Allometry of axis length, diameter, and taper in the devil's walking stick (Aralia spinosa; Araliaceae)

The allometry of axis length, diameter, and taper is described for the trunk, rachis, and rachilla of nonbranching ramets of Aralia spinosa. Significant log-linear relationships were found between length and diameter for all axis categories, and in all cases, scaling was negatively allometric. Linear models best described the relationship between length and diameter for the rachis and rachilla, while a quadratic model best described this relationship for the trunk. During the trunk-building stage, the safety factors for trunk height were size dependent, with larger trunks exceeding their predicted critical buckling height. Taper was described by a linear relationship between diameter and position along the axis for all axis categories. All rachises and rachillas sampled exhibited taper along the length of the axis, however, only 51% of the trunks showed continuous taper. The trunk was less tapered than the rachis, but no differences in taper were found between the trunk and the rachilla, or the rachis and the rachilla. In unbranched ramets the large bipinnately compound leaves occupy the space normally occupied by lateral branches. We suggest that the rachis and rachilla are functionally equivalent to branches, that is, acting as axes of exploration and exploitation of the environment.     

Mechanical Properties of Black Locust (Robinia pseudoacacia L.) Wood. Size- and Age-dependent Variations in Sap- and Heartwood

Variations in the density and stiffness (Young's elastic modulus)of fresh wood samples drawn from different parts of the threemain trunks of a 32-year-old black locust tree,Robinia pseudoacacia(measuring 19.8 m at its highest point), were studied to determinewhether tree ontogeny can achieve a constant safety factor againstmechanical failure. Based on the properties of isolated woodsamples, the fresh density of sapwood decreased along radialtransects from bark to pith, while that of progressively olderheartwood samples increased, on average, towards the centreof each of the three trunks. Along the same radial transects,the Young's elastic modulus of sap- and heartwood increased.In terms of longitudinal changes in wood properties, mean woodmoduli (averages of sap- and heartwood samples) increased, onaverage, towards the base of each of the three trunks of thetree. However, the mean fresh densities of wood samples increasedtowards the top and the bottom of each trunk and were lowestroughly near trunk mid-length. The mean density-specific stiffness(the quotient of Young's modulus and fresh density) of woodwas thus lower toward the top and the bottom of the trunks andhighest near trunk mid-length. Mean values of fresh wood density-specificstiffness were used to estimate the critical buckling heightsfor sections of the trunks differing in diameter and age. Theseestimates indicated that ontogenetic variation in the physicalproperties and relative amounts of sap- and heartwood in trunkscould maintain a constant factor of safety (approximately equalto 2) as a sapling grows in height and girth into a mature tree.This expectation was supported by data from 16 black locusttrees differing in height and diameter at breast height (DBH). Wood; elastic properties; tree height; biomechanics     

Age versus size determination of radial variation in wood specific gravity: lessons from eccentrics

Radial increases in wood specific gravity have been shown to characterize early successional trees from tropical forests. Here, we develop and apply a novel method to test whether radial increases are determined by tree age or tree size. The method compares the slopes of specific gravity changes across a short radius and a long radius of trees with eccentric trunks. If radial changes are determined by size, then the slope of the change should be the same on both radii. If radial changes are determined by age, then the slope should be greater on the short radius. For 30 trees from 12 species with eccentricity of at least 4%, the ratio of the slopes of the linear regressions of specific gravity on radial distance (short radius slope/long radius slope) was regressed on the ratio of radii lengths (long radius/short radius). The regression was highly significant, and the faster increase in specific gravity on the short radius was sufficient to compensate for the difference in radius lengths, so the specific gravity of wood along the short radius was equal to the specific gravity on the long radius at any given proportional distance on the radius. Therefore, trees that are producing xylem faster on one radius than another produce wood of comparable specific gravity on both radii at the same time, so radial increases in specific gravity are dependent on tree age, not tree size.     

Chlorophyll distribution in the stems and trunk of beech trees

The distribution of chlorophyll was examined in cross-sections of 2- and 6-year-old stems as well as in the bark of the stump trunk of beech trees, utilising chlorophyll autofluorescence. The investigations were conducted using a confocal microscope. The tests carried out on 2 – 6-year old stems showed a large presence of chlorophyll in the bark, in primary and secondary rays as well as in the pith, but smaller amounts in wood parenchyma cells. There was no chlorophyll in the cork, sclerenchyma: in wood in vessels, tracheids and fibers. A reduction in the chlorophyll content in 6-year-old stems was not observed. In the bark of the trunk, chlorophyll was found in large amounts directly under the cork and in vestigial amounts in the primary phloem.     

Are radial changes in vascular anatomy mechanically induced or an ageing process? Evidence from observations on buttressed tree root systems

To investigate the effect of changes in mechanical loading conditions on radial anatomical patterns, we here compare the trunk with the roots in two locations of three species of buttressed trees. The proximal part of the buttress roots is highly mechanically loaded throughout juvenile growth whereas the distal part of the buttresses is though to be mechanically unimportant at formation but become progressively more mechanically loaded during growth. We measured the frequency and diameter of the vessels and the vessel area fraction, and from this calculated the specific conductivity of tissue samples of the core-, intermediate- and outer wood. As in previous studies there was an increase in vessel size, vessel area fraction and specific conductivity from the pith to the bark in the trunk. In the proximal part of the buttress roots, however, there was no increase in vessel size and conductivity from core wood and out in agreement with the high mechanical loading found here throughout growth. There was instead a decrease in vessel size, vessel area fraction and specific conductivity from core- to outer wood in the distal part of the buttress roots in accordance with the increase in mechanical loading. Hence, it appears that the radial anatomical patterns are not a passive function of cambial ageing but may be modified in response to local mechanical loading.     

福建龙岩城区园林树木木材密度和生材含水率研究

对福建龙岩城区栽植的30种园林树木测定木材基本密度、生材密度和生材含水率。结果表明,针叶树木材基本密度以柏木Cupressus funebris最高(0.636 g·cm-3),南洋杉Araucaria cunninghamii最低(0.462 g·cm-3);阔叶树以相思树Acacia confusa最高(0.757 g·cm-3),美丽异木棉Ceiba speciosa最低(0.228 g·cm-3)。生材密度针叶树竹柏Podocarpus nagi最高(0.975 g·cm-3),南洋杉最低(0.838 g·cm-3);阔叶树相思树最高(1.204 g·cm-3),石栗Aleurites moluccana最低(0.799 g·cm-3)。生材含水率针叶树竹柏最高(105%),柏木最低(30%);阔叶树以美丽异木棉最高(319%),光皮梾木Swida wilsoniana和木麻黄Casuarina equisetifolia最低,均为56%。南北两向的基本密度、生材密度和生材含水率差异不大。在距树皮8 cm范围内,基本密度和生材密度的径向变化模式可归纳为五种类型：(1)密度从髓心向树皮方向递增;(2)密度从髓心向树皮方向递减;(3)距树皮8 cm范围内密度变化不明显;(4)距树皮3～5 cm范围内密度较低;(5)距树皮3～5 cm范围内密度较高。生材含水率径向变化趋势仅限于上述前四种类型。     

Wood specific gravity and anatomy in Heliocarpus appendiculatus (Tiliaceae)

Specific gravity exhibits extremely large radial increases with distance from the pith in Heliocarpus appendiculatus Turcz. (Tiliaceae), a pioneer of neotropical wet forests. To determine some of the wood anatomical changes associated with this increase, wood samples taken at breast height from three trees were divided into 1.0-cm-long segments from pith to bark. Measurements were made of fiber wall thickness, fiber lumen diameter, and percentages of fibers, axial parenchyma, ray parenchyma, and vessels on sections prepared from each segment. The extreme radial increases in specific gravity were associated with increases in fiber wall thickness, decreases in fiber diameter, decreases in fiber lumen diameter, and changes in the relative proportions of fibers and parenchyma. The increase in percent fiber concomitant with a decrease in axial parenchyma was the most important contributor to the increase in specific gravity in this species. The best predictor of specific gravity was percent fibers (r = 0.91, 0.92, 0.94) or percent axial parenchyma (r = -0.92, -0.91, -0.95), two variables that were highly intercorrelated (r = -0.95, -0.98, -0.99).     

The lichen flora on Picea abies in a suboceanic spruce forest area in Central Norway with emphasis on the relationship to site and stand parameters

The lichen flora on 400 Picea abies trees (branches, trunks and trunk bases) in 100 patches of suboceanic spruce forest in Central Norway has been investigated. Relationships between occurrence of the species and a number of habitat and tree variables were analysed by detrended correspondence analysis (DCA). A total of 122 lichen species were recorded. Total species number was found to be about the same on branches and trunk bases (considerably lower on trunks), but with higher β-diversity on trunk bases. Most species could be classified as branch specialists, generalists, trunk or trunk base specialists. Among the measured habitat variables, stand age, altitude and vegetation type were found to be the most important for explaining the patterns of species distributions. Alectoria sarmentosa, Mycoblastus sanguinarius and several dry bark species on trunks, including Caliciales species, were more or less confined to old forests, while Usnea spp. were more abundant in young form. Trentepohlia-containing trunk base species like Arthonia vinosa, Dimerella pineti, Lecanactis abietina and Sclerophora coniophaea showed preference for vegetation types indicating nutrient-rich substrates. The number of branch species was highest on lower altitudes while the opposite was true for trunk species. Larger trees with rough bark in older stands had a more species-rich lichen flora, probably because of higher substratum area and availability of more diverse microsites.     

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.     

温带不同材性树种树干非结构性碳水化合物的径向分配差异

温带森林不同树种具有不同的非结构性碳水化合物(NSC)存储和利用策略, 树干是成年树木NSC主体储存库。但树干NSC径向变异和种间差异仍不清楚, 无孔材(裸子植物)、散孔材和环孔材(被子植物)所代表的木材孔性功能群对树干NSC浓度的影响尚缺乏定论。为探索温带森林主要树种树干NSC浓度随树木木材孔性和组织的变化特征, 该研究在黑龙江省穆棱市的东北典型阔叶红松(Pinus koraiensis)林中选择32个树种, 采集胸高位置树皮、边材和心材3种组织, 分析NSC浓度随木材孔性和组织的变化特征。结果表明: (1)树种、组织和木材孔性均显著影响树干的NSC浓度。3种组织可溶性糖、淀粉、总NSC浓度和糖/淀粉的种间变异较大, 变异系数最低为37% (树皮总NSC浓度), 最高达到101% (心材淀粉浓度), 树干组织、树种及其交互作用均显著影响NSC浓度。(2)总体上可溶性糖、淀粉和总NSC浓度均随径向深度增加而降低。无孔材树皮的可溶性糖浓度和糖/淀粉显著高于散孔材和环孔材, 而边材中的淀粉和总NSC浓度为环孔材>散孔材>无孔材。(3)无孔材可溶性糖、淀粉和总NSC浓度边材和心材比均在1左右, 显著低于散孔材和环孔材, 而且无孔材边材和心材之间淀粉浓度相关较紧密, 表明被子植物的边材、心材功能分化较裸子植物更为明显。研究结果表明木材孔性影响了温带树种树干NSC存储策略, 研究整树NSC以及树木生理生态学功能需要区分树干组织。     

Ontogeny of the proventitious epicormic buds in Quercus petraea.

In the present work, we described the fate of proventitious epicormic buds on the trunks of 40-year-old Quercus petraea trees and in parallel the vascular trace they produced in the wood. Our results show that small and large individual epicormic buds can survive as buds for 40 years and that both are composed of a terminal meristem and scales. Meristematic areas are detected in the scale axils of small buds; in addition to these meristems the large buds also have secondary bud primordia. The small buds are connected to the pith of the main stem by a unique trace, whereas the large buds are connected by one or multiple traces. A single trace might imply that the whole bud is still alive and multiple traces might indicate that the terminal meristem has died. In the latter case, each trace is connected to a secondary bud of the large bud. The buds found in a cluster are composed of a terminal meristem and scales with axillary meristems in the scale axils. A cluster is connected to the pith of a stem either by a unique trace when it seems to be the result of partial abscission of an epicormic shoot or multiple traces when it might have originated from an epicormic bud in which the terminal meristem has died. Whatever the type of the bud, the vascular trace in the bark is composed of a cambium, secondary xylem and parenchyma cells and the trace present in the wood had parenchyma cells with vestiges of secondary xylem. Each year, the vascular trace should be produced in the bark by the cambium of the tree but not by the bud itself. On 40-year-old Q. petraea, we observed a proliferation of epicormic buds and in parallel a multiplication of the number of vascular traces in the trunk, but the knots caused by the traces of epicormic buds in the wood, either as individuals or in clusters, are minor since their colours are only slightly darker than those of woody rays and they are less than 2 mm in diameter. The knots will appear when epicormic buds develop into shoots. Received: 30 March 1999 / Accepted: 09 June 1999     

Long-distance transport of 35S-sulphur in 3-year-old beech trees (Fagus sylvatica)

³⁵S-L-cysteine was fed to a mature leaf of 3-year-old beech trees via a flap. After 1 to 4 h the distribution of ³⁵S-radioactivity was analysed in the leaves as well as the bark and wood of the trunk and the main root. Transport of ³⁵S out of the fed leaf amounted to 0.3–1.2% of the total ³⁵S taken up. The branches of the trees did not act as sink organs for the exported radioactivity. The main portion of the ³⁵S-radioactivity transported out of the fed leaf was found in basipetal parts of the trunk. Only a small portion of ³⁵S-radioactivity was transported in acropetal direction. The distribution of the ³⁵S-radioactivity within the trunk showed a higher portion of ³⁵S in the bark than in the wood. In both tissues, bark (70 to 80%) and wood (60 to 70%), the ³⁵S was predominantly found in the HCl soluble fraction. However, ³⁵S-cysteine, the compound fed to the leaves was not exported out of the fed leaf. Along the trunk ³⁵S-cysteine was neither determined in bark nor in wood sections. The only low molecular mass S-compounds found was ³⁵S-glutathione (GSH). The ³⁵S-sulphate detected in bark and wood origined from cysteine oxidation in the leaf tissue and from contamination of the ³⁵S-cysteine feeding solution. The ratio of GSH to sulphate decreased with increasing distance from the fed leaf. Apparently, ³⁵S-radioactivity was transported as sulphate and GSH in the phloem in basipetal direction, but GSH was removed preferentially out of the phloem along the transport path. ³⁵S-radioactivity exported out of the phloem and transported into the wood of the trunk was not retranslocated in the xylem. It may therefore be assumed that part of the ³⁵S translocated was stored in ray cells, medullary sheath cells and/or pith parenchyma cells. Girdling experiments in which the bark of the trunk was peeled off basipetal to the branch containing the fed leaf support these assumptions.     

Pattern of Substrate Preferences of Free Living Protists (Myxomycetes) on Decaying Wood

We have studied the influence of the stage of decomposition and acidity of wood, as well as the illumination of the microhabitat on the species composition, abundance, and occurrence of slime molds (Myxomycetes) of the xylobiontic (inhabitants of the wood) substrate complex of forest communities in Siberia (Altai krai, Altai Republic, and Novosibirsk oblast). This work is based on a study of 1777 samples of fruit bodies (sporophores) of myxomycetes. In the analysis of data for communities of Myxomycetes of the xylobiontic substrate complex, we recognize a successional series which clearly correlates with the stage of wood decomposition. The study of the distribution of the species composition of the slime mold on wood of various stages of decomposition shows that the maximum number of species is observed on dead trunks where the wood is of medium density and the bark can easily be separated (W3). The lowest specificity and diversity of species composition is observed on the fallen trunks of trees with very dense wood and dense bark (W1). These dead trees have low water-retaining capacity, tight bark, and almost intact wood containing large amounts of lignin, preventing the invasion of plasmodia and myxamoebae of Myxomycetes into the trunk. A study of the location of slime-mold colonies in relation to the illumination level shows that the greatest number of species is found on the front, side, and bottom parts of dead trunks of woody plants. The least specificity and the least variety of Myxomycetes species are found on apical parts of dead tree trunks facing the sun. The exception are species with large fruit bodies such as Fuligo septica and Reticularia splendens, which are most often observed on the upper parts of the sun facing trunks of woody plants. In the research area, the complex of species typical for wood of coniferous trees is described. It is noted that acidophilic slime molds of the genera Comatricha and Cribraria can be traced in xylobiontic and epiphytic–corticuloid substrate complexes.     

The Late Triassic Araucarioxylon Arizonicum trees of the Petrified Forest National Park, Arizona, USA

Examination and measurement of many of the trunks attributed to Araucarioxylon arizonicum Knowlton eroded from the Late Triassic Chinle Formation in the Petrified Forest National Park, Arizona demonstrate that the living tree did not closely resemble any of the present-day Araucaria trees of the southern hemisphere as postulated in past reconstructions. The research indicates that it was a tall monopodial tree with branches occurring in a disordered manner on the trunk from the base to the crown. Calculations using the allometric method of Niklas indicate that the trees were of considerable size. The largest recorded trunk has a basal diameter of nearly 3 m and may represent a tree 59 m high, when living. The root system of the A. arizonicum tree consisted of a ring of four to six steeply inclined lateral roots and a massive, vertically directed tap root. Many of the trunks still have their root systems attached, a circumstance that indicates their felling by the cut-bank operations of the local river system. The massive roots of these trunks, particularly the large tap root, are consistent with growth in soft, deep, alluvial soil, and the thin scale bark is to be expected in a tropical climate free from frost.     

WOOD SPECIFIC GRAVITY GRADIENTS IN TROPICAL DRY AND MONTANE RAIN FOREST TREES

Pith to bark specific gravity (SG) trends were investigated in 18 tropical dry forest and six montane rain forest tree species of Costa Rica. Eleven dry forest species showed statistically significant increases in SG with distance from pith. The increases ranged from 20–80%; the greatest changes were exhibited by species which are known to occur in tropical wet as well as tropical dry forests. The other seven species showed no change in SG with distance from pith. Of the montane forest species, one showed a significant decrease of 20%, and three showed significant increases ranging from 20–40%. Two species exhibited no change in SG. Comparison of these changes with trends found in tropical wet forest and temperate forest suggests that the increase in SG with size is most common in tropical wet forest, least common in temperate forest, and intermediate in tropical dry and montane forests.     

Are tree trunks habitats or highways? A comparison of oribatid mite assemblages from hoop-pine bark and litter

Abstract Oribatid mites (Acari: Oribatida) are among the most diverse and abundant inhabitants of forest soil and litter, but also have species-rich assemblages on bark and in the canopies of trees. It is unclear whether the trunk of a tree acts simply as a 'highway' for movement of mites into and out of the canopy, or whether the trunk has a distinctive acarofauna. We compare oribatid assemblages from the trunk bark of hoop pine ( Araucaria cunninghamii ) with those from litter collected beneath the same trees. A 1.0 by 0.5 m area of bark was sampled from three trees at each of five sites using a knockdown insecticide. A 1-L sample of leaf litter was collected as close as possible to the base of each sampled tree. Mites were extracted using Tullgren funnels, identified to genus and morphospecies, and counted. Assemblages were almost 100% distinct, with only one oribatid morphospecies ( Pseudotocepheus sp.) collected from both litter and bark. Litter had a higher taxon richness than bark in total and per sample, but oribatids made up a greater percentage of the acarofauna in the bark samples. We had expected that the more consistent physical substrate of bark would be reflected in greater similarity of oribatid faunas on trunks than in litter; however, the opposite proved to be the case. We conclude that hoop-pine trunks are habitats rather than highways for oribatid mites. Based on the observed higher turnover among bark faunas, tree trunks may represent habitat islands whose colonisation by particular oribatid species is more stochastic than that of the more continuous 'sea' of litter.     

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.     

Vertical and radial profiles in tracheid characteristics along the trunk of Douglas-fir trees with implications for water transport

The main stems of three young Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirbel) Franco) trees were dissected to obtain samples of secondary xylem from internodes axially along the trunk and radially within each internode. From these samples, measurements were obtained of tracheid diameter, length, the number of inter-tracheid pits per tracheid, and the diameter of the pit membranes. In addition, samples were obtained along the trunks of three old growth trees and also a small sample of roots for measurement of tracheid diameter. A gradient was apparent in all measured anatomical characters vertically along a sequence among the outer growth rings. These gradients arose not because of a gradient vertically along the internodes, but because of the strong gradients present at each internode among growth rings out from the pith. Tracheid characteristics were correlated: wider and longer tracheids had more numerous pits and wider pits, such that total pit area was about 6% of tracheid wall area independent of tracheid size. A stem model combining growth rings in parallel and internodes in series allowed for estimates of whole trunk conductance as a function of tree age. Conductance of the stem (xylem area specific conductivity) declined during the early growth of the trees, but appeared to approach a stable value as the trees aged.     

Mesostigmatid Mites (Acari: Mesostigmata) on Rainforest Tree Trunks: Arboreal Specialists, but Substrate Generalists?

Predatory mites (Acari: Mesostigmata) on tree trunks without significant epiphytic growth in a subtropical rainforest in Eastern Australia were assessed for habitat specificity (i.e. whether they are tree trunk specialists or occupying other habitats) and the influence of host tree and bark structure on their abundance, species richness and species composition. The trunks of nine tree species from eight plant families representing smooth, intermediate and rough bark textures were sampled using a knockdown insecticide spray. In total, 12 species or morphospecies of Mesostigmata (excluding Uropodina sensu stricto) were collected, most of which are undescribed. Comparison with collections from other habitats indicates that epicorticolous Mesostigmata are mainly represented by suspended soil dwellers (six species), secondarily by generalists (four species) and a bark specialist (one species). A typical ground-dwelling species was also found but was represented only by a single individual. In terms of abundance, 50.5% of individuals were suspended soil dwellers, 40.7% bark specialists, and 8.3% generalists. Host species and bark roughness had no significant effect on abundance or species richness. Furthermore, there was no clear effect on species composition. The distribution of the most frequently encountered species suggests that most mesostigmatid mites living on bark use many or most rainforest tree species, independent of bark roughness. These findings support the hypothesis that some epicorticolous Mesostigmata use tree trunks as ‘highways’ for dispersing between habitat patches, while others use it as a permanent habitat.