Larch Stands Research Articles

Linking Post-fire Tree Density to Carbon Storage in High-Latitude Cajander Larch (Larix cajanderi) Forests of Far Northeastern Siberia

AbstractWith climate warming and drying, fire activity is increasing in Cajander larch (Larix cajanderi Mayr.) forests underlain by continuous permafrost in northeastern Siberia, and initial post-fire tree demographic processes could unfold to determine long-term forest carbon (C) dynamics through impacts on tree density. Here, we evaluated above- and belowground C pools across 25 even-aged larch stands of varying tree densities that established following a wildfire in ~ 1940 near Cherskiy, Russia. Total C pools increased with increased larch tree density, from ~ 9,000 g C m−2 in low-density stands to ~ 11,000 g C m−2 in high and very high-density stands, with increases most pronounced at tree densities < 1 stem m−2 and driven by increased above- and belowground (that is, coarse roots) and live and dead (that is, woody debris and snags) larch biomass. Total understory vegetation and non-larch coarse root C pools declined with increased tree density due to decreased shrub C pools, but these pools were relatively small compared to larch biomass. Fine root, soil organic matter (OM), and near surface (0–30 cm) mineral soil (MS) C pools varied little with tree density, although soil C pools held most (18–28% in OM and 44–51% in MS) C stored in these stands. Thus, if changing fire regimes promote denser stands, C storage will likely increase, but whether this increase offsets C lost during fires remains unknown. Our findings highlight how post-fire tree demographic processes impact C pool distribution and stability in larch forests of Siberian permafrost regions.

Stand Structure and Functional Traits Determine Productivity of Larix principis-rupprechtii Forests

Forest productivity (FP) depends not only on tree species diversity but also on functional traits, stand structure, and environmental factors; however, causation and relative importance remain controversial. The effects of tree species diversity (species richness), trait community-weighted mean (CWM), forest structure (forest density and maximum DBH), and environmental factors (soil nutrients and elevation) on larch (Larix principis-rupprechtii Mayr) forests’ productivity were investigated, and the relative importance of each factor in determining productivity was quantified. Our results showed that stand structure and functional traits had significant positive effects on the basal area increment (BAI) of larch stands (p < 0.05) and were more important than tree diversity and environmental factors in explaining BAI variations. The contribution ratio of each influencing factor was as follows: stand structure (59%), functional composition (30%), environmental factors (9%), and species diversity (SD) (2%). The biomass ratio hypothesis was more important than the niche complementarity hypothesis in explaining the relationship between species diversity and productivity. The structural equation model showed that environmental factors did not directly affect the BAI in larch forests but indirectly affected the BAI through tree diversity and stand structure. Therefore, in larch forests with low species richness, it is more important to adjust stand structure to maintain overyielding while also considering the influence of environmental factors.

Effects of Stand Density, Age, and Drought on the Size–Growth Relationship in Larix principis-rupprechtii Forests

The size–growth relationship (SGR) quantifies growth partitioning among different sized trees in a stand and helps to elucidate stand growth dynamics during stand development. SGR strongly correlates with stand density, stand age, and drought severity. This study focused on larch (Larix principis-rupprechtii (Mayr)) forests with different stand ages (17–19 years, 20–29 years, 30–39 years, and 40–46 years) and stand densities (300–1400 trees·ha−1 and 1400–3300 trees·ha−1) as the research subjects. Employing a linear mixed model, we aimed to quantify the effects of stand density, stand age, and drought index on SGR. The results revealed that the Gini coefficient had a significant variation between high-density and low-density larch stands (p < 0.01). Stand age, stand density, and drought index exerted varying degrees of influence on the growth dominance coefficient (GD) and SGR of larch forests. In stands aged less than 39 years, a pronounced growth advantage of large trees over small trees was evident (typically SGR > 1 and GD > 0), indicating a positive growth dominance stage where large trees dominated. Compared to high-density stands, low-density stands exhibited a notably greater positive growth dominance. After 40 years, the growth stage transitioned to a relatively symmetric stage (SGR approximately equal to 1), with a discernible shift towards a reverse growth dominance stage (GD < 0). Compared to stand density and stand age, the drought index had a more influential effect on SGR. As drought severity increased, SGR increased, amplifying the growth advantage of large trees over small ones. The findings underscored the significance of adjusting stand density and optimizing tree size structure to enhance larch resilience against the warming and drying effects.

Low persistence of Phytophthora ramorum (Werres, De Cock, and Man in ‘t Veld) in western France after implementation of eradication measures

Key messagePresence of Phytophthora ramorum (Werres, De Cock, and Man in ‘t Veld) in western France was studied after the detection of this invasive pathogen in 2017 in Larix kaempferi (Lamb.) and eradication of the affected stands. P. ramorum was seldom detected in the area of the outbreak in the year following eradication. However, we confirm that P. ramorum can multiply to epidemic level on chestnuts (Castanea sativa Mill.) in the absence of larch (Larix spp.). This represents the major risk in France.ContextPhytophthora ramorum is an invasive oomycete that causes significant damage in the USA and Europe. Although the pathogen has been present in nurseries in France since 2002, the first outbreaks in forest stands were identified in 2017 in plantations of Larix kaempferi in two forests in western France (Saint-Cadou and Hanvec). In order to limit the development of the epidemic, neighboring larch stands were clear-cut.AimThis study investigated the presence of P. ramorum in the affected area after the eradication treatment.MethodsLarch stands located within a 18-km radius of the reported outbreaks were investigated. We also monitored the native woody hosts present in infected clear-cut larch stands and in the vicinity of seven ornamental nurseries that had been infected by P. ramorum on several occasions in the past.ResultsOverall, a very limited presence of P. ramorum was detected in 2018–2021. Two new stands of infected L. kaempferi were found close to the main initial outbreak, in Saint-Cadou and Saint-Rivoal. The pathogen was only detected on rhododendrons and chestnut trees (Castanea sativa Mill.) in the vicinity of the outbreaks. In the Saint-Cadou state Forest, an outbreak of the disease developed in 2019–2021 on chestnut trees even though all the mature larch trees had been felled. P. ramorum was also detected near two of the formerly infected ornamental nurseries, on Castanea sativa and on rhododendrons.ConclusionWhile larches and rhododendrons are uncommon in the forests of north-western France, chestnut trees are present in 21–25% of the forest and therefore represent the major risk for the survival of P. ramorum in the region.

Representation of the genus Larix Mill. in the protected areas of Ukrainian Polissia

Larix decidua Mill. may become more important than Picea abies (L.) Karst for reforestation and restoration of the natural balance, and therefore it is necessary to investigate this species. Therefore, the purpose of this study was to conduct an inventory of Larix taxa in the protected areas of the mixed forest zone of Ukrainian Polissia, to analyse their distribution, age structure, and use. Research methods used: route, analytical, comparative analysis, systematisation. It was found that 5 species, one variety and two hybrids of larch grow in the protected areas of the mixed forest zone of Ukraine. It was established that L. decidua is the most widespread – it grows in parks-monuments of landscape art, natural monuments, protected tracts, reserves in pure mixed plantings, alleys, row plantings, groups and as a solitaire tree. L. sibirica, L. kaempferi grow as solitaire trees and in groups of 3 to 10 specimens in 9 and 10 protected objects, respectively. L. gmelinii is present in two arboretums, L. laricina – in one. Larix decidua var. polonica (Racib. ex Wóycicki) Ostenf. & Syrach is not widespread, represented in groups in 6 parks-monuments of landscape art and Bereznivskyi denrorark. Larix × eurolepis A. Henry. is widespread in pure and mixed stands, grows in an alley in the Slavianskyi park-monument of landscape art, in groups – in the Lisova Aleia Botanical Reserve, Bereznivskyi denrorark, and in mixed stands of the Riznolissia General Zoological Reserve. The age structure is quite diverse, represented by L. decidua, L. sibirica, L. decidua var. polonica aged from 100 to 200 years. Other species, varieties, and hybrids are represented by specimens aged from 3 years (L.×eurolepis) to 80 years (L. kaempferi). 69.2% of larch stands are in good condition, 28.9% are in satisfactory condition, and only 1.9% are in poor condition. The results of the research can be used in the further creation of pure and mixed stands, alleys, etc. in the mixed forest zone

Biological Productivity of the Post-Fire Larch Forests in the Mountain Regions of Krasnoyarsk Krai

Peculiarities of the compositionally pure larch stands formation following forest fires were studied in the northern (Evenkia, middle course of the Nizhnyaya Tunguska river, geographic coordinates 64°03′ N 101°10′ E) and southern (Ermakovskiy district, geographic coordinates – 52°23′ N, 93°33′ E) areas of Krasnoyarsk Krai. The structure, growth and biological productivity of the forest restoration successions were analyzed based on the materials from the sample plots. The highest value of phytomass (in terms of total productivity) in larch stands registered was 1055.5 t abs. dry substances/ha at the age of 93 years. The structural ratio of the forest stands phytomass fractions naturally changes with an increase in their average age and density. With an increase in the average age of a stand, its above-ground and root phytomasses increase; at the same time, the relative share of crown and needle wood mass in the total above-ground phytomass of a stand decreases. In 38-year-old larch forests, the share of crown mass is 18%, and the share of stems is 82%. In 60-year-old forest stands, crown wood with needles accounts for 14%, and the rest 86% are stem weight. In the 93-year-old larch forest, the proportion of stem phytomass increases to 89%, and the proportion of crown wood with needles falls up to a minimum share of 11%. The maximum growth potential of the 56-year old larch stands, according to the current increase in phyomass (in terms of total productivity), is realised at about 14.69 t abs. dry substances/ha per year. The young and middle-aged larch forests formed on the burnt areas have higher rates of growth and phytomass accumulation; in terms of the amount of fixed atmospheric carbon, they exceed the mature and overmature stands by more than two times.

Growth and Timber Quality of European Larch Planted in Areas Reclaimed After Coal Mining in Central Poland

Understanding the impact of reclamation measures on the quality of timber produced in post-mining areas is crucial for the proper establishment of future forest cultures on such sites. We studied European larch trees (Larix decidua Mill.) grown since 1981 on the external dump of a brown coal mine in Bełchatów (Central Poland). In particular, the effects of stand admixture and the intensity of mineral fertilization, applied in the initial phase of tree growth, on the increments and quality of larch wood were evaluated. Total tree height and stem diameter of 4-meter sections were measured. Qualitative timber classification took into account the share of wood defects, which excluded the timber from a higher quality-dimensional class. Larch trees grown in a monoculture had a better quality of wood compared to larch grown mixed with other species. Fertilization, applied in the initial afforestation period, had only a limited effect on the growth of larch trees. Curvature and knots determined timber quality most significantly. While knots had a decisive importance in larch growing in the monoculture stands, curvature determined wood quality in the admixed larch stands.

Distribution, growth and productivity of Larix decidua Mill. plantations in the western Forest-Steppe of Ukraine

This study provides an analysis of the distribution of European larch in artificial forest stands in Ukraine. It was found that the potential area for the successful cultivation of this species can be not only the Western but also the Right-Bank and Left-Bank Forest-Steppe. The study has confirmed that European larch plantations, with the appropriate technology for planting and cultivation, are marked by rapid growth, high productivity and resistance. Under the forest site conditions of types C2, D2, and D3, in which the largest number of larch stands were built, a tendency was revealed towards an increased volume of stemwood with an increasing share of larch in the stand composition. Constructed regression models formalize this dependence. With advancing age, the influence of larch on an increase in the growing stock of plantations is reduced. Productivity and growth character of larch plantations in different types of forest growth conditions are different. European larch can form steady-state and highly productive plantations not only in fresh, but also in moist types of forest growth conditions. Under conditions of a fresh fertile site type (D2), as evidenced by the results of ANOVA, the share of larch in the composition of the stand has a significant impact on the main mensuration indices of the stand. The highest values for the average height are characteristic of larch with its significant share in the composition of plantations (6-10 units), and the highest values for the average stem diameter were observed with an average share of the species (3, 5-8 units). It is noted that the technology for the establishment and management of artificial larch plantations should be differentiated depending on the type of forest growth conditions by using optimal mixing and spacing schemes and appropriate silviculture regimes that regulate the share of larch in these stands. Keywords: European larch, forest plantation, forest stand, type of site conditions, stand composition

Mixed forest specific calibration of the 3-PGmix model parameters from site observations to predict post-fire forest regrowth

Fire disturbance has been one of the main reasons for the alteration of forest succession trajectory and forest composition in the Daxing’anling Mountain of Inner Mongolia. Therefore, predicting the dynamic process of post-fire regrowth is critical for understanding the specific forest succession trajectory of this region. The 3-PGmix model (i.e., Physiological Principles in Predicting Growth for mixed stands) has been reported as a powerful tool for predicting the growth of mixed forest species. However, simulating post-fire regrowth of mixed forest with 3-PGmix remains challenging due to the uncertainty of species-specific as well as site-specific model parameters. Based on the field measurements from a wide range of environmental conditions, the 3-PGmix model was calibrated by conducting the sensitivity analysis and optimization of species-specific parameters for mixed forest stands of larch (Larix gmelinii) and birch (Betula platyphylla) with the PEST model (Model-Independent Parameter Estimation), and by using our newly developed methods to accurately estimating site-specific parameters (e.g., fertility rating, stand density, climate factors). The calibrated 3-PGmix model was tested against the independent sites and predicted the characteristic of post-fire forest regrowth. The sensitivity analysis shows that the parameters describing the forest canopy are more sensitive to the objective function of the PEST model. The calibrated 3-PGmix model performed well on independent sites, resulting in agreement with the field-measured diameter at breast height (DBH), the biomass of components, and stand density with a bias of less than 15% on most sites. The 3-PGmix model prediction of post-fire forest recovery characteristics found that the highest recovery rate of 5.5% per year was predicted from the moderate burn severity scenarios. A higher fertility rating was predicted to accelerate the process of post-fire forest successional and shorten the duration time when the species proportion achieves balance. The mixed-forest specific calibration of the 3-PGmix model in this study enables the explicit prediction of post-fire forest succession, and more simulations over different spatial scales with a wide range of environmental conditions by coupling with remote sensing observations can be expected.

Classification of Fire Damage to Boreal Forests of Siberia in 2021 Based on the dNBR Index

Wildfire in Siberia is extensive, affecting up to 15 Mha annually. The proportion of the vegetation affected by severe fires is yet unknown, and it is a problem that requires a solution because post-fire mortality of tree stands in Siberian taiga has a strong effect on the global budget of carbon. The impact of fire in our area of interest in eastern Siberia was analyzed using the normalized burn ratio (NBR) and its pre- versus post-fire difference (dNBR) applied to Landsat-8 (OLI) collected in 2020–2021. In this paper, we present the classification of fire impact in relation to dominant tree stands and vegetation types in boreal forests of eastern Siberia. The dNBR of post-fire plots ranged widely (0.30–0.60) in homogeneous larch (Larix sibirica, L. gmelinii) forests, pine (Pinus sylvestris) forests, dark coniferous stands (Pinus sibirica, Abies sibirica, Picea obovata), sparse larch stands, and Siberian dwarf pine (Pinus pumila) stands. We quantified the proportions of low, moderate, and high fire severity (37%, 39%, and 24% of the total area burned, respectively) in dense tree stands, which were varied to 30%, 57%, and 13%, respectively, for sparse stands and tundra vegetation dominated in the north of eastern Siberia. The proportion of severe fires varied according to the transition from dominant larch stands (33.2% of the area burned) to pine (12.6%) and dark coniferous (up to 26.4%). The current proportion of stand-replacement fires in eastern Siberia is 12–33%, depending on vegetation type and tree density, which is about 2500 thousand hectares in 2021 in the region. According to our findings, the “healthy/unburned vegetation” class was quantified as well at least 700 thousand hectares in 2021.

Молекулярно-генетическая идентификация грибов рода Fomitopsis из Иркутской области

Basidiomycetes of the genus Fomitopsis are an extensive group of more than 100 species that have ecosystem significance and high biotechnological potential. One of these species, Fomitopsis pinicola, is known as a widespread tinder fungus, a saprophyte that causes brown rot on deciduous and coniferous trees. The modern taxonomy of F. pinicola, economic significance, relevance of pharmacological research and the possibility of using them as medicines and food additives are discussed. F. pinicola has an important ecosystem function as it promotes the nutrient circulation in the forest. Recent studies show that this is a species complex and that morphological markers alone are not sufficient for precise identification of the species, which emphasises the importance of a molecular genetic approach to the taxonomy of this group. Although F. pinicola can be detrimental to forestry by causing rotting of wood, this basidiomycete has long been used by humans. For a long time, extracts of the conks (fruiting bodies) of F. pinicola, like many other tinder fungi, have been used by various cultures in traditional medicine, but modern pharmacological studies of the health-saving properties of the substances produced by F. pinicola are still insufficient. However, the relevance of such studies is very high, since ergosterol, fomitopic acids, and fomitosides produced by fungi demonstrate a proapoptotic effect and affect the metabolic pathway of prostaglandins. Promisingly, some compounds isolated from other Fomitopsis species have anticancer properties. Despite this, in fungal taxonomy, the correct species identification of biotechnological strains remains a problem. Due to intraspecific morphological variation, modern taxonomy emphasizes genetic markers. Here the data of molecular-genetic and phylogenetic identification of two biotechnological strains of basidiomycetes collected from the affected larch stands of the Irkutsk region are presented. Genetic identification of strains of Fomitopsis spp. was carried out using the sequence of variable regions of the ITS1 ribosomal operon. For phylogenetic analysis, ITS1 gene sequences of 25 species of basidiomycetes evolutionarily closest to Fomitopsis spp. were used. The studied strains were identified as the F. pinicola species with an accuracy of 97.98% and 99.21%, respectively. Further study of the biotechnological properties of the two identified strains of F. pinicola seems to be very relevant.

Enzymatic Activity of Soils Forming on an Afforested Heap from an Opencast Sulphur Mine

Post-mining areas require reclamation. The main aim of reclamation is to restore the soil as a basic element of the terrestrial ecosystem. This paper presents the results of an evaluation of the enzymatic activity of soils formed on an afforested heap from an opencast sulphur mine. Six research sites were selected on the overburden heap of the Piaseczno sulphur mine, afforested 50 years ago. They differed in the type of soil in the subsoil and in the species composition of the stand. The activity of dehydrogenases, phosphatases, urease, total organic carbon, and total nitrogen was determined and statistical analysis of the obtained results showed that the activity of the evaluated enzymes in the soils formed in the reclaimed areas was significantly dependent on the type of substrate and the species composition of the plants. The activity of the evaluated enzymes was significantly positively correlated with the content of total nitrogen and the C/N ratio, and the activity of phosphatases and urease with the total organic carbon content. Within soils developed on the same texture, the influence of stand species was revealed. In soils formed on clay, the soils under the beech stand and under the birch stand were characterized by higher activity of enzymes. The soil developing under the stands of European larch and red oak was characterized by higher enzymatic activity on weakly clayey sands. On loose sands, the activity of dehydrogenases and urease was significantly higher under acacia robinia than under hornbeam.

CHANGES IN THE CONTENT OF BIOAVAILABLE HEAVY METAL COMPOUNDS IN THE SOILS OF THE CRIMEAN MOUNTAIN PLATEAUS AFTER AFFORESTATION

About 3 thousand hectares of forest stands were created on the surface of the Crimean mountain plateaus in the middle of the 20th century as a result of afforestation. Studies on the influence of these stands on the properties of mountain meadow soils (Phaeozems) showed that under the forest vegetation, the consolidation of structural aggregates, a decrease in the humus content, and an increase in acidity compared to the soils under the meadow vegetation, which could also affect other soil properties, including the mobility of some metals, were observed. The work objective of this research is to conduct a comparative analysis of the content of Pb, Mn, Cu, and Zn compounds available for biota (1 M ammonium acetate) in the soil under mountain meadows, natural beech forest, and artificial forest stands. Following the obtained results, the available Pb, Mn, and Cu compounds accumulated in the afforested mountain meadow soils relative to the adjacent mountain meadows areas. Thus, the average Pb content in the soil layer of 0–10 cm under the mountain pine stands in comparison with the soil under meadow vegetation was 1.6 times higher, Mn – 1.2 times, Cu – 1.2 times. The Pb content was 2.5 times higher, Mn – 1.5 times higher, and Cu – 1.2 times higher under the silver birch stands. The Pb content was 2.2 times higher, Mn – 2.4 times higher, and Cu – 1.5 times higher under Siberian larch stands. The Pb content was 1.9 times higher, Mn – 1.1 times higher, Cu – 1.3 times higher under the sycamore maple stands, compared to the meadow. Differences between afforested and meadow soils in the content of these elements in most cases were significant, except for the Zn content, signs of accumulation of which under artificial stands were not revealed. The Pb, Mn, and Cu content in the brown forest lessive soil (Luvisols) under the oriental beech corresponded to their concentration under the larch, and the Zn content was significantly higher compared to the soil under all species. The main reason for the increase in the mobility of some elements under tree stands is their transition from immobile forms under the influence of increased acidity of afforested soils. Wood litter due to the low content of trace elements in its composition cannot be a source of their accumulation in the topsoil.

Postglacial Vegetation and Climate History of the Oka Plateau (East Sayan Mountains, South Siberia)

The first results of palynological analysis of the bottom deposits of Kaskadnoe Lake and a reconstruction of vegetation and climate on the Oka Plateau over the last 14.2 ky are reported. It is shown that approximately 1.2–12.9 cal ka BP (GI-1) the regional climate was sufficiently warm and humid to allow the development of a forb–shrub tundra with spruce and larch stands. Cooling at approximately 12.9–11.5 cal ka BP (GS-1) led to the predominance of the forb–shrub tundra in the lake basin. Siberian pine settled on the Oka Plateau in a moderate–cold and humid climate at approximately 11.5–9.0 cal ka BP. The warmer and drier climate, which prevailed in the Middle Holocene approximately 9.0–4.5 cal ka BP, resulted in the retreat of dark-coniferous forests from the Kaskadnoe Lake basin. The spreading of larch and Siberian pine coincided with the onset of Neoglacial conditions in the Late Holocene. It was established that the environmental conditions on the Oka Plateau in the Late Glacial Period and Holocene were generally controlled by the interaction of the western atmospheric transport and the East Asian summer monsoon, the temperature variations caused by the insolation level, and the specific features of regional atmospheric circulation.

Age-Dependent Changes in Soil Respiration and Associated Parameters in Siberian Permafrost Larch Stands Affected by Wildfire

The observed high spatial variation in soil respiration (SR) and associated parameters emphasized the importance of SR heterogeneity at high latitudes and the involvement of many factors in its regulation, especially within fire-affected areas. The problem of estimating CO2 emissions during post-fire recovery in high-latitude ecosystems addresses the mutual influence of wildfires and climate change on the C cycle. Despite its importance, especially in permafrost regions because of their vulnerability, the mutual influence of these factors on CO2 dynamics has rarely been studied. Thus, we aimed to understand the dynamics of soil respiration (SR) in wildfire-affected larch recovery successions. We analyzed 16-year data (1995–2010) on SR and associated soil, biological, and environmental parameters obtained during several field studies in larch stands of different ages (0–276 years) in the Krasnoyarsk region (Russia). We observed a high variation in SR and related parameters among the study sites. SR varied from 1.77 ± 1.18 (mean ± SD) µmol CO2 m−2 s−1 in the 0–10-year-old group to 5.18 ± 2.70 µmol CO2 m−2 s−1 in the 150–276-year-old group. We found a significant increasing trend in SR in the 88–141-year old group during the study period, which was related to the significant decrease in soil water content due to the shortage of precipitation during the growing season. We observed a high spatial variation in SR, which was primarily regulated by biological and environmental factors. Different parameters were the main contributors to SR in each group, an SR was significantly affected by the inter-relationships between the studied parameters. The obtained results can be incorporated into the existing SR databases, which can allow their use in the construction and validation of C transport models as well as in monitoring global fluctuations in the C cycle in response to climate change.

Phytomass Reserves and Distribution of Biogenic Elements in Gmelin Larch Stands in Central Evenkia (Using the Example of a Small Drainage Basin)

For the first time, for a small watershed in Central Evenkia, using the method of model trees, a change in the composition and structure, as well as in the phytomass and biogenic elements reserves in larch forests, depending on the age of the stands, was revealed. It was found that the main mass-forming components in the phytomass of all stands are the trunk and root fractions. The proportion of the trunk phytomass increases and the proportion of branches and needles decreases with age. It was found that the composition of the roots changes little with the age of the stand, which confirms the hypothesis of the annual primary carbon investment into larch roots in the permafrost zone. It is shown that the largest carbon reserves are accumulated in overmature stands, while nitrogen reserves accumulates in the needles of young stands.

Forest plantation productivity – soil interactions within Western Forest-Steppe of Ukraine: effects of pH and cations

Abstract Dark grey podzolized soils on the loess like loams, which are represented in the soil cover within fresh and humidity gradients in the Western Forest Steppe of Ukraine, are characterized by high forest vegetation potential, which ensure the formation of mostly pure and mixed larch and spruce stands with high level of the productivity. Despite the fact that both species are coniferous, their effect on the soil, in particular, on its acid-base indicators (actual and potential forms of acidity, sum of absorbed bases, degree of saturation of bases, content of mobile aluminium), which are important components of soil fertility, are specific. Due to the fact that there is a close interaction between forest plantations and soil properties, changing the participation of species in the stand, it is possible to adjust the actual soil fertility. The soils under both pure and mixed spruce and larch stands are characterized by a high level of potential acidity that reaches the high acidic values in the upper horizons. A similar reaction of soil solution under coniferous forests is caused by acid hydrolysis of aluminosilicates and accumulation of mobile Al in the rhizosphere zone. Simultaneously, the same acidic characteristics, including the presence of movable aluminium, are also found in soils under broadleaved plantations. In general, acid-exchange properties of soils (high potential acidity, unsaturation of bases and availability of movable aluminium) traditionally are considered as unfavourable for vegetation. However, our researches refute it and prove that within certain values, these indicators do not limit the productivity of pure and mixed spruce and larch stands.

Структура и распространение лиственничников на территории Среднего Урала

The results of research describing the structure and distribution patterns of stands with larch (Larix sukaczewii Dyl.) in the forests of the Middle Urals of the Sverdlovsk region are presented. Larch forests grows on an area of 17,146 ha in all forest districts. The distribution of larch forests by age groups is heterogeneous, and its dependence is described by a third-order polynomial trend line with a reliable approximation value of 0,9671. The share of larch young forests of the 1st and 2nd age classes was 43,1 % of the total area of larch forests 7387 ha. Medium-aged larch forests grow on an area of 4493 ha (26,2 %). There is a low proportion of plantings (6,5 % or 1118 ha) that are older than average, but have not reached technical maturity. Forests with larch at the age of technical maturity and old-growth forests grow on an area of 4148 ha (24,2 %). The maximum average stock of larch stands (268 m3/ha) was recorded at the age of older than average, but did not reach technical maturity. Since larch is a light-loving species, natural thinning of stands occurs with increasing age and density decreases, so there is a decrease in average forest reserves at the age of technical maturity and old-growth forests (248 and 197 m3/ha, respectively). Intensive forest use has a significant impact on the distribution of the area of plantings by age groups, but a large proportion of young and middle-aged forests is noted as a positive fact, which indicates the success of larch reforestation in the forest-growing conditions of the Middle Urals. It is concluded that increasing the share of larch trees in the forest fund of the Middle Urals is advisable due to measures to care for the forest in the mountainous part of the taiga zone, and in the flat part of it is necessary to increase the share of artificial larch plantations.

Taxonomic and interpretation links in coniferous and mixed larch forests of the Altai-Sayan region

Currently, methods for interpreting various indicators of plantings by aerial and satellite images based on GIS technologies have gained significant development. They actively implement regression relationships between taxation indicators of stands. The object of the study are modal larch stands of the Altai-Sayan region, which are characterized by both coniferous and mixed forests with larch (Larix Sibirica L.) fraction from 40 to 90 % and an admixture of birch (Betula pendula R.), aspen (Populus tremula L.), fir (Abies sibirica L.) and cedar (Pinus sibirica D.). Comparison of coniferous and mixed forests did not reveal significant differences in the growth lines. Based on paired and multiple linear regression equations for coniferous and mixed modal larch forests, a set of taxation interpretation models is obtained with the aim of approximating the average diameter, age and standing volume of stands according to such interpretation indicators as average height, completeness, bonitet class and larch fraction in the composition. Thus, a number of equations have been developed for modal larch forests, which are recommended for remote sensing of larch forests in the Altai-Sayan region.

Soil respiration in larch and pine ecosystems of the Krasnoyarsk region (Russian Federation): a latitudinal comparative study

Based on the long-term (12 years) data on soil respiration (SR) measurements in representative conifer forests of the Krasnoyarsk region (Central Siberia), we demonstrated specific characteristics of SR. The study sites located closely to Arctic Circle were related to different latitudes, including 56° N (SAE site, Krasnoyarsk), 60° N (ZOTTO site, Zotino), and 64° N (Tura site, Evenkia). Study sites were selected in forest ecosystems (> 41 years old) and represented a wide range of the climate, stand, permafrost availability, and soil types. However, the mean seasonal values of SR (mean ± SD) varied in a relatively narrow range from 2.11 ± 0.69 in the forest-steppe zone (SAE) to 2.82 ± 1.77 μmol CO2 m−2 s−1 in northern larch taiga (Tura). Nevertheless, a twofold difference in the duration of growing season among northern and southern locations results in a variation of total seasonal CO2 emissions (mean ± SD) from 216 ± 136 g C m−2 in larch stands of northern taiga to 369 ± 115 g C m−2 in larch stands of southern forest-steppe zone. Evaluation of the multiannual dynamics of SR over the past 1.5 decades (1995–2010) showed the escalation of SR in the permafrost larch stands (Tura) in 2005–2010. That has been coupled with the enhanced activity of the soil heterotrophic microbiota in 2007–2010. Our study highlights the importance of further monitoring of SR in permafrost Siberian ecosystems.