Size of conducting phloem: The “key” factor for bark recovery of 12 tropical medicinal tree species

For rural populations in Africa, tree bark is widely used for medicinal purposes. Despite its importance, no anatomical studies exist which detail the recovery of medicinal tree species in Africa to bark harvesting. This present study aims to determine the anatomical variable(s) that could help to predict the differing recovery rates of 12 medicinal tree species. Discs of branches were collected from non-harvested trees of 12 different African species. A total of 12 anatomical variables were measured in the wood, the cambium and the phloem zone, and the correlation between the bark recovery rate and each variable was tested. Among the 12 anatomical variables tested, the thickness of the conducting phloem zone emerged as the most important one to explain the bark recovery rate. The presence of sclereids within the conducting phloem zone was also found to be an explanatory variable and was negatively correlated with the bark recovery rate. For 10 out of the 12 species, the thickness of the cambial zone varied significantly with the season. Nevertheless, this variable did not contribute significantly to the explanation of the bark recovery rate. Given that the 12 studied species showed a large range of bark recovery rates (0.1–10.0 cm y^?1), we assume that they may be representative of the variety of wound healing responses (i.e. wood and bark tissue production) in many of African tree species. Consequently, our results could offer the advantage to foresee the potential of wound closure in any tree from which bark could be harvested.     

Harvesting Increases Reproductive Activity in Himatanthus drasticus (Mart.) Plumel (Apocynaceae), a Non‐Timber Forest Product of the Brazilian Savanna

The harvesting of non‐timber forest products (NTFP) can influence the pattern of resource allocation in plants, affecting their growth, survival, and reproduction. However, only a small number of studies have addressed the impacts of NTFP harvesting on the reproductive phenology of the exploited species. The aim of this observational study was to assess the effects of harvesting and climatic variables on the reproductive phenology of Himatanthus drasticus, a highly exploited medicinal tree from the Brazilian savanna (Cerrado). We evaluated the effects of two different debarking levels (50 and 100%) in comparison to a control (no harvesting). We performed monthly counts of the number of buds, flowers in anthesis, unripe and ripe fruits in each sampled tree (intensity index), as well as the number of trees in each phenophase (activity index), over 2 yr. We used circular statistics tools to compare the effects of each treatment on flower and fruit production and to test whether the reproductive peaks were related to climatic variables. Both the activity and intensity indexes exhibited the same patterns; flower and fruit production were lower in the control, intermediate in the 50 percent debarking group and higher in the 100 percent debarking group. To the best of our knowledge, this is the first study of NTFP to demonstrate an increase in reproductive activity after several years of harvesting. All phenophases were positively correlated with higher temperature and precipitation, as it is common in the Cerrado.     

Diversity of xylophagous beetles and vulnerability of debarked-medicinal plants in southern of Benin

We studied the impact of debarking of medicinal tree species on the diversity of xylophagous beetles in Lama Forest Reserve, in Lokoli swampy forest and in crop fields surrounded Lokoli forest. A total of 108 interception traps were set up on debarked and nondebarked trees covering nine medicinal plants that are Anogeissus leiocarpa, Dialium guineense, Khaya senegalensis in Lama Forest; Nauclea diderrichii, Ficus trichopoda, Syzygium owariense in swampy forest; and Parkia biglobosa, Bridelia ferruginea, Pterocarpus erinaceus in crop fields. A total of 116 beetle species were collected belonging to 19 coleoptera families with higher xylophagous beetles than predators. Specific richness and individual abundance of xylophagous beetles were significantly higher in crop fields than in forests. Furthermore, in all habitats, debarked-tree species were more attractive to xylophagous beetles than control trees and were significantly more attacked in crop fields than forests. The most vulnerable medicinal trees to debarking were P. biglobosa, D. guineense, F. trichopoda and P. erinaceus. Three groups of indicator insects according to habitat type, debarking and tree species have been distinguished. Our results clearly imply that by exploiting natural resources humans can impact on the abundance and specific richness of xylophagous beetles by modulating their resources.     

Ants,fire, and bark traits affect how African savanna trees recover following damage

Bark damage resulting from elephant feeding is common in African savanna trees with subsequent interactions with fire, insects, and other pathogens often resulting in tree mortality. Yet, surprisingly little is known about how savanna trees respond to bark damage. We addressed this by investigating how the inner bark of marula (Sclerocarya birrea), a widespread tree species favoured by elephants, recovers after bark damage. We used a long‐term fire experiment in the Kruger National Park to measure bark recovery with and without fire. At 24 months post‐damage, mean wound closure was 98, 92, and 72%, respectively, in annual and biennial burns and fire‐exclusion treatments. Fire exclusion resulted in higher rates of ant colonization of bark wounds, and such ant colonization resulted in significantly lower bark recovery. We also investigated how ten common savanna tree species respond to bark damage and tested for relationships between bark damage, bark recovery, and bark traits while accounting for phylogeny. We found phylogenetic signal in bark dry matter content, bark N and bark P, but not in bark thickness. Bark recovery and damage was highest in species which had thick moist inner bark and low wood densities (Anacardiaceae), intermediate in species which had moderate inner bark thickness and wood densities (Fabaceae) and lowest in species which had thin inner bark and high wood densities (Combretaceae). Elephants prefer species with thick, moist inner bark, traits that also appear to result in faster recovery rates.     

Cork oak vulnerability to fire: the role of bark harvesting, tree characteristics and abiotic factors

Forest ecosystems where periodical tree bark harvesting is a major economic activity may be particularly vulnerable to disturbances such as fire, since debarking usually reduces tree vigour and protection against external agents. In this paper we asked how cork oak Quercus suber trees respond after wildfires and, in particular, how bark harvesting affects post-fire tree survival and resprouting. We gathered data from 22 wildfires (4585 trees) that occurred in three southern European countries (Portugal, Spain and France), covering a wide range of conditions characteristic of Q. suber ecosystems. Post-fire tree responses (tree mortality, stem mortality and crown resprouting) were examined in relation to management and ecological factors using generalized linear mixed-effects models. Results showed that bark thickness and bark harvesting are major factors affecting resistance of Q. suber to fire. Fire vulnerability was higher for trees with thin bark (young or recently debarked individuals) and decreased with increasing bark thickness until cork was 3-4 cm thick. This bark thickness corresponds to the moment when exploited trees are debarked again, meaning that exploited trees are vulnerable to fire during a longer period. Exploited trees were also more likely to be top-killed than unexploited trees, even for the same bark thickness. Additionally, vulnerability to fire increased with burn severity and with tree diameter, and was higher in trees burned in early summer or located in drier south-facing aspects. We provided tree response models useful to help estimating the impact of fire and to support management decisions. The results suggested that an appropriate management of surface fuels and changes in the bark harvesting regime (e.g. debarking coexisting trees in different years or increasing the harvesting cycle) would decrease vulnerability to fire and contribute to the conservation of cork oak ecosystems.     

Analysing the long-term effects of artificial pruning of wild cherry by computer tomography

The wild cherry (Prunus avium L.) is a species that does not exhibit fast natural pruning. Artificial pruning is consequently a prerequisite for the production of valuable timber, which is at the same time often accompanied by unwanted decay that decreases wood quality. This study aims to reveal the factors affecting the speed of branch stub occlusion, and the relationship between stub occlusion and the subsequent formation of decay within stem wood. For this study, 11- and 23-year-old wild cherry trees with documented pruning history were sampled at two experimental sites in Bavaria with varying site class, spacing and thinning variants. The wood structure of the specimens was analysed by computer tomography (CT scanning), which allows for the examination of occlusion of pruned knots as well as the presence of decay. No significant differences between the branch diameters determined by CT scanning and manual measurement were found, proving the reliability of measurements from CT scans. Decay reduced the wood density by 40–60% compared to sound wood. Even small fluctuations in wood density caused by decay that were not visually recognisable could be detected in the CT images. The results suggest that the speed of stub occlusion is significantly positively affected by the diameter growth of the tree stem. The average wound occlusion was 1.3 mm per 1 mm stem diameter growth with a significant difference between sites. A relation between stub occlusion duration and the presence of decay was also found. Serious decay was detected after 3 years on the better, and after 4 years on the less favourable site. Based on these results, reliable pruning recommendations could be derived with regards to maximum branch diameter for pruning depending on a tree’s specific diameter growth, without risking severe stem decay.     

Effects of flooding on wood and bark anatomy of four species in a mangrove forest community

Variation in the wood and bark anatomy of the dominant species of a mangrove forest community in Mexico was evaluated in relation to some environmental factors, and their physiological adaptations to salinity and flooding period are discussed. The forest is characterized by three zones according to the presence of dominant tree species and flooding periodicity. Vessel arrangement and wood and bark ray height are strongly associated with flooding zones where trees are growing. Variance analyses revealed significant differences among zones for these anatomical characteristics. Soil texture and water salinity were the most useful parameters for the prediction of values of anatomical characteristics. More abundant vessels in radial multiples in a shorter flooding period suggest a functional advantage of multiple vessel groups. Taller wood and bark rays in response to prolonged flooding period can be attributed to anoxic conditions. Among zones, significant differences in the vulnerability index of the species were detected, but not with respect to relative conductivity. Significant differences among zones exist for wood and bark characteristics involved in vertical and horizontal water transport, photosynthates and gas exchange.     

Relative importance of tree genetics and microhabitat on macrofungal biodiversity on coarse woody debris

Understanding the contribution of genetic variation within foundation species to community-level pattern and diversity represents the cornerstone of the developing field of community genetics. We assessed the relative importance of intraspecific genetic variation, spatial variation within a forest and microhabitat variation on a macrofungal decay community developing on logs of the Australian forest tree, Eucalyptus globulus. Uniform logs were harvested from trees from eight geographic races of E. globulus growing in a 15-year-old genetic trial. Logs were placed as designed grids within a native E. globulus forest and after 3 years of natural colonisation the presence of 62 macrofungal taxa were recorded from eight microhabitats on each log. The key factor found to drive macrofungal distribution and biodiversity on structurally uniform coarse woody debris was log-microhabitat, explaining 42% of the total variation in richness. Differences between log-microhabitats appeared to be due to variation in aspect, substrate (bark vs wood) and area/time of exposure to colonisation. This findings demonstrates the importance of considering fine-scale (within substrate) variation in the conservation and management of macrofungal biodiversity, an area that has received little previous attention. While a number of recent studies have demonstrated that the genetics of foundation tree species can influence dependent communities, this was not found to be the case for the early log decay community associated with E. globulus. Despite genetic variation in wood and bark properties existing within this species, there was no significant effect of tree genetics on macrofungal community richness or composition. This finding highlights the variation that may exist among guilds of organisms in their response to genetic variation within foundation species, an important consideration in a promising new area of research.     

Fire‐induced tree mortality in a neotropical forest: the roles of bark traits,tree size,wood density and fire behavior

Large‐scale wildfires are expected to accelerate forest dieback in Amazônia, but the fire vulnerability of tree species remains uncertain, in part due to the lack of studies relating fire‐induced mortality to both fire behavior and plant traits. To address this gap, we established two sets of experiments in southern Amazonia. First, we tested which bark traits best predict heat transfer rates (R) through bark during experimental bole heating. Second, using data from a large‐scale fire experiment, we tested the effects of tree wood density (WD), size, and estimated R (inverse of cambium insulation) on tree mortality after one to five fires. In the first experiment, bark thickness explained 82% of the variance in R, while the presence of water in the bark reduced the difference in temperature between the heat source and the vascular cambium, perhaps because of high latent heat of vaporization. This novel finding provides an important insight for improving mechanistic models of fire‐induced cambium damage from tropical to temperate regions. In the second experiment, tree mortality increased with increasing fire intensity (i.e. as indicated by bark char height on tree boles), which was higher along the forest edge, during the 2007 drought, and when the fire return interval was 3 years instead of one. Contrary to other tropical studies, the relationship between mortality and fire intensity was strongest in the year following the fires, but continued for 3 years afterwards. Tree mortality was low (≤20%) for thick‐barked individuals (≥18 mm) subjected to medium‐intensity fires, and significantly decreased as a function of increasing tree diameter, height and wood density. Hence, fire‐induced tree mortality was influenced not only by cambium insulation but also by other traits that reduce the indirect effects of fire. These results can be used to improve assessments of fire vulnerability of tropical forests.     

Radial and vertical variation of wood nutrients in Bornean tropical forest trees

Nitrogen, phosphorus, potassium, calcium, and magnesium concentrations in woody tissue are poorly documented, but are necessary for understanding whole-tree nutrient use and storage. Here, we report how wood macronutrient concentrations vary radially and along the length of a tree for 10 tropical tree species in Sabah, Malaysia. Bark nutrient concentrations were consistently high: 2.9–13.7 times greater than heartwood depending on the nutrient. In contrast, within the wood both the radial (sapwood vs. heartwood) and vertical (trunk bottom vs. trunk middle) variation was modest. Higher concentrations in sapwood relative to heartwood provide empirical support for wood nutrient resorption during sapwood senescence. Dipterocarp species showed resorption rates of 25.3 ± 7.1% (nitrogen), 62.7 ± 11.9% (phosphorus), and 56.2 ± 12.5% (potassium), respectively, while non-dipterocarp species showed no evidence of nutrient resorption in wood. This suggests that while dipterocarps have lower wood nutrient concentrations, this family is able to compensate for this by using wood nutrient resorption as an efficient nutrient conservation mechanism. In contrast to other nutrients, calcium and magnesium tended to accumulate in heartwood. Wood density (WD) showed little vertical variation along the trunk. Across the species (WD range of 0.33 to 0.94 mg/cm³), WD was negatively correlated with wood P and K concentration and positively correlated with wood Ca concentration. As our study showed exceptionally high nutrient concentrations in the bark, debarking and leaving the bark of the harvested trees on site during logging operations could substantially contribute to maintaining nutrients within forest ecosystems.     

Allometric equations and biomass expansion factors of Japanese red pine on the local level

This study was conducted to evaluate site-specific allometric equations and biomass expansion factors (BEF) of Japanese red pine (Pinus densiflora S. et Z.) at five sites in the Hadong, Hamyang, Jinju, Sancheong, and Uiryeong regions, situated in the western part of Gyeongnam province, Korea. Biomass in each tree component, i.e., needle, branch, stem wood, and stem bark, was quantified by destructive tree harvesting. Site-specific as well as generalized allometric equations were developed for each tree component across the entire sites. Both allometric regression equations were significant (P < 0.05), with diameter at breast height (DBH) accounting for 69–99% of the variation (as indicated by coefficients of determination, r ²) in aboveground biomass. The stem densities at different sites were significantly different (P < 0.05) from each other, but no significant difference was observed for stem bark density. The aboveground BEFs also showed a significant variation (P < 0.05) at a landscape scale and ranged from 1.19 to 1.46 among the sites. The results suggest that application of site-specific allometric equations and aboveground BEFs are likely to improve the reliability of biomass estimates on the local level.     

Stem and root anatomical correlations with life form diversity, ecology, and systematics in Moringa (Moringaceae)

Four life forms (habits) are identified in the 13 species of Moringa (bottle trees, sarcorhizal trees, slender trees, and tuberous shrubs) which are examined for wood anatomical correlations with habit, ecology, and systematic. Wood anatomy is similar within habit classes except for the sarcorhizal trees. The four bottle tree species and M. arborea (one of the sarcorhizal trees) are characterized by bands of confluent paratracheal parenchyma alternating with bands of libriform fibres, some of which may be parenchyma-like. The other sarcorhizal tree, M. ruspoliana , is characterized by alternating bands of parenchyma-like and long, slender libriform fibres. Root secondary xylem of all these species is characterized by bands of parenchyma and fibres. Slender trees do not show bands of fibres of different shapes and have fibrous roots with less parenchyma than the other species. Tuberous shrubs have stems mostly composed of long, slender fibres and large underground tubers mostly composed of parenchyma. Quantitative trends between ecologically different localities include wider vessel elements and higher conductive area in moister localities. Wood anatomy provides characters that are of potential phylogenetic utility at a variety of levels of relationship. Based on wood anatomy and geography, the most likely sister taxon to Moringa is Cylicomorpha (Caricaceae).     

Double jeopardy: bark harvest for malaria treatment and poor regeneration threaten tree population in a tropical forest of Uganda

Several forest plants known to supply medicine are under pressure worldwide. We carried out a study of four tree species (Warburgia ugandensis Sprague, Fleroya rubrostipulata (K.Schum.) Y.F.Deng, Syzygium guineense DC. and Zanthoxylum chalybeum Engl.) that are highly demanded for malaria treatment. The study was undertaken between 2006 and 2009 in the Sango Bay Forest Reserve, southern Uganda. The aim was to determine the conservation status of trees targeted for malaria treatment. We assessed the level of damage inflicted on trees during harvesting of medicinal parts and determined the population density of target species in the forest. We used 95 plots established along nineteen transects. Survival of the most preferred species, F. rubrostipulata, is of particular concern as its population suffered from a combination of extensive damage due to poor methods of harvesting and poor regeneration. The density of trees with diameter ≥5 cm differed between species and sites, demonstrating different recruitment and survival strategies. Management of Protected Areas should augment strategies to monitor the legal and illegal harvest of medicinal plants, by adopting low impact harvesting methods, and designating the temporal and spatial patterns of harvesting. This might reduce tree damage and mortality.     

Rainfall pattern and nutrient content influences on African elephants’ debarking behaviour in Samburu and Buffalo Springs National Reserves,Kenya

The magnitude of debarking by elephants was investigated in Samburu and Buffalo Springs National Reserves. About 1617 plants were monitored for debarking intensities for 6 months spanning through dry and wet seasons. Debarking indices ranged from no debarking at all during the wet months to complete stem girding at the height of the dry season. A negative correlation was found between rainfall and debarking indices. It was hypothesized that nutrient content of the bark influenced the magnitude to which trees were debarked. Bark samples were collected from least, moderate and intensely debarked plants throughout the 6 months. These were analysed for calcium (Ca), sodium (Na), phosphorus (P), magnesium (Mg), potassium (K), nitrogen (N), iron (Fe), copper (Cu), manganese (Mn) and zinc (Zn). Significant positive correlations were found between debarking intensity and each of the nutrients N [crude protein (CP)], P, K and Zn. Bark was found to be richest in CP and Calcium. Neutral detergent fibre content was on average 67%. Monthly variations in nutrient composition were minimal. Acacia elatior, the most preferred species had significantly higher quantities of each of the four elements N, P, K and Zn than Acacia tortilis, the second most preferred woody species.     

Radial Gradients in Wood Specific Gravity,Water and Gas Content in Trees of a Mexican Tropical Rain Forest

Cell walls, water, and gas that have mechanical and physiological functions in wood, and wood specific gravity (WSG) is related to demographic traits. To understand variation in wood structure and function, we analyzed radial changes in WSG, in the gas and the water fractions from trees growing in four different habitats in a southern Mexican rain forest. Mean WSG was 0.55 ± 0.16, slightly lower than reported for other tropical forests. In 27 species, WSG decreased and in two species, it increased from pith to bark with a strong (r² = 0.65) negative correlation between WSG in the center of the tree and the radial WSG gradient. Habitat had some effect on mean WSG and trees growing on karst had significantly higher WSG than the same species growing on alluvial soil. The cell wall, water, and gas fractions accounted for 35 percent (range: 16–50), 42 percent (28–65), and 23 percent (2–56), respectively, of wood volume, with a negative correlation between the gas and the cell wall and between the gas and the water fractions, but not between the cell wall and water fractions. Radially increasing WSG is advantageous for pioneer trees with fast initial growth. We found that the water displacement method may result in biased WSG estimates. To increase the accuracy of WSG data, we suggest to measure sample volume geometrically using a constant diameter (that of the borer tip), to include radial variation in WSG, and to consider for possible site effects on species‐specific WSG.     

Distribution and hosts of Callidiellum rufipenne (Coleoptera: Cerambycidae), an asian cedar borer established in the eastern United States

The distribution and hosts of the exotic cedar-boring beetle, Callidiellum rufipenne (Motschulsky) (Coleoptera: Cerambycidae), were determined in five northeastern U.S. states by capturing adults on cedar trap logs and by rearing adults from various conifers. This beetle was detected in the coastal states of Massachusetts, Rhode Island, Connecticut, New York, and New Jersey. In these states, adults emerged from the live or dead wood of four genera and eight species of Cupressaceae; species of Pinaceae were not hosts. Through its entire range, C. rufipenne is reported to infest at least 14 species of Cupressaceae, four species of Pinaceae, and one species of Taxaceae; but, records of Pinaceae and possibly Taxaceae are suspect. Based on the number of adults that emerged from coniferous poles in a five-way choice test in the field, the infestation level was significantly greater in Chamaecyparis thyoides (L.) Britton, Sterns, and Poggenburg and Juniperus virginiana L. than in Pinus rigida Miller, Pinus strobus L., and Tsuga canadensis (L.) Carribre (last three species uninfested). In a second test of host preference in the wild, beetles infested four cupressaceous species, but not Abies balsamea (L.) Miller, Picea rubens Sargent, Pinus rigida, P. strobus, and Ts. canadensis in the Pinaceae. Infestation level was highest in Ch. thyoides, followed in decreasing order by Juniperus communis L., Thuja occidentalis L., and J. virginiana. In a comparison of live and dead J. virginiana, beetles developed to adults only in dead trees (36 beetles per tree). When trunk sections of Th. occidentalis with and without bark were offered to females in cages, beetles of the next generation emerged exclusively from wood with bark. In the Northeast, only species of Cupressaceae apparently are suitable hosts for C. rufipenne. Infestation of these species may be prevented or reduced by proper care of live plants and by debarking trees after harvesting.     

Seasonal dimorphism in wood anatomy of the Mediterranean Cistus incanus L. subsp. incanus

In Mediterranean-type ecosystems, seasonal dimorphism is an adaptive strategy aimed to save water by developing brachyblasts with xeromorphic summer leaves as opposed to dolichoblasts with more mesomorphic winter leaves. The aim of this study was to analyse the anatomical properties of 1-year-old twigs of Cistus incanus subsp. incanus, a seasonally dimorphic shrub, to highlight properties allowing its adaptation to the Mediterranean environment. A more specific purpose was to verify the occurrence of seasonal dimorphism in wood anatomy in order to understand: (a) whether and to what extent the traits of efficiency/safety of water transport are expressed in brachyblasts and dolichoblasts, and (b) the effects on the formation of growth ring boundaries in wood. Our overall analysis showed that anatomical features of branches in C. incanus are designed to: (a) protect from desiccation by developing thick cuticle and suberized epidermal and sub-epidermal layers; (b) defend the plant from predators by accumulating phenolics; and (c) regulate water transport through the development of specific wood anatomy, according to the season, thus optimising properties of efficiency/safety. Regarding the latter point, our results indicated that brachyblast wood is safer than dolichoblast wood insofar as it has narrower and more frequent vessels; measurement of other specific anatomical traits, such as vessel wall thickness, suggested that brachyblast wood has a higher resistance to implosion due to drought-induced embolism. Finally, peculiar anatomy of brachyblast and dolichoblast wood results in the formation of so-called false rings. Hence, wood rings in C. incanus should be considered to be “seasonal” rather than “annual”.     

Wood borer performance and wood characteristics of drought‐stressed Scots pine seedlings

Four‐year‐old Scots pine [Pinus sylvestris L. (Pinaceae)] seedlings were exposed to medium and severe drought stress for two consecutive years. The anatomical properties of drought‐stressed Scots pine wood and their impact on the performance of destructive wood boring early instars of Hylotrupes bajulus L. (Coleoptera: Cerambycidae) were studied. Drought stress significantly decreased diameter of earlywood tracheids in both growing years and diameter of latewood tracheids after the second growing season only. Cell lumen area was significantly decreased by both medium and severe drought stress compared to well‐watered controls. In addition, area of cell lumen was significantly smaller in severe drought than in medium drought treatment. The drought stress marginally increased the number of resin canals in the wood, but did not affect the size of resin canals either in wood or bark. The relative growth rate of xylophagous H. bajulus neonatal larvae was not significantly affected by drought stress during the 106‐day feeding period on Scots pine wood blocks. The results show that although water availability was an important factor affecting the development and anatomy of wood cells, observed changes in wood characteristics did not affect the performance of early instars feeding on wood processed from drought‐stressed young Scots pine seedlings.     

Diversity in specific gravity and water content of wood among Bornean tropical rainforest trees

Wood properties were measured for trees in lowland dipterocarp forests in West Kalimantan. In 1993 and 1994, 353 samples of 286 species were collected from trunk base of trees of approximately 5 cm in diameter, and the specific gravities (SG: oven dry weight/fresh volume) and water contents of wood including bark were measured. The SG of each species ranged from 0.21 to 0.84, and the mean ± SD was 0.53 ± 0.13. The wide range of SG suggests that the forest had a high diversity in wood properties. The most dominant and diversified genus in this area was Shorea, and the SG of 15 species varied from 0.21 to 0.71. The range covered SG of pioneer (six Macaranga, 0.29–0.43) and small trees in primary forests (nine Eugenia and 10 Xanthophyllum, 0.55–0.77). The SG average for tree species of secondary forests of 2–6 years old was 0.31. It was significantly smaller than that of primary forests (0.58). In a primary dipterocarp forest plot, light-wood species grew faster in diameter than heavy-wood species. Water content ranged from 0.26 to 0.76. Heavy wood had low water content. Among light-wood species, some (Shorea, Artocarpus) had low water contents and others (Ficus) had high water contents. Some riverine trees also had high water contents. These wood properties appear strongly related to the life history of trees and successional stage.     

Hydraulic efficiency compromises compression strength perpendicular to the grain in Norway spruce trunkwood

The aim of this study was to investigate bending stiffness and compression strength perpendicular to the grain of Norway spruce (Picea abies (L.) Karst.) trunkwood with different anatomical and hydraulic properties. Hydraulically less safe mature sapwood had bigger hydraulic lumen diameters and higher specific hydraulic conductivities than hydraulically safer juvenile wood. Bending stiffness (MOE) was higher, whereas radial compression strength lower in mature than in juvenile wood. A density-based tradeoff between MOE and hydraulic efficiency was apparent in mature wood only. Across cambial age, bending stiffness did not compromise hydraulic efficiency due to variation in latewood percent and because of the structural demands of the tree top (e.g. high flexibility). Radial compression strength compromised, however, hydraulic efficiency because it was extremely dependent on the characteristics of the “weakest” wood part, the highly conductive earlywood. An increase in conduit wall reinforcement of earlywood tracheids would be too costly for the tree. Increasing radial compression strength by modification of microfibril angles or ray cell number could result in a decrease of MOE, which would negatively affect the trunk’s capability to support the crown. We propose that radial compression strength could be an easily assessable and highly predictive parameter for the resistance against implosion or vulnerability to cavitation across conifer species, which should be topic of further studies.