Larch Trees Research Articles

Isotopic compositions of ground ice in near-surface permafrost in relation to vegetation and microtopography at the Taiga-Tundra boundary in the Indigirka River lowlands, northeastern Siberia.

The warming trend in the Arctic region is expected to cause drastic changes including permafrost degradation and vegetation shifts. We investigated the spatial distribution of ice content and stable isotopic compositions of water in near-surface permafrost down to a depth of 1 m in the Indigirka River lowlands of northeastern Siberia to examine how the permafrost conditions control vegetation and microtopography in the Taiga–Tundra boundary ecosystem. The gravimetric water content (GWC) in the frozen soil layer was significantly higher at microtopographically high elevations with growing larch trees (i.e., tree mounds) than at low elevations with wetland vegetation (i.e., wet areas). The observed ground ice (ice-rich layer) with a high GWC in the tree mounds suggests that the relatively elevated microtopography of the land surface, which was formed by frost heave, strongly affects the survival of larch trees. The isotopic composition of the ground ice indicated that equilibrium isotopic fractionation occurred during ice segregation at the tree mounds, which implies that the ice formed with sufficient time for the migration of unfrozen soil water to the freezing front. In contrast, the isotopic data for the wet areas indicated that rapid freezing occurred under relatively non-equilibrium conditions, implying that there was insufficient time for ice segregation to occur. The freezing rate of the tree mounds was slower than that of the wet areas due to the difference of such as soil moisture and snow cover depends on vegetation and microtopography. These results indicate that future changes in snow cover, soil moisture, and organic layer, which control underground thermal conductivity, will have significant impacts on the freezing environment of the ground ice at the Taiga–Tundra boundary in northeastern Siberia. Such changes in the freezing environment will then affect vegetation due to changes in the microtopography of the ground surface.

Aboveground Biomass Of Mongolian Larch (Larix Sibirica Ledeb.) Forests In The Eurasian Region

We used our database of tree biomass with a number of 433 sample trees of Larix from different ecoregions of Eurasia, involving 61 trees from Mongolia for developing an additive model of biomass tree components. Our approach solved the combined problem of additivity and regionality of the model. Our additive model of tree aboveground biomass was harmonized in two ways: first, it eliminated the internal contradictions of the component and of the total biomass equations, secondly, it took into account regional (and correspondingly species-specific) differences of trees in its component structure. A significant excess of larch biomass in the forest-tundra is found that may be explained by permafrost conditions, by tree growth in low-yielding stands with a high basic density of stem wood and relatively high developed tree crown in open stands. The aboveground biomass of larch trees in Mongolia does not stand out against the background of the most ecoregions of Eurasia. Based on our results, we conclude that the growing conditions of larch in Mongolia are not as tough as it was suggested earlier by other scientists. Biomass relations between regions may be explained by unknown and unaccounted factors and errors of measurements in all their phases (assessment of age, diameter, height of a tree, the selection of supposedly representative samples of component biomass, their drying, weighing, etc.). The question what explains the regional differences in the structure of biomass of trees with the same linear dimensions of their stems, remains open. Undoubtedly, the differences in tree age here play an important role. Also, important factor is the variation in the morphological structure of stands, which, in turn, is determined by both climatic and edaphic factors. The obtained models allow the determination of larch forest biomass in different ecoregions of Eurasia with the help of height and diameter data.

Effects of extreme drought and wet events for tree mortality: Insights from tree‐ring width and carbon isotope ratio in a Siberian larch forest

AbstractRecent studies suggest that forest vulnerability to tree mortality has increased as a result of extreme climate events such as severe drought and heavy rain. However, little is known about the mortality processes, particularly when they are induced by heavy rain. A dendroecological analysis was conducted on living and dead trees in a Siberian larch forest using the chronologies of 30 years of radial growth and carbon isotope (Δ13C) discrimination. The analysis demonstrates the relationship between heavy rain and larch tree mortality. Radial growth and Δ13C patterns in dead trees at a wet subsite diverged from those of living trees only during the heavy rain period in 2005–2007. On the other hand, the radial growth and Δ13C patterns in dead trees at the dry subsite diverged from those of living trees after severe drought events in 1998 and in 2002–2003. At the wet subsite, the heavy rain was intense enough to push the larch trees past their mortality threshold, whereas previous drought conditions also contributed to tree mortality at the dry subsite. Our results demonstrated that the process of larch tree mortality differs with site‐specific topographical soil moisture conditions, even when synchronous tree death occurs in a specific year of climatic extremes.

Phenology of wood formation in larch (Larix decidua Mill.) trees growing along a 1000-m elevation gradient in the French Southern Alps

Spring temperature increase is the main driver of larch tree wood formation onset along a 1000-m elevation gradient in the Southern Alps, while its cessation is more probably controlled by water stress at the lowest elevation and photoperiod at higher ones. The survival of perennial plants depends on their adaptation to changing environment and specially temperature, which in trees is notably implemented through wood formation process. Our main objective is to understand how the phenology of wood formation is related to environmental factors and to temperature in particular. We monitored the xylogenesis of 60 larch trees, distributed in four stands along an elevation gradient of 1000 m in the French Southern Alps. Cambial activity started around mid-May at the lowest site (1350 m) and around mid-June at the highest one (2300 m), showing a delay of 5.4 days per °C. The onset of wall-thickening and mature phenophases followed the same linear trend with a delay of 5.2 and 3 days per °C, respectively. Phenophase cessations followed a parabolic trend with trees from the lowest site finishing their growth the first, while those from 1700 m finished the last. Our results show that the onset of xylem formation is mainly driven by spring temperature increase, while its cessation is more related to photoperiod, with water shortage being able to hasten it. Future climatic changes will most probably increase growing season length (but not necessarily wood production) and shift upwards the optimal elevation for larch growth in the Southern Alps.

Effects of Radial Growth Rate on Wood and Lumber Properties of 67-Year-Old Japanese Larch (Larix Kaempferi) Trees Planted in Tochigi, Japan

The wood and lumber properties were examined for 67-yr-old Japanese larch (Larix kaempferi) trees with different radial growth rates planted in Tochigi Prefecture, Japan. The trees were categorized into slow-, medium-, and fast-growing groups based on the stem diameter. No significant difference in stresswave velocity of stems, which is closely related with Young’s modulus of wood, was found among three radial growth categories (stem diameter classes). The boundary between juvenile wood (JW) and mature wood (MW) determined by latewood tracheid length (TL) existed about the 20th annual ring from the pith in all sample trees. Significant differences between JW and MW were found in most of examined wood and lumber properties. It was found that trees with fast growth do not always cause lower grade lumberproperties.

Genetic Mapping of Prince Rupprecht's Larch (Larix principis-rupprechtii Mayr) by Specific-Locus Amplified Fragment Sequencing.

A high-density genetic linkage map is essential for plant genetics and genomics research. However, due to the deficiency of genomic data and high-quality molecular markers, no genetic map has been published for Prince Rupprecht’s larch (Larix principis-rupprechtii Mayr), a conifer species with high ecological and commercial value in northern China. In this study, 145 F1 progeny individuals from an intraspecific cross between two elite clones of L. principis-rupprechtii and their parents were employed to construct the first genetic map in this important tree species using specific-locus amplified fragment sequencing (SLAF-seq). After preprocessing, the procedure yielded 300.20 Gb of raw data containing 1501.22 M pair-end reads. A total of 324,352 SNP markers were detected and 122,785 of them were polymorphic, with a polymorphism rate of 37.86%. Ultimately, 6099 SNPs were organized into a genetic map containing 12 linkage groups, consistent with the haploid chromosome number of larch and most other species in the Pinaceae family. The linkage map spanned 2415.58 cM and covered 99.6% of the L. principis-rupprechtii genome with an average of 0.4 cM between adjacent markers. To the best of our knowledge, this map is the first reference map for L. principis-rupprechtii, as well as the densest one obtained in larch species thus far. The genome-wide SNPs and the high-resolution genetic map will provide a foundation for future quantitative trait loci mapping, map-based cloning, marker-assisted selection, comparative genomics, and genome sequence assembly for larch trees.

Селекционно-генетический анализ лиственниц сибирской и Сукачева, интродуцированных в Москву и Подмосковье

The question of taxonomic status of Sukachev’s larch is still not understood to a full degree. There are arguments both in favor of separation of Siberian and Sukachev’s larches into individual species, and in favor of association them into the one. The issues of great importance are the works on the introduction of larch trees in the center of the European part of Russia in order to increase the resource potential of forests in this region. The study of variability of Siberian and Sukachev’s larches in the new climatic conditions, which take place during the introduction, can give interesting results important not only for discussion of their taxonomic rank, but for practical purposes of introduction. The paper presents comparative analysis of Siberian and Sukachev’s larches according to their individual variability of morphological characteristics and molecular genetic analysis. The studies were carried out in the conditions of introduction in Moscow (Main Botanical Garden named after N.V. Tsitsin) and Moscow region (Ivanteevskiy Arboretum). The morphological features of cones, needles and seeds were studied: length and width of cones, number of scales in them, length of needles, length and width of seeds. The arithmetic mean values of characters, the error of the arithmetic mean values of characters and the coefficient of variation were counted. On the basis of the obtained results, significant differences in morphological characteristics of cones, seeds and needles are established, which gives reasons to distinguish Sukachev’s larch as a geographical race; a subspecies of Siberian larch.For citation: Bryntsev V.A., Lavrenov M.A. Genetic Selection Analysis of Siberian and Sukachev’s Larches Introduced in Moscow and Moscow Region. Lesnoy Zhurnal [Forestry Journal], 2019, no. 4, pp. 9–21. DOI: 10.17238/issn0536-1036.2019.4.9

A 400-year reconstruction of wintertime Arctic sea-ice extent using a high-elevation, mid-latitude tree-ring record.

We examined relationships between wintertime Arctic sea-ice extent (ASIE) and radial growth rates of alpine larch trees (LALY) in the northern Rockies, USA, during 1979-2015 (r= - 0.71, p< 0.01) and reconstructed ASIE fluctuations from 1613 to 2015. Wintertime ASIE corresponds with summertime mid-latitude upper-level atmospheric flow patterns with ridging (troughing) and warmer (cooler) conditions prevailing in the Rockies when ASIE are below (above) average. In turn, warmer (cooler) summertime conditions favor (disfavor) growth of LALY, thus "recording" interannual variations in ASIE. Both 1000hPa temperatures and 500hPa geopotential heights during years of anomalously high or low radial growth negatively correspond with ASIE, suggesting that a disjunct spatial influence on atmospheric conditions may be associated with interannual variability of ASIE. Reconstructed ASIE values show that 1996-2015 was the lowest 20-year period on record, but the mean value is not significantly different from six other distinct periods of below-average ASIE.

Identification of antimicrobial compounds in different hydrophilic larch bark extracts

Larch bark is an undervalued material, but it has unique and valuable characteristics and compounds. The objective of this study was to extract and characterize molecular compounds of bark materials from different larch trees and to test these for their antimicrobial properties. The extractions were performed using methanol or water. The obtained extracts were analysed by gas chromatography coupled to mass spectrometry (GC-MS). Antimicrobial properties also were determined using different microbial strains, for example, Staphylococcus aureus. The GC-MS analysis showed that long chain alcohols, fatty acids, and polyphenols were present in the extracts. According to the results of the agar diffusion tests, only the methanol extract of larch bark had an inhibitory effect on the growth of Staphylococcus aureus. Two compounds of flavonoids and stilbenoids were shown to affect the microbial activity of the larch bark. Therefore, larch bark can be used for the extraction of compounds with specific anti-microbial properties.

Tree spatial patterns modulate peak snow accumulation and snow disappearance

Forests and snow covered regions frequently co-occur across the northern hemisphere. In these environments, forests are structurally and spatially complex mosaics of tree neighborhoods that are intrinsically linked to ecosystem functions. Tree and canopy structures influence snow accumulation and disappearance processes through interception and radiation attenuation. However, it is unclear if spatial heterogeneity within the forest canopy induces heterogeneity in snow accumulation and persistence. We quantitatively identified different tree neighborhoods and tested the differential effects of these within-stand neighborhoods on snow processes. Neighborhood types included individual ponderosa pine (Pinus ponderosa), Douglas-fir (Pseudotsuga menziesii) and western larch (Larix occidentalis) trees, dense overstory tree clumps, openings, and regeneration patches. Intensive measurements of snow accumulation (density and depth) and persistence (disappearance date) were made within replicate neighborhoods for three years. Overall, neighborhood type and year had a significant effect on accumulation and snow disappearance. Openings were significantly different from clumps and individuals, always accumulating more snow. Openings retained snow significantly later than clumps but were not significantly different from individuals. Within the individual tree neighborhood type, a nested species effect indicated no differences in accumulation but significant differences in disappearance between deciduous and evergreen conifers, with snow persisting longer beneath deciduous western larch. Our results suggest that canopy interception is the primary mechanism driving the accumulation phase, while snow disappearance patterns are largely a consequence of spatial variation of longwave radiation. Reducing canopy interception and longwave radiation by increasing the abundance of widely spaced single trees and small openings with silvicultural treatments should increase snow depth and duration, and thus snow water storage. Maintaining a heterogeneous canopy structure that includes tree clumps can be used to meet multiple objectives such as provision of ungulate winter range habitat, and heterogenous understory plant phenology.

Compound-specific carbon isotope patterns in needles of conifer tree species from the Swiss National Park under recent climate change

Elevated CO2 along with rising temperature and water deficits can lead to changes in tree physiology and leaf biochemistry. These changes can increase heat- and drought-induced tree mortality. We aim to reveal the impacts of climatic drivers on individual compounds at the leaf level among European larch (Larix decidua) and mountain pine (Pinus mugo) trees, which are widely distributed at high elevations. We investigated seasonal carbon isotope composition (δ13C) and concentration patterns of carbohydrates and organic acids in needles of these two different species from a case study in the Swiss National Park (SNP). We found that average and minimum air temperatures were the main climatic drivers of seasonal variation of δ13C in sucrose and glucose as well as in concentrations of carbohydrates and citric acid/citrate in needles of both tree species. The impact of seasonal climatic drivers on larch and mountain pine trees at the needle level is in line with our earlier study in this region for long-term changes at the tree-ring level. We conclude that the species-specific changes in δ13C and concentrations of carbohydrates and organic acids are sensitive indicators of changes in the metabolic pathways occurring as a result of climatic changes.

Types and rates of decomposition of Larix sibirica trees and logs in a mixed European boreal old-growth forest

Information on pathways and rates of decomposition of coarse woody debris (CWD) from one of the dominant boreal tree species – Siberian larch (Larix sibirica Ledeb.) – is scarce. We examined presence and distribution of internal decay in its living trees and decomposition rates in an 88-year chronosequence of logs in an old-growth mesic mixed European boreal forest. Fifty-two percent of the trees started decaying prior to death. Butt or stem rot was caused by white- and brown-rot biotrophic fungi in almost equal proportions. Those trees lost on average 29% of their initial wood mass. The mean decomposition rate of wood as related to initial conditions was 0.007 yr−1 for wood with initial biotrophic decay and 0.010 yr−1 for wood with saprotrophic decay. Bark lost its mass and volume faster – at a rate of 0.056 yr−1. The rate of carbon (C) loss for the whole stem was 0.024 yr−1 in wood affected by saprotrophic fungi and 0.007 yr−1 when the tree was affected by biotrophic fungi. When calculating C losses due to decomposition, separating bark and wood with different C concentrations and decomposition patterns as well as the rate of biotrophic and saprotrophic decay enables us to refine estimates of the role of Siberian larch CWD in C cycling. Further research is still needed to resolve uncertainties around the role of fungal communities and the origins and decomposition rates of butt rots and stem rots in living trees of Siberian larch, as well as the distribution patterns of these fungi and decomposition processes in individual trees and at the ecosystem level.

Canopy transpiration of a Larix sibirica and Pinus sylvestris forest in Central Siberia

Russian boreal forests represent the largest forested region on Earth and comprise one-fifth of the world's forest cover. The two most common genera in Siberia are Larix and Pinus, which together cover more than 80% of the region’s forested area. One observable ongoing effect of climate warming is that natural populations of Siberian larch are gradually being replaced by Scots pine. The present work focuses on comparing effects of environmental variables on sap flow density in two even-aged stands of Larix sibirica and Pinus sylvestris. While the two study stands were identical in age (49 years) with similar basal areas and leaf area index, they exhibited very different transpiration rates and response mechanisms to environmental signals. Stand water use was higher for larch than it was for pine, even though transpiration for deciduous larch trees occurred over shorter time periods. The cumulative annual transpiration of the larch stand was 284 ± 4 mm measured over two consecutive growing seasons (2015–2016), while for pine this was 20% lower. Seasonal transpiration accounted for 50% and 40% of the reference evapotranspiration and 91% and 67% of growing season precipitation for larch and pine, respectively. Water stored in soil provided an important source of water for transpiration, observed as roughly 100 mm, which was then replenished from snowmelt the following spring. The greatest difference between two species related to how well they controlled transpiration, notably in the context of high vapor pressure deficit; under these conditions, pine maintained greater control over transpiration than larch. For all soil moisture levels measured, larch transpired more water than pine. Importantly, our results point to potential future effects of global warming, most notably an increasing decline of larch forests, changes in the ratio between latent and sensitive heat fluxes, and significant modifications in ecosystem water availability.

Формування лісової підстилки в деревостанах за участю модрини європейської в умовах Кременецького горбогір'я

Досліджено формування лісової підстилки в 14–109-річних деревостанах за участю модрини європейської. У складі деревостанів частка модрини змінюється в межах 1–10 одиниць. Встановлено, що під наметом деревостанів за участю модрини європейської запас лісової підстилки в абсолютно сухому стані становить 0,30–1,96 кг/м². У її складі маса листя і хвої змінюється в межах 0,22–1,18 кг/м², або 9,4–84,9 %, а пагонів, шишок, кори тощо – від 0,08 до 1,55 кг/м², або 15,1–90,6 % від загальної її маси. У модрини у віці молодняків розпочинається і продовжується в середньовікових деревостанів до 50–60 років інтенсивне відмирання пагонів та очищення стовбурів дерев від сучків. Воно призвело до збільшення у складі лісової підстилки маси пагонів і кори до 50–90 %. У чистих модринових деревостанах нагромаджується більший запас лісової підстилки, ніж у мішаних. У молодняків запас лісової підстилки в чистому модриновому деревостані перевищує мішані на 2,1–88,6 %. У середньовікових, стиглих і перестиглих деревостанів такі відмінності становлять 4,7–75,4 %. Показано, що лісостани характеризуються різним варіюванням маси лісової підстилки загалом чи її фракцій у межах деревостану. Коефіцієнт варіації маси лісової в деревостанах виявився в основному середнім і рідше слабким (V = 6,1–20,5 %). Поряд з цим значно зростає варіювання фракцій лісової підстилки. Так, варіювання маси хвої і листя змінюється в межах 6,8–33,1 %, а фракції пагонів, шишок, кори тощо – 6,1–42,9 %.

Water Yield Responses to Gradual Changes in Forest Structure and Species Composition in a Subboreal Watershed in Northeastern China

Relationships between forest cover and streamflow have been studied worldwide, but only a few studies have examined how gradual changes in forest structure and species composition due to logging and climate change affect watershed water yield (Q) and flow regimes. In this study, we analyzed long-term (45 years) hydrologic, climate and forest dynamics data from the subboreal Tahe watershed in northeastern China. Our purpose was to evaluate the effects of forest logging and regeneration on changes in forest biomass and species and to quantify the subsequent impact on mean annual streamflow and flow regime under a changing climate. The study watershed was dominated by old-growth larch (Larix gmelinii Rupr.) during the 1970s, but gradually transformed into young deciduous larch mixed with deciduous broad-leaved birch (Betula platyphylla Sukaczev) during the 2010s. During the same period, the watershed experienced climate change with a significant increase in air temperature of 0.028 ℃/year. We applied eight sensitivity-based techniques to separate the effects of climate change on water yield from those due to forest changes. We used flow duration curves (FDCs) to characterize flow regimes by dividing the study into four key periods based on the proportional change of larch and birch trees. We found that the mean annual streamflow decreased by 10 mm (−16 mm attributed to forest change and +6 mm to climate change) between the 1984–1994 period and the 2006–2016 period when the proportion of birch increased by 20% with a similar total forest volume in the later period. The mean annual streamflow increased from 216 mm to 270 mm (+35.5 mm due to forest change vs +17.7 mm due to climate change) when forest volume decreased by 18.7% (17 m3/ha) between the 1970s and 1984–1994. Water yield changed only slightly (3.5 mm) when forest volume increased by 8.7% (6 m3/ha) from 2000 to 2011. In addition, the magnitude of high flow and low flow increased following deforestation and a shift in species composition from a period (1984–1994) with 70% larch with 30% birch to a later period (2006–2016) with 50% larch with 50% birch. Both high flow and low flow decreased coinciding with a reforestation period (2006–2016). Our results highlight complex interactions among climate, forest structure, total biomass, and plant diversity (trees species composition) in influencing watershed hydrology. Further study is needed to examine the effects of ecohydrological processes such as evapotranspiration in larch and birch forests on hydrologic changes across multiple scales.

Siberian larch (Larix sibirica Ledeb.) chloroplast genome and development of polymorphic chloroplast markers

BackgroundThe main objectives of this study were sequencing, assembling, and annotation of chloroplast genome of one of the main Siberian boreal forest tree conifer species Siberian larch (Larix sibirica Ledeb.) and detection of polymorphic genetic markers – microsatellite loci or simple sequence repeats (SSRs) and single nucleotide polymorphisms (SNPs).ResultsWe used the data of the whole genome sequencing of three Siberian larch trees from different regions - the Urals, Krasnoyarsk, and Khakassia, respectively. Sequence reads were obtained using the Illumina HiSeq2000 in the Laboratory of Forest Genomics at the Genome Research and Education Center of the Siberian Federal University. The assembling was done using the Bowtie2 mapping program and the SPAdes genomic assembler. The genome annotation was performed using the RAST service. We used the GMATo program for the SSRs search, and the Bowtie2 and UGENE programs for the SNPs detection. Length of the assembled chloroplast genome was 122,561 bp, which is similar to 122,474 bp in the closely related European larch (Larix decidua Mill.). As a result of annotation and comparison of the data with the existing data available only for three larch species - L. decidua, L. potaninii var. chinensis (complete genome 122,492 bp), and L. occidentalis (partial genome of 119,680 bp), we identified 110 genes, 34 of which represented tRNA, 4 rRNA, and 72 protein-coding genes. In total, 13 SNPs were detected; two of them were in the tRNA-Arg and Cell division protein FtsH genes, respectively. In addition, 23 SSR loci were identified.ConclusionsThe complete chloroplast genome sequence was obtained for Siberian larch for the first time. The reference complete chloroplast genomes, such as one described here, would greatly help in the chloroplast resequencing and search for additional genetic markers using population samples. The results of this research will be useful for further phylogenetic and gene flow studies in conifers.

Nitrogen loading increases the ozone sensitivity of larch seedlings with higher sensitivity to nitrogen loading

Larch (Larix sp.) tree is a critical species for the future afforestation in Northeast Asia. The impacts of elevated concentrations of ground-level ozone (O3) and nitrogen (N) deposition are raising concerns. However, knowledge of the combined effects of elevated O3 and N loading are still limited. We investigated whether nitrogen loading mitigates the negative impacts of ozone on two larch species: the Japanese larch (L. kaempferi) and its hybrid larch F1 (L. gmelinii var. japonica × L. kaempferi) or not. We used open-top cambers and compared responses of the larch seedlings. Results showed the N loading mitigated the negative effects of O3 on Japanese larch. However, in hybrid larch F1, N loading did not mitigate O3-induced inhibition of growth and photosynthetic capacity. Mitigation effect of N loading on negative O3 impacts may vary between the two Larix spp., Hybrid larch F1 could be more affected by the combined effects of O3 and N loading due to its higher growth response to N loading. Elevated O3 also reduced leaf nitrogen/phosphorus (N/P) ratio by elevated O3, with significant effects in hybrid larch F1, particularly under N loading. In the present study, leaf N/P ratio was utilized to validate the hypothesis that a positive effect of N loading may be observed if O3 does not induce P limitation in Larix spp. We demonstrated a potential leaf N/P ratio function, which could reflect responses to O3 and N loading in hybrid larch F1.

БІОЕКОЛОГІЧНИЙ АНАЛІЗ ФЛОРИ БІОТОПУ ЗАЛІЗНИЦЬ м. ДНІПРО

Наведено біоекологічний аналіз флори та аналіз адвентивної фракції біотопу залізниць м. Дніпро. Список флори складено на основі власних польових досліджень. Флора залізниць м. Дніпро представлена 167 видами судинних рослин, які належать до 42 родин та 138 родів. Адвентивна фракція флори представлена 47 видами судинних рослин.

The quality comparison of particleboards produced from heartwood and sapwood of European larch

In this paper, the impacts of heartwood and sapwood usage on the physical, mechanical, and surface properties and formaldehyde emission of particleboard are investigated. European Larch (Larix decidua) trees are chosen as a raw material. The logs are divided into three segments: sapwood, heartwood and total wood. The highest amounts of cellulose (51,54%), and hemicelluloses (22,24%) in the sapwood, followed by total wood, and the heartwood, respectively. However, the highest amount of lignin (30,54%) was found in the heartwood. The highest extractives values are obtained from heartwood, followed by total wood, and the sapwood, respectively. While the lowest pH value (3,03) is found in heartwood, the sapwood samples provide the highest values (4,95). The highest ash (0,49%) content and amount of condensed tannin (13,89%) are extracted from heartwood, followed by total wood, and sapwood, respectively. The test panels manufactured from sapwood have the smoothest surface (7,49 µm (Ra), 48,86 µm (Ry), and 35,12 µm (Rz)) and the lowest contact angles (67,8°), while the roughest surface (14,20 µm (Ra), 68,05 µm (Ry), and 50,02 µm (Rz)) and highest contact angle (96,9°) are obtained from the panels of heartwood. The thickness swelling (19,88%) and formaldehyde emission (7,28%) values of the panels manufactured from heartwood are significantly lower than the panels manufactured from the total wood and sapwood. The highest modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond (IB) values are observed on sapwood, respectively, 15,60 MPa (MOR), 2201 MPa (MOE), and 0,523 MPa (IB). These mechanical strength values (MOR, MOE, and IB) are followed by total wood, and the heartwood, respectively. Surface smoothness and wettability of the particleboards manufactured from sapwood are better than those of total wood and heartwood.

Біоелектричні потенціали модрини європейської в деревостанах Кременецького горбогір'я

Досліджено біоелектричні потенціали модрини європейської, дуба звичайного, ялини європейської і сосни звичайної, які формують деревостани в різних типах лісорослинних умов Кременецького горбогір'я. Вік деревостанів становить 12–109 років. Частка модрини в їх складі змінюється в межах 1–10 одиниць. Модрина європейська в умовах суборів і сугрудів характеризується нижчими абсолютними показниками БЕП кореневої шийки, порівняно з сосною звичайною, а в умовах грудів – вищими, порівняно з дубом звичайним і ялиною європейською. Встановлені відмінності між деревними видами зберігаються упродовж дня. Відмінності між модриною і дубом за абсолютними показниками біопотенціалів посилюються у другій половині дня. У модрини в мішаних молодняках і середньовікових деревостанах абсолютні значення БЕП виявились вищими, ніж у чистих деревостанах. Встановлено три типи денних біопотенціалограм, які характеризують динаміку проходження метаболічних процесів у деревних видів у деревостанах різних лісорослинних умов та видового складу. Між біометричними показниками модельних дерев різних деревних видів і середньоденними показниками біопотенціалів переважно спостережено помірний і значний прямий кореляційний зв'язок. Більш тісною залежність денної зміни біопотенціалів виявлено від денної динаміки температури і вологості повітря, аніж від інтенсивності світла. Між вологістю повітря і біоелектричними потенціалами існує зворотний кореляційний зв'язок.