Bark Growth Research Articles

To protect or to hide: Why not both? An investigation of fire-related strategies in Cerrado woody species

Two key strategies enable woody species persistence and survival in fire-prone ecosystems after fire: the aboveground protection of stems and buds by thick bark and the allocation of biomass belowground to specialized bud bearing storage organs – both strategies allowing plants to resprout new branches after the aboveground parts are damaged by fire. Here we investigate whether those two strategies can be combined with each other. We compared 24 woody species from the Cerrado (tropical savannas from Brazil) and analyzed their underground storage organs (USOs) in relation to their aboveground bark production and aerial bud protection – two key traits allowing species to first survive and then persist after fire – together with plant potential height. We then compared if bark growth rate, aerial bud protection and plant potential height are linked to the ecological function of the underground storage organs (on spot persistence vs clonal growth through lateral spreading). Species with woody rhizomes (capable of spreading laterally) better protected their aboveground stems with thicker bark when compared to species with xylopodium and root-crown organs (adapted for on spot basal resprouting). A clear division was found concerning how well species are protecting their aerial buds and the type of underground storage organ, with species spreading laterally displaying a greater aerial bud protection. The results suggest that the presence of a specialized organ belowground does not appear to be mutually exclusive with producing thick bark on aboveground stems. It does exist, however, a different expression of bark production and aerial bud protection between species displaying lateral spread and those persisting on spot, suggesting the existence of a trade-off between above- and belowground strategies in species displaying on spot persistence. This highlights that Cerrado species can combine different fire-survival strategies, further questioning which fire conditions promote each strategy and their combination and in which cases trade-offs occur.

Bark production of generalist and specialist species across savannas and forests in the Cerrado.

Bark allows species to survive fire, protecting their inner tissues and allowing new branches to resprout from aerial buds. Thus, bark production is likely to be selected with aerial bud protection in fire-prone ecosystems. By considering the coexistence of fire-prone and fire-free ecosystems, in addition to the different impacts of flames on different growth forms, in this study we tested whether: (1) species from areas with higher fire frequencies have a faster bark production; (2) bark growth rate differs between trees and shrubs; (3) generalists adjust their bark production according to their environment (fire-prone or fire-free ecosystems); and (4) fast bark production results in better aerial bud protection. We sampled two different types of forests and savannas in the Cerrado and registered every woody individual with height between 1.5 and 3 m tall (directly exposed to the flames). For the 123 species registered, we sampled three different individuals in each vegetation type where the species occurred to assess their bark production and aerial bud protection. We then checked, for each species, their preferred habitat (savanna and forest specialists or generalists) and their predominant growth form. A minimal threshold of 0.13 mm per growth unit of bark production differentiated woody communities from savannas and forests. Shrubs and trees did not differ in terms of bark growth rate, despite being exposed to the flames in a different manner. Generalist species in savannas were able to produce bark above the threshold. However, when these species were in forests they produced bark below the threshold. Finally, a higher bark growth rate accounted for a better aerial bud protection. Generalist species are likely to be capable of displaying plasticity in their bark production, which could be important for their success in contrasting ecosystems. The relationship between aerial bud protection and bark growth rate suggests that bark production plays an important role in protecting the dormant buds, in addition to being selected in fire-prone ecosystems.

Variation in eucalypt bark allometry across Australia

Positive bark allometry (hyperallometry), characterised by rapid early bark growth, is expected where fire selects for thicker bark to resist cambial damage and topkill. We examine this prediction for 52 Australian eucalypt species. An effective bark allometric coefficient (α) was estimated from the first segment of breakpoint regression, which included fire-affected young trees. Eucalypts presented a negative–positive bark allometry continuum. Contrary to expectation, 73% of species (n = 38) displayed negative effective bark allometry. Early rapid bark growth was observed (α = 0.92 ± 0.04, x ± s.e., n = 168 sites), but was slower than isometry and bark was thinner overall than expected. Fire type (crown-fire propensity) and net primary productivity (resource availability) most influenced bark allometry. Productive ecosystems experienced crown-fire and bark was thicker at standardised diameter (x ± s.e. = 2.04 ± 0.20 cm) than in less productive ecosystems under surface fire (x ± s.e. = 1.68 ± 0.18 cm). Bark morphology types did not differ in their stem diameter (x ± s.e. = 21.47 ± 1.06 cm) or bark thickness (x ± s.e. = 1.88 ± 0.08 cm) thresholds, representing putative stable alternative evolutionary solutions. Fundamentally, many eucalypts possess negative bark allometry with a relatively thin bark compared to non-eucalypts, because unique bark bud traces sustain post-fire resilience through epicormic resprouting. The resource allocation trade-off to thin bark v. height growth, selected by fire and resource limitation, accounts for eucalypt persistence and domination of Australia’s flammable ecosystems.

The variation in essential oils composition, phenolic acids and flavonoids is correlated with changes in antioxidant activity during Cinnamomum loureirii bark growth

Cinnamomum loureirii is one of the most important medicinal and aromatic plants. It is used by the food, perfumery, cosmetic, and pharmaceutical industries. The objective of this study was to examine the relationships between the chemical composition and antioxidant activity of essential oil (EOs) and ethanol extracts from 10 samples of the bark from C. loureirii trees (6–15 years old). Obtained results showed that C. loureirii bark EO content at 12–15 years old had high oil yields (4.52–5.48%). The major components in the EOs were trans-cinnamaldehyde (50.2–92.9%) and α-copaene (0.5–21.3%). The highest content of trans-cinnamaldehyde in bark EOs was obtained from 10 to 12-year-old trees, while the highest content of α-copaene was obtained at 13–15 years. The highest total phenolic (429.85 and 474.45 mg TAE /g DW) and total flavonoid contents (85.54 and 102.80 mg RE /g e DW) were obtained from the 13- to 14-year-old trees. Our results indicated that the EO and ethanol extract of 13- to 14-year-old bark showed the strongest antioxidant properties. Moreover, GC–MS, PCA and correlation analysis indicated that the changes in α-copaene, beta-caryophyllene, τ-muurolene, γ-muurolene, δ-cadinene and τ-muurolol were positively correlated with the changes in antioxidant activity in oils. Meanwhile, procyanidin B2 and hyperoside were the main contributors to the antioxidant activity of the ethanol extract from C. loureirii bark. This study is the first one that report the antioxidant potential and phenolic profile of C. loureirii plant. These results provide reference information for the rational utilization of C. loureirii resources and the harvest of C. loureirii bark as medicinal materials during the optimal period.

Genetic Characterization, Agro-Morphological and Physiological Evaluation of Grafted Tomato under Salinity Stress Conditions

This study aims to determine grafting’s efficiency to improve tomato growth and production under salinity stress conditions. A commercial tomato hybrid (cv. Bark) and eight wild tomato accessions were evaluated at molecular, physiological and agronomic levels. At the molecular level, two robust gene-targeting marker systems (Conserved DNA-Derived Polymorphism; CDDP and Start Codon Targeted Polymorphism; SCoT) were employed. Bark cv. was grafted as a scion onto the four tomato genotypes’ roots as stocks. The rootstocks effect was evaluated by growing plants at 0, 100 and 200 mM NaCl. Our results showed that grafting enhanced plant shoots and roots growth (plant height, number of branches, plant fresh weight, root length, and root fresh and dry weight), fruit yield (total yield, number and weight of fruits) and fruit quality (Vitamin C, firmness and total soluble solids) in Bark on most tested rootstocks. A significant interaction between salinity levels and rootstocks for all measured hormones, antioxidants and proline was observed. In conclusion, our consistent results from the three approaches (molecular, physiological and agronomical) revealed that the four genotypes (LA1995, LA2711, LA2485 and LA3845) were found to be grouped and exhibit better performance under salinity stress conditions. Furthermore, grafting could be a low-cost alternative method to improve salt tolerance in sensitive tomato genotypes.

Towards sustainable valorisation of Acacia melanoxylon biomass: Characterization of mature and juvenile plant tissues

In Mediterranean area, Acacia melanoxylon biomass is an abundant waste material from non-native and invasive tree species control actions, requiring suitable disposal. Valorisation of such biomass residues requires its complete characterization to best approach the full potential of each plant material that could suit specific applications. This study compares mature and juvenile A. melanoxylon plant tissues (wood and bark) from two stands in different locations, regarding their chemical characteristics and organic growing media properties, such as mineral content and phytotoxicity effect for Lepidium sativum seeds. Juvenile bark (JB) showed greater total extractives (29%) extracted using solvents of increasing polarity (dichloromethane, ethanol, and water), followed by mature bark (MB) (21%). MB revealed the highest lignin content (>50%) suggesting material resistance to microbial biodegradation in horticultural applications. High barks phenolic content proved to be phytotoxic for cress seeds (null JB root index), although the toxic substances may be removed. After 1 week, ageing effect reduced MB phytototoxicity (root index > 60%) improving seed performance. Bark presented more mineral elements availability than wood. Wood high cellulose (>50%), low extractive (<9%) and moderate total lignin (<30%) contents can be attractive for pulp production, while bark growth medium profile may potentiate its application for horticultural uses. The future research on novel uses of A. melanoxylon plant residues can result in economic benefits that may alleviate management costs.

Stem and leaf structure of Searsia erosa (Thunb.) Moffett (Anacardiaceae) with systematic, ecological and ethnobotanical implications

The anatomy of stems and leaves of the southern African evergreen shrub Searsia erosa (Anacardiaceae) was studied. This species shows the suite of typical traits of Anacardiaceae, such as the presence of secretory canals in the cortex, secondary phloem, wood rays and vascular bundle of leaf midrib, pericyclic fibres in nearly continuous bands, compound sieve plates on oblique walls, simple perforation plates, alternate intervessel pitting, and septate libriform fibres. Like other Searsia species, S. erosa has abundant sclereids in non-conducting secondary phloem, multicellular peltate glandular trichomes on leaf epidermis, short vessel elements and minute intervessel pits; two latter characters are thought to be diagnostic for this genus. Unlike Asian species of Searsia, S. erosa lacks marginal axial parenchyma as well as prismatic crystals in axial parenchyma and in libriform fibres, but it shows the helical thickenings on vessel walls. The presence of the last trait in a southern African species agrees with association of helical thickenings with the regions that experience water stress. The tangential expansion of secondary phloem in S. erosa and probably in other Searsia species is mainly performed by considerable increase in volume of its cells by their sclerification. Such a way of bark growth in girth is out of scope of bark anatomists. Searsia erosa is distinctive from other congeneric species in its hypostomatous leaves with abundant glandular trichomes on adaxial side. This condition demonstrates a labor division between the adaxial side with glandular trichomes that may contribute to leaf protection, and the stomata-bearing abaxial side providing the gas exchange. Unlike most members of Anacardiaceae, the secretory canals of S. erosa produce the oleoresin containing terpenoids (essential oils) and lipids, but lack polysaccharides. The abundance of glandular trichomes and secretory canals producing terpenoids is a presumable reason of the use of S. erosa in traditional medicine by the Basotho people.

Effect of stand density on longitudinal variation of wood and bark growth in fast-growing Eucalyptus plantations

Abstract: The influence of tree spacing on the wood/bark ratio is unknown in young fast-growing Eucalyptus trees. The objective of this study was to evaluate the effect of plant spacing on the wood and bark production along the Eucalyptus stem. Four genetic materials were planted in four spacings: 3×1 m, 3×2 m, 3×3 m and 3×4 m. Three 5-year-old trees from each clone and in each plant spacing were harvested. Cross-sectional discs (thickness: 30 mm) were cut from each tree along the stem (0%, 25%, 50%, 75% and 100% of the total tree height) and at 1.3 m above ground, totaling 288 disks (4 spacings × 4 clones × 3 replicates × 6 axial positions). The wood thickness was measured at six random and equidistant points around the perimeter using a gauge and means were calculated from each disc. Six cross diameters were measured for each debarked disc. After obtaining the averaged bark thickness and wood diameter, the bark content was calculated as the ratio between the surface area occupied by the bark and the total area of the stem in each level. In the narrowed plant spacing (3×1), the trees had a mean diameter of 7.4 cm, while at the spacing 3×4 the diameter of the trees was 91% higher (14.11 cm) at breast height. The increase in plant spacing from 3 to 12 m2 per tree resulted in an increase in bark thickness (56.7%) from 1.94 mm to 3.04 mm, but caused a reduction of bark content (16%) from 9.66% to 8.11%. Our findings show that trees grown under wider spacing tend to produce thicker bark. The bark thickness and the effect of plant spacing on the bark thickness decreased in the base-top direction. The correlation between bark thickness and wood diameter increases from 0.682 to 0.825 with the increase of spacing between trees. In contrast, the bark thickness to bark content correlation decrease from 0.735 to 0.15 with increased plant spacing. The stand density significantly affected the variation of the stem diameter, bark thickness and bark content of Eucalyptus plantations.

Patterns of bark growth for juvenile trees of six common hardwood species in the eastern United States and the implications to fire-tolerance

Bark allocation patterns did not follow fire-tolerance grouping of tree species in all cases; more studies are needed on bark development from juvenile to adult trees. Thick bark is presumed to be a trait of fire-tolerant trees that were historically subjected to frequent surface fires. To be recruited into the forest canopy, a tree must be able to survive fire and grow thick enough bark during the fire-free interval. Previous studies have also suggested that fire-tolerant species grow disproportionately thick bark lower on the stem, where the threat of fire is greatest. The objectives of this study were to quantify how bark develops in six juvenile hardwood species of the Appalachian Piedmont and compare bark allocation between fire-tolerant (Carya tomentosa, Quercus alba, and Quercus velutina) and mesophytic species (Acer rubrum, Fagus grandifolia, and Liriodendron tulipifera). We sampled up to 32 individuals of each species and modeled bark area as a function of wood area and measure height using mixed effect models. Bark area increased approximately 0.4 cm2 for Q. velutina and C. tomentosa, 0.2 cm2, for L. tulipifera and Q. alba, and 0.1 cm2 for A. rubrum and F. grandifolia for each cm2 increase in wood area, holding measure height constant. For Q. velutina, C. tomentosa, and L. tulipifera, the measure height was found to decrease bark area by approximately 0.02, 0.01, and 0.01 cm2 for each cm increase in height, holding diameter constant. A paired sample Wilcoxon test comparing bark:wood ratio at 0 and 140 cm heights yielded similar results. Differences in bark allocation among the six species were not consistent with current groupings of “fire-tolerant” and “mesophytic” species.

Suitability of Sphagnum Moss, Coir, and Douglas Fir Bark as Soilless Substrates for Container Production of Highbush Blueberry

The purpose of the present study was to investigate the suitability of different soilless substrates for container production of highbush blueberry (Vaccinium sp.). Young plants of ‘Snowchaser’ blueberry were grown in 4.4-L pots filled with media containing 10% perlite and varying proportions of sphagnum moss, coconut (Cocos nucifera L.) coir, and douglas fir [Pseudotsuga menziesii Mirb. (Franco)] bark, as well as a commercially available mix of peatmoss, perlite, and other ingredients for comparison. Total plant dry weight (DW) was similar among the treatments at 72 days after transplanting, but at 128 days, total DW was nearly twice as much in the commercial mix and in media with ≥60% peat or coir than in media with ≥60% bark. Inadequate irrigation likely played a role in poor plant growth in bark. Bark had lower porosity and water holding capacity than peat, coir, or the commercial mix and, therefore, dried quickly between irrigations. Bark also reduced plant uptake efficiency of a number of nutrients, including N, P, K, S, Ca, Mg, Mn, B, Cu, and Zn. Uptake efficiency of P, K, and Mg also differed between plants grown in peat and coir, which in most cases was a function of the initial concentration of nutrients in the media. Before planting, peat had the highest concentration of Mg and Fe among the media, whereas coir had the highest concentration of P and K. Leachate pH was initially lowest with peat and highest with coir but was similar among each of the media treatments by the end of the study. Electrical conductivity (EC) of leachate never exceeded 0.84 dS·m−1 in any treatment. Overall, peat and coir appear to be good substrates for container production of highbush blueberry. Bark, on the other hand, was less suitable, particularly when it exceeded 30% of the total media composition.

Strategies towards sustainable bark sourcing as raw material for plant-based drug development: a case study on &lt;i&gt;Garcinia lucida&lt;/i&gt; tree species

Objectives : To appraise the amount of sustainable bark stripped and time to complete bark recovery as basis for sourcing of raw materials for plant-based drugs Methodology and Results : A two-year experiment was conducted and several local harvest practices were tested on Garcinia lucida (named Essok in Boulou language). For each harvest method, 20 healthy trees were selected and harvested. Tree health was monitored every month and the total bark regrowth was calculated using planimetric techniques. The mean bark mass was 2.54 kg/tree (range, 0.5-15 kg/tree; SD, 2.40; n=80) and increased with bark thickness, ranging from 1.28 kg tree-1 (0.4-0.8 cm thin) to 4.38 kg tree-1(1.2 – 1.8 cm thick). The mean rate of bark regeneration was 787±601 cm²/tree/year (range, 452±166-1870±1042 cm²/tree/yr; n=53) and positively correlated to harvest method (p < 0.01) and surface debarked (p < 0.05). Standard Deviation values were higher, suggesting that each tree had its proper bark growth rate patterns, and that bark regrowth process may be tree-specific and strongly correlated to intrinsic factors. Conclusions and application of findings : Peeling off pieces of bark using a machete and debarking over 1/3 of the stem circumference at breast height, once every 3 years for small trees or every 5 years for large trees, has been found to be the best harvest method for G. lucida species. This is to tackle the challenge of availability of raw material and harvest sustainability. As the increased trade and processing of bark has shifted from subsistence use to large-scale commercial use, posing a threat to supply of raw material and species conservation, sustainable harvesting methods should constitute important tools of the guidelines on good collection practices for medicinal plants that would help to ensure safety and quality at the first and most important stage of the harvest of medicinal plants. This study has provided information on the species-specific bark harvest prescriptions to assist in developing such guidelines, thereby promoting the processing and trade of the most valued medicinal species for plant-based drug development in Africa. Keywords : Garcinia lucida , medicinal plant, bark, raw material, sustainable bark stripping.

Impacts of elevated temperature and CO2 concentration on growth and phenolics in the sexually dimorphic Populus tremula (L.)

Future climatic changes may alter the balance between the sexes of dioecious species due to differential effects on resource allocation to growth and defense. Our purpose was to study the impacts of elevated temperature and CO2 concentration on the relative changes in growth and phenolics accumulation in stem bark of the dioecious Populus tremula, a keystone species for boreal forest biodiversity and one that is browsed by many mammalian herbivores. In a greenhouse experiment, four female and four male genotypes of P. tremula were grown under single and combined treatments of elevated temperature (1.5°C on average) and CO2 concentration (720ppm) for one growing season. Elevated temperature increased the height, diameter, leaf and stem biomass, and in addition decreased the concentration of phenolics including salicylates, flavonoids, phenolic acids, salireposide and lignan. Elevated CO2 concentration, on the other hand, reduced the height growth (other growth parameters were unchanged) and increased the concentration of phenolics, especially salicylates and phenolic acids. In the combined treatment, P. tremula tended to grow more, but elevated temperature counteracted the effect of elevated CO2 concentration on phenolics accumulation. Although statistically not significant, males tended to have greater growth and a lower level of phenolics than females. The smaller sexual differences were also not strongly affected by climatic factors. Under future elevated temperature and CO2 concentration, both sexes of P. tremula will probably grow more and possibly accumulate lower levels of phenolics, but intersexual differences in growth and phenolics accumulation may be more pronounced after sexual maturation.

Shrub growth rate and bark responses to soil warming and nutrient addition – A dendroecological approach in a field experiment

Tundra shrubs are slow-growing species limited by low air temperature and scarce nutrient availability. However, shrub expansion has been widely observed in the Arctic during the last decades and attributed to climate warming. Shift in shrub growth, wood structure and abundance affects the surface albedo and permafrost thawing and these changes may feedback to climate. Despite the importance of shrub–climate feedbacks, uncertainties about shrub growth sensitivity to climate remain. Here, we explored the indirect effects of climate warming on shrub growth (vertical and radial), bark thickness, and bark investment in four arctic shrub species. We combined a field experiment addressing two suggested growth drivers – thawing depth and nutrient availability – with dendroecology in a Siberian tundra ecosystem. We used heating cables to increase the thawing depth. To enhance the nutrient availability, we fertilized the surface soil layers. We found that shrub growth was mainly limited by nutrient availability, as indicated by the fertilization treatment effects on shrub growth ring widths. We also found a bark thickness decrease with the combined soil heating and nutrient addition treatment and a negative correlation between bark investment and growth rate for two of the species. These findings suggest that tundra shrubs, especially deciduous species, will grow faster and taller driven by an increasing nutrient availability in the surface soil layers. However, shrubs might become more vulnerable to pests, herbivory, and climate extremes, such as frost or drought events, due to thinner bark and lower bark investment. Using dendroecological approaches in field experiments simulating projected climate scenarios for the Arctic, and an increasing number of study species and locations will reduce uncertainties related to shrub growth sensitivity to climate and other processes driving shrub dynamics.

The ACEII recombinant Trichoderma reesei QM9414 strains with enhanced xylanase production and its applications in production of xylitol from tree barks

BackgroundACEII transcription factor plays a significant role in regulating the expression of cellulase and hemicellulase encoding genes. Apart from ACEII, transcription factors such as XYR1, CRE1, HAP2/3/5 complex and ACEI function in a coordinated pattern for regulating the gene expression of cellulases and hemicellulases. Studies have demonstrated that ACEII gene deletion results in decreased total cellulase and xylanase activities with reduced transcript levels of lignocellulolytic enzymes.ResultsIn this study, we have successfully transformed the ACEII transcription factor encoding gene in Trichoderma reesei to significantly improve its degrading abilities. Transformation experiments on parental strain T. reesei QM9414 has resulted in five genetically engineered strains T/Ace2-2, T/Ace2-5, T/Ace2-8, T/Ace5-4 and T/Ace10-1. Among which, T/Ace2-2 has exhibited significant increase in enzyme activity by twofolds, when compared to parental strain. The T/Ace2-2 was cultured on growth substrates containing 2% bark supplemented with (a) sugar free + MA medium (b) glucose + MA medium and (c) xylose + MA medium. The bark degradation efficiency of genetically modified T/Ace2-2 strain was assessed by analyzing the xylitol production yield using HPAEC. By 6th day, about 10.52 g/l of xylitol was produced through enzymatic conversion of bark (2% bark + MA + xylose) by the T/Ace2-2 strain and by 7th day the conversion rate was found to be 0.21 g/g. Obtained results confirmed that bark growth medium supplemented with d-xylose has profoundly increased the conversion rate of bark by T/Ace2-2 strain when compared to sugar free and glucose supplemented growth media. Results obtained from scanning electron microscopy has endorsed our current results. Bark samples inoculated with T/Ace2-2 strain has showed large number of degraded cells with clearly visible cavities and fractures, by exposing the microfibrillar interwoven complex.ConclusionWe propose a cost effective and ecofriendly method for the degradation of lignocellulosic biomass such as bark to produce xylitol by using genetically modified T. reesei. Efficient conversion rate and production yield obtained in our current study provides a great scope for the xylitol industries, as our method bypasses the pretreatment of bark achieving clean and low-cost xylitol production.

Transcriptomic profiles of Heterobasidion annosum under abiotic stresses and during saprotrophic growth in bark, sapwood and heartwood

The success of many wood decaying fungi lies in their ability to overcome unfavourable environmental conditions within and outside of litter and wood debris. Although so much has been learned about the ecology, taxonomy and physiology of several wood decaying basidiomycete fungi, the molecular basis for their survival in a diverse range of substrates and ecological habitats has been very little studied. Using the wood decay fungus (Heterobasidion annosum s.s.) as a model, we investigated its transcriptomic response when exposed to several environmental stressors (high and low temperature, osmotic stress, oxidative stress and nutrient starvation) and during growth on specific pine wood compartments (bark, sapwood and heartwood). Among other genes and pathways, we documented the specific induction of the major facilitator superfamily 1 and cytochrome P450 families at low temperature, and protein kinases together with transcription factors during starvation. On the other hand, during saprotrophic growth, we observed the induction of many glycosyl hydrolases, three multi-copper oxidases (MCO), five manganese peroxidases (MnP) and one oxidoreductase which are specific for wood degradation. This is the first study providing insights on the potential mechanisms for adaptation to abiotic stresses and pine heartwood degradation in H. annosum s.s.

The effect of management systems and ecosystem types on bark regeneration in Himatanthus drasticus (Apocynaceae): recommendations for sustainable harvesting

Bark and exudates are widely commercialized non-timber forest products. However, the ecological impacts of the harvesting of these products have seldom been studied. The aim of this study is to investigate the relationship of tree resilience to harvesting intensity in Himatanthus drasticus, a tree that is highly exploited in the Brazilian savanna (Cerrado) for its medicinal latex. Although the traded product is the latex, the traditional harvesting systems involve the removal of the bark of the trees to allow exploitation. A 3-year experiment was conducted in two different Cerrado ecosystems (open savanna and savanna woodland). Trees were debarked at four debarking intensities to simulate the effects of traditional management systems. Measurements of bark growth were taken every 6 months, and quantitative and qualitative indexes of bark regeneration were obtained. The mortality of the debarked trees was low and could not be related to the intensity of harvesting. No signs of attack by fungi or insects were recorded. Compared with other species exploited for bark, H. drasticus is very resilient to harvesting; however, bark regeneration is relatively slow. In both analyzed ecosystems, the regeneration indexes showed higher values in the controls than in the treatments, indicating that 3 years is not sufficient for total recovery of the rhytidome. Bark regeneration occurred primarily by sheet growth and was more rapid in open savanna than in savanna woodland. No differences in the rate of bark recovery were found among management treatments. Based on the results, sustainable harvesting guidelines are suggested for the species.

Variations in essential oil yield and composition during Cinnamomum cassia bark growth

To extract essential oil for industrial use, the yields and compositions of bark oil during Cinnamomum cassia growth (1–3 years old for the branch bark; 5–12 years old for the stem bark) were determined. The branch bark fraction had a higher essential oil yield than the whole branch. The essential oil yield from branch bark varied within 2.70–3.11% (w/w), while that from stem bark was 0.41–2.61% (w/w) due to differences in age and segment (top, center and lower) of the tree. There were 41 volatile compounds identified in bark oil, among which the majority presented high fluctuations in percentage of composition both in different growth stages and segments. Variations in oil yields did not present the same pattern as the percentages of trans-cinnamaldehyde. The results suggest that choosing bark according to trees’ growth stages and separating stem barks into top, center and lower sections within a tree should significantly improve the extraction efficiency.

Estimating ages of bear claw marks in Southeast Asian tropical forests as an aid to population monitoring

Abstract Asiatic black bears (Ursus thibetanus) and sun bears (Helarctos malayanus) in Southeast Asia leave claw marks on climbed trees that provide a cumulative history of their presence and activities, but this record can be difficult to interpret without knowing the age of the marks. We conducted an experiment to estimate ages of bear claw marks by monitoring 212 fresh claw mark sets (most of which we created to mimic real claw marks) on 122 trees from 17 families in Thailand. We categorized marks as looking fresh (presence of woody grit, sharp edges), recent (absence of woody grit), or old (bark growth in the gouges), and estimated the duration of these age categories using Kaplan-Meier survival analysis. Most marks (81%) remained fresh for at least 2 months, but by 3 months, 75% had transitioned to recent (median 2.6 months). By 10 months, 90% of fresh marks became old (median 7.3 months). Wood hardness had no effect on aging rates. Marks created in the rainy season and those on thin-barked trees age...

Diversity and Antimicrobial and Plant-Growth-Promoting Activities of Endophytic Fungi in Dendrobium loddigesii Rolfe

Endophytic fungi are ubiquitously distributed in orchids and have a great impact on the host plant. The diversity of endophytic fungi in the medicinal orchid Dendrobium loddigesii Rolfe was investigated and their bioactivities in microbe and plant growth were explored here. Endophytic fungi were identified by using morphological and molecular biological methods. Antimicrobial activity was determined by a standard disk assay. Activity in promoting plant growth was confirmed by root inoculation of endophytic fungi in seedling tray and pot experiments. Overall, 48 isolates were isolated from D. loddigesii and identified to belong to 18 genera, with Fusarium and Acremonium being the most dominant populations. A total of 17 isolates belonging to 9 genera were screened for their antimicrobial activity, and Fusarium spp., 8 of the 17 isolates, was also the dominant population. In the seedling tray experiment, two isolates, one of Fusarium named DL26 and the other of Pyrenochaeta named DL351, were shown to enhance plant growth in alder bark–humus medium, and the latter displayed weak activity against Bacillus subtilis (As 1.308) and Aspergillus fumigatus (As 3.2910). In the pot experiment, after inoculation of DL26 and DL351, five out of seven media were fit for plant-endophyte symbionts. Medium #1 of red brick fragments and sphagna was optimal in accelerating plant growth. In conclusion, a great diversity of endophytic fungi in D. loddigesii was first confirmed in a considerable proportion of antimicrobial isolates. Furthermore, two endophytes exhibited the ability to enhance plant growth although their activities were influenced by the growth media.

Effects of artificial amendments in potting media on Orthosiphon aristatus growth and development

Artificial polyacrylamide gel (PAG) and urea-formaldehyde resin foam (UFRF) amendments are used for putative enhancement of soil physical properties, including increasing their water holding capacity (WHC). Effects were investigated of these two amendments alone and combined on growth and development of Orthosiphon aristatus (Cats’ Whiskers) grown in either composted pine bark or washed river sand, including under transient water deficit stress. UFRF and PAG were incorporated into these potting media substrates at recommended rates of 30% (v/v) and 0.1% (w/w), respectively. UFRF incorporation reduced bulk density and increased air-filled porosity of composted pine bark from 0.24 g cm −3 and 43.3% to 0.18 g cm −3 and 50.2%, respectively. UFRF also reduced bulk density of sand from 1.43 g cm −3 to 1.17 g cm −3 and increased its air-filled porosity from 18.5% to 25.3%. PAG slightly decreased bulk density of composted pine bark to 0.23 g cm −3 and also reduced sand bulk density to 1.32 g cm −3. Water content of composted pine bark and sand was increased by PAG addition from 47.6% and 27.7% to 51.0% and 34.2%, respectively. However, UFRF and/or PAG did not increase plant available water (PAW) in either composted pine bark or sand. PAW was 23.8% and 14.4%, 23.6% and 15.8%, 22.8% and 14.8%, and 25.2% and 17.8% for composted pine bark and sand controls, these two substrates amended with UFRF, these substrates amended with PAG, and these substrates with UFRF plus PAG, respectively. Neither shoot length nor number was increased by adding UFRF and/or PAG. Similarly, neither shoot fresh nor dry weight was increased by UFRF and/or PAG amendments. UFRF and, moreso, UFRF plus PAG slightly delayed the onset of wilting by 4–15 h in water deficit stressed O. aristatus compared to control and PAG alone in composted pine bark (experiment 1), but PAG did not. However, in experiment 2, UFRF and/or PAG did not delay wilting in either composted pine bark or sand. Thus, when incorporated at suppliers recommended rates, neither UFRF nor PAG conferred appreciable benefits for O. aristatus plant growth in either composted pine bark or sand potting media.