Variation In Bark Thickness Research Articles

Variation and Driving Mechanisms of Bark Thickness in Larix gmelinii under Surface Fire Regimes

Bark is vital for woody plants, providing protection, transporting nutrients and water, and storing essential resources. For fire-prone ecosystems, bark thickness is a key adaptive trait conferring fire resistance. Few studies have been conducted on the drivers of variation in bark thickness of the widely distributed Larix gmelinii (Rupr.) Kuzen in the Great Xing’an Mountains region, on the southern edge of East Siberia, where surface fire disturbances are frequent. To elucidate the relationships between variation in bark thickness (inner vs. outer bark) of L. gmelinii and plant size, environmental factors, and co-variation with other fire-tolerance traits, we selected 26 sites to set up plots and carried out a survey and bark sampling. Results showed that stem diameter primarily determines variation in bark thickness, especially outer bark. The proportion of outer bark to total bark increased accordingly as the tree increased in size. We also observed stronger correlated variation in outer bark thickness, tree height, and self-pruning capacity, implying that larger trees have thicker protective outer bark and taller heights with greater self-pruning, mitigating crown fire risks. Environmental factors appear to have a relatively limited effect on changes in bark thickness in L. gmelinii. Mean air temperature, annual precipitation, and total soil nitrogen content had some effect on outer bark thickness, and mean air temperature had some effect on inner bark thickness.

Bark thickness models for oak forests being converted from coppice to high forests in Northwestern Turkey.

The research was carried out in the coppice-originated pure oak stands that are being converted to high forests in northwest Turkey. The main goal of the research was to determine the bark thickness (BT) based on tree variables, such as tree diameter at breast height (DBH), total tree height (H), crown diameter (CD), and age (AGE) of the stem sections taken from a total of 350 trees that were destructively sampled from different sites, different oak species (Quercus petraea, Quercus frainetto, Quercus cerris), and different development stages. Models were developed with stepwise multiple regression analysis to predict BT based on the variables.For all oak species, all models obtained by stepwise multiple regression analysis were found to be significant at p = 0.001 level. In Quercus petraea, only the DBH-dependent model explained the variation in BT at a rate of 73%, estimating with an absolute error rate of 21%. The fit statistics of the models (based on DBH and DBH-H explanatory variables) obtained for Quercus frainetto are very close to each other, and they explained the variation in BT at a rate of 69% and estimated with an error rate of 26%. Models (based on DBH and DBH-H explanatory variables) explain the variation in BT in Turkey oak at a rate of 91%, indicating species-specific results. The models based on only DBH can be used with high accuracy to estimate BT.

Application of resistance drilling to genetic studies of growth, wood basic density and bark thickness in Eucalyptus globulus

ABSTRACT Tree breeders are increasingly using resistance drilling (RESI) for the non-destructive assessment of wood basic density, but its application to the measurement of stem diameter at breast height (DBH) and bark thickness is less reported. Using Eucalyptus globulus progeny trials established with open-pollinated families from native trees representing 13 subraces, and adjusting bark thickness for its inherent phenotypic relationship with DBH, we: (1) quantified the genetic correlation between RESI and analogous traditional measurements of these traits; and (2) studied their genetic architecture and associations with subrace home-site climate. Significant variation was detected for all traditional and RESI-derived traits at the family and subrace level. High family and subrace-level correlations (>0.90) were found between RESI and traditional methods for all three traits. Bark thickness exhibited among the highest subrace differentiation (QST > 0.63) reported to date for E. globulus, signalling divergent selection. Increasing bark thickness was positively associated with home-site temperature annual range and seasonality. Although subrace differentiation for wood density (RESI and traditional measures) was less (QST = 0.18–0.21), a similar climate association was detected, and the subrace-level correlation with bark thickness was positive and significant (0.61–0.75). However, the non-significant correlations between bark thickness and wood density at the family level suggest that selective covariance rather than pleiotropy have caused the correlated patterns of subrace variation. Variation in bark thickness (adjusted) and wood density was independent of DBH at the family and subrace level. Given the importance of these traits, RESI provides a useful approach for non-destructive assessments for silvicultural, genetics and ecological studies of forest trees.

Potential tradeoffs between intraspecific and interspecific trait variations along an environmental gradient in a subtropical forest

There has been growing attention to intraspecific variation in trait-based plant ecology. However, studies on these changes across ontogenetic stages and the potential trade-offs with interspecific traits along environmental gradients are rare. In this study, we measured six wood and bark traits of 1030 trees of six species (Castanopsis nigrescens; C. carlesii; Lithocarpus polystachyus; L. synbalanos; Ormosia glaberrima; O. pachycarpa) from a 10-ha plot in a subtropical forest. Mean intraspecific variation in bark thickness and bark percentage to DBH was more than twice that for wood density and bark density. Bark thickness and bark percentage showed a consistent trend with increasing tree size. Small-tree traits were more variable than the same traits in larger trees. Altitude, convexity and soil nutrients explained the majority of the variations in the six traits, while sibling species had similar relationships between traits and environmental variables. Trees with dense wood and thin bark were usually found on steep slopes at lower altitudes. Our findings show intraspecific trait variability has different spatial patterns compared with interspecific variabilities along an environmental gradient.

Updating Bark Proportions for the Estimation of Tropical Timber Volumes by Indigenous Community-Based Forest Enterprises in Quintana Roo, Mexico

Sustainable management of tropical forests is essential for conserving the ecosystem services they provide and protecting the livelihoods of the millions of people who depend on these forests. Community-based forest management in Quintana Roo, Mexico, has shown that conserving forests while generating economic benefits is achievable in the tropics. However, this management is carried out with technical gaps that jeopardize sustainable use of these resources. Crucial among these gaps is a lack of equations for precise calculations of logged timber volumes. Current equations employ a proportion of bark volume (PBV) of 0.14 for mahogany and a flat 0.10 for species with dense woods, despite their wide variation in bark thickness. Here, using Meyer’s method, we calculated species-specific PBVs for the most commercially-important species in the Felipe Carrillo Puerto community-based logging operation. For most species, the new PBVs were smaller, indicating that wood volumes are currently underestimated. However, for two species, PBVs were higher. New values could influence the profits of the local enterprise and on the management of some of the most commercially-important species of Mexico’s tropical forests through changes in the numbers of individuals felled.

Comparison of models for estimating bark thickness of Picea abies in southwest Germany: the role of tree, stand, and environmental factors

Bark thickness was shown to vary between regions, stands, and trees. Bark thickness prediction equations of different model complexity can be suggested depending on the purpose of application. Site and stand conditions, which influence variation of growth rate to a large extent, seem to have a strong influence on bark thickness, with better site quality leading to smaller relative bark thickness. For many applications in forestry and forest science, local or regional species-specific bark thickness equations are used to estimate inside-bark diameters with outside-bark diameter measurements. The objectives of this study were (1) to assess variation in bark thickness due to tree and stand factors in two Norway spruce (Picea abies (L.) Karst) datasets from different time periods, (2) to compare and evaluate alternative established model forms for estimating bark thickness, and (3) to assess spatial variation in bark thickness to estimate the effects of environmental factors on bark thickness. Different bark thickness models were chosen from the literature and compared for their predictive quality for new measurements and a dataset from the 1970s. Mixed-effect modelling was applied to account for the hierarchical data structure, and generalized additive mixed models were used to analyse spatial effects and the influence of climatic factors, such as precipitation and temperature. A strong positional autocorrelation of bark thickness within trees and within plots could be shown. Bark thickness was smaller in the new data compared to the measurements from the 1970s. The variation between stands could not be explained by the tested environmental factors, but tree age had a strong positive effect on bark thickness. In the study region, the variation of site productivity and individual growth rate seem to have a strong influence on bark thickness, whereas no significant effect of large scale climatic factors could be found.

Bark thickness across the angiosperms: more than just fire.

Global variation in total bark thickness (TBT) is traditionally attributed to fire. However, bark is multifunctional, as reflected by its inner living and outer dead regions, meaning that, in addition to fire protection, other factors probably contribute to TBT variation. To address how fire, climate, and plant size contribute to variation in TBT, inner bark thickness (IBT) and outer bark thickness (OBT), I sampled 640 species spanning all major angiosperm clades and 18 sites with contrasting precipitation, temperature, and fire regime. Stem size was by far the main driver of variation in thickness, with environment being less important. IBT was closely correlated with stem diameter, probably for metabolic reasons, and, controlling for size, was thicker in drier and hotter environments, even fire-free ones, probably reflecting its water and photosynthate storage role. OBT was less closely correlated with size, and was thicker in drier, seasonal sites experiencing frequent fires. IBT and OBT covaried loosely and both contributed to overall TBT variation. Thickness variation was higher within than across sites and was evolutionarily labile. Given high within-site diversity and the multiple selective factors acting on TBT, continued study of the different drivers of variation in bark thickness is crucial to understand bark ecology.

Shifts in functional traits elevate risk of fire‐driven tree dieback in tropical savanna and forest biomes

Numerous predictions indicate rising CO2 will accelerate the expansion of forests into savannas. Although encroaching forests can sequester carbon over the short term, increased fires and drought-fire interactions could offset carbon gains, which may be amplified by the shift toward forest plant communities more susceptible to fire-driven dieback. We quantify how bark thickness determines the ability of individual tree species to tolerate fire and subsequently determine the fire sensitivity of ecosystem carbon across 180 plots in savannas and forests throughout the 2.2-million km(2) Cerrado region in Brazil. We find that not accounting for variation in bark thickness across tree species underestimated carbon losses in forests by ~50%, totaling 0.22PgC across the Cerrado region. The lower bark thicknesses of plant species in forests decreased fire tolerance to such an extent that a third of carbon gains during forest encroachment may be at risk of dieback if burned. These results illustrate that consideration of trait-based differences in fire tolerance is critical for determining the climate-carbon-fire feedback in tropical savanna and forest biomes.

Measurement and prediction of bark thickness in Picea abies: assessment of accuracy, precision, and sample size requirements

Tree and log diameters are usually measured outside bark, but inside-bark diameters are of greater economic interest and are often derived with local or regional bark thickness equations. To date, the influence of measurement method, sampling design, and sample size on bark thickness equation accuracy and precision has received limited attention. The objectives of this study were to use an extensive regional bark thickness dataset for Norway spruce (Picea abies (L.) Karst) in southwestern Germany to (1) quantify the accuracy and precision of bark thickness measurements with a Swedish bark gauge, (2) determine the required number of measurements to assess the within-tree variation, and (3) estimate the required sample sizes per plot and per region to develop an accurate bark thickness prediction equation. Bark gauge readings were validated with measurements derived from X-ray computed tomography (CT) and indicate that Swedish bark gauges generally overestimated bark thickness by 13.6% ± 28.4% (mean ± standard deviation). Results suggested having at least one measurement location every 2 m along a tree bole and at least five bark thickness measurements per each of these locations to achieve an allowable error of <15%. For the study area, Monte Carlo simulations indicated that a total sample size of 50–250 trees was needed, depending on the complexity of the desired bark thickness model. Overall, this analysis indicated that there was relatively high within- and between-tree variation in bark thickness, but adequate sampling methods and sample sizes produced highly accurate bark thickness equations.

Functional and environmental determinants of bark thickness in fire-free temperate rain forest communities.

In fire-prone ecosystems, variation in bark thickness among species and communities has been explained by fire frequency; thick bark is necessary to protect cambium from lethal temperatures. Elsewhere this investment is deemed unnecessary, and thin bark is thought to prevail. However, in rain forest ecosystems where fire is rare, bark thickness varies widely among species and communities, and the causes of this variation remain enigmatic. We tested for functional explanations of bark thickness variation in temperate rain forest species and communities. We measured bark thickness in 82 tree species throughout New Zealand temperate rain forests that historically have experienced little fire and applied two complementary analyses. First, we examined correlations between bark traits and leaf habit, and leaf and stem traits. Second, we calculated community-weighted mean (CWM) bark thickness for 272 plots distributed throughout New Zealand to identify the environments in which thicker-barked communities occur. Conifers had higher size-independent bark thickness than evergreen angiosperms. Species with thicker bark or higher bark allocation coefficients were not associated with "slow economic" plant traits. Across 272 forest plots, communities with thicker bark occurred on infertile soils, and communities with thicker bark and higher bark allocation coefficients occurred in cooler, drier climates. In non-fire-prone temperate rain forest ecosystems, investment in bark is driven by soil resources, cool minimum temperatures, and seasonal moisture stress. The role of these factors in fire-prone ecosystems warrants testing.

Effects of seed source origin on bark thickness of Douglas-fir (Pseudotsuga menziesii) growing in southwestern Germany

Provenance-specific variation in bark thickness in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) is important for accurate volume calculations and might carry ecological implications as well. ...

Variation in wood anatomical properties of selected indigenous, multipurpose tree species grown in research trials at LRS Thiruvazhamkunnu, Palakkad, Kerala

The present study is an attempt to study the variation in wood physical and anatomical properties of Artocarpus heterophyllus Lam., Artocarpus hirsutus Lam. and Pterocarpus marsupium Roxb. raised as part of a provenance trial of the Kerala Agricultural University at the Livestock Research Station, Thiruvazhamkunnu, in Palakkad district of Kerala. The objectives were to study the variation in bark thickness, heart wood content, specific gravity, fibre morphology, vessel morphology, and ray morphology between above species as well as to understand the radial variation within the trees under the prevailing agro climatic conditions. Results showed higher values for heart wood content, ray height, ray width, vessel frequency; and lower bark thickness in A. hirsutus, compared to the other two species while, P. marsupium had the highest air dry and oven dry specific gravity. A. heterophyllus had superior values for vessel diameter, vessel area, fibre length and fibre diameter. The information obtained from this study indicates the potential of these hitherto under-estimated multipurpose indigenous species for various end-uses. The results also points to the pertinent need to undertake long term tree improvement trials of the above species for efficient utilization of these promising species for the state of Kerala.

Functional explanations for variation in bark thickness in tropical rain forest trees

Summary 1. The complex structure of tree bark reflects its many functions, which include structural support as well as defence against fire, pests and pathogens. Thick bark, however, might limit respiration by the living tissues of the trunk. Nevertheless, little research has addressed community‐level variation in bark thickness, and to the best of our knowledge, no one has tested multiple hypotheses to explain variation in bark thickness. 2. We conducted an extensive survey of bark thickness within and among species of trees in the tropical rain forests of French Guiana. Trunk bark thickness increased by 1·2 mm per 10 cm increase in stem diameter, and varied widely at all taxonomic levels. Mean trunk bark thickness was 4·5 mm (range: 0·5–29 mm), which was less that found in two Amazonian rain forests in previous studies. This survey of bark thickness should be of use for forest management since tree survival through fire is strongly predicted by bark thickness. 3. We combined the survey data with multiple datasets to test several functional hypotheses proposed to explain variation in bark thickness. We found bark to provide an average of 10% of the flexural rigidity of tree stems, which was substantially less than that found in the only other study of bark stiffness. Bark thickness was uncorrelated with species’ association with fire‐prone habitats, suggesting that the influence of fire on bark thickness does not extend into moist Forests. There was also little evidence that bark thickness is affected by its function as a defence against herbivory. Nor was there evidence that thick bark limits trunk respiration. 4. A re‐analysis of previously collected anatomical data indicated that variation in rhytidome (non‐conducting outer bark) thickness explains much of the variation in overall bark thickness. As rhytidome is primarily involved in protecting the living tissues of the trunk, we suggest that bark thickness is driven mostly by its defensive function. 5. Functional explanations for the variation in bark thickness were not clear‐cut. Nevertheless, this study provides a foundation for further investigation of the functional bases of bark in tropical trees.

Functional explanations for variation in bark thickness in tropical rain forest trees

Functional explanations for variation in bark thickness in tropical rain forest trees

Variation in bark thickness in a tropical forest community of Western Ghats in India

1. We examined the relation between bark thickness and girth in a large sample of trees from evergreen and semi‐evergreen rain forest. 2. There is a significant tendency for bark thickness to increase with tree girth. Removing this tendency, we find a significant trend for species from more disturbed habitats to possess thicker bark. 3. Species from more disturbed habitats also have a greater propensity for secreting gums and resins. 4. Nine of the 29 species occurring in more than one habitat type and with a sample size of at least 11 individuals show a tendency for possession of a thicker bark by individuals in the more disturbed habitats. 5. We conclude that bark thickness and occurrence of gums and resins are physiognomic–structural attributes of value in characterizing tree communities created by different levels of disturbance.