Bark Layer Research Articles

Strain transfer from xylem to bark surface analyzed by digital image correlation

The goal of the study was to investigate the influence of bark of Turkish hazel (Corylus colurna L.) on strain transfer from xylem to bark surface. The study addresses issues of tree biomechanics that calls for a high-quality deformation data measured on trees’ surfaces in a noninvasive way. For these purposes, the optical technique employing 3D digital image correlation (3D-DIC) was used and tested against extensometers commonly used for such applications. The measured tree was subjected to bending by two pulling tests to induce the strain in tree stem, during which the analyzed area of interest (AOI) on the tree was studied in both variants with and without bark. The DIC technique successfully provided strain fields on a tree with bark and without despite its highly complicated structure. The absolute values of vertical strain measured by both techniques agree with each other in order of magnitude. However, 3D-DIC returns generally lower values than extensometers. Statistical tests proved (at p < 0.05) that the vertical strain measured on a bark was lower than that measured on wood, which confirms the hypothesis that bark layers reduce the strain transfer from wood to tree surface. The extent of strain reduction is highly dependent on force and was statistically detectable when the force reached ca. 5 kN. This is an important fact especially for practical use of optical measurements that are to replace standard extensometers. Measured displacements agreed with each other for both variants within a whole range of loads.

Cas de suie de l'érable et de chancre du peuplier dans le canton de Genève

A case of sooty bark disease and Cytospora poplar canker in the Canton of Geneva In summer 2014, a case of sooty bark disease caused by Cryptostroma corticale on an individual field maple (Acer campestre) and two cases of poplar canker due to Cytospora chrysosperma on Populus x euramericana were identified genetically for the first time on the territory of the Canton of Geneva. In both cases, the trees presented signs of very advanced dieback, accompanied by specific symptoms such as bark peeling and sooty plaques for the maple, and loose twisted bark layers and black colouring of the wood in structural branches of the poplars. Sampling was carried out in the symptomatic areas and components of the fungal flora were isolated in pure cultures in order to identify any pathogenic fungi. The molecular analysis of the rDNA internal transcribed spacer (ITS) sequences made it possible to identify precisely all pure isolates obtained. The results showed a majority presence of C. corticale in the maple tree, and of C. chrysosperma in the two poplars. Both these fungi are little known in Switzerland and Europe, and their presence is maybe associated with changes in the climate.

Levels of Road Traffic Heavy Metals in Tree Bark Layers of Cassia fistula Tree

Levels of Road Traffic Heavy Metals in Tree Bark Layers of Cassia fistula Tree

The benefits of recycling: how photosynthetic bark can increase drought tolerance.

[Extract] Understanding the drought physiology of woody plants has become an increasingly important focus of plant science research in recent years, spurred on by concern about the potential for widespread tree mortality in response to drought stress caused by global warming (McDowell et al., 2008; Allen et al., 2010). However, there is one aspect of how woody plants cope with water deficits that has received very little attention: the role of carbon fixation by photosynthetic bark. This process may become especially important for maintaining physiological activity in woody tissues of drought-stressed trees as the supply of photosynthate from leaves dwindles, due to stomatal closure and impaired phloem translocation. In this issue of New Phytologist, Vandegehuchte et al. (pp. 998–1002) bring this process into the spotlight, and provide a compelling argument for why we should take more notice of that often-hidden, green layer of tissue that is ubiquitous beneath the smooth-bark surfaces of woody plants (Scott, 1907; Pfanz et al., 2002; Dima et al., 2006; Rosell et al., 2015).

Dynamic mechanical analysis, surface chemistry and morphology of alkali and enzymatic retted kenaf fibers

Bast fibers grow in the bark layer of many plants and have been used for textiles and cordage for over 6000 years. Bast fibers are expanding into new markets of non-woven fabrics and composite materials, and a comparative assessment of surface reactive groups and mechanical properties after different retting procedures is of value. Here, bast fiber of kenaf ( Hibiscus cannabinus L., Malvaceae) were prepared by (1) alkali retting with 2% NaOH and (2) enzymatic retting with pectinase, and compared with commercially-available fiber retted by the natural microbe population in ocean water. Fiber structure was analyzed by fluorescence and electron microscopy; fiber chemistry was assessed by Raman and X-ray photoelectron spectroscopy, and by carbohydrate analysis; and mechanical properties were determined by dynamic mechanical analysis. Collectively, these show that enzymatic and microbial retting preserve the natural fiber structure and result in superior mechanical properties compared with alkali retting, which disrupts structure and degrades quality. The impacts of the retting procedure on fiber chemistry, morphology and mechanical properties are discussed.

Remediation of nitrate–nitrogen contaminated groundwater using a pilot-scale two-layer heterotrophic–autotrophic denitrification permeable reactive barrier with spongy iron/pine bark

A novel two-layer heterotrophic–autotrophic denitrification (HAD) permeable reactive barrier (PRB) was proposed for remediating nitrate–nitrogen contaminated groundwater in an oxygen rich environment, which has a packing structure of an upstream pine bark layer and a downstream spongy iron and river sand mixture layer. The HAD PRB involves biological deoxygenation, heterotrophic denitrification, hydrogenotrophic denitrification, and anaerobic Fe corrosion. Column and batch experiments were performed to: (1) investigate the NO3−–N removal and inorganic geochemistry; (2) explore the nitrogen transformation and removal mechanisms; (3) identify the hydrogenotrophic denitrification capacity; and (4) evaluate the HAD performance by comparison with other approaches. The results showed that the HAD PRB could maintain constant high NO3−–N removal efficiency (>91%) before 38 pore volumes (PVs) of operation (corresponding to 504d), form little or even negative NO2−–N during the 45 PVs, and produce low NH4+–N after 10 PVs. Aerobic heterotrophic bacteria played a dominant role in oxygen depletion via aerobic respiration, providing more CO2 for hydrogenotrophic denitrification. The HAD PRB significantly relied on heterotrophic denitrification. Hydrogenotrophic denitrification removed 10–20% of the initial NO3−–N. Effluent total organic carbon decreased from 403.44mgL−1 at PV 1 to 9.34mgL−1 at PV 45. Packing structure had a noticeable effect on its denitrification.

The bark of Scots pine (Pinus sylvestis L.) as a biological indicator of atmospheric air pollution

In dead bark layer 0f Scots pines (&lt;i&gt;Pinus sylvestris&lt;/i&gt; L.) exposed to the emission of aluminium works and the electric power plant "Skawina" as well as of chemical plants in Cracow, pH was determined and the content of F, S, Mg, Na, P, K, and Ca. The F content in the dead pine bark varied from 0.018 to 0.386 mg/g, and that of sulphur from 1.00 to 3.83 mg/g. A significant correlation was demonstrated between pH, and fluorine and calcium content in the bark. On the other hand, sulphur content was dependent on the amount of Na, K and Ca. For demonstrating contamination of the surface bark layer a test was applied consisting in evaluation of the germinating and development capacity of seeds. Fluorine content in pine dead bark layer reflects the F concentration in atmospheric air, it may, therefore, serve as indicator of the degree of air pollution with fluorine compounds.

VLIV ZPŮSOBU MĚŘENÍ A ODPOČTU TLOUŠŤKY KŮRY NA VÝslednou hodnotu OBJEMU KULATINY PŘI JEJÍ PŘEJÍMCE

Thickness of the bark has serious influence on the round wood volume inside bark, if the diameter is measured over bark. The measured value of the bark thickness depends on measuring method. To analyse the possible bark thickness differences of spruce, given by different measuring methods and Peintinger´s bark thickness tables and to calculate the corresponding round wood volume differences, given by different bark thickness deduction compared with the Czech Standard is the principle goal of presented research. Three ways of bark thickness measuring were realized: by using bark gauge, increment hammer and slide caliper. Bark gauge gives the highest bark thickness values – 2,2 mm higher compared with our standard, corresponding volume decrease is 3,4%. Measuring by this method is very carefully to the bark and it gives the real values of the thickness of the undamaged bark layer. It is close to the results of electronic diameter measuring. Slide caliper give the values 0,9 mm higher compared with our standard, corresponding volume decrease is 1,5%. Slide caliper partly damages the surface layer of the bark. Increment hammer gives 0,1 mm higher values of the bark thickness compared with our standard thanks to the destruction of the surface bark layer. Corresponding volume decrease can be approx. 0,1%. Peintinger’s bark thickness tables give 1,3 mm higher spruce bark thickness, it means to 1,9 % lower round wood volume. It means, Peintingers tables correspond better with the measured values than with the Czech Standard.We can recommend the using of Peintinger’s table for deduction of spruce bark thickness in electronic measuring of the round wood over bark and to use the bark gauge for test measuring. Both two methods gave the closest results to real values while our tests and it is very simple to use this instrument.

Yield of stilbene glucosides from the bark of young and old Norway spruce stems

Bioactive stilbene glucosides are the major constituents of the acetone extracts of the phloem and bark of Norway spruce (Picea abies (L.) Karst.) trees. We studied their variation patterns across phloem and bark within the stems of Norway spruce. The total yields of stilbene glucosides (astringin, isorhapontin, and piceid) from trees were estimated. Bark samples were collected from young (18 years-old) and older trees (37 years-old), representing age and size typical for energy wood harvesting and the first commercial thinning, respectively. Different bark layers of younger trees had 10%–63% lower average amount of stilbene glucosides than the bark layers of older trees. The inner bark had the highest mass fraction of stilbene glucosides (2.7%–4.8% of dry weight (d.w.)) and the outermost bark showed the lowest amount (0.4%–1.2% d.w.). Axially along the stem, the highest amount of stilbene glucosides was found at the stem base in the young trees (average over bark zones 2.1% d.w.) and at the breast height and the base of the living crown in the older trees (average over bark zones 3.6% d.w.). Astringin and isorhapontin yielded the highest amounts, while the share of piceid was the smallest. The total yield of stilbene glucosides was dependent on the bark biomass, and positively correlated with total wood and bark volume. The basal stem was the most valuable stilbene source in both younger and older trees. The bark of Norway spruce from the first commercial thinnings, especially of butt and middle logs, can provide feasible source for high-value extracts.

Concentration of Radiocesium in the Wild Japanese Monkey (Macaca fuscata) over the First 15 Months after the Fukushima Daiichi Nuclear Disaster

Following the massive earthquake that struck eastern Japan on March 11, 2011, a nuclear reactor core meltdown occurred at the Fukushima Daiichi Nuclear Power Plant, operated by Tokyo Electric Power Company, and was followed by the release of large amounts of radioactive materials. The objective of this study was to measure the concentration of radiocesium 134Cs and 137Cs in the muscle of Japanese monkeys (Macaca fuscata) inhabiting the forest area of Fukushima City and to determine the change in concentration over time as well as the relationship with the level of soil contamination. Cesium concentrations in the muscle of monkeys captured at locations with 100,000–300,000 Bq/m2 were 6,000–25,000 Bq/kg in April 2011 and decreased over 3 months to around 1,000 Bq/kg. However, the concentration increased again to 2,000–3,000 Bq/kg in some animals during and after December 2011 before returning to 1,000 Bq/kg in April 2012, after which it remained relatively constant. This pattern of change in muscle radiocesium concentration was similar to that of the change in radiocesium concentration in atmospheric fallout. Moreover, the monkeys feed on winter buds and the cambium layer of tree bark potentially containing higher concentrations of radiocesium than that in the diet during the rest of the year. The muscle radiocesium concentration in the monkeys related significantly with the level of soil contamination at the capture locations.

Using Bark as a Heat Insulation Material

Spruce bark particles were used as an insulation fill material for the thermal insulation of a timber frame wall which was subjected to a simulated winter temperature difference between indoor and outdoor climate. The temperature profile development of the wall’s cross section was modeled using Fourier’s transient heat flow theory. It was shown that bark layers conducted heat more slowly than commonly known blow-in insulation materials because of their low thermal diffusivity. Moreover, material moisture development due to water vapor streams caused by vapor pressure differences between the inside and outside climate was studied, and it supported general timber construction rules.

Photosynthetic bark: Use of chlorophyll absorption continuum index to estimate Boswellia papyrifera bark chlorophyll content

Quantification of chlorophyll content provides useful insight into the physiological performance of plants. Several leaf chlorophyll estimation techniques, using hyperspectral instruments, are available. However, to our knowledge, a non-destructive bark chlorophyll estimation technique is not available. We set out to assess Boswellia papyrifera tree bark chlorophyll content and to provide an appropriate bark chlorophyll estimation technique using hyperspectral remote sensing techniques. In contrast to the leaves, the bark of B. papyrifera has several outer layers masking the inner photosynthetic bark layer. Thus, our interest includes understanding how much light energy is transmitted to the photosynthetic inner bark and to what extent the inner photosynthetic bark chlorophyll activity could be remotely sensed during both the wet and the dry season. In this study, chlorophyll estimation using the chlorophyll absorption continuum index (CACI) yielded a higher R2 (0.87) than others indices and methods, such as the use of single band, simple ratios, normalized differences, and conventional red edge position (REP) based estimation techniques. The chlorophyll absorption continuum index approach considers the increase or widening in area of the chlorophyll absorption region, attributed to high concentrations of chlorophyll causing spectral shifts in both the yellow and the red edge. During the wet season B. papyrifera trees contain more bark layers than during the dry season. Having less bark layers during the dry season (leaf off condition) is an advantage for the plants as then their inner photosynthetic bark is more exposed to light, enabling them to trap light energy. It is concluded that B. papyrifera bark chlorophyll content can be reliably estimated using the chlorophyll absorption continuum index analysis. Further research on the use of bark signatures is recommended, in order to discriminate the deciduous B. papyrifera from other species during the dry season.

Genetic and hormonal regulation of cambial development

The stems and roots of most dicot plants increase in diameter by radial growth, due to the activity of secondary meristems. Two types of meristems function in secondary plant body formation: the vascular cambium, which gives rise to secondary xylem and phloem, and the cork cambium, which produces a bark layer that replaces the epidermis and protects the plant stem from mechanical damage and pathogens. Cambial development, the initiation and activity of the vascular cambium, leads to an accumulation of wood, the secondary xylem tissue. The thick, cellulose-rich cell walls of wood provide a source of cellulose and have the potential to be used as a raw material for sustainable and renewable energy production. In this review, we will discuss what is known about the mechanisms regulating the cambium and secondary tissue development.

Some indices of biological cycle of 137Cs and 39K in forest ecosystems of Bryansk woodland in the remote period after chernobyl fallouts

The features of the biological cycle of 137Cs and 39K in the remote period after Chernobyl fallouts are considered on the example of forest ecosystems of Bryansk woodland. It is demonstrated that the maximum amount of 137Cs in the total phytomass is concentrated in wood, the minimum amount of 137Cs, in the external bark layers; for the annual production, in assimilating organs and the external bark layers, respectively. The distribution of 39K in the total phytomass and the annual production is almost identical to that of 137Cs. The arrival of 137Cs to the soil with litter in pine and birch forests has recently been equal approximately to 50% of the capacity of the biological cycle. It mostly arrives with the assimilating organs (needles and leaves). In pine forests the return of 39K into the soil with litter is closest to that observed for 137Cs.

Microwave assisted preparation of efficient activated carbon from grapevine rhytidome for the removal of methyl violet from aqueous solution

Grapevine rhytidome (the outer layer of bark on trunk), as an abundant and low-cost precursor, was used to prepare granular activated carbon with high surface area for the removal of methyl violet from aqueous solution. Microwave heating source was used to reduce the treatment time and energy consumption. To optimize the preparation, the effects of the different parameters, such as phosphoric acid concentration, acid/precursor weight ratio, impregnation time, microwave power, radiation time, and oven heating time on the ability of the samples for removal of methyl violet were studied. The obtained activated carbon was characterized by N 2 adsorption/desorption, SAXS, TEM and SEM methods. The adsorption of methyl violet onto the activated carbon was studied from both equilibrium and kinetic point of view and the results were compared with the commercial granular activated carbon. The rate of adsorption onto the prepared activated carbon was faster than commercial activated carbon. Different kinetic models were used to analyze the experimental kinetic data. The obtained activated carbon showed higher adsorption capacity (more than twice) for the adsorption of methyl violet in comparison with the commercial one. The equilibrium data were analyzed using different isotherm models. Adsorption was found to be maximum in the pH range 7–9.

New 5-deoxyflavonoids and their inhibitory effects on protein tyrosine phosphatase 1B (PTP1B) activity

In the course of our program to search for protein tyrosine phosphatase 1B (PTPB) inhibitors, five new 5-deoxyflavonoids along with eight known derivatives were isolated from EtOAc layer of the root bark of Erythrina abyssinica. Their structures were elucidated on the basis of spectroscopic (IR, UV, MS, CD, 1D- and 2D-NMR) and physicochemical analyses. All isolates exhibited moderate inhibitory effects on the enzyme assay with IC 50 values ranging from 14.9 ± 1.6 to 98.1 ± 11.3 μM. Compounds with prenyl and methoxy groups in the B ring ( 1, 2, 4, 8, and 13) possessed strong activity (IC 50 14.9 ± 1.6 to 19.2 ± 1.1 μM), while compounds ( 3, 5, and 9) with 2,2-dimethylpyrano ring showed less inhibitory effect (IC 50 22.6 ± 2.3 to 72.9 ± 9.7 μM). These results suggest that prenyl and methoxy groups may be responsible for the increase on the activity of 5-deoxyflavonoids against PTP1B, but the presence of 2,2-dimethylpyrano ring on the B ring may be induced the decrease of PTP1B inhibitory activity.

Study of the variability in chemical composition of bark layers of Quercus suber L. from different production areas

Cork is the bark of the cork oak tree (Quercus suber L), a renewable and biodegradable raw bioresource concentrated mainly in the Mediterranean region. Development of its potential uses as a biosorbent will require the investigation of its chemical composition; such information can be of help to understand its interactions with organic pollutants. The present study investigates the summative chemical composition of three bark layers (back, cork, and belly) of five Spanish cork samples and one cork sample from Portugal. Suberin was the main component in all the samples (21.1 to 53.1%), followed by lignin (14.8 to 31%), holocellulose (2.3 to 33.6%), extractives (7.3 to 20.4%), and ash (0.4 to 3.3%). The Kruskal-Wallis test was used to determine whether the variations in chemical composition with respect to the production area and bark layers were significant. The results indicate that, with respect to the bark layer, significant differences were found only for suberin and holocellulose contents: they were higher in the belly and cork than in the back. Based on the results presented, cork is a material with a lot of potential because of its heterogeneity in chemical composition.

Suberin composition from different bark layers of Quercus suber L. by PY-GC/MS in the presence of tetramethylammonium hydroxide (TMAH)

In previous studies we found significant differences in the suberin content with respect to the bark layer of Quercus suber samples. In this study the monomer composition of suberin from the two bark layers (i.e., back and cork) of three provenances (Extremadura, Castile-la Mancha, and Portugal) was investigated using pyrolysis in the presence of tetramethylammonium hydroxide (TMAH) with gas chromatography-mass spectrometry (GC/MS). The major compounds released were octadec-9-enedioic acid, docosanedioic acid, and 9,10-epoxyocta-decanedioic acid with mean values of 17%, 14.5%, and 11%, respectively. The former is more abundant in back than in cork, and the latter in cork than in back with mean differences, in terms of percentages, between the back and cork of 4.3 ± 0.81 and 2.2 ± 0.52, respectively.

Azimuthal variations in xylem structure and water relations in cork oak (Quercus suber)

Azimuthal variations in xylem conductivity and transpiration can occur in trees and may be due to heterogeneity in environmental factors. In cork oak (Quercus suber L.), it can be hypothesized that such modifications may be more pronounced because the insulating layer of bark is harvested every 9–10 years, thus cambial cells will be exposed to fluctuations in the microenvironment. To investigate whether xylem structure and water relations differed around the stems of mature cork oak, sap flow per section and xylem structure were measured on the northern (N) and southern (S) sides of nine trees during three months in Portugal, using the Trunk Sector Heat Balance method. Crown size was measured on both sides of each tree and increment wood cores were extracted from the sites where sap flow was measured in five trees. Wood moisture content, earlywood (EW) vessel size and density were measured and theoretical hydraulic conductivity for individual vessels (Lth) was calculated along the N and S stem radial profiles. No significant differences in crown size between the two sides of the tree were found, but sap flow was higher on the S side of the tree in May only. No differences in wood moisture content were observed along the length of each wood core throughout the heartwood. Significant differences in vessel size occurred, with a greater diameter and surface area on the N side of the tree, and consequently Lth was significantly greater. These conduit diameters on the S facing side of the tree may be smaller in response to a combination of signals and trade-offs due to the heterogeneous air and soil environment around the tree.

Stable isotopes reveal the contribution of corticular photosynthesis to growth in branches of Eucalyptus miniata.

The deciduous bark habit is widespread in the woody plant genus Eucalyptus. Species with deciduous bark seasonally shed a layer of dead bark, thereby maintaining smooth-bark surfaces on branches and stems as they age and increase in diameter. This has a significant cost in terms of fire protection, because smooth-barked species have thinner bark than rough-barked species that accumulate successive layers of dead bark. Eucalypts are closely associated with fire, suggesting that the smooth-bark habit must also provide a significant benefit. We suggest that this benefit is corticular photosynthesis. To test this, we quantified the contribution of corticular photosynthesis to wood production in smooth-barked branches of Eucalyptus miniata growing in tropical savanna in northern Australia. We covered branch sections with aluminum foil for 4 years to block corticular photosynthesis and then compared the oxygen and carbon stable isotope composition of foil-covered and uncovered branch sections. We developed theory to calculate the proportion of wood constructed from corticular photosynthate and the mean proportional refixation rate during corticular photosynthesis from the observed isotopic differences. Coverage with aluminum foil for 4 years increased wood δ(13)C by 0.5‰ (P = 0.002, n = 6) and wood δ(18)O by 0.5‰ (P = 0.02, n = 6). Based on these data, we estimated that 11% ± 3% of wood in the uncovered branch sections was constructed from corticular photosynthate, with a mean δ(13)C of -34.8‰, and that the mean proportional refixation rate during corticular photosynthesis was 0.71 ± 0.15. This demonstrates that corticular photosynthesis makes a significant contribution to the carbon economy of smooth-barked eucalypts.