Forest Floor Research Articles

Исследование влияния климатических факторов на скорость разложения лесной подстилки

The decomposition of the litter changes its indicators under the influence of climatic changes. Taking into account the impact of this process on the global carbon cycle, the decomposition process is a feedback affecting future climate change. The special role of the litter decomposition process in the overall carbon cycle on a regional and global scale determines the importance of studying the regularity of the influence of climatic parameters on the rate of decomposition of forest litter. Known approaches to solving this problem are based on a probabilistic analysis of the relationship between climatic factors. It is indicated that the task of determining the relationship between temperature and soil moisture when assessing their joint impact on the decomposition rate of forest litter can be formulated in a slightly different way. From the point of view of the ecology of the forest ecosystem, the following statement of the problem is no less interesting: under what relationship of these factors can the decomposition rate reach extreme values? The author proposes a representation of the problem being solved in the form of an extreme problem, taking into account some restrictive conditions imposed on the desired function of the relationship between temperature and soil moisture. The proposed new approach to solving the problem of the influence of climatic factors such as soil temperature and humidity, which consists of calculating the conditions leading to an extremum of the decomposition rate of forest litter, allows us to determine the function of the relationship between these factors and the point at which the decomposition rate reaches a peak. The solution to the problem allowed us to calculate the optimal type of the studied relationship, at which the rate of decomposition of the forest litter reaches an extreme. The results of the study can be used in modeling the processes of the influence of climatic factors on the overall carbon cycle of the forest ecosystem

Cryphonectria carpinicola discovered in Japan: first report of the sexual state on Carpinus tree.

Cryphonectria carpinicola is an ascomycetous fungus that has been regularly found in its asexual form on European hornbeam (Carpinus betulus) in Europe over the past two decades. Here we describe the discovery of C. carpinicola in Japan and report for the first time its sexual state on Carpinus species. No symptomatic trees were observed, but stromata were found saprotrophically on broken branches of Carpinus species on the forest floor. The sexual structures of C. carpinicola resembled that of other Cryphonectria species and strongly resembled those of the closely related species C. radicalis. A phylogenetic tree based on the internal transcribed spacer sequences showed monophyly for the Japanese and European isolates of C. carpinicola. Further studies on the distribution and host range of C. carpinicola in Japan and on the life history strategies of this fungus are needed.

Analisis Produksi Serasah Mangrove pada Hutan Mangrove Desa Kurau Timur, Kabupaten Bangka Tengah, Bangka Belitung

Mangrove forests have many ecological functions such as retaining and trapping sediments, dampening waves, providing protection for fish and other biota, and assimilating nutrients. Most of the nutrients returned to the forest floor are in the form of litter. Litter has an important role for the soil and the microorganisms in it. This study aims to measure the productivity of mangrove litter in the mangrove forest of Kurau Timur Village, Central Bangka Regency, Bangka Belitung. The method used to measure litter production is litter storage using a 1m x 1m litter trap with litter collection every 7 days for 3 months. Environmental parameter data analysis was performed by PCA (Principal Component Analysis). The rate of litter production in the mangrove forest of East Kurau Village is with a dry weight of 2.72 gr/m2/day. The components that make up litter are grouped into 3 components, namely leaves (66%), stems (18%), and flowers/fruits (16%). The litter layer on the mangrove forest floor of Kurau Timur Village is with an average dry weight of 69.02 grams, a water content of 40.73%, and an estimated average biomass of 3.08 tons/ha.

Diversity and species richness of land snails inhabiting an impacted macro-zone-Mfamosing limestone hill in Sub-Saharan Region

The land snail diversity and abundance and some ecological aspects of the fauna in a threatened limestone hill in Mfamosing, Cross Rivers state, Nigeria was investigated between May 2017 and June 2018. Twelve plots of 10 m x 10 m each using a combination of leaf litter in the forest floor (litter and topsoil in a total of ninety sample bags) were sampled from which shells were extracted by handpicking. A total of 289 (two hundred and eighty-nine) specimens representing twenty-three species in seven molluscan families were recorded. The carnivorous Streptaxidae family dominated the fauna regarding species richness while the family Urocyclidae dominated species abundance. The families Eucolinidae and Aillyidae accounted for the least dominant species. The family Streptaxidae with seven species accounted for over 30% of the mollusk abundance, while Urocyclidae had the highest number of individual specimens. True estimates of diversity using Chao2 and second-order Jack-Knife estimators yielded 25 and 24 species respectively. The Land Snail diversity in Mfamosing limestone hill when compared with those from other parts of Nigeria (Okomu in Edo State) and some other parts of the world (Sabah, Malaysia) is relatively high, with moderate levels of species abundance, showing relatively high differentiation, local dominance and endemism by few species. This reveals that Mfamosing limestone hill is one of the biodiversity hotspots for terrestrial mollusks and requires urgent conservation measures, given the current rate of Limestone quarrying in the region.

Effects of Forest Gaps on Forest Floor Microbial Community Composition in Pinus tabulaeformis Forests in a Rocky Mountain Area, Beijing, China

Forest gaps induce environmental heterogeneity, but their effects on the local forest floor microbial communities are not fully understood. This research investigated the impact of forest gap positions on the forest floor microbial community composition to provide baseline information for projects to accelerate nutrient cycling and forest regeneration and enhance ecosystem services. A one-year-old forest gap and an area of 40–50 m2 in Pinus tabulaeformis plantations were selected in the Beijing mountainous area. Forest floor samples were collected from the following positions: gap center, gap border, and adjacent closed canopy. Our study demonstrated that gap positions significantly influenced the forest floor microbial community composition. The Gram-positive bacteria, Gram-negative bacteria, and total bacteria, as well as the fungi, were significantly greater in the forest gap center and gap border compared to those in the closed canopy, and the dissolved organic carbon, readily oxidized organic carbon, ammonia nitrogen, and nitrate nitrogen followed the same trend. Compared with those of the closed canopy, the Gram-positive bacteria, Gram-negative bacteria, total bacteria, and fungi in the gap center were markedly greater by 23%, 25%, 22%, and 24% and by 14%, 14%, 11%, and 16% in the gap border, respectively (p < 0.05). Redundancy analysis demonstrated that shifts in the litter microbial community composition were predominantly predicted by litter moisture and β-1,4-glucosidase. In addition, we discovered that the microbial community composition was greater in the undecomposed forest layer than that in the semi-decomposed layer. In summary, gap positions and forest floor layers have a significant impact on microbial community composition. Nevertheless, additional long-term investigations are needed. Our study provides a reference for the promotion of nutrient cycling to guide future ecological management.

Non-native earthworms increase the abundance and diet quality of a common woodland salamander in its northern range.

The online version contains supplementary material available at 10.1007/s10530-023-03168-3.

Organic Agriculture in Bhutan: Dream of 100% Organic is Stalled at Reality of 1% Organic

Bhutan is a poor country with 51% of the population employed in agriculture, and little manufacturing. Forests accounts for 71% of Bhutan, and agriculture 8%. The average landholding is 1.4 hectares per household. Many farmers practice ‘traditional’ farming using forest litter and farm yard manure. The inputs for chemical agriculture (synthetic fertilisers and pesticides) are generally imported and expensive. Bhutan announced a goal of 100% organic agriculture in 2006. Looking after the environment and animal welfare, and not poisoning insects and other living things are precepts congruent with Buddhism, the national religion of Bhutan. So, organic agriculture appears to be a ‘good fit’ for Bhutan. Yet, nearly two decades after declaring the 100% goal, there appears to have been near zero progress based on the parameter of certified organic agriculture. Longitudinal data of organic agriculture hectares for the past two decades reveal that the goal of 100% appears to be wishful thinking, with the reality of 1.09% organic agriculture. In the meantime, a neighbouring Indian state of India, Sikkim, with many geographic, climatic and demographic comparables, has achieved its goal of 100% organic. Sikkim is a blueprint of how to achieve 100% organic, while Bhutan is a blueprint for how not to (so far).

Altitudinal Patterns of Foliar Nutrients in Dominant Tree Species: Are Central Himalayan Forests Nutrient Stressed?

In forest ecosystems nutrient availability is one of the most important drivers of tree growth and ecosystem function. We studied changes in soil and foliar nutrients (N, P & K) and leaf N and P stoichiometry in eight dominant canopy and sub-canopy forest tree species of Central Himalayan forests occurring between 300 and 2200 m asl. Nutrient (N, P & K) concentration in leaves at bud break, mature and senescent stage varied significantly across the tree species. The nutrient resorption efficiency (NRE) varied significantly across the species and found ranging for N from 48.7 - 76.8%. Both the nitrogen resorption efficiency (NRE) and phosphorus resorption efficiency (PRE) increased linearly with altitude (R2= 0.647 for NRE significant at p< 0.05; and R2 for PRE= 0.525; NS) pointing out that trees growing in temperate climate conserve nutrients more efficiently to withstand the slow mineralization due to cold climate. With the increasing altitude leaf life-span increases significantly (R2= 0.0025; p< 0.0074). ANOVA indicates that the foliar N and P and altitude were unrelated. The low N: P ratio, a measure of nutrient status of forest ecosystems at senescent leaf stage, found ranging from 9.97 in Q. floribunda to 18.8 in P. roxburghii points out that forests of the study region are nutrient stressed, partly due to low P mineralization in temperate climate, leaching of nutrients due to heavy monsoon rain, and poorly developed underlying geology. Thus, the Central Himalayan forests are characterized by high NRE and low growth rate with increasing altitude. Winter season warming might help improve the nutrient availability in the forest floor and nutrient uptake to enhance nutrient cycling and biomass productivity in these forests.

Climate effects of post-use wood materials from the building sector in a system perspective

This study investigates the climate change effects in terms of greenhouse gas emissions and radiative forcing resulting from different pathways of processing wood materials when they reach the end-of-life stage. The shares of combustion, landfill, recycling, and reuse, which vary with the pathways of post-use wood, influence the material and energy production systems. The dynamics of CO2 and CH4 emissions, together with the cumulative radiative forcing of each pathway, are evaluated from various regional system perspectives. The results show that the choice of a treatment pathway for post-use wood could strongly influence the profile of greenhouse gas emissions and, consequently, the global warming potential. Taking into account the situation of the reference material and energy production systems, the post-use wood can have unfavorable consequences for the climate, as in the case when the material and energy production systems are based on the low-carbon energy of natural gas. However, from the perspective where the treatment of post-use wood influences the quantity of forest biomass on the forest floor, the increased share of reuse and recycling contributes positively to the climate change mitigation, but only during the early stage. Under such a context, options relying on carbon capture and storage to handle biogenic CO2 emissions at energy conversion facilities could cause a cooling effect on the Earth's atmosphere.

Effect of the seasonal precipitation regime on shrub litter decomposition in a subtropical forest

Changes in the seasonal precipitation regime induced by global climate change may alter moisture and the dynamics of related microbes and enzymes, thereby significantly affecting forest litter decomposition; however, the specific mechanisms remain unclear. Hence, a precipitation manipulation experiment including the treatments of control (CK), decreased precipitation in the dry season with extremely increased precipitation in the wet season (IE) and decreased precipitation in the dry season with proportionally increased precipitation in the wet season (IP) was performed from October 2020 to October 2021 in a subtropical evergreen broad-leaved forest in China. The moisture, chemical properties, microbial biomass, enzyme activity, and decomposition rates of two dominant shrub species foliar litter, Phyllostachys violascens and Alangium chinense, were measured at six stages during the dry and wet seasons. The results showed that both IE and IP significantly increased the litter decomposition rates (more than 2.0% for P. violascens and more than 4.7% for A. chinense, respectively), while the effects of IE were the most significant, which was mainly related to the precipitation availability and the frequency of dry-wet cycle. Furthermore, the IE and IP increased the wet season’s contribution to the annual total decomposition regardless of litter species, and more significant effects were also observed in IE. Additionally, the results of structural equation model indicated that the seasonal precipitation regime could regulate the decomposition process directly by changing moisture and the contents of elements and refractory substances, as well as indirectly by influencing the related microbial biomass and enzyme activity. These results deepen the understanding of the biogeochemical cycle in forest ecosystems under the global climate change scenarios.

Research Progress on the Decomposition Process of Plant Litter in Wetlands: A Review

Wetland is a transitional area where terrestrial ecosystems and aquatic ecosystems interact and influence each other, and it is an important ecosystem on the Earth’s surface. Due to the special characteristics of wetland ecology, the decomposition of wetland plant litter is slightly different from litter in forests, grasslands, and meadows and other traditional areas. The role of litter mineralization in the wetland ecological C cycle and the functional role of plant litter have been neglected. This study analyzes the decomposition mechanism and decomposition model of wetland litter material and focuses on the effects of the decomposition process of wetland litter material on the structure of the soil fauna community, decomposition of soil organic matter, sediment properties, and the dynamic changes in the C cycle of the biological system by combining domestic and international studies from recent years. Finally, we propose that the direction of future research on wetland litter decomposition should be to reveal the mechanism of wetland biodiversity and ecology, as well as the ecological correlation between aboveground and belowground biodiversity, with a view to providing a decision-making basis for wetland phytoremediation and wetland wastewater treatment.

Nutrient pools and loss due to the removal of harvesting residue in cedar plantations (a case study from Türkiye).

Determining the nutrient stocks and revealing the extent to which these stocks will be affected by the interventions in forest ecosystems are crucial for sustainable forest management. This study aimed to determine the nutrient stock of cedar (Cedrus libani A. Rich.) plantations at different stands with various diameter classes and estimate the nutrient stock to be removed from the forest due to harvesting. Soil and plant samples were collected from 40 plots in Eskişehir and Afyonkarahisar provinces in Turkey. The variation in the nutrient concentrations and stocks of different components of the ecosystem were evaluated by analysis of variance and the decrease via harvesting by regression analysis. The results showed that the concentrations of N, P, K, Mg, S, Fe, Zn, and Mn were highest in the needles, Ca in the bark, Cu in the needles, dead branches, and root. In the large-diameter forest (LDF), dbh=20.0-35.9 cm, the highest P stock was found in the trees, Fe stock in the forest floor, and S stock in the soil and trees. As a result, the forest floor should be protected as it is the crucial component of both the nutrient cycle and the Fe stock in the ecosystem. In LDF, 28.4-37.3% of the nutrient stored in the trees would be removed from the ecosystem in the case of moderate thinning with whole-tree harvesting, while only 5.9-14.1% of the nutrient stock in the case of stem-only harvesting. For these reasons, leaving logging residues after harvesting in the forest would minimize nutrient loss. The study results showed that improved nutrient management in a forest ecosystem will make a significant contribution to the sustainability of forests.

A bizarre layer cake: Why soil animals recolonizing polluted areas shape atypical humus forms

During soil recolonization by macrofauna in areas previously defaunated by industrial pollution, non-typical humus forms are produced. Given that the evidence of zoogenic activity cessation with increased forest litter depth in these humus forms, we tested the hypothesis that the lower organic layers are more toxic than the upper ones. The studies were conducted in the southern taiga, near the Middle Ural Copper Smelter (Revda city, Russia), in spruce-fir and birch forests. We investigated the series of degraded humus forms at different recovery stages, including those without signs of regradation, as well as at the initial and advanced recovery stages. In the organic layers, each of which were 1–2 cm thick and 6–8 cm in total, we measured the following parameters: pH(water), total acidity, the content of exchangeable Ca2+ and Mg2+, acid-soluble and exchangeable metals (Cu, Pb, Fe, Cd, and Zn), organic carbon, and total nitrogen. Simultaneously, we diagnosed the degree of zoogenicity of the organic layers following the European morpho-functional classification of humus forms. Concentrations of the metals increased with forest litter depth, reaching a maximum at the boundary between the organic and organic-mineral horizons (the difference exceeded an order of magnitude). In the same direction, the acidity increased, but the saturation of the exchange complex with Ca2+ and Mg2+ decreased. Within a particular forest litter profile, metal concentrations and acidity were lower in the layer with the highest zoogenicity compared to the layer with the lowest zoogenicity. Based on the metals, pH(water), and exchange complex, the accuracy of the predictions of the degree of layer zoogenicity within the OF horizon in the discriminant analysis reached 100 %. These findings suggest that the vertical gradient of toxic burden persisting in the forest litter after pollution cessation can explain the recovery pattern of humus forms in the contaminated areas.

Two decades of carbon dynamics in an actively-managed, naturally-regenerated longleaf/slash pine forest

Naturally regenerated pine ecosystems cover 11.7 Mha of the southeastern United States, comprising 13.8% of the forested land, and represent an important component in the carbon balance for the region. These forests are exposed to strong climatic variability from extreme multiyear droughts to above average precipitation years, many are actively managed with prescribed fire and some modification of tree density by cutting. This study is unique in assessing the effects of management and climatic variability for two decades on the carbon (C) dynamics and long-term net ecosystem C balance (NECB) for an actively-managed naturally regenerated pine ecosystem. We used 21 years of eddy covariance estimates of net ecosystem C production (NEP), combined with periodic tree inventories, understory biomass and forest floor assessments. Forest management included six prescribed fire cycles on a three-year rotation beginning in the third year of the study, and a preparatory cut which reduced basal area by 20% from 17.05 ± 0.66 m2/ha during the spring of 2016. The mean annual NEP was 3.32 ± 1.37 Mg C/ha yr−1, with a range of 5.35 Mg C/ha (1.30 to 6.65 Mg C ha/yr), was not significantly affected by fire and was mainly controlled by water availability. A combination of aboveground C assessments (tree and understory) and NEP indicates that C stored belowground accounted for 23% of NEP, with part of this used to support aboveground understory growth after fire. Net ecosystem carbon balance (NECB, integrated NEP and C losses from management) fluctuated in a range of 15.5 Mg Cha−1 (6.7 to −8.8 Mg C ha -1) and was sensitive to management. However, a higher NECB during the second decade than in the first (15.3 Mg C/ha vs. 2.7 Mg C/ha) reflected increased NEP (40 Mg C/ha vs. 25.4 Mg C/ha) as it responded to a greater water availability, despite similar amounts of C lost from management activities during both decades. At the end of the 21 years study, the ecosystem had incorporated 22.6 Mg C ha -1, indicating that actively managed naturally regenerated pine ecosystems in the region can mitigate C dioxide emissions under a broad range of climatic conditions, reduce wildfire risks, while providing numerous ecosystem services.

Tree-ring δ15N as an indicator of nitrogen dynamics in stands with N2-fixing Alnus rubra.

Tree-ring δ15N may depict site-specific, long-term patterns in nitrogen (N) dynamics under N2-fixing species, but field trials with N2-fixing tree species are lacking and the relationship of temporal patterns in tree-ring δ15N to soil N dynamics is controversial. We examined whether the tree-ring δ15N of N2-fixing red alder (Alnus rubra Bong.) would mirror N accretion rates and δ15N of soils and whether the influence of alder-fixed N could be observed in the wood of a neighboring conifer. We sampled a 27-year-old replacement series trial on south-eastern Vancouver Island, with red alder and coastal Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) planted in five proportions (0/100, 11/89, 25/75, 50/50 and 100/0) at a uniform stem density. An escalation in forest floor N content was evident with an increasing proportion of red alder, equivalent to a difference of ~750kgNha-1 between 100% Douglas-fir versus 100% alder. The forest floor horizon also had high δ15N values in treatments with more red alder. Red alder had a consistent quadratic fit in tree-ring δ15N over time, with a net increase of $\sim$1.5‰, on average, from initial values, followed by a plateau or slight decline. Douglas-fir tree-ring δ15N, in contrast, was largely unchanged over time (in three of four plots) but was significantly higher in the 50/50 mix. The minor differences in current leaf litter N content and δ15N between alder and Douglas-fir, coupled with declining growth in red alder, suggests the plateau or declining trend in alder tree-ring δ15N could coincide with lower N2-fixation rates, potentially by loss in alder vigor at canopy closure, or down-regulation via nitrate availability.

Tree Stem Detection and Crown Delineation in a Structurally Diverse Deciduous Forest Combining Leaf-On and Leaf-Off UAV-SfM Data

Accurate detection and delineation of individual trees and their crowns in dense forest environments are essential for forest management and ecological applications. This study explores the potential of combining leaf-off and leaf-on structure from motion (SfM) data products from unoccupied aerial vehicles (UAVs) equipped with RGB cameras. The main objective was to develop a reliable method for precise tree stem detection and crown delineation in dense deciduous forests, demonstrated at a structurally diverse old-growth forest in the Hainich National Park, Germany. Stem positions were extracted from the leaf-off point cloud by a clustering algorithm. The accuracy of the derived stem co-ordinates and the overall UAV-SfM point cloud were assessed separately, considering different tree types. Extracted tree stems were used as markers for individual tree crown delineation (ITCD) through a region growing algorithm on the leaf-on data. Stem positioning showed high precision values (0.867). Including leaf-off stem positions enhanced the crown delineation, but crown delineations in dense forest canopies remain challenging. Both the number of stems and crowns were underestimated, suggesting that the number of overstory trees in dense forests tends to be higher than commonly estimated in remote sensing approaches. In general, UAV-SfM point clouds prove to be a cost-effective and accurate alternative to LiDAR data for tree stem detection. The combined datasets provide valuable insights into forest structure, enabling a more comprehensive understanding of the canopy, stems, and forest floor, thus facilitating more reliable forest parameter extraction.

Soil carbon pools and fluxes following the regreening of a mining and smelting degraded landscape

Increasing forest cover by regreening mining and smelting degraded landscapes provides an opportunity for global carbon (C) sequestration, however, the reported effects of regreening on soil C processes are mixed. One of the world's largest regreening programs is in the City of Greater Sudbury, Canada and has been ongoing since 1978. Prior to regreening, soils in the City of Greater Sudbury area were highly eroded, acidic, rich in metals, and poor in nutrients. This study used a chronosequence approach to investigate how forest soil C pools and fluxes have changed with stand age in highly “eroded” sites with minimal soil cover (n = 6) and “stable” sites covered by soil (n = 6). Encouragingly, the relationship between stand age and soil C processes (litterfall, litter decomposition, soil respiration, fine root growth) at both stable and eroded sites were comparable to observations reported for jack pine (Pinus banksiana Lamb.) and red pine (Pinus resinosa Ait.) plantations that have not been subject to over a century of industrial impacts. There was a strong “home-field advantage” for local decomposers, where litter decomposition rates were higher using a site-specific pine litter compared with a common pine litter. Higher soil respiration at eroded sites was linked to higher soil temperature, likely because of a more open tree canopy. Forest floor C pools increased with stand age while mineral soil C and aggregate C concentrations decreased with stand age. This loss of soil C is small relative to the substantial increases in aboveground tree and forest floor C pools, leading to a sizeable increase in total ecosystem C pools following regreening.

Carbon Dioxide Emission from the Soil Surface of the 10-Year Felled Area of the Pine Forest in the European North-East of Russia

Experimental data on soil respiration are need for estimating role of industrial logging on carbon cycle of forest ecosystems. Investigations were carried out during snowless periods 2019–2021 years on felled area of pine forest 10 years after clear cutting (Komi Republic, Russia). The soil type is a Gleyic Folic Albic Podzol (Arenic). Emission CO2 was measured by LI COR 8100. The characteristic of weather conditions and soil temperature dynamic at 10 cm depth were given. The weather conditions were strongly influenced on soil respiration rate. More intensive CO2 flux from soil surface was observed in warm summer with insufficient precipitation. The mean month CO2 emission was less by 1.3–1.9 times in apiaries, parts of felled area with low soil cover damages, comparing to skidding tracks where logged trees were extracted. The significant positive correlation (R2 = 0.12–0.86) was detected between soil temperature at 10 cm depth and soil respiration investigated technological elements. A reliable interrelation between CO2 flux and moisture of forest floor was observed in skidding tracks in a year with abundant precipitation while in a dryer year it wasn’t. It is differ from apiaries where found reverse dependencies. Apiaries emitted in atmosphere 303–379 g С m–2 with soil respiration during snowless period, skidding tracks – 419–573 g С m–2 which is 60–75 tons of CO2 in terms of the area of the entire felled area (5 ha). The growing season formed most part (86–90%) of carbon efflux from May to October and input of summertime was 56–65%. The data obtained will serve to determine the role of timber harvesting in the carbon cycle of taiga forests.

Canopy Leaching Rather than Desorption of PM2.5 From Leaves Is the Dominant Source of Throughfall Dissolved Organic Carbon in Forest

AbstractDissolved organic carbon (DOC) in throughfall plays a vital role in providing carbon and energy to organisms in forests. We utilized carbon isotope analysis to allocate the sources of throughfall DOC, including leaching from plant tissues, PM2.5 deposition on plant foliage, and precipitation. Rainwater, PM2.5, and throughfall samples were collected from pine and oak forests between March and November 2021. The mean concentration of throughfall DOC was 7.9 mg L−1, approximately six times higher than that of rainfall. The mean Δ14C of throughfall DOC was −38.2‰, ∼200‰ higher than that of rainwater or PM2.5. Mass balance estimates revealed that canopy leaching contributed to ∼83% of throughfall DOC, while desorption of PM2.5 and rainwater accounted for only ∼3% and ∼14% of throughfall DOC, respectively. These results clearly highlight canopy leaching as the primary source of carbon input to the forest floor, with a relatively minor contribution from PM2.5 desorption on leaves.

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.