Bark Structure Research Articles

Effect of Micro- and Macro-Mechanical Characteristics of Jujube Bark on Jujube Girdling Quality

Jujube girdling is an important method to improve the yield and quality of jujube fruit. However, girdling usually causes the tearing of jujube bark, resulting in the slow healing and even death of jujube trees. These problems directly affect the economic benefits of jujube planting. In this paper, in order to reveal the tearing mechanism of jujube bark caused by girdling, and provide the basic mechanical parameters of jujube bark for the research and development of automatic girdling equipment, the structure and mechanical characteristics of jujube bark were studied through theory and experimental methods. The results of microscopic observation showed that jujube bark is a biological composite material mainly composed of the phloem, periderm and epidermis. Furthermore, a mathematical model-based analysis of the growth stress of jujube bark showed that growth stress can be regarded as a biaxial stress state, which can promote the longitudinal tearing of jujube bark during girdling. The tensile test results of jujube bark showed that jujube bark belongs to the category of anisotropic and biologic material. Its longitudinal and transverse mechanical characteristics are significantly different. The maximum longitudinal tensile load was in the range of 105.9~293 N, the longitudinal tensile strength was 16.3 MPa and the elastic modulus was 255.6 MPa. The average transverse tensile load was only 27.9% of the longitudinal tensile load. The transverse tensile strength was 3.5 Mpa and its elastic modulus was 724.14 MPa. The transverse cutting test of jujube bark showed that the average cutting force was 118.2 N and the cutting strength was 9.8 MPa. The results of this study showed that both the growth stress and the anisotropic natural polymer of jujube bark have adverse effects on girdling. Subsequently, issues relating to the selection of appropriate girdling tools and the matters needing attention in the process of the girdling operation were proposed, so as to guide the correct application of girdling technology. In addition, some suggestions on the research and development of girdling tools in the future are put forward.

Structural deviations in secondary phloem of young shoots of Spiraea beauverdiana near magma volcanoes

We performed a comparative analysis of the internal structure of the secondary phloem of one, two and three-year-old stems of Spiraea beauverdiana growing in extreme conditions of solfataric fields of Golovnin Volcano caldera and Mendeleyev Volcano and in normal conditions. The combination of environmental factors in conditions of solfataric activity, such as high temperatures in the soil and in the near-surface air, as well as saturation with gases toxic to plants, rare elements accumulating in the nearby substrate, and lack of soil moisture, interfere with normal phellogen and cambium activity. Deviations from the normal structure involve changes in the following parameters of the internal structure of a year-old stem of S. beauverdiana. Secondary phloem parameters in the studied habitats are normal, except for the length of the segments of sieve tubes, the height of single-row rays, the length of parenchymal girder; these are shorter in S. beauverdiana stems from volcanos. At two and three years of age in volcanic conditions we see reduction in the width of the secondary phloem (both conductive and non-conductive) and the diameter of the segments of sieve tubes. In samples from Golovnin Volcano we see reduction in tangential diameter, while in the samples from Mendeleyev Volcano it’s the radial diameter. We also see reduction in the height of multiple-row rays. At that age we see changes in the structure of the radial parenchyma; namely, we find no double-row rays in samples from Golovnin Volcano caldera. One of the signs of impact of volcanic activity on the bark structure is development of non-specific anomalies in the internal structure of the S. beauverdiana bark, namely, in the outer bark, or in deeper levels, such as the secondary phloem. That causes sclerification and dilatation of parenchyma, and multiple layers in some tissues.

К ВОПРОСУ О МОРФОЛОГИИ ГЕНЕРАТИВНЫХ РАСТЕНИЙ MYRICA GALE L.

The distribution of Myrica gale on the coast of the Gulf of Finland is confined to regularly flooded coastal habitats, characterized by milder environmental conditions compared to the uplands and under the residual influence of the Gulf Stream. In Russia, M. gale is located on the northeastern border of the range. The study of the features of the species that contribute to the dispersal in the northern direction, and the properties of the environment that prevent such dispersal, is always of great interest. Growth in colder conditions in comparison with other members of the family, mainly inhabitants of the tropical and subtropical areas, affected the formation of such adaptations as deciduousness, changes in the structure of flowers and bark, as well as the presence of a large number of protective leaf organs. Their quantitative and qualitative analysis made it possible to establish the presence of 4 lignified parchment-like scales that do not fall completely and 6 membranous with partially lignified tops scales that stretch out while unfolding. An attempt was made for the first time to analyze the spatial structure of the shoots of the species. A sympodial growth of shoots and the phenomenon of acrotonia, as well as a spiral formation of lateral shoots, were established. In the structure of the mature generative branch of M. gale there were identified 3 types of shoots: long growth, medium and short, and also their leaf series were analyzed.
 Leaf series of short and medium shoots are characterized by significant asymmetry compared to leaf series of long shoots and are incomplete. The curves were constructed on the basis of such characteristics of leaf organs as their total number, length along the central vein, including the petioles (if they are presented), and internode lengths. A large number of rudiments of leaf organs determines the gradual formation of the buds, and the imperfection of the structure of the scales reflects the weak protective ability of these organs. Both features indicate the deep ancientness of the species and the difficulty in adapting to cold environmental conditions. Mature generative branches of M. gale are similar in habit to small trees, which is of particular interest in the context of modeling possible directions of adaptation during the spread of species of subtropical origin to more northern regions.

Identifying old Norway spruce and Scots pine trees by morphological traits and site characteristics

ABSTRACT Old trees are important for biodiversity, and the process of their identification is a critical process in their conservation. However, determining the tree age by core extraction, ring counts, and eventually, cross-dating by means of dendrochronology is labor-intensive and expensive. Here we examine the alternative method of estimating determining tree age by visual characteristics for old Norway spruce and Scots pine trees. We used forest stands previously identified as “Old tree habitats” by visual criteria in Norwegian boreal forests. The efficiency of this method was tested using pairwise comparison of the age of core samples from trees within these sites, and within neighboring sites. Age regression models were constructed from morphological traits and site variables to investigate how accurately old trees can be detected. Cored trees in the Old-tree habitats were on average 41.9 years older than compared to a similar selection of trees from nearby mature forests. Several characteristics such as bark structure, stem taper and visible growth eccentricities can be used to identify old Norway spruce and Scots pine trees. Old trees were often found on less productive sites. Due to the wide range of environments included in the study, we suggest that these findings can be generalized to other parts of the boreal zone.

Bark Thickness and Heights of the Bark Transition Area of Scots Pine

The estimation of forest biomass is gaining interest not only for calculating harvesting volumes but also for carbon storage estimation. However, bark (and carbon) compounds are not distributed equally along the stem. Particularly when looking at Scots pine, a radical change in the structure of the bark along the stem can be noted. At the bark transition area, the bark changes from thick and rough to thin and smooth. The aim of our study was (1) to analyze the height of the bark transition area where the bark structure changes and (2) to analyze the effect of cardinal direction on the bark thickness. Regression analyses and forward selection were performed including measured tree height, DBH, bark thickness, crown base height and upper and lower heights of the bark transition areas of 375 trees. While the cardinal direction had no effect on bark thickness, DBH was found to have a significant effect on the heights of the bark transition areas, with stand density and tree height having a minor additional effect. These variables can be used to estimate timber volume (without bark) with higher accuracy and to predict the carbon storage potential of forest biomass according to different tree compartments and compounds.

Comparison of chemical compositions in wood and bark of Persian silk tree (Albizia julibrissin Durazz.)

ABSTRACT This research was conducted to identify and compare the chemical compositions in Persian silk tree (Albizia julibrissin Durazz.) from different parts of wood and bark, using Fourier Transform Infrared (FTIR) Spectroscopy, gas and liquid chromatography coupled to mass spectrometry (GC-MS, LC-MS), and elemental analysis. FTIR analysis showed significant differences in the chemical structure of bark and wood at peaks that belong to the cellulose and hemicelluloses. According to the results, the C-O-C asymmetric stretch vibration in cellulose and hemicelluloses peak of Persian silk tree was lower in the bark and ѵC=O in quinone or p-quinone peak was higher in the bark. The results of GC-MS showed 12 chemical constituents in the bark and 43 in the wood, respectively. Among these, hexadecanoic acid and inositol were in common. According to the LC-MS analyses, bark samples were rich in lignan compositions and triterpenoid saponins, whereas wood was poor in these compositions. Altogether 61 compositions have been tentatively identified and described from bark and wood tissues; many of them were identified for the first time. Energy-dispersive X-ray (EDX) spectrometry illustrated that the bark contained iron and aluminium, sodium, phosphorus, sulphur and chlorine, while these elements did not exist in wood.

Fire and drought: Shifts in bark investment across a broad geographical scale for Neotropical savanna trees

Savanna tree communities occurring in confluence zones with other biomes likely experience different environmental pressures, resulting in shifts in the selection of individual traits, the combinations of such traits, and species composition. In seasonally dry fire-prone environments, plant survival is presumably associated with adaptive changes in bark properties related to fire protection and water storage. Here, we integrated the multiple functions of the bark to investigate whether different selective pressures could influence patterns of variation in bark structure and allocation across species in a broad geographical range. We measured thickness, density, and water content of the inner and outer bark in branches and the main stem of the 51 most abundant species in three savanna communities differing in climatic aridity, one located at the core region of Cerrado in Central Brazil and the other two at its periphery, in the transition zones with Amazonia and Atlantic forest biomes. We found no difference in outer bark thickness but markedly difference in inner bark thickness between the three plant communities. In the central region, where dry season is long and fire is frequent, branches and main stem showed thicker inner bark. Contrastingly, in the south periphery region, where dry season is short, species showed thinner inner bark in both branches and main stem. Species from the north periphery region, where mean annual precipitation is higher, but fire is frequent and the dry season is also long, showed similar main stem inner bark thickness, but thinner branch inner bark compared to core region species. Our findings support the idea that investing in inner bark thickness and bark moisture may be the most advantageous strategy in plant communities that suffer from high evaporative demand during a long period and are at a high risk of fire.

Intersexual segregation in winter foraging of great spotted woodpecker Dendrocopos major in riparian forests infested with invasive tree species

ABSTRACT We investigated the pre-breeding intersexual foraging habitat preferences of the great spotted woodpecker Dendrocopos major in six old, unmanaged riparian forest stands in Central Hungary, which are composed mainly of the invasive North American green ash Fraxinus pennysylvanica and boxelder Acer negundo, and native poplar Populus sp. and willow Salix sp. trees in lower abundances. With the influence of river management, the two invasive species have usurped native tree species in numerous Central European riparian forests. We studied the intersexual utilization of tree species, tree condition, stem diameter, foraging height, horizontal sections, substrate diameter, substrate condition, and foraging technique. The birds showed intersexual segregation in numerous studied variables despite the high niche overlap between sexes. Similar patterns were also found in other woodpecker species as well. We think that the most important part of this segregation could be the difference revealed in the choice of tree species, as males tended to be more specialized for native softwood tree species with rougher bark structure. Despite the high abundance of invasive tree species, neither sex preferred them. The further population decrease of native tree species could increase within-species competition and negatively affect the studied bird species.

Fire tolerance strategies in woody species from Pantanal riparian forests involve phenolic compounds and structure of the inner bark

Fire is common in seasonally dry areas in many parts of the world, and its effects on vegetation in these areas have been well studied. In riparian forests of the Pantanal, where fuel accumulation (dead plants) in the dry season can be a substantial driver of fire occurrence, little is known about the role of bark traits to fire protection in woody plants. Herein we evaluated some physical, chemical and anatomical bark traits to determine if they are associated with fire tolerance in tree riparian species of the Pantanal. To accomplish this, we selected three fire-sensitive species and seven fire-tolerant species in riparian forest of the Paraguay River. Bark samples were analyzed for relative total, outer and inner bark thickness, bark density, concentration of phenolic compounds and tannins, thermogravimetric behavior and their anatomical structure. We observed higher concentration of phenol and tannins and higher percentage of sclerenchyma in bark from fire-tolerant species than fire-sensitive species. Bark of fire-tolerant species also showed more sclerenchyma cells near vascular cambium and higher temperatures of thermal decomposition. In contrast, relative total, outer and inner bark thickness, and bark density did not differ between species groups. The high concentration of phenol and tannins, combined with higher percentage of sclerenchyma in secondary phloem, appear as the major bark traits that could mitigate fire damage in species from riparian forest of the Brazilian Pantanal.

Bark Effects on Stemflow Chemistry in a Japanese Temperate Forest I. The Role of Bark Surface Morphology

Stemflow can be an important pathway for the drainage of precipitation and related solutes through tree canopies to forest soils. As stemflow must drain along bark surfaces, the effects of bark structure on stemflow chemical composition is merited. This study examines the relationship between stemflow chemistry and bark surface structure for six species of varying bark morphology (four deciduous broadleaf trees and two evergreen coniferous trees) at a montane and an urban site in Japan. Stemflow from smooth-barked species contained greater concentrations of solutes that appear to be rinsed from the stem surface (i.e., sea salt aerosols); while, rougher-barked tree species contained greater or less concentrations of solutes that appear to be leached (e.g., Ca2+) or taken-up (e.g., inorganic N) by the bark, respectively. Site-specific atmospheric environments also influenced thee bark-stemflow chemistry relationships—where the greater elemental deposition in the urban plot generally resulted in greater stemflow chemistry than observed in the lower-deposition montane plot. Our results therefore suggest that the dynamics of dry deposition wash-off by stemflow, and the exchange of dissolved solutes between stemflow and the bark surface, are influenced by the surface structure of the bark and the site’s atmospheric environment. Therefore, the interactions between bark surface structure and its surrounding atmospheric environment are important factors in the stemflow-related elemental cycling between the tree and precipitation.

Hypothesis and Theory: Fungal Spores in Stemflow and Potential Bark Sources

The study of stemflow fungi began over 50 years ago. Past work has been performed in different climatic regions of the world, with different sampling methods, by mycologists focusing on different taxonomical groups. Therefore, we aim to synthesize this work to delineate major conclusions and emerging hypothesis. Here, we present: (1) a systematic compilation of observations on stemflow conidial concentration, flux, and species composition; (2) an evaluation of the methods underlying these observations; (3) a testable theory to understand spatiotemporal dynamics in stemflow (including honeydews) conidial assemblages, with a focus on their relationship to bark structure and microhabitats; and (4) a discussion of major hypotheses based on past observations and new data. This represents a knowledge gap in our understanding of fungal dispersal mechanisms in forests, in a spatially-concentrated hydrologic flux that interacts with habitats throughout the forest microbiome. The literature synthesis and new data represent observations for 228 fungal species’ conidia in stemflow collected from 58 tree species, 6 palm species, and 1 bamboo species. Hypothetical relationships were identified regarding stemflow production and conidial concentration, flux, and species composition. These relationships appear to be driven by bark physico-chemical properties, tree canopy setting, the diversity of in-canopy microenvironments (e.g., tree holes, bark fissures, and epiphytes), and several possible conidia exchange processes (teleomorph aerosols, epi-faunal exchanges, fungal colonization of canopy microhabitats, and droplet impacts, etc.). The review reveals a more complex function of stemflow fungi, having a role in self-cleaning tree surfaces (which play air quality-related ecoservices themselves), and, on the other hand, these fungi may have a role in the protection of the host plant.

Phylogenetic structure of lichen metacommunities in Amazonian and Northeast Brazil

AbstractAmazon, Atlantic forest, Brejos de Altitude, Caatinga, Carrasco, Cerradão and Restinga are major vegetation units in North and Northeast Brazil. Little is known about lichen metacommunity structure in these habitats. While species richness and composition generally depend on climatic factors, in azonal vegetation edaphic factors may have a filtering effect on tree bark structure and hence the composition of epiphytic lichen communities. We hypothesized that climatic stress and a tree bark filtering effect would result in reduced richness and phylogenetic clustering in Caatinga, Carrasco, Cerradão and Restinga, whereas high richness and phylogenetic overdispersion were predicted for Amazon and Atlantic Forest. To test this, we analyzed 2,090 lichenized species in the study area, with a supertree to assess phylogenetic metacommunity structure. Amazon and Atlantic forest exhibited high richness and phylogenetic diversity, with phylogenetic overdispersion only in the Amazon. The zonal Caatinga with drought stress and the extrazonal Brejos both exhibited phylogenetic clustering. Among the azonal, edaphic vegetation units, Cerradão exhibited phylogenetic overdispersion, whereas Restinga showed phylogenetic clustering. Nearest taxon phylogenetic distance indicated a close relationship between Amazon and Atlantic forest, Atlantic forest and Brejos and Atlantic forest and Caatinga. Carrasco was mostly closely related to Cerradão, and Restinga was distantly related to any other unit. These findings indicate more complex patterns in the phylogenetic structure of lichen metacommunities, partly reflecting those of plant metacommunities, as a result of concurrent macroecological evolutionary histories. Our data supported floristic evidence that Carrasco is part of the Cerrado complex and not related to Caatinga.

Hygroscopic contributions to bark water storage and controls exerted by internal bark structure over water vapor absorption

Key messageHygroscopicity is a crucial element of bark water storage and can reach >60% of water holding capacity of bark depending on tree speciesBark forms the outer layer of woody plants, and it is directly exposed to wetting during rainfall and reacts to changes in relative humidity, i.e., it may exchange water with the atmosphere through absorption and desorption of water vapor. A current paradigm of bark hydrology suggests that the maximum water storage of bark empties between precipitation events and is principally controlled by bark thickness and roughness. We hypothesize that (1) the ability of bark to absorb water vapor during non-rainfall periods (i.e., hygroscopicity) leads to partial saturation of bark tissues during dry periods that may alter the rate of bark saturation during rainfall, and (2) the degree of bark saturation through hygroscopic water is a function of internal bark structure, including porosity and density, that varies among species. To address these questions, we conducted laboratory experiments to measure interspecific differences in bark physical structure as it relates to water storage mechanisms among common tree species (hickory (Carya spp.), oak (Quercus spp.), sweetgum (Liquidambar styraciflua), and loblolly pine (Pinus taeda)) in the southeastern United States. Furthermore, we considered how these properties changed across total bark, outer bark, and inner bark. We found a distinct difference between hickory and oak, whereby hickory had 5.6% lower specific density, 31.1% higher bulk density, and 22.4% lower total porosity of outer bark resulting in higher hygroscopicity compared to oaks. For all species, hygroscopicity increased linearly with bulk density (R2 = 0.65–0.81) and decreased linearly with total porosity (R2 = 0.64–0.88). Overall, bark hygroscopicity may constitute an average of 30% of total bark water storage capacity. Therefore, in humid climates like those of the southeastern USA, the proportion of bark that remains saturated during non-storm conditions should not be considered negligible.

Bark anatomy of Melastomataceae species in the Brazilian Cerrado, a neotropical savanna

The bark (all tissues outside the cambium) is a morphologically diverse and functionally important part of the stem. Outer bark (periderm) has a protective function, and inner bark (secondary phloem) is involved in the long-distance transport. In savannas, the relationship between bark structure, life form and habitat is controversial. We studied the morphology and anatomy of bark of Melastomataceae species with different habits growing at different sites in the Brazilian Cerrado (a neotropical savanna), from well-drained to temporarily or permanently waterlogged soils. Bark samples were processed by standard anatomical techniques. Regarding the outer bark, the species studied are grouped into two main categories: with a single periderm (with nonstratified or stratified phelem) and with multiple periderms, that is, with a rhytidome. Although a formal test has not been carried out in this work to assess the existence of a correlation between the microscopic structure of the periderm and the habit and growth distribution of plants, there seems to be no correlation for most of the species studied here, except for a subshrub species inhabiting waterlogged soils. Sclerified cells, calcium oxalate crystals, and phenolic content are abundant through the secondary phloem. Microscopic bark features are useful to distinguish species.

Влияние методов измельчения бересты на выход биологически активных веществ

Introduction. Birch bark contains biologically active substances (BAS). In this regard, the search for ways to increase yield of its bioactive agents is relevant. Aim. To study the effect of birch bark grinding methods on the extract of its BAS during extraction. Materials and methods. Samples of birch bark of silver birch (Betula pendula Roth.) and downy birch (Betula pubescens Ehrh.) were ground up on devices with various force effects on plant material — disk (mainly squeezing, shear, tensile and shearing forces), three-roll annular (crushing and abrasive forces) and ball (crushing, abrasive and shock-shear forces) mills. Morphological and microscopic studies were carried out, the content of extractive substances and moisture in the ground up samples was determined. The composition and content of BAS were analyzed. Results. The smallest changes in the morphological and anatomical structure of plant material were observed when using a disk mill (the morphological features of birch bark and its cellular structure are preserved), grinding on three-roll ring and ball mills leads to serious changes in the morphological and anatomical structure of birch bark (the morphological and anatomical structure is lost, cell walls are destroyed). Comparative analysis of the yield of extractive substances from ground up birch bark samples, depending on the grinding method and the extractant used (purified water and ethyl alcohol of different concentrations: 96, 80, 70, 40, 20 and 10%) showed that the best extractant is 80% ethyl alcohol. The highest yield of extractive substances was noted for a sample of birch bark ground up in a ball mill — 36.85%, for ground up in a disc mill — 29.96%, on a three-roll ring mill — 30.88%. When studying the yield of the main groups of BAS (saponins, tannins, coumarins, hydroxycinnamic acids) from ground up birch bark samples, it was found that when using grinding methods that do not lead to the destruction of cell walls, the yield of BAS is limited by the capillary-porous structure of the plant material. Conclusion. When using grinding methods that lead to the destruction of cell walls, the greatest yield of BAS from birch bark is observed in the case of using a more severe impact on it, including not only abrasion, crushing, but also impact (ball mills).

Wood and bark anatomy of South African Picrodendraceae with systematic and ecological implications

Wood and bark structure of Androstachys johnsonii and Hyaenanche globosa (Picrodendraceae) is described. Two species share simple perforation plates, minute to small intervessel pits, and nonseptate fibres; these traits also reported in other Picrodendraceae. Androstachys is distinctive in having scanty paratracheal axial parenchyma and uniseriate rays with vessel-ray pits restricted to marginal cells. Bordered pits on fibre walls is an ancestral condition for the African Picrodendraceae. High vessel frequency and vessel grouping in Androstachys can be adaptive for semi-arid climate with wet summer. Both genera share the subepidermal phellogen initiation and the presence of thick-walled fibers and sclereids in secondary phloem. In Hyaenanche, the bark is dilated by stretching and divisions of parenchyma cells with formation of pseudocortex. Androstachys shows no ray dilatation, but sclerification of its parenchyma can make substantial contribution in bark expansion. Abundant trichomes on epidermis of young shoots of Androstachys are presumably involved in the water uptake from mists.

Vitality versus cambium, xylem, and phloem characteristics in Cedrus libani

Abstract In many regions, such as the Mediterranean, anticipated climate change is seen as a serious threat to tree vitality and forest productivity. Recent studies show that wood and bark structure as well as the number of dormant cambial cells bear valuable information about the growth condition and vitality of trees and thus could function as indicators to help manage forests in the future. Microcores and tree cores were sampled from stems of adult Cedrus libani trees growing at different altitudes in SW-Turkey. Trees were divided into two groups based on basal area increments: vital trees (positive growth trend), and trees of diminishing vitality (negative growth trend). Histological cross-sections were investigated for their number of dormant cambial cells as well as their xylem and phloem characteristics. We measured the widths of the conducting phloem, most recent xylem ring, earlywood, and latewood. We further calculated the ratio between the width of xylem ring and conducting phloem (XR:CPH ratio), and earlywood to latewood ratio. Vital trees had a significantly higher number of dormant cambial cells (on average 32%), higher xylem (67%), and conducting phloem (36%) widths, and a higher XR:CPH ratio (47%). The XR:CPH ratio ranged between 1.8:1 and 21.4:1. The number of dormant cambial cells was closely related to xylem and conducting phloem widths and showed a significant decrease with tree age. Altitude showed no direct effect on the measured and calculated parameters. Our results indicate the potential of dormant cambium, xylem, and phloem characteristics to assess the vitality and growth conditions of C. libani trees.

Diurnal Pine Bark Structure Dynamics Affect Properties Relevant to Firebrand Generation

Firebrands are an important agent of wildfire spread and structure fire ignitions at the wildland urban interface. Bark flake morphology has been highlighted as an important yet poorly characterized factor in firebrand generation, transport, deposition, and ignition of unburned material. Using pine species where bark flakes are the documented source of embers, we conducted experiments to investigate how bark structure changes in response to diurnal drying. Over a three-day period in a longleaf pine (Pinus palustris Mill.) stand in Florida, we recorded changes in temperature, moisture content, and structure of bark across different facing aspects of mature pine trees to examine the effects of varying solar exposure on bark moisture. We further compared results to bark drying in a pitch pine (Pinus rigida Mill.) plantation in New Jersey. Under all conditions, bark peeled and lifted away from the tree trunk over the study periods. Tree bole aspect and the time of day interacted to significantly affect bark peeling. General temperature increases and moisture content decreases were significantly different between east and west aspects in pitch pine, and with time of day and aspect in longleaf pine. These results illustrate that bark moisture and flakiness is highly dynamic on short time scales, driven largely by solar exposure. These diurnal changes likely influence the probability of firebrand production during fire events via controls on moisture (ignition) and peeling (lofting).

Climber infestation and relationship with host tree species abundance and structure in a Nigerian secondary lowland rainforest

The composition, diversity, structure and host preference of climbers in a tropical lowland rain forest at Ile-Ife were examined in this study. Six plots (0.25 ha) were established in the secondary forest. In each plot, all the tree species ≥ 2 m in height were identified to species level and enumerated. The trees were examined for the presence of climbers and the number of climbers counted. The girth at breast height (gbh) of both trees and lianas were measured. The data collected were used to establish the floristic composition, density, diversity, evenness, basal area and climber infestation on tree species in the forest. Relationship and association of climber infestation on host species and the climber structural parameters were examined. Host bark texture was determined visually. There were 61 climber species distributed into 53 genera and 28 families. Host species bark structure had no significant relationship with climber infestation in the forest. There was a positive relationship between the abundance of host species and climbers. Although bark structure and climber infestation showed no significant association with infestation, girth sizes of host species and abundance of tree species had more influence on climber infestation in the forest.

Wood and bark of Buddleja: uniseriate phellem, and systematic and ecological patterns

Abstract Wood anatomy of Buddleja is well-explored but not in many southern African members, which form a grade of species and small clades that form successive sister groups to the rest of the genus, and its bark structure has not been studied at all. We provide new descriptions of wood anatomy for twelve species, including nearly all Buddleja from southern Africa and two species of Freylinia in the sister group of Buddleja. We also describe bark structure from fifteen species. To assess if wood anatomy provides phylogenetic and/or ecological signal, we compiled data on wood traits and climatic variables from the distributions of 53 species. Wood traits counteracting cavitation correlated with higher temperature and precipitation seasonality; simultaneously they were better expressed in species with smaller maximal plant height. It is likely that hotter and drier areas harbour smaller plants which have traits conveying higher conductance safety. Bark structure varies considerably. In bark of Buddleja section Gomphostigma, periderm is initiated in the outer cortex and develops thin-walled phellem, and sclerification of their phloem does not occur. This resembles bark in Freylinia, supporting the position of section Gomphostigma as sister to the rest of Buddleja. In the remaining Buddleja species, bark is characterised by formation of periderm with phelloid cells in the secondary phloem. The phellem is often uniseriate, a condition not reported elsewhere. Its formation occurs close in time to solid sclerification of the cut-off phloem, suggesting a possible novel ontogenetic mechanism.