Late Wood Research Articles

Воздействие климатических факторов на приросты сосны обыкновенной (Pinus sylvestris L.) на побережье Кандалакшского залива Белого моря

The purpose of this study is a comparative analysis of linear and radial increments of Scots pine (Pinus sylvestris L.) as a response to the growing conditions on the coast of the Kandalaksha Bay of the White Sea, as well as an evaluation of the temperature and precipitation influences of the current and previous growing seasons. These were applied to the conventional methods of measurement and data analysis. The dynamics of growth in height and diameter were employed as indicators of the stands' response to habitant conditions. A statistical analysis of the growth rates was performed, which vary depending on habitat type, as well as an assessment of the connection between biometric indicators of the stands and the amount of precipitation and mean temperature. The significant differences in the series of linear increment increases were found as distinctions between biotopes, but they were absent for the radial increment. Therefore, it is possible to monitor the typical behavior of tree diversity independent of the biotope type using radial growth series. This provides the foundation for a long-term retrospective analysis of environmental impact on the stands by using the annual rings of the trees without taking growing conditions into account. Precipitation was determined to be a limiting factor for radial and linear growth throughout the phenophase of internodal growth and early wood formation. Temperature was identified as a limiting factor for radial development only during the stages of late wood formation and resource accumulation for the following growing season. The high sensitivity of linear increases to climatic conditions was revealed, which makes it useful as a criterion for assessing the state of forest ecosystems over short time periods (up to 30 years). However, this, in turn, dictates the impossibility of forming long-term linear increment series, as for radial growth, which is a significant limitation of this method. The choice of linear or radial growth analysis methods is concluded to be determined by the goals of the intended study, i.e., monitoring forest ecosystems under current climate change conditions or long-term paleoclimate analysis. For citation: Koukhta A.E., Maksimova O.V., Kuznetsova V.V. Influence of Climatic Factors on Scots Pine (Pinus sylvestris L.) Growth on the Coast of the Kandalaksha Bay of the White Sea. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 4, pp. 105–119. (In Russ.). https://doi.org/10.37482/0536-1036-2023-4-105-119

The Early- to Latewood Transition Phenology Is Asynchronous between the Different Parts of Abies forrestii var. smithii in Jiaozi Mountain, Yunnan, China

Phenological synchronicity of different tree parts and habitats can provide valuable insights into the physiological relationships and regulatory factors of different phenologies. The earlywood (EW) to latewood (LW) transition of the xylem is a critical process closely related to the key functions and physiological processes of trees. This study investigated the phenology phase of the EW–LW transition in branches and stems of Smith fir (Abies forrestii var. smithii Viguié & Gaussen) along an altitude gradient (3600 m, 3800 m, and 4000 m) in Jiaozi Mountain, Yunnan, China, in 2021. The study aimed to test the hypothesis that branches transition earlier than stems, but the elevation does not affect the transition time. We monitored the EW–LW transition dates weekly using microcores and then correlated them to the climatic conditions and developmental processes. Our findings revealed that the EW–LW transition timing varied among the different parts of the tree but was synchronized across the different elevations. Furthermore, the transition always occurred earlier in branches than in the stem, but the difference narrowed with increasing altitude. The EW–LW transition was mainly influenced by photoperiod, which plays a crucial role as a signaling factor. Additionally, the tree crown was more sensitive to environmental changes than the stem. The transition time of stems was less sensitive to environmental factors than that of branches. Therefore, our results suggest that the earlywood to latewood transition is regulated by developmental factors, and the photoperiod may indirectly regulate the developmental process of trees as a signaling factor, thus regulating the earlywood to latewood transition time. Our study provides new insights into the developmental regulation and climate sensitivity of tree ring formation.

CHANGES IN HEMICELLULOSE STRUCTURE ASSOCIATED WITH THE TRANSITION FROM EARLYWOOD TO LATEWOOD AT JUVENILE WOOD IN CRYPTOMERIA JAPONICA

The chemical composition and variations in chemical structure of hemicellulose in earlywood (EW) and latewood (LW) of two individual Japanese cedar trees (C-Boka and T-Boka) were investigated. The trees were cultivated under different growth conditions: C-Boka grew slowly in a forest, while T-Boka grew rapidly in a location rich in nutrients and sunshine. For the chemical structure of hemicellulose, arabinoglucuronoxylan (AGX) showed varied side-chain substitution rates with glucuronic acid and different molecular weights in the transition between EW and LW. In contrast, the fundamental composition of glucomannan/galactoglucomannan (GM/GGM) was relatively unchanged between EW and LW. The modification of AGX and GM/GGM from EW to LW differed between C-Boka and T-Boka and might be influenced by the growth rate of the trees.

The North American Monsoon buffers forests against the ongoing megadrought in the Southwestern United States.

The US Southwest has been entrenched in a two-decade-long megadrought (MD), the most severe since 800 CE, which threatens the long-term vitality and persistence of regional montane forests. Here, we report that in the face of record low winter precipitation and increasing atmospheric aridity, seasonal activity of the North American Monsoon (NAM) climate system brings sufficient precipitation during the height of the summer to alleviate extreme tree water stress. We studied seasonally resolved, tree-ring stable carbon isotope ratios across a 57-year time series (1960-2017) in 17 Ponderosa pine forests distributed across the NAM geographic domain. Our study focused on the isotope dynamics of latewood (LW), which is produced in association with NAM rains. During the MD, populations growing within the core region of the NAM operated at lower intrinsic and higher evaporative water-use efficiencies (WUEi and WUEE , respectively), compared to populations growing in the periphery of the NAM domain, indicating less physiological water stress in those populations with access to NAM moisture. The disparities in water-use efficiencies in periphery populations are due to a higher atmospheric vapor pressure deficit (VPD) and reduced access to summer soil moisture. The buffering advantage of the NAM, however, is weakening. We observed that since the MD, the relationship between WUEi and WUEE in forests within the core NAM domain is shifting toward a drought response similar to forests on the periphery of the NAM. After correcting for past increases in the atmospheric CO2 concentration, we were able to isolate the LW time-series responses to climate alone. This showed that the shift in the relation between WUEi and WUEE was driven by the extreme increases in MD-associated VPD, with little advantageous influence on stomatal conductance from increases in atmospheric CO2 concentration.

Nanomechanical/Micromechanical Approach to the Problems of Dendrochronology and Dendroclimatology

The most widespread approach in dendrochronology (wood dating) and dendroclimatology (climate reconstruction) is based on measurement of the width of annual growth rings by analyzing optical images of wood cross sections. This approach is quite efficient and easy to implement but it has inherent drawbacks. Raw data for these techniques originate from the optical properties of the wood surface, which are not directly related to other properties of wood, mechanical properties in particular. This paper describes a new quantitative approach applicable to dendrochronology and dendroclimatology based upon measurement of the micromechanical properties of wood by employing nanoindendation and digital sclerometry. It yields not only the width of annual growth rings and early and late wood layers with an accuracy not inferior to optical methods, but also rich data on the mechanical properties of the wood with a high spatial resolution that could be brought to subcellular scale if necessary. This data can be used for the dendrochronological analysis of archeological finds and the evaluation of climatic parameters during tree growth with a time resolution of up to a month or even better, which is unlike other common methods with a time resolution of one year. Moreover, the detailed continuous profiling of local mechanical properties can form a basis for improving our understanding of the nature and mechanisms of the formation of macromechanical properties important for applications and can clarify the climate factors that have the greatest impact on such properties.

EVOLUTION AND DISTRIBUTION OF SHAKES IN LARCH LOGS DURING AIR DRYING

This paper analyzed the length, width, and location of shakes in the air-drying process of larch log (Larix principis-rupprechtii Mayr) 1 m long and 66% initial moisture content. The development law and distribution characteristics of shakes during log drying of larch were studied and shake generation and development law were analyzed from two aspects of microstructure and growth defects. The variation of dry shrinkage deformation along the radial direction and knot influence on it was analyzed using the split-shaped stress test strips. At the cellular level, the cell wall shrinkage behavior of heartwood and sapwood and the microstructure of knots were observed. The results showed a significant relationship between eccentricity and shake distribution; the IIa region is the most prone to dry shake. The evolution of shakes is closely related to the drying rate. In the high-speed drying stage (MC ≥ 40%), shakes almost do not occur; in the decelerating drying stage (40% ≥ MC ≥ 20%), the amount, length, and width of shakes increase rapidly. In the low-speed drying stage (20% ≥MC), the area of shakes tends to stabilize or even decline. The main reasons for dry shaking are the dry shrinkage difference between tangential and radial cell walls, early and late wood, heartwood and sapwood, and moisture content gradient during the drying process.

An Overview of Extreme Years in Quercus sp. Tree Ring Records from the Northern Moldavian Plateau

In this study, we made use of a regional oak tree-ring network from six stands that cover the northern Moldavian Plateau (eastern Europe) to analyze how different tree ring parameters (i.e., early wood tree-ring width, late wood tree-ring width, and total tree-ring width) of Quercus sp. are influenced by the occurrence of extreme climatic events (e.g., long-lasting drought events). In order to explore the influence of extreme hydroclimatic events on tree ring width, we have selected each of the six most extreme positive and negative years of tree growth and addressed the seasonal cycle of tree growth in comparison with the main climatic parameters, then evaluated both the current and lagged consequences of extreme hydroclimatic events on tree ring width and the capacity of trees to recover. Our results indicate that the variability of oak tree ring width from the Moldavian Plateau is mainly influenced by the availability of water resources, and that an important limiting growth factor for Quercus sp. is the occurrence of long-lasting drought events, e.g., at least two years in a row with severe drought conditions.

The effects of intrinsic water-use efficiency and climate on wood anatomy.

Climate warming may induce growth decline in warm-temperate areas subjected to seasonal soil moisture deficit, whereas increasing atmospheric CO2 concentration (Ca) is expected to enhance tree growth. An accurate understanding of tree growth and physiological processes responding to climate warming and increasing Ca is critical. Here, we analyzed tree-ring stable carbon isotope and wood anatomical traits of Pinus tabuliformis from Qinling Mountains in China to understand how lumen diameter (LD) determining potential hydraulic conductivity and cell-wall thickness (CWT) determining carbon storage responded to climate and Ca. The effects of climate and Ca on intrinsic water-use efficiency (iWUE) were isolated, and iWUE values due to only-climate (iWUEClim) and only-CO2 effects (iWUECO2) were obtained. During a low-iWUE period, the influences of climate on earlywood (EW) LD and latewood (LW) CWT prevailed. During a high-iWUE period, CO2 fertilization promoted cell enlargement and carbon storage but this was counteracted by a negative influence of climate warming. The limiting direct effects of iWUEClim and indirect effects of climate on EW LD were greater than on LW CWT. P. tabuliformis in temperate forests will face a decline of growth and carbon fixation, but will produce embolism-resistant tracheids with narrow lumen responding to future hotter droughts.

Плотность древесины сосны обыкновенной в осушаемом сосняке сфагновом

The task of increasing forest productivity has been and remains one of the current interests of the European North of Russia, especially after the period of primary development of the forest areas. In the European Northeast, excessive humidity is observed at rather low average temperatures, which prevents active surface evaporation. In the twentieth century, the hydrotechnical reclamations were conducted on the large areas of swampy forests that increased the total productivity. The ecologists have an ambivalent attitude concerning forest draining. The supporters, who try to protect the undisturbed forest territories, counteract such activities. At the same time, the cultivation of highly productive forests of the right composition and quality requires measures for natural afforestation, or artificial forests must be created. Besides the total productivity of the stands, wood quality is an important factor in the hydroamelioration. It is mainly determined by density and the ratio between early and late wood. The influence of the landscape peculiarities of the drained forests on the quality of the wood was examined by the devotion of the areas according to the most typical groups of microrelief: flat areas, elevations, transitional areas. In cases of extensive humidity, the death of seedlings and artificial forest plantings was observed (soaking, frost extrusion, etc.). The creation of micro-elevations and the drainage of the excessive moisture guarantee the regeneration and establishment of the highly productive forests. The differences in the density of pine wood before and after the hydrotechnical reclamation were detected according to the landscape. The largest changes in the indicator were determined at the elevations and the flat areas, with the increase and the decrease, respectively. The trees that grow on the flat terrain after the reclamation show a relative excess of early wood over late wood, while at the elevations the presence of the late wood is predominant. For citation: Zagorodski M.A., Tretyakov S.V., Koptev S.V. Density of Scots Pine Wood in Drained Sphagnum Pine Forest. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 2, pp. 160–171. (In Russ.). https://doi.org/10.37482/0536-1036-2023-2-160-171

Effects of the Most Appropriate Proportion of Phytohormones on Tree-Ring Growth in Clones of Hybrid Larch

The increase in the atmospheric carbon dioxide concentration promotes its accumulation in trees by regulating the synthesis and transportation genes for endogenous hormones, such as IAA and GA, which are key factors in regulating various life activities, including growth rings. To explore the impact of changes in endogenous hormone levels such as IAA and GA on the growth of tree rings, and to provide a basis for improving the management of hybrid larch clonal forests, we investigated the effects of exogenous indole-3-acetic acid (IAA), gibberellic acid 3 (GA3), and their combination on tree-ring growth in hybrid larch. IAA, GA3, and a combination treatment were sprayed on the leaves of one clone of a hybrid larch seedling every three days. Small blocks were collected at the base stems for sequential anatomical observations. The phytohormone type, instead of the concentration, had a more significant effect on wood formation. Specifically, IAA treatment at 300 mg L−1 significantly increased latewood (LW) layers until 90 days after treatment (DAT). The 500 mg L−1 treatment significantly increased the wall radial thickness (WRT) of latewood (LW) cells. GA3 treatment at 100 mg L−1 significantly decreased the layers and width of total wood (TW), LW, and earlywood (EW). The 300 mg L−1 treatment significantly increased the WRT of EW. The IAA 100 mg L−1 + GA3 100 mg L−1 combination treatment significantly increased the layers and width of TW and LW by inducing cambium activity and increasing the rate of wood cell development. The WRT and lumen radial diameter (LRD) of EW or LW in this treatment were similar to those observed with the corresponding single phytohormone treatment. These results indicate that combination treatment at 100 mg L−1 + 100 mg L−1 was a better way to promote tree-ring growth. Our study suggests that changes in phytohormone levels and ratios are important factors that affect tree-ring formation. Hormone levels and ratios should be regarded as important indicators to guide the improvement of management practices in hybrid larch clonal plantations.

Multiscale wood micromechanics and size effects study via nanoindentation

Wood as a material is a natural composite with a complex hierarchically arranged structure. All scale levels of wood structure contribute to its macroscopic mechanical properties. The nature of such characteristics and deformation modes differs radically at different scale levels. Wood macroscopic properties are well studied, and the relevant information can be easily found in the literature. However, the knowledge of the deformation mechanisms at the mesoscopic level corresponding to the cellular structure of early and late wood layers of annual growth rings is insufficient. It hinders building the comprehensive multiscale model of how wood mechanical properties are formed. This paper described the results of scanning of mechanical properties of softwood and hardwood samples, such as common pine, small-leaf lime, and pedunculate oak, by means of nanoindentation (NI). The NI technique allows varying the size of deformed region within a wide range by altering maximal load (Pmax) applied to the indenter so that one can repeatedly and non-destructively test wood structural components at different scale levels on the same sample without changing the technique or equipment. It was discovered that the effective microhardness (Heff) and Young's modulus (Eeff) decreased manifold with Pmax growing from 0.2 to 2 000 mN. This drop in Heff was observed when the locally deformed region grew, and resulting from Pmax increase generally follows the rule similar to the Hall-Petch relation for yield stress, strength, and hardness initially established for metals and alloys, though obviously in those cases the underlying internal mechanisms are quite different. The nature and micromechanisms of such size effect (SE) in wood revealed using NI were discussed in this study. At Pmax < 0.2 mN, the deformed area under the pyramidal Berckovich indenter was much smaller than the cell wall width. Hence, in this case, NI measured the internal mechanical properties of the cell wall material as long as free boundaries impact could be neglected. At Pmax > 200 mN, the indentation encompassed several cells. The measured mechanical properties were significantly affected by bending deformation and buckling collapse of cell walls, reducing Heff and Eeff substantially. At Pmax ≈ 1–100 mN, an indenter interacted with different elements of the cell structure and capillary network, resulting in intermediate values of Heff and Eeff. Abrupt changes in Heff and Eeff at annual growth ring boundaries allow accurate measuring of rings width, while smoother and less pronounced changes within the rings allow identification of earlywood and latewood layers as well as any finer changes during vegetation season. The values of ring width measured using NI and standard optical method coincide with 2%−3% accuracy. The approaches and results presented in this study could improve the understanding of nature and mechanisms lying behind the micromechanical properties of wood, help to optimize the technologies of wood farming, subsequent reinforcement, and utilization, as well as to develop new highly informative techniques in dendrochronology and dendroclimatology.

Geographical variation in cool and warm season responses of earlywood and latewood tree‐ring chronologies in Athrotaxis selaginoides

ABSTRACTOur understanding of land‐based cool season temperature variability over the past millennium is limited by the relative lack of annually resolved temperature proxies, especially in the Southern Hemisphere. Here, we develop the first earlywood (EW) and latewood (LW) width chronologies from Australia based on the Tasmanian endemic conifer Athrotaxis selaginoides in the far southeast of Australia. We also develop total ring width (RW), EW and LW chronologies from a new site in the far south. We compare the climate responses of RW, EW and adjusted LW chronologies of three A. selagnoides sites near the southern extent of the species with three sites of the species near the northern extent of the species. RW and EW at the southern sites are strongly and positively related to cool season temperature (July–October), but in the north, RW and EW are more strongly and positively related with summer (December–February) temperatures. Once adjusted for the influence of the same growing season EW, LW in the north is very strongly negatively correlated with January–February temperatures across southeastern Australia. The new southern RW and EW chronologies can be used to extend one of only two annually resolved regional cool season temperature reconstructions in the Southern Hemisphere back a further 180 years.

A late Pleistocene Wood Turtle (&lt;i&gt;Glyptemys insculpta&lt;/i&gt;) from Iowa, USA: response of the taxon to glaciation and formation of the current range

The partial shell of a Wood Turtle (Glyptemys insculpta) was collected from the West Branch of the East Nishnabotna River in southwestern Iowa, near Malvern. By direct accelerator mass spectrometry, it radiocarbon dates to the late Pleistocene (10 220 ± 30 years before present [BP], 11 975–11 813 calibrated years [cal] BP). Other subfossil evidence indicates that Wood Turtles moved far south of their current range, into the southeastern United States, in response to late Pleistocene glaciation. The specimen suggests that the species also moved south and west, into a previously undocumented western range, where favourable habitat and, in particular, somewhat cooler summer temperatures prevailed until ~10 200 cal BP. My assessment of the Holocene subfossil record suggests that establishment of the western portion of the current range may have occurred within the past 1000 years. Phylogenetic analysis and direct radiometric dating of subfossil specimens are needed to determine additional details about the late Pleistocene dispersal of Wood Turtle and the postglacial formation of their current range.

Revealing how intra- and inter-annual variability of carbon uptake (GPP) affects wood cell biomass in an eastern white pine forest

Forests are major terrestrial carbon (C) sinks and play a crucial role in climate change mitigation. Despite extensive studies on forest C sequestration, the relationship between seasonal C uptake and its allocation to woody biomass is poorly understood. Here we used a novel dendro-anatomical approach to investigate the relationships between climate variability, C uptake, and woody biomass growth in an 80 year-old eastern white pine (Pinus strobus) plantation forest in Ontario, Canada. We used eddy covariance (EC) gross primary productivity (GPP) from 2003–2018 and woody biomass estimated from chronologies of cell wall area (CWA, a proxy for C storage in individual wood cells) and ring wall area (RWA) for earlywood (EW) and latewood (LW) from 1970–2018. Warm temperatures in early spring and high precipitation in mid-spring and summer positively and strongly affected GPP, while high temperature and high vapor pressure deficit in the summer had a negative effect. From 2003 to 2018, there was a steady increase in both GPP and woody cell biomass. Moreover, we found strong positive correlations between GPP and CWA both in EW (May—July GPP, r= 0.65) and LW (July—August GPP, r = 0.89). Strong positive correlations were also found between GPP and RWA both in EW and LW (April—September, r =⩾ 0.79). All these associations were stronger than the association between annual GPP and tree-ring width (r = 0.61) used in previous studies. By increasing the resolution of tree-ring analysis to xylem-cell level, we captured intra-annual variability in biomass accumulation. We demonstrated a strong control of seasonal C assimilation (source) over C accumulation in woody biomass at this site. Coupling high-resolution EC fluxes (GPP) and wood anatomical measurements can help to reduce existing uncertainties on C source-sink relationships, opening new perspectives in the study of the C cycle in forests.

REVIEW OF DYNAMIC PROPERTIES OF WOOD

This review considers the state of the art in the field of theoretical and experimental studies of dynamic deformation and destruction of wood materials. The orthogonal properties of wood, features of early and late wood are considered, the dynamic properties of wood are analyzed, as well as the influence of the strain rate during dynamic compression. It is noted that wood of different species is mainly used as one of the materials that dampen dynamic loads as a result of impacts or explosions. For example, it can mitigate the effects of high-velocity impacts on the contents of containers during the transport of hazardous materials by air, road and rail. It has been established that the cause of the effects of internal friction in wood are the areas of lignin, in which bundles of cellulose molecules (microfibrils) with a diameter of 25-30 nm are immersed, which are crystalline in their structure, which leads to viscoelastic behavior - internal damping. To improve the damping properties, it is recommended to choose wood with a low microfibril angle. It is noted that the stress-strain curve under dynamic compression of wood consists of three separate parts: the initial elastic region, the yield region and the compaction region. The main characteristics of compression, that is, the components of the stress-strain curve and the destruction of the fibers, do not depend on temperature. Young's modulus is much larger in the longitudinal direction than in the radial and tangential directions. The rate of deformation, temperature and humidity have a great influence on the strength properties of wood. The features of the mechanical behavior of the zones of early and late wood in the massif of a tree trunk are considered. Late wood is more rigid than early wood. As a result, differences in the mechanical properties of the wood fibers during compression may cause the early wood fibers to be destroyed while the late wood fibers remain intact. Due to the complexity of the wood structure, its reliable description by a numerical model requires complex models that take into account not only the influence of temperature, strain rate, and the type of stress-strain state, but also the angle between the direction of loading and the direction of wood fibers. Two main groups of wood material models are considered: micromechanical models simulating the details of the wood structure, and continuum models simulating the behavior of wood as a whole.

Micromechanics of non-embedded spruce wood: Novel polishing and indentation protocol

Since the start of nanoindentation in wood, cell walls have been supported by epoxy resin during the microtoming of surfaces. However, wood embedding in epoxy resin was initially developed to harvest thin sections destined for transmission electron microscopy. In nanoindentation, embedding can affect the identified mechanical properties and might be difficult for modified wood samples. For this reason, we propose a protocol that does not involve resin within the wood specimen, uses a more robust miller to achieve surfaces with root means squared roughness of around 35 nm, and can exclude invalid edge indents through a novel evaluation procedure based on fitting 2D histograms with a linear combination of bi-variate lognormal probability density functions. We examined twelve samples of Norway spruce (Picea abies) late wood and their counterparts soaked with a biological preservation pretreatment. A nanoindentation protocol on every sample led to a mean reduced modulus and mean hardness of around 12 % and 26 %, respectively, lower than those found in the literature for embedded Norway spruce. These results agree well with previous results found for Loblolly pine (Pinus taeda L.) when comparing embedded and non-embedded specimens.

Comparative Wood Anatomy of Nepalese Ulmaceae

Wood structure of three Nepalese genus Ulmus, Celtis and Trema belonging to the family Ulmaceae are described. Altogether 12 wood samples of these three genus are collected from different localities and studied. The study showed ring porous, semi-ring porous or diffuse porous wood. Transition from early wood to late wood was abrupt in ring porous wood. Early wood pores one to three layered. Late wood pores arrangement in dendritic or ulmiform pattern. Perforation plate is simple and inter-vessel pit alternate. Fiber tracheids, tracheids and libriform fibers were non-perforated tracheal elements while wood parenchymatous cell was apotracheal, marginal and paratracheal. Rays were homo-or heterogeneous. Ulmus differs from Celtis in having ray structure and crystal location. A tentative key is prepared to identify the species based on wood character.

Effect of Vacuum Heat Treatment on Larch Earlywood and Latewood Cell Wall Properties

The aim of this study was to evaluate the hygroscopicity and nanomechanics of earlywood (EW) and latewood (LW) larch after thermal modification under vacuum conditions. Wood samples were heat-treated in a vacuum atmosphere at 180–220 °C for 6 h, then their cell wall properties were observed using dynamic water vapor sorption (DVS), imaging Fourier-transform infrared (FTIR) microscopy, and nanoindentation. The results showed that the vacuum heat treatment reduced the hygroscopicity of EW and LW and increased hysteresis between the adsorption and desorption branches of the isotherm. Compared with EW, the treatment temperature had a more pronounced influence on the hygroscopicity of LW. The Hailwood-Horrobin model was found to accurately fit the experimental data. Imaging FTIR microscopy revealed degradation of hemicellulose, cross-linking, condensation reactions, and redistribution of lignin in the cell wall. The elastic modulus for the heat-treated EW and LW cell walls increased at first and then decreased as the treatment temperature increased; the increase in LW was more intense than that in EW. Cell wall hardness also markedly increased after heat treatment. Our analysis suggests that vacuum heat treatment decreases hygroscopicity and alters the chemical composition distribution of cell walls, thus improving wood cell wall mechanics.

The impact of soil, altitude, and climate on tree form and wood properties of plantation grown Pinus patula in Mpumalanga, South Africa

Abstract Plantation forests were originally established in South Africa to meet an increasing demand for solid wood products as there was a limited supply from native forests. The majority of the commercial softwood plantations were established with Mexican Pinus patula. Since growing conditions are known to impact tree growth, tree form, and wood quality of P. patula, sample plots were established over a cross-section of plantations in the Lowveld Escarpment and Highveld forestry regions of South Africa that covered an array of geologies and altitudes. Each sample plot was classified according to soil properties, rainfall, and temperature, and trees within the plots were measured for growth, form, and wood properties. Soil, growing days, and temperature were found to have little impact on tree form and wood properties. However, rainfall and specifically, spring rainfall, was found to have a highly significant impact on late wood formation, proportion of juvenile core, and wood density. In addition, tree height was found to be strongly correlated with maximum annual temperature.

Early аnd Late Wood оf Scots Pine under Conditions of Varying Degrees of Lighting

The condition of pine stands in Polissia is deteriorating due to an increase in the number of outbreaks of sharp-dentated bark beetle (Ips acuminatus) against the background of climate change, therefore, the relevance of this problem is beyond doubt. The purpose of the study is to identify the features of the dynamics of late and early Scots pine wood (Pinus Sylvestris L.) in areas with varying degrees of illumination after continuous cutting in the foci of the sharp-dentated bark beetle (Ips acuminatus) in Polissia. Standard dendrochronological, dendroclimatic, and statistical methods are used. It is established that after continuous logging in 2013 in the adjacent areas, on the one hand, there was an increase in the radial growth of pine trees, because the nutrition areas increased and the lighting conditions of trees improved, and on the other hand, trees growing next to the logging area are weakened and have fragile cores, which indicates a loss of wood quality. After cutting, during 2014-2020, the average values of late pine trees of illuminated time trial areas compared to the corresponding values in the control were 43-45%. For early wood, these values ranged from 38-42%. The growth change indices showed, that after the 2013 logging, violations occurred for trees in illuminated temporary trial areas as opposed to the control. The most sensitive to climatic factors were tree-ring chronologies of late wood in the most illuminated trial area. An increase in the sensitivity of the radial growth of pine trees was found depending on the increase in the degree of illumination. The weakening of plantings in the most illuminated area is indicated by the fact that the greatest number of significant relationships between growth and climate were found for the tree-ring chronology of early and late wood, while there was no critical decrease in trends in late and early wood layers. The findings can be used for planning forest management activities