional life history framework to describe temporal and spatial life history traits that species use to resist wildfire effects or to recover after wildfire disturbance at a metapopulation scale. The role of fire refuge is explored for metapopulations of species. In aquatic systems, recovery of assemblages postfire may be faster for smaller fires where unburned tributary basins or instream structures provide refuge from debris and sediment flows. We envision that more‐frequent, lower‐severity fires will favor opportunistic species and that less‐frequent high‐severity fires will favor better competitors. Along the spatial dimension, we hypothesize that fire regimes that are predictable and generate burned patches in close proximity to refuge will favor species that move to refuges and later recolonize, whereas fire regimes that tend to generate less‐severely burned patches may favor species that shelter in place. Looking beyond the trees to forest fauna, we consider mitigation options to enhance resilience and buy time for species facing a no‐analog future.

Absorptive and transport roots differ in terms of their impacts on rhizosphere soil carbon storage and stability in alpine forests

The fine roots of woody plants can be classified as absorptive roots and transport roots based on their distinct morphological, physiological, and functional traits. The potential ecological consequences of roots with different functional classifications on soil biogeochemical processes have been widely recognized. However, the magnitude of rhizosphere soil C stocks and the associated C stabilization mechanisms driven by these two root functional modules remain unknown. We quantified the soil organic C (SOC) contents and the C fractions in the rhizospheres of absorptive and transport roots in mineral soil in a spruce (Picea asperata Mast.) plantation and further estimated the rhizosphere SOC stocks of the two root functional modules by establishing a numerical model based on the extent of the rhizosphere. We also determined the characteristics of the SOC chemistry and metal-organic complexation in the rhizosphere to distinguish how the two root functional modules differentially impact rhizosphere SOC stability. The SOC content of the rhizosphere of absorptive roots was 15.7% higher than that of the rhizosphere of transport roots. This result can be mainly attributed to the higher stability of SOC (i.e., chemical recalcitrance and metal-organic bond) in the rhizosphere of absorptive roots. The numerical model analysis showed that the rhizosphere SOC pool of absorptive roots (0.27–2.7 kg C/m2) was twice as large as that of transport roots (0.18–1.36 kg C/m2). The contribution of the rhizosphere SOC stock of absorptive roots (63.5%) to the total rhizosphere SOC accrual was much higher than that of the rhizosphere SOC stock of transport roots (36.5%) in the scenario with a 1-mm extent. The rhizosphere soil C stock of absorptive roots plays a predominant role in the total rhizosphere soil C stock in alpine coniferous forests. Our findings highlight the importance of integrating function-based fine root classifications with rhizosphere soil C storage into land surface models of C cycling, which would be instrumental for accurately predicting soil C dynamics in alpine coniferous forest ecosystems.

Dynamics of carbon storage and status of standing vegetation in temperate coniferous forest ecosystem of north western Himalaya India.

Natural ecosystems, which operate as a sink, play an important role in determining the concentration of CO2 in the atmosphere and have a large storage capacity, assisting in mitigation of problem that has a negative impact on the human population. Forests are one of the most important carbon sinks in the terrestrial ecosystem, with the best example being the Western Himalaya, where healthy and sustainable vegetation is prized. Standard methodology was adopted for assessing the different parameters of carbon related information to enumerate the status of carbon storage and its trend in sustaining the ecosystem of the area. The current research displays the annual increment and carbon dynamics in various vegetation components and levels. Trees, shrubs, and herbs help to fix atmospheric carbon in a variety of forms, including AGC, BGC, and TC. The concentration of carbon-fixing potential was measured on an annual and seasonal basis, with herbs having the highest mean annual increment, followed by shrubs and trees. Pinus wallichiana had the largest annual carbon stock change among trees, followed by Cedrus deodara, Picea smithiana, and Abies pindrow. P. wallichiana topped the increase percentage with 60.58%, followed by C. deodara 33.35%, P. smithiana 5.61%, and A. pindrow 0.45%. Litter was also investigated as a potential source of mitigation, with the best results observed during the autumn months. Natural coniferous forests provide a regulating ecological service in the region by maintaining carbon dioxide levels in the form of biomass, according to the study.

Changes in Forest Ecosystem Disturbances in the Forest–Steppe Zone of Russia’s Central Chernozem Region in the Late 20th and Early 21st Century

Results are presented from assessing forest ecosystem disturbances in the forest–steppe zone of Russia’s Central Chernozem region in the periods 1985–2000 and 2000–2018. Geoinformation mapping of disturbed forests areas that appeared during the corresponding time periods is done using an automated approach. The share of disturbed forest ecosystems in the forest–steppe zone of the Central Chernozem region grows from 2.5% at the end of the 20th century to 6% at the beginning of the 21st. The share of disturbed forest ecosystems in coniferous forests grows by 9 times. In deciduous forests, the proportion of disturbed plots is slightly increased. The increased share of disturbed forests is due mainly to a rise in the disturbances of coniferous forest ecosystems. In contrast, the share of deciduous forests in the structure of disturbed forests is almost halved. A map of categories of forest ecosystems disturbances is prepared that characterizes forests according to the time elapsed since the last exposure to disturbing factors.

Changes in the Summer Wild Bee Community Following a Bark Beetle Outbreak in a Douglas-fir Forest.

The status of wild bees has received increased interest following recent estimates of large-scale declines in their abundances across the United States. However, basic information is limited regarding the factors affecting wild bee communities in temperate coniferous forest ecosystems. To assess the early responses of bees to bark beetle disturbance, we sampled the bee community of a Douglas-fir, Pseudotsuga menziesii (Mirb.), forest in western Idaho, United States during a Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins (Coleoptera: Curculionidae), outbreak beginning in summer 2016. We resampled the area in summer 2018 following reductions in forest canopy cover resulting from mortality of dominant and codominant Douglas-fir. Overall, results from rarefaction analyses indicated significant increases in bee diversity (Shannon's H) in 2018 compared to 2016. Results from ANOVA also showed significant increases in bee abundance and diversity in 2018 compared to 2016. Poisson regression analyses revealed percent tree mortality from Douglas-fir beetle was positively correlated with increases in total bee abundance and species richness, where community response variables displayed a cubic trend with percent tree mortality. Percent reduction in canopy cover from 2016 to 2018 was also correlated with bee species richness and diversity. These findings suggest that wild bee communities may benefit from changes in forest structure following bark beetle outbreaks.

Вміст 90Sr та 137Cs в депо і біогенних потоках типових насаджень Чорнобильської зони відчуження

The paper reports results of the study of depots and biogenic fluxes of 90Sr and 137Cs in the typical coniferous (Scots pine) and deciduous (Silver birch) forest ecosystems of the Chernobyl Exclusion Zone during 2016 - 2018. Data on activity concentrations and shares of the total activity of the studied radionuclides in the components of aboveground and underground biomass and their vertical distributions by 10 cm layers of the soil profile up to a depth of 1 m are presented. The downward and upward fluxes of 90Sr and 137Cs activity (including the processes of their deposition as a result of growth and formation biomass) are calculated in annual terms. Significantly higher 90Sr mobility in elements of forest ecosystems than 137Cs is confirmed. The estimated flux values for the investigated forest areas indicate a gradual further increase in the share of these radionuclides in the aboveground biomass components (up to 0.9 %·year-1 from the total activity in forest ecosystems) owing to the increase of organic matter stocks.