Tracheid Walls Research Articles

Effects of aluminum sulfate soaking pretreatment on dimensional stability and thermostability of heat-treated wood

Acidic aluminum sulfate hydrolysis solutions can be used to catalyze the thermal degradation of wood in a mild temperature environment, and thus reduce the temperature required for heat treatment process. To improve the dimensional and thermal stability of Chinese fir during heat treatment at 120 °C, 140 °C and 160 °C, this study investigated the effects of soaking pretreatment with 5%, 10% and 15% aluminum sulfate on the chemical and structural changes of the heat-treated Chinese fir. The results indicated that the samples treated at 15% aluminum sulfate concentration and 160 °C heat treatment achieved the best dimensional and thermal stability. Chemical analyses by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated that the catalysis of aluminum sulfate resulted in degradation of hemicelluloses during the heat treatment, and an increase in the soaking concentration and heat treatment temperature also affected the thermal degradation of celluloses. The scanning electron microscope (SEM) and mass changes test results proved that the hydrolyzed aluminum flocs mainly adhered to the inner wall of the wood tracheid as spherical precipitates, and when the soaking concentration reached 10% and 15%, a uniform soaking effect could be achieved. The thermogravimetric (TG) analysis revealed the soaking pretreatment effectively improved the thermal stability of the heat-treated wood by physically wrapping and promoting the formation of a carbon layer on the wood surface during heat treatment. Thus, aluminum sulfate soaking pretreatment exerted a great effect on the dimensional and thermal stability of wood, allowing heat treatment to be performed at a lower temperature.

The first report of Lesbosoxylon Süss & Velitzelos from the early-middle Miocene of eastern Anatolia

A new fossil pine species from eastern Turkey is described and its botanical affinities are discussed. The sample was collected from the city of Kemaliye, Erzincan province, Turkey, and derives from the early-middle Miocene Divriği formation. Transverse, tangential and radial sections were taken from the petrified wood, and its palaeoxylotomical features were investigated. Based on its anatomical features including idioblastic cells in rays a new fossil-species of the genus Lesbosoxylon Süss & Velitzelos was identified as Lesbosoxylon kemaliyensis Akkemik & Mantzouka, sp. nov. Diagnostic features of the new species are: Transition from earlywood to latewood mostly gradual; axial and radial resin canals with thin-walled epithelial cells present; latewood tracheids thin to thick walled; bordered pits on radial walls of tracheids 1-2(-3) seriate; crassulae common; rays heterocellular, uniseriate, partly biseriate; uniseriate rays up to 27 cells high; fusiform rays up to 30 cells high; axial parenchyma occasionally present; ray tracheids 2-3 rows; cell walls of ray tracheids smooth; cross-field pitting pinoid, 1-2(-6) pits per cross-field. Detailed investigation of the botanical affinities of the new fossil wood suggested that the most closely related modern species is Pinus canariensis C. Sm in Buch, a relict species from the Canary Islands.

THE EFFECT OF ALTITUDE ON THE GROWTH AND DEVELOPMENT OF TROJAN FIR (Abies nordmanniana subsp. equi-trojani [Asch. & Sint. ex Boiss] Coode & Cullen) SAPLINGS

The altitude is an important factor to affect the growth and development of saplings of the tree. However, the effect of altitude on the growth and properties of wood during their young stage it has been little studied. This study, therefore, aimed to evaluate the influence of two different altitude steps: 795 m (a.s.l. low-altitude) and 1350 m (a.s.l. high altitude) on the morphological, anatomical and wood density properties of saplings of Abies nordmanniana subsp. equi-trojani [Asch. & Sint. ex Boiss] Coode & Cullen (Trojan fir). Trojan fir is an endemic species in Turkey and its morphology and anatomy have less studied in the literature. The functional traits and wood density properties differed significantly between the two altitudes. The saplings grown at low-altitude showed greater taper degree, pith radius, pith proportion, and bark proportion than high-altitude. However, stem height, stem diameter, node number, and xylem proportion were found to be higher in saplings grown at high-altitude than low-altitude. Wood cell anatomy also varied significantly between two altitudes such that ring width, ray numbers, tracheid length, and tracheid width were higher at low-altitude, whereas ray height, ray width, tracheid lumen width, and tracheid wall thickness were greater at high-altitude. This study, therefore, suggested that the growth and development of fir saplings were better when they were grown at high-altitude than low-altitude.

An Early Devonian actinostelic euphyllophyte with secondary growth from the Emsian of Gaspé (Canada) and the importance of tracheid wall thickening patterns in early euphyllophyte systematics

AbstractSecondary growth is a tracheophyte structural feature whose earliest known occurrence dates to the late Pragian – early Emsian. Armoricaphyton, Franhueberia and an unnamed plant from eastern Canada represent the only instances of secondary growth documented to date for the Early Devonian. Here, we describe a new Early Devonian euphyllophyte exhibiting secondary growth, from the Emsian (c. 400–395 Ma) Battery Point Formation (Québec, Canada): Gmujij tetraxylopteroides gen. et sp. nov., which is characterized by a mesarch actinostele with Psilophyton‐type (P‐type) tracheid wall thickening, and which exhibits a new type of anatomical organization in Early Devonian wood‐producing euphyllophytes. Gmujij differs from coeval euphyllophytes, but lack of data on branching patterns, reproductive structures and other traditional diagnostic features precludes classification in previously recognized euphyllophyte groups. We experiment with a numerical approach to tracheid size distributions, to compare Gmujij with younger euphyllophytes exhibiting secondary growth. Comparisons indicate similarity between Gmujij and aneurophytalean progymnosperms, such as Tetraxylopteris. However, its plesiomorphic P‐type tracheids set Gmujij apart from younger actinostelic euphyllophytes, questioning the importance of tracheid thickening patterns as diagnostic characters separating major lineages. Answers to this question hinge on whether transitions between wall thickening patterns require simple or complex changes in developmental regulation, a matter that requires improved understanding of regulatory programs that determine tracheid thickening patterns. Irrespective of these, Gmujij adds a new component to the diversity of anatomically preserved plants known in the Early Devonian, an incompletely explored interval of tracheophyte anatomical diversification, contributing information that will facilitate understanding of the evolutionary origins of secondary growth.

Oldest Jurassic wood with Gondwanan affinities from the Middle Jurassic of Tibetan Plateau and its paleoclimatological and paleoecological significance

Jurassic flora of the Tibetan Plateau is poorly known, with limited fossil records. The paleobiogeography of terrestrial biota is, however, one of the major evidences to reconstruct the intricate paleogeography of an area. Well-preserved fossil wood is described from the Middle Jurassic Xiali Formation (Callovian) in the South Qiangtang terrane of the Tibetan Plateau, SW China. The wood specimen is a well-preserved secondary xylem without growth rings. Bordered pits on the radial tracheid walls are mostly uniseriate distant, locally contiguous. Cross-fields have 1–2 large oopores. A systematic study indicates that the current fossil wood represents a new species, Circoporoxylon tibetense sp. nov. This is the earliest Laurasian data for the genus Circoporoxylon, which has a Gondwanan origin and subsequently became common in Laurasia during the Cretaceous. The present new finding indicates that Circoporoxylon might have reached the Laurasia via a Tibetan terrane. The presence of fungal remains and wood rotting structures resembling the extant white-rot testifies for the plant–fungal interaction in the Callovian. The absence of growth rings in Circoporoxylon wood and the absence of gypsum layers in the South Qiangtang terrane, together with the widely occurrence of gypsum layers in the North Qiangtang terrane, suggests the South Qiangtang terrane might be wetter than the latter during the Callovian age. The paleogeomorphological highlands of Central Uplift were most likely the boundary between the two. This paleoclimate zonation implies that the Permian to Mesozoic megamonsoon of the supercontinent Pangaea might have terminated in the northern of Paleo-Tethys before the Callovian.

Effects of Microwave Treatment on Microstructure of Chinese Fir

Microwave (MW) treatment is an effective method to increase refractory wood permeability, thereby reducing drying time and defects. The extent of modification depends on the damage extent of the wood microstructure. In this study, MW intensities of 43 kWh/m3 (low intensity) and 57 kWh/m3(high intensity) were adopted to treat Chinese fir lumber. Microstructural changes in wood samples were observed using scanning electron microscopy (SEM) and pore structure was characterized using mercury intrusion porosimetry (MIP). Results were as follows: After low-intensity MW treatment, parts of the bordered pit membranes in tracheids were damaged, and micro-fibrils on the margo were ruptured, while the torus basically remained intact. Micro-cracks were observed at both ends of the cross-field pit apertures, propagating to the cell walls of tracheids. The middle lamellar between ray parenchyma cells and longitudinal tracheids cracked, and the width of cracks was in the range of 1–25 μm. After high-intensity MW treatment, damage to the wood microstructure was more severe than that in the low-intensity MW treatment, with macro-cracks having a width range of 100–130 μm being generated. In addition, on the fracture surface of macro-cracks, the bordered pit membranes in tracheids fell off, cross-field pit membranes disappeared and the ray parenchyma cells were seriously damaged, exhibiting fracture of the tracheid walls. Both low-intensity and high-intensity MW treatment can increase the pore diameter corresponding to the margo capillaries (peak value increased from 674.7 nm to 831.8 nm and 1047.6 nm, respectively). The number of pores in the tracheid lumen diameter range also significantly increased. These results provide a theoretical support forMW treatment processes’ improvement and high-value utilization of Chinese fir.

Woody charcoal with traces of pre-charring decay from the Late Oligocene (Chattian) of Norken (Westerwald, Rhineland-Palatinate, W Germany)

A variety of traces of pre-charring decay are described from coniferous charcoals from the Norken locality, stratigraphically positioned within the Breitscheid Formation (Late Oligocene, Chattian) of the Westerwald area (Rhineland-Palatinate; W Germany). The traces include three-dimensionally preserved as well as collapsed fungal hyphae, collapsed filamentous structures (maybe related to ascomycetes), so-called shot-like holes of different diameters in cell walls of tracheids, as well as crater-like structures on the surface of tracheid walls. The latter occur on tracheids with bordered pits, in the direct vicinity of charred phloem (so far only rarely reported from pre-Quaternary charcoal). These observations, together with evidence that some of the charcoal fragments originated from wood that dried out prior to charring, point to a surface fire as the most likely source of the charcoal, although it cannot totally be ruled out that (partly) dead but still standing trees were affected during a crown fire. The data from the Late Oligocene of Norken provide further evidence that pre-Quaternary charcoal can be used as an additional, so far largely underutilized source for additional information about plant– microorganism interactions in deep time.

New petrified gymnosperms from the Permian of Maranhão (Pedra de Fogo Formation), Brazil: Ductolobatopitys nov. gen. and Kaokoxylon

Continuing the study of petrified gymnosperm trunks recovered from the Pedra de Fogo Formation, we identify here two new taxa from the Permian deposits of the Parnaíba Basin, northeastern Brazil. One taxon is an endemic form named Ductolobatopitys mussae Conceição, Neregato et Iannuzzi, nov. gen., nov. sp., characterized by solenoid, lobed and non-septate heterocellular pith, cauline bundles with endarch maturation, and secondary xylem with araucarian radial pitting on the tracheid walls. The other form is assigned to the genus Kaokoxylon, which has been recorded from most of Gondwana, including the Parnaíba Basin, but is recorded for the first time from the Pedra de Fogo Formation with the new species Kaokoxylon brasiliensis. It is characterized by solid, non-septate heterocellular pith with sclerenchyma cells, endarch cauline bundles, and uni-to triseriate radial pitting on the walls of the tracheids. The sedimentological interpretations of the outcrops where the fossils were collected indicate that these plants lived on the shores of large continental lakes, with relatively high humidity but possibly periods of drought. These inferences are supported by growth interruptions in the secondary xylem, the presence of calamitalean and tree-fern stems, and microbialites that crop in the same area. These new finds not only increase the known diversity of the flora in the Pedra de Fogo Formation, but also provide more accurate information for understanding the floristic elements that formed the subtropical flora during the Cisuralian in this basin in Western Gondwana.

Changes in wood anatomical traits in Scots pine under different climate-change scenarios

Abstract Although cell-anatomical variables are promising proxies reflecting seasonal as well as annual climate changes, their interdependencies are not yet fully understood. In the present study we assessed the changes in tree-ring width and various wood anatomical traits, including wall thickness, lumen diameter and tracheid diameter in the radial direction in saplings of Pinus sylvestris under six climatic conditions: 5°C warmer alone (ET) or combined with drought in June (ETJ) and in August (ETA) and CO2 enrichment alone (EC, 770 ppm) or combined with drought in June (ECJ) and in August (ECA). The experiments related to temperature conditions using 2-year saplings and CO2 conditions using 3-year saplings were completed in 2009 and 2010 in a greenhouse, respectively. Results showed that tree-ring width and tracheid diameter were not affected by any of the conditions applied, but the lumen diameter was larger and the wall thickness was thinner than those under control conditions. These reactions were verified under ETJ in the warming treatment and under all conditions under CO2 enrichment conditions. Our results indicated that drought counteracted the effects of elevated CO2 concentrations on wood anatomical properties, signifying complex interactions between the two major effects of climate change. Our comparison of wood parameters through experiments highlight the potential effect of climate change — increased drought stress due to higher temperatures and water shortage as well as elevated ambient CO2, on tracheid lumen diameter and wall thickness. Whereas the ring-width and tracheid diameter practically remained unaffected under the above-mentioned conditions.

Anatomical and Morphological Changes with Needle Removal Treatments on the Seedlings of Pinus nigra Arn. (Anatolian black pine)

The effect of needle removal treatments on the morphology, anatomy and wood density was less studied in the literature. Therefore, the aim this study was to investigate the effect of needle removal on the morphological, anatomical and wood density properties of the seedlings of Pinus nigra Arn. (Anatolian black pine). The needles of the seedlings were removed in four different amounts (0%, 25%, 50% and 75%) to determine whether there is a relationship between the properties of seedlings and the needle removal treatments. The morphological (stem diameter, node numbers, pith percentage, bark percentage, xylem percentage), anatomical properties (average annual ring width, tracheid number per mm2, tracheid height/width, tracheid lumen width, tracheid wall thickness, ray number per mm2, ray height/width) and wood densities were individually determined for each treatment. The morphological results showed that stem diameter was greatest in 0% and 25% needle removal treatments than that of two treatments. Bark% was also found to be higher in the 0% needle removal treatments than others. However, node numbers, pith% and xylem% did not differ significantly between four removal treatments. The density results showed that the seedlings of 0% and 25% needle treatments were denser than 50% and 75% needle removal treatments. The results of anatomical analysis also found surprising results between four treatments. Ray height/width, tracheid number per mm2and tracheid length were significantly greater in the 0% removal of needles than that of three treatments. 25% needle removal treatment also showed larger tracheid area and tracheid wall thickness than that of three needle removal treatments.

Severe insect defoliation at different timing affects cell wall formation of tracheids in secondary xylem of Larix kaempferi

Severe insect defoliation induced non-lignified tracheids and thin-walled latewood tracheids in the defoliation year in Larix kaempferi. These anomalous tracheids had heterogenous lignin deposition of S2 layer. Severe insect defoliation induces the formation of light ring consisted of thin-walled latewood tracheids in larch trees, which would affect wood quality. However, the identity of the secondary wall layers affected by insect defoliation remains unclear. The aim of this study is to clarify the effects of insect defoliation on the formation of secondary cell walls of tracheids in Larix kaempferi with focus on the defoliation timing. We observed by light microscopy and transmission electron microscopy (TEM) the secondary cell walls of tracheids produced in a defoliation year in L. kaempferi trees on which needles were attacked in July (gypsy moth, GM samples) or August (larch sawfly, LS samples). Light microscopy observations revealed that GM samples produced non-lignified tracheids in the transition zone between earlywood and latewood, as well as thin-walled latewood tracheids, and non-lignified tracheids were observed near the cambial zone in LS samples following defoliation for two consecutive years. TEM observations revealed that the tracheids in both samples had anomalous layers in secondary walls such as thin S2 layers with heterogeneous lignin deposition. The production of non-lignified tracheids corresponded to defoliation date in both samples, unlike changes in the layer composition of anomalous tracheids. Our study suggests that changes in wood structure depend on the date of insect defoliation and that insect defoliation affects the formation of secondary cell walls of tracheids, presumably in response to inadequate photosynthate supply as a result of defoliation.

New petrified gymnosperms from the Permian of Maranhão (Pedra de Fogo Formation), Brazil: Novaiorquepitys and Yvyrapitys

Anatomically preserved gymnosperm stems are relatively abundant in the Permian outcrops of the Parnaíba Basin, but their anatomy has rarely been studied in detail. Here we describe two new fossil gymnosperm trunks from the Lower Permian (Cisuralian) strata of the Pedra de Fogo Formation in the municipality of Nova Iorque, southern Maranhão State, northeastern Brazil. Two new genera et species are described, Novaiorquepitys maranhensis and Yvyrapitys novaiorquensis. These taxa have a broad, non-septate pith containing sclerenchyma and secretory cells, a parenchyma sheath, and a system of lacunae. Pycnoxylic secondary xylem with growth interruptions and the radial bordered pits on the tracheid walls are araucarian and mixed types. The recognition of two endemic forms indicates both a high degree of endemism for the flora of the Pedra de Fogo Formation and a higher taxonomic diversity of gymnosperm woods than hitherto noted. In addition, the anatomical characters of these taxa, together with sedimentological data and the presence in the same area of plants that live on the banks of water bodies or in wetlands (e.g., tree ferns and tree-calamitaleans), indicate that these woody plants lived near the shores of large lakes. These findings show that studies of Paleozoic woods in this region are potentially valuable.

Warming induced changes in wood matter accumulation in tracheid walls of spruce

The warming-driven increase of the vegetation season length impacts both net productivity and phenology of plants, changing an annual carbon cycle of terrestrial ecosystems. To evaluate this influence, tree growth along the temperature gradients can be investigated on various organization levels, beginning from detailed climatic records in xylem cells’ number and morphometric parameters. In this study, the Borus Ridge of the Western Sayan Mountains (South Siberia) was considered as a forest area under rapid climate change caused by massive Sayano-Shushenskoe reservoir. Several parameters of the xylem anatomical structure in Siberian spruce (Picea obovata Ledeb.) were derived from normalized tracheidograms of cell radial diameter and cell wall thickness and analyzed during 50 years across elevational gradient (at 520, 960, and 1320 m a.s.l.). On the regional scale, the main warming by 0.42°C per decade occurs during cold period (November–March). Construction of the reservoir accelerated local warming substantially since 1980, when abrupt shift of the cold season temperature by 2.6°C occurred. It led to the vegetation season beginning 3–6 days earlier and ending 4–10 day later with more stable summer heat supply. Two spatial patterns were found in climatic response of maximal cell wall thickness: (1) temperature has maximal impact during 21-day period, and its seasonality shifts with elevation in tune with temperature gradient; (2) response to the date of temperature passing +9.5°C threshold is observed at two higher sites. Climate change yielded significantly bigger early wood spruce tracheids at all sites, but its impact on cell wall deposition process had elevational gradient: maximal wall thickness increased by 7.9% at the treeline, by 18.2% mid-range, and decreased by 4.9% at the lower boundary of spruce growth; normalized total cell wall area increased by 6.2%–6.8% at two higher sites but remained stable at the lowest one. We believe that these patterns are caused by two mechanisms of spruce secondary growth cessation: “emergency” induced by temperature drop versus “regular” one in warmer conditions. Therefore, autumn lengthening of growth season stimulated wood matter accumulation in tracheid walls mainly in cold environment, increasing role of boreal and mountain forests in carbon cycle.

СРАВНИТЕЛЬНЫЙ АНАЛИЗ МОРФОЛОГО-АНАТОМИЧЕСКОЙ СТРУКТУРЫ ГОДИЧНЫХ СЛОЕВ СОСНЫ ОБЫКНОВЕННОЙ В МШИСТОМ И ОРЛЯКОВОМ ТИПАХ ЛЕСА

It is a well-known fact that life form of any plant is determined by its genetic characteristics. However, depending on the conditions of natural habitat, there are certain variations of not only external specific features of the same plants, but also of their anatomic organization. The article provides the results of the cell structure examinations of the Scots pine (Pinus sylvestris L.) growing in moss-covered (Pinetum pleurozium) and bracken (Pinetum pleurozium) forests. Ten temporary experimental sites for each type of forest were set according to methods used in forest sciences and forest taxation. Taking into account the structure of annual layers of conifers, the study determined the quantitative parameters of radial growth and the main size indicators of early and late tracheids. It is revealed that the width of an annual layer and the quantity of tracheids in a radial row belong to the most changeable parameters, while tangential dimensions of tracheids belong to the least changeable parameters. In general, the analyses of obtained data from 18 dimensional characteristics showed that moss-covered pine forest is characterized by the greater value of a radial diameter of early tracheids (6 %) and their cavities (3 %), as well as greater cavity areas (3 %); a bracken pine forest, in turn, has a greater width of latewood in an annual layer (16 %) and thickness of a cell wall of late tracheids (10 %). Therefore, it is recommended to measure only these specific parameters to reduce the time spent on conducting researches in future. The cluster analysis confirmed that the morphological and anatomical characteristics are effective indicators to define the forest type.

Protaxodioxylon from the Late Jurassic to Early Cretaceous Kota Formation, Pranhita-Godavari Basin, India

The xylotomy of the silicified wood from the Late Jurassic to Early Cretaceous Kota Formation of the Pranhita-Godavari Basin is studied and its systematic affinity is identified here. The wood is characterised by distinct growth rings with mixed pitting on radial tracheid walls, and taxodioid cross-field pits. The combination of the features observed in the present wood indicates that, it belongs to Protaxodioxylon of the taxodiaceous Cupressaceae s. l., as a new species Protaxodioxylon sahnii sp. nov. The comparison of wood with the modern representatives of the family suggests its relation with Taxodium. The present fossil wood with distinct growth rings characterised by their low percentage of latewood suggests that the growth conditions were favorable. The riparian habitat was inferred for the Protaxodioxylon sahnii sp. nov., based on sedimentological and other associated plant fossils. The vegetation in the study area is possibly favored by the influence of a subtropical climate with seasons, and by high levels of precipitation along the river banks.

Localization of actin filaments and cortical microtubules in wood-forming tissues of conifers

ABSTRACT The aim of the present study was to investigate the orientation and localization of actin filaments and cortical microtubules in wood-forming tissues in conifers to understand wood formation. Small blocks were collected from the main stems of Abies firma, Pinus densiflora, and Taxus cuspidata during active seasons of the cambium. Bundles of actin filaments were oriented axially or longitudinally relative to the cell axis in fusiform and ray cambial cells. In differentiating tracheids, actin filaments were oriented longitudinally relative to the cell axis during primary and secondary wall formation. In contrast, the orientation of well-ordered cortical microtubules in tracheids changed from transverse to longitudinal during secondary wall formation. There was no clear relationship between the orientation of actin filaments and cortical microtubules in cambial cells and cambial derivatives. Aggregates of actin filaments and a circular band of cortical microtubules were localized around bordered pits and cross-field pits in differentiating tracheids. In addition, rope-like bands of actin filaments were observed during the formation of helical thickenings at the final stage of formation of secondary walls in tracheids. Actin filaments might not play a major role in changes in the orientation of cortical microtubules in wood-forming tissues. However, since actin filaments were co-localized with cortical microtubules during the formation of bordered pits, cross-field pits and helical thickenings at the final stage of formation of the secondary wall in tracheids, it seems plausible that actin filaments might be closely related to the localization of cortical microtubules during the development of these modifications of wood structure.

Extractive distribution in Pseudotsuga menziesii: effects on cell wall porosity in sapwood and heartwood

ABSTRACT Douglas-fir (Pseudotsuga menziesii) has distinctly colored heartwood as a result of extractive deposition during heartwood formation. This is known to affect natural durability and treatability with preservatives, as well as other types of wood modification involving infiltration with chemicals. The distribution of extractives in sapwood and heartwood of Douglas-fir was studied using fluorescence microscopy. Several different types of extractive including flavonoids, resin acids, and tannins were localized to heartwood cell walls, resin canals, and rays, using autofluorescence or staining of flavonoids with Naturstoff A reagent. Extractives were found to infiltrate the cell walls of heartwood tracheids and were also present to a lesser extent in sapwood tracheid cell walls, especially in regions adjacent to the resin canals. Förster resonance energy transfer measurements showed that the accessibility of lignin lining cell wall micropores to rhodamine dye was reduced by about 50%, probably as a result of cell wall-bound tannin-like materials which accumulate in heartwood relative to sapwood, and are responsible for the orange color of the heartwood. These results indicate that micro-distribution of heartwood extractives affects cell wall porosity which is reduced by the accumulation of heartwood extractives in softwood tracheid cell walls.

НАКОПИЧЕННЯ УШКОДЖЕНЬ В ОСНОВНИХ НЕСУЧИХ КОНСТРУКЦІЯХ СПОРУД, РЕЗЕРВ ПРАЦЕЗДАТНОСТІ

The article presents the results of experimental studies of the strength and deformability of load bearing structures made of wood under the action of static loads. In most major cities of Ukraine there are a huge number of buildings that have historical and architectural value. To preserve these structures for centuries, it is necessary to constantly receive such information about the state of their supporting structures for making timely decisions about reinforcement, replacement, overhaul, etc. In the materials of building structures, changes occur during the period of operation associated with the appearance, development and accumulation of structural damage. These damages cause submicron and microcracks, which are the result of external mechanical effects on the structure and therefore the transition to the boundary state is the result of a slow accumulation of damage. Having developed a technique for registering damage, you can get a tool that allows you not only to monitor the current state of the structure, but also to predict the change in its bearing capacity over time. In the period of operation there is a change in the structure of materials bearing structures The development of this process consists of several stages, the main of which are: deformation of interatomic bonds, nucleation of a sub-microcrack as a result of breaking macromolecules that form the walls of tracheids. This turns out to be suddenly and is accompanied by weak sound signals, resembling a micro explosion. The interaction of submicrocracks leads to their merging and the occurrence of microcracks, and the merging and increase of microcracks - to the occurrence of macrocracks (trunk crack), which leads to the destruction of the material. This dynamic process, depending on the size, nature and time of action of the load, may stabilize over time or, continuing, lead to the destruction of the structure. Mechanical and electrical devices currently used (indicators, strain gauges and other devices) are not suitable for detecting and recording material damage. For this purpose, it is necessary to use non- destructive research methods that allow continuous observation of submicro- and micro-processes that take place in the structure of the material of the structure. Such methods for estimating the residual life are currently being successfully applied only in aviation and on important equipment (thermal, hydraulic, nuclear power plants, etc.) The processes are obvious. There is a need to comprehensively investigate the issue of damage accumulation in wooden structures under load, and the associated processes of changing the cross-sectional area and carrying capacity and use the results of the study in the calculation of structures. This makes it possible to reduce the consumption of materials and make the sections of wooden structures more economical, and also allows you to avoid excessive margins. The direction of improving the methods of designing and calculating wooden structures and determining the residual life of the main wooden structures of structures are not yet reflected in the technical literature. In this regard, it requires a comprehensive study. To study the processes of damage accumulation in the material of construction, a method was used that does not destroy the structure. This is an acoustic emission method, which is associated with the propagation in the material of elastic waves caused by the dynamic local restructuring of its structure. Acoustic emission signals appear at the onset of micro and macro defects and accompany the entire process of material deformation. This allows you to diagnose the state of the structure, since the emission of sound vibrations can be detected at the stage when the structure as a whole is still operational.

Xuanweioxylon damogouense sp. nov., a gymnosperm stem from the Lopingian (late Permian) of southwestern China and its systematic and paleoecological implications

A new species of permineralized gymnosperm stem is described from volcaniclastic tuffs in Lopingian (late Permian) Xuanwei Formation from eastern Yunnan province, China. The stem comprises well-preserved tissues of the pith, primary and secondary xylem. Pith is divided into a thick-walled parenchymatous peripheral zone and an inner parenchymatous part. Primary xylem strands are numerous and indistinct with mesarch maturation. Secondary xylem is pycnoxylic with scalariform bordered pits on radial tracheid walls, with rays normally uniseriate or partly biseriate. Cross-field pits are mixed and including circular, elliptical and scalariform pitting. Comparisons indicate a close affinity with the contemporaneous plant Xuanweioxylon scalariforme, but differences with it lead to the erection of Xuanweioxylon damogouense sp. nov. We evaluate the systematic affinity of both species of Xuanweioxylon and conclude they represent conifers based on features of their wood anatomy. We consider the Xuanwei Formation includes at least four species of conifer, and show that X. damogouense possessed weak growth rings and false rings that suggest it grew in a climate with low seasonality and occasional periods of drought.

Acoustic-Based Prediction of End-Product-Based Fibre Determinates within Standing Jack Pine Trees

The objective of this study was to specify, parameterize, and evaluate an acoustic-based inferential framework for estimating commercially-relevant wood attributes within standing jack pine (Pinus banksiana Lamb) trees. The analytical framework consisted of a suite of models for predicting the dynamic modulus of elasticity (me), microfibril angle (ma), oven-dried wood density (wd), tracheid wall thickness (wt), radial and tangential tracheid diameters (dr and dt, respectively), fibre coarseness (co), and specific surface area (sa), from dilatational stress wave velocity (vd). Data acquisition consisted of (1) in-forest collection of acoustic velocity measurements on 61 sample trees situated within 10 variable-sized plots that were established in four mature jack pine stands situated in boreal Canada followed by the removal of breast-height cross-sectional disk samples, and (2) given (1), in-laboratory extraction of radial-based transverse xylem samples from the 61 disks and subsequent attribute determination via Silviscan-3. Statistically, attribute-specific acoustic prediction models were specified, parameterized, and, subsequently, evaluated on their goodness-of-fit, lack-of-fit, and predictive ability. The results indicated that significant (p ≤ 0.05) and unbiased relationships could be established for all attributes but dt. The models explained 71%, 66%, 61%, 42%, 30%, 19%, and 13% of the variation in me, wt, sa, co, wd, ma, and dr, respectively. Simulated model performance when deploying an acoustic-based wood density estimate indicated that the expected magnitude of the error arising from predicting dt, co, sa, wt, me, and ma prediction would be in the order of ±8%, ±12%, ±12%, ±13%, ±20%, and ±39% of their true values, respectively. Assessment of the utility of predicting the prerequisite wd estimate using micro-drill resistance measures revealed that the amplitude-based wd estimate was inconsequentially more precise than that obtained from vd (≈ <2%). A discourse regarding the potential utility and limitations of the acoustic-based computational suite for forecasting jack pine end-product potential was also articulated.