The abundance,distribution and structural characteristics of tree‐holes in Nothofagus forest,New Zealand

Tree‐holes provide an important microhabitat that is used for feeding, roosting and breeding by numerous species around the world. Yet despite their ecological importance for many of New Zealand's endangered species, few studies have investigated the abundance or distribution of tree‐holes in native forests. We used complementary ground and climbed tree surveys to determine the abundance, distribution and characteristics of tree‐holes in undisturbed Nothofagus forest in the Lewis Pass, New Zealand. We found that hole‐bearing trees were surprisingly abundant compared with many other studies, including Australian Eucalyptus species and American beech. In fact, we estimated as many as 3906 tree‐holes per hectare, of which 963 holes per hectare were potentially large enough to provide roost sites for hole‐nesting bats in New Zealand, while only eight holes per hectare were potentially suitable for specialist hole‐nesting birds. This was of great interest as primary cavity‐excavating animals are absent from New Zealand forests, compared with North America and Australia. Moreover, tree‐hole formation in New Zealand is likely to be dominated by abiotic processes, such as branch breakage from windstorms and snow damage. As has been found in many other studies, tree‐holes were not uniformly distributed throughout the forest. Tree‐holes were significantly more abundant on the least abundant tree species, Nothofagus fusca, than on either N. menziesii or N. solandri. In addition to tree species, tree size was also an important factor influencing the structural characteristics of tree‐holes and their abundance in this forest. Moreover, these trends were not fully evident without climbed tree surveys. Our results revealed that ground‐based surveys consistently underestimated the number of tree‐holes present on Nothofagus trees, and illustrate the importance of using climbed inspections where possible in tree‐hole surveys. We compare our results with other studies overseas and discuss how these are linked to the biotic and abiotic processes involved in tree‐hole formation. We consider the potential implications of our findings for New Zealand's hole‐dwelling fauna and how stand dynamics and past and future forest management practices will influence the structural characteristics of tree‐holes and their abundance in remnant forest throughout New Zealand.     

Nest-site competition between bumblebees (Bombidae), social wasps (Vespidae) and cavity-nesting birds in Britain and the Western Palearctic

Capsule There is no evidence of widespread significant nest-site competition in Britain or the Western Palearctic between cavity-nesting birds and bumblebees or social wasps.

Aims To investigate competition between cavity-nesting birds and bumblebees and wasps, particularly the range-expanding Tree Bumblebee, Saxon Wasp and European Hornet in Britain, and review evidence throughout the Western Palearctic.

Methods We compared field data from English and Polish studies of tits and woodpeckers breeding in nest-boxes and/or tree holes to assess nest-site competition with bumblebees and wasps. We reviewed the literature quantifying nest-site competition between birds and these insects in the Western Palearctic.

Results Bumblebees and wasps are capable of usurping small passerines from nests. In England, these insects commandeered a mean annual 4.1% of tit nests initiated in nest-boxes; occurrence of hornets showed a long-term increase, but not other wasps or bumblebees. Across the Western Palearctic, insect occupation of nest-boxes was generally low, and was lower in England than in Poland. No insects were discovered in tree cavities, including those created by woodpeckers (Picidae).

Conclusion Nest-site competition between cavity-nesting birds and bumblebees and wasps appears to be a ‘nest-box phenomenon’, which may occasionally interfere with nest-box studies, but appears negligible in natural nest-sites.     

Phorophyte preferences of epiphytic bryophytes in a stream valley in the Carpathian Basin

Abstract

Epiphytic bryophytes were studied on two tree species with different bark characteristics (Alnus glutinosa and Carpinus betulus) in two vertical ranges (0–60 and 60–200 cm height above ground on the trunk) in a stream valley in the Carpathian Basin (N.W. Hungary). There is a significant difference in the species composition of the trees. Dicranum montanum and Platygyrium repens occurred significantly more often on Alnus glutinosa, whereas Frullania dilatata and Radula complanata were more often on Carpinus betulus in both vertical ranges. Orthotrichum species were typical only in the vertical range 60–200 cm on Carpinus betulus, whereas Plagiothecium nemorale and Metzgeria furcata were typical of Alnus glutinosa and Carpinus betulus, respectively, in the vertical range 0–60 cm. Although most of the bryophyte species have significant phorophyte preferences, Hypnum cupressiforme (in both vertical ranges) and Isothecium alopecuroides (in vertical range 0–60 cm) are indifferent in this respect. Our findings showed clearly that phorophyte preference and vertical position on the trunk are not independent variables. We investigated the independence of the frequencies and abundances of bryophyte species in the two vertical ranges separately on the two tree species. The species form four different groups: (1) species with greater abundance in the higher vertical range; (2) species with smaller abundance in the higher vertical range; (3) indifferent species with nearly uniform abundances in both vertical ranges; (4) species present only in one vertical range. It was found that even a single bryophyte species can show different vertical preferences depending on tree species. No significant relationships were found between the abundances of bryophytes and distance from the stream, slope of the bark surface and trunk circumference. Species-specific traits appear to explain individual phorophyte preferences; however, in several cases chemically mediated effects of the bark appeared to be important.     

Occurrence and development of Eucryptorrhynchus brandti and E. chinensis (Coleoptera: Curculionidae) on Ailanthus altissima trees subjected to different levels of mechanical damage

Eucryptorrhynchus brandti (Harold) and E. chinensis (Oliver) are herbivores of Ailanthus altissima (Mill.) Swingle (tree of heaven) in China. Eucryptorrhynchus brandti has been recommended as a potential biological control agent of A. altissima in North America. In China, the majority of adults of both species were found on tree trunks 0–5 m above the ground, from May to September. In October and November, most adults were found at the base of A. altissima trees. Trees were subjected to different levels of mechanical injury: very low mechanical injury, one to two 0.015 m² bark sections were removed; low, two to four bark sections were removed; moderate, 8 to 22 bark sections removed; high, tree was girdled; and extreme, tree was felled and the remaining stump was sampled. Very low and low mechanical injury trees had very few adult emergence holes with few larvae developing beyond the first or second instar after 29 months. The health of these trees remained good. An increase in adult emergence holes occurred in moderately injured trees that appeared as healthy as very low to low mechanically injured trees. This may indicate that only a small increase in tree stress can increase the adult emergence rate and thus hasten a decline in tree health. Moderate, high and extreme mechanically injured trees had significantly more emergence holes/m than very low and low injured trees and late larval stages were present. The development of Eucryptorrhynchus species was more successful the greater the degree of mechanical injury. Based on this study both Eucryptorrhynchus species appear to be secondary pests of A. altissima in China.     

Nest survival of Woodpigeons (Columba palumbus) in North African forests

Capsule The nesting success of the Woodpigeon Columba palumbus in oak forests in Morocco is affected by human disturbance and nest-site characteristics.

Aims To determine factors affecting the nesting success of Woodpigeons subject to two levels of disturbance in a holm oak Middle Atlas forest.

Methods Woodpigeon nests were monitored in highly disturbed (n?=?30) and less-disturbed sites (n?=?60) over two years (2010–11). Logistic-exposure models were used to estimate daily nest-survival rate and evaluate mechanisms (altitude, temporal factors, nest location, nest-site habitat and degree of human influence) affecting nest survival.

Results Daily nest-survival rate was higher in less-disturbed sites (0.987; 95% CL: 0.980–0.991) than in high-disturbance sites (0.967; 95% CL: 0.949–0.978). Increasing density of trees surrounding nest sites and distance from the nest tree to the closest track increased daily nest-survival rate.

Conclusions Less-disturbed sites confer better nesting conditions than highly disturbed ones. Management measures should control the access of vehicles, especially trucks, in the forest of the Middle Atlas and introduce a grazing regime that will allow the forest regeneration, which would improve Woodpigeon nesting success by increasing the density of holm oak trees.     

Distribution and survival of overwintering adults of the Dutch elm disease vector, Hylurgopinus rufipes (Coleoptera: Scolytidae), in American elm trees in Manitoba

Abstract 1 The native elm bark beetle, Hylurgopinus rufipes, is the principal vector of Dutch elm disease in Manitoba, Saskatchewan and North Dakota, and disease management measures include applying residual insecticides to the lower part of elm tree trunks where the adult beetles overwinter. 2 In American elm trees in southern Manitoba, we counted entrance holes produced by beetles then felled and dissected trees to determine numbers of tunnels and numbers and survival of overwintering beetles. 3 Densities of entrance holes, tunnels and beetles followed a logistic relationship with tree trunk diameter; densities were near zero at diameters < 10 cm and reached a site‐specific asymptote at diameters > 20 cm. 4 Asymptotic densities of holes, tunnels and beetles in samples from 55 to 190 cm above the ground were, respectively, 22%, 22% and 0.7% of those within 25 cm of the ground. 5 Within the height range 0–190 cm, the proportion of living beetles declined steeply with increasing height. 6 Average density of holes at height 0–25 cm estimated from a sample of several trees of diameter ≥15 cm could be used to predict the asymptotic maximum density of overwintering beetles in the site; predictions of beetle densities for individual trees were not reliable.     

Tree Holes Used for Resting by Gray Mouse Lemurs (Microcebus murinus) in Madagascar: Insulation Capacities and Energetic Consequences

I studied the insulation capacity of tree holes used by gray mouse lemurs (Microcebus murinus) in a primary dry deciduous forest in western Madagascar during the cool dry season. Tree holes had an insulating effect, and fluctuations of air temperatures were less extreme inside the holes than outside them. The insulation capacity of the tree holes peaked between 0800 and 1100 hr, when ambient temperatures ranged between 25 and 30°C. To compare tree holes, I calculated the mean difference between the internal temperature )(T_i ) and the external temperature (T_e ) for each tree hole. Thus large differences indicate good insulation capacities. The mean difference of tree holes in living trees was significantly larger than that of tree holes in dead trees, which shows that insulation in living trees is more effective. During the dry season, the insulation capacity of tree holes in living trees decreased and was lowest in July, whereas the insulation capacity of holes in dead trees remained approximately constant. Physiological studies under natural temperature and light condition in Microcebus murinus reveal that daily torpor saves around 40% of the daily energy expenditure compared to normothermia. However, torpor can be maintained only up to the threshold body and ambient temperature of 28°C, whereat Microcebus murinus have to terminate torpor actively. By occupying insulating tree holes, mouse lemurs may stay longer in torpor, which increases their daily energy savings by an extra 5%.     

Anti-predator adaptations in nesting Marsh Tits Parus palustris: the role of nest-site security

A proposal that nest predation is the most important selective pressure shaping nest-site use of Marsh Tits Parus palustris was checked in a long-term study (almost 500 nests) carried out in the Białowieża National Park (eastern Poland) in primeval conditions, where the birds breed in natural holes and their nests are at risk from a variety of predators. It was predicted that predation rates would depend on hole attributes, so that Marsh Tits should use the most secure holes. Predation was responsible for 70% of total nest losses. Predation risk depended on hole attributes. Nests in dead wood were predated significantly more often than those in live wood. Nests in old woodpecker holes were predated more frequently than nests in holes of other origin, and nests situated closer to the entrance were more at risk than ones further from it. The entrance size did not influence overall predation risk, but small entrance size was important in preventing access by larger predators. These differences can account for the very rare use of holes in dead wood or of woodpecker holes, the fact that they nest in holes with small entrances and relatively far from the entrance. It is concluded that the patterns of nest-site use found in this species are best explained as anti-predator adaptations, which have evolved and are maintained by the pressure of nest predators. This study also indicates the possible limits of, and constraints on, these adaptations.     

Effects of dwarf bamboo, Fargesia nitida (Mitford) Keng f. ex Yi, on bark stripping by ungulates in a subalpine Abies faxoniana Rehder & E. H. Wilson forest, southwest China

Incidence and intensity of bark stripping of trees by ungulates was investigated at no bamboo (Fargesia nitida (Mitford) Keng f. ex Yi) (B-) site and understory bamboo dominant (B+) site of a subalpine Abies faxoniana Rehder & E. H. Wilson forest, southwest China. The percentage of damaged trees in B-site was higher than in B+ site. Bark stripping obviously occurred more frequently on Abies faxoniana compared to other tree species. Appearance of stripped bark and dead stems of the trees in different size-classes of A. faxoniana strongly depended on the density of dwarf bamboo at the site, and also on the size and bark structure of the trees, with highest damage rates occurring on the smaller DBH classes (10–40 cm) in B-site. The bark stripping intensity of A. faxoniana decreased significantly with higher density and coverage of F. nitida around damaged trees. Therefore, there is an indirect negative effect of the distribution of dwarf bamboo, F. nitida, on bark stripping of tree species. We suggest the indirect effects of dwarf bamboo species should be taken into account while considering the succession and regeneration of natural forests.     

Hip holes: kangaroo (Macropus spp.) resting sites modify the physical and chemical environment of woodland soils

Abstract Hip holes are shallow, reniform‐shaped depressions found next to the trunks of many trees and shrubs in arid and semi‐arid Australia. They are constructed by kangaroos (Macropus spp.), who use them as diurnal resting sites, particularly during hot weather. Physical and chemical properties of soils in hip holes were compared with non‐hole microsites adjacent to the trunk (‘trunk’), microsites below the canopy (‘canopy’) and microsites out in the open (‘open’) under two trees (Eucalyptus intertexta, Alectryon oleifolius) and one shrub (Dodonaea viscosa) in a semi‐arid woodland in eastern Australia. Overall, there were few effects under D. viscosa apart from a greater (10‐fold) mass of litter in the hip holes compared with the trunk microsite. Hip holes under E. intertexta and A. oleifolius, however, contained six times more dung compared with the trunk microsite. For the two tree species, soils in the hip holes were significantly more erodible, as measured by aggregation levels, compared with the other microsites, but there were no significant differences in bulk density nor pH. Steady‐state infiltration rates at the hip hole and trunk microsites were significantly greater than those in the open, but there was no significant hip hole effect. Soils in the hip holes contained greater levels of exchangeable calcium and magnesium (E. intertexta) and greater exchangeable sodium (A. oleifolius) compared with trunk microsites. Hip holes under E. intertexta contained approximately 68% more organic carbon, total carbon and nitrogen, and 86% more sulfur compared with trunk microsites. Similarly, hip holes under A. oleifolius contained on average 38% more organic and total carbon, and 47% more nitrogen than trunk microsites. Given the density of hip holes and their impact on soil chemistry, kangaroos are considered to be important elements in the maintenance of heterogeneity in these woodlands.     

The role of body size in nest-site selection by secondary cavity-nesting birds in a subtropical Chaco forest

Most bird species that nest in tree cavities globally occur in diverse assemblages in little-studied tropical and subtropical forests which have high rates of habitat loss. Conservation of these communities will require an understanding of how species traits, such as body size, influence nest-site selection. We examined patterns of nest-site selection of secondary cavity-nesting birds at the nest patch, tree and cavity scale, and investigated how these patterns are influenced by body size. Using conditional logistic regression, we compared characteristics of 155 nest tree cavities paired with 155 unused tree cavities in quebracho Schinopsis balansae forests in Chaco National Park, Argentina (2016–2018). The odds of a cavity being used for nesting increased with its depth and height above ground, decreased with entrance size, and were greater for dead trees than live. Small-bodied (13–90 g) species used floor diameters in proportion to availability, but medium- (150–200 g) and large-bodied (400–700 g) species selected cavities with larger floors. Model selection indicated that characteristics at the nest patch scale (canopy cover, tree density) had little effect on nest-site selection when cavity-scale variables were included. Cavity floor diameter, entrance size, cavity height and tree diameter (but not cavity depth) increased with body mass, and larger bird species more often used live trees. Two tree species proved to be key for the community: large and medium-sized birds used almost exclusively large live Schinopsis balansae, whereas small birds used live and dead Prosopis spp. in a proportion greater than its availability. Small birds could be differentiated according to species-specific cavity characteristics, but medium and large species overlapped considerably with one another. Although body mass explained much of the overall variation in tree and cavity characteristics between small and medium/large species, several small-bodied species consistently used cavities outside of the expected characteristics for their body size, suggesting that other natural history traits may play important roles in nest-site selection by small-bodied birds. To retain the full suite of secondary cavity-nesters in species-rich tropical and subtropical forests, it is necessary to conserve a diversity of trees and cavities that meet the full range of nesting requirements of these trait-diverse communities.     

Heterogeneity of tree diversity and carbon stocks in Amazonian oil palm landscapes

ABSTRACT

Background: Quantitative effects of large-scale oil palm expansion in the Neotropics on biodiversity and carbon stocks are still poorly documented.

Aims: We evaluated differences in tree species composition and richness, and above-ground carbon stocks among dominant land cover types in Pará state, Brazil.

Methods: We quantified tree species composition and richness and above-ground carbon stock in stands in remnant primary rain forest, young secondary forest, oil palm plantation and pastures.

Results: We sampled 5,696 trees with a DBH ≥ 2 cm, of 413 species in 68 families, of which 381 species were recorded in primary forest fragments. We found significant differences in species richness and carbon stock among the four land cover classes. Carbon stocks in remnant primary forest were typically over 190 Mg ha^?1, while those in other land cover types were typically less than 60 Mg ha^?1.

Conclusion: Oil palm plantations have a species-poor tree community given active management; old plantations have a standing carbon stock which is comparable to that of secondary forest and far greater than that of pastures. Private forest reserves within oil palm company holdings play an important role in preserving primary forest tree diversity in human-modified landscapes in Amazonia.     

新疆北部白冠攀雀的巢与巢址选择

2008年4—7月,在新疆北部对白冠攀雀巢址选择进行了研究。白冠攀雀的营巢习性特殊,巢呈囊袋状,结构甚为精致。对于白冠攀雀巢的研究,采用总面积调查法,进行地毯式的搜寻,并结合标图法对其进行标记,绘制分布图。研究结果共发现巢125个,营巢位于于临近湖泊、河流等水域附近的柳树、杨树、桦树等阔叶树上。营巢树种以柳树为主,占68.80%。巢的高度平均为(5.3±2.5)m,营巢于乔木的中下部（约1/3处）,约70%的巢离河边不足30 m。对于巢址选择的研究,将原始记录中与巢址选择有关的特征变量进行主成分分析,分析表明,影响白冠攀雀巢址选择的主要因素有4种,依次为：郁闭度因素（包括营巢树胸径、巢上郁闭度）、营巢树种因素(包括营巢树种、树高、巢位高度和乔木种类)、方位因素（包括距河边距离和巢向）、食物与巢材因素。     

Nest site characteristics of four sympatric species of hornbills in Khao Yai National Park, Thailand

Characteristics of nest sites, nest trees and nest holes were documented for four sympatric species of hornbills in Khao Yai National Park: the Great Buceros bicornis. Wreathed Rhy-ticeros undulatus , Oriental Pied Anthracoceros albirostris and Brown Hornbills Ptilolaemus tickelli. Nearly all hornbills nested in cavities in the trunks of at least 13 different genera of living trees. Sixty percent of the 80 nests found were in two tree genera, Dipterocarpus (34%) and Eugenia (26%), which comprised only 7% and 3%, respectively, of all large trees in 302 sample plots. Hornbills tended to prefer holes high in large, emergent trees for nesting, except for the Brown Hornbills, which preferred nest holes within or below the main forest canopy (15–25 m high). Most nest sites were between 700 and 800 m a.s.l. (79% of the total of 80 nests). Brown Hornbill nests were located in areas with a significantly higher altitude than were those of the Oriental Pied Hornbill. Hornbills tended to select nest entrances according to their body size, and all four hornbill species used oval to elongated nest entrances, with the Great Hornbill preferring the most elongated entrances. Hornbills did not select a specific nest entrance orientation.     

Integrated control of apple pests in New Zealand

In a study at Appleby Research Orchard, Nelson, examination of the fruit from mature ‘Delicious’ apple trees sprayed with ryania over 5 years showed that less than 10% of 5th‐instar larvae of the codling moth (Laspeyresia pomonella) seeking cocooning sites originated from fruit on the ground. In 1972 and 1973 the survival of such larvae was studied by tagging with cobalt‐58 and releasing them beneath mature trees. In both years about 25 % of the tagged larvae returned to the tree to spin cocoons. Larvae released on bare ground 0–1 m from the tree trunks were more successful than those released in the sward 1–2 m away. Once on the trees, most larvae spun cocoons beneath exfoliating bark on the lower parts of the leaders and the trunk. Fifty‐two percent of the cocoons located were formed on the ground, and overwintering mortality of these was estimated to be near 100%. The pre‐cocooning mortality of larvae released on the ground was similar to that of larvae released on the trees in the same year. It was concluded that larvae from windfalls could be ignored in estimating 5th‐instar larval mortality of codling moth on ‘Delicious’ trees. On the cultivars ‘Dunn's Favourite’ and ‘Cox's Orange Pippin’, however, the higher percentage of larvae in windfalls made their inclusion in mortality estimates essential.     

Structure of tree vegetation may reduce costs of territory defence in Eurasian Nuthatch Sitta europaea

Capsule In pastured old oak woodland, breeding pairs of Eurasian Nuthatch selected territories with significantly higher densities of trees and cavities.

Aims To define territorial borders that exist within a nuthatch population and to compare densities of trees and cavities between used and non-used parts of their available habitat in order to determine habitat preferences.

Methods The number and location of territories was estimated by mapping the individual positions of colour-ringed birds. We measured habitat characteristics in regular sampling grid (number of trees and number of cavities per 50?×?50?m) during three successive seasons and modelled probability of occurrence of nuthatch territories in the area.

Results Breeding pairs were observed to defend territories of median size between 1.46 and 2.93?ha. These sizes correspond well to high-quality habitat territories for this species. We found that pairs tended to occupy territories with higher densities of trees and cavities. Based on generalized linear mixed-effects model estimates, we found that in pastured oak woodland habitat with density of 60 trees per ha, the estimated probability of occurrence (with 95% confidence interval) of a nuthatch territory was about 96% (83?99). For cavity density, the probability of territory occurrence was about 74% (52?89) at the level of 60 cavities per ha.

Conclusion We suggest that higher tree and cavity densities reduce territory defence costs in the species because birds may use less energy during foraging, predation avoidance and competition for a nest hole.     

Patterns in the within-tree distribution of the emerald ash borer Agrilus planipennis (Fairmaire) in young, green-ash plantations of south-western Ontario, Canada

1 The emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) is a serious exotic pest of ash trees (Fraxinus spp.) in North America, and is responsible for the deaths of millions of trees in Ontario and Michigan. One of the greatest challenges facing the successful management of the pest is the ability to accurately detect its presence in a tree. 2 Observations were made on A. planipennis larval feeding galleries found within 65 young, green‐ash trees cut from plantations in Essex County, Ontario, Canada. The within‐tree distributions of feeding galleries were described in relation to height‐above‐ground, stem diameter, bark thickness and stem aspect. 3 Galleries were not distributed randomly or evenly; minimum boundaries of stem diameter and bark thickness and a maximum boundary of height‐above‐ground were detected. Indications of maximum boundaries for stem diameter and bark thickness were also observed. Galleries were found most often on the south‐west side of the tree. 4 Using the technique of upper boundary regression, we were able to identify significant quadratic relationships between A. planipennis gallery density and stem diameter and bark thickness, as well as a significant negative linear relationship between gallery density and height‐above‐ground. 5 Agrilus planipennis gallery density in newly‐infested trees was lower than in previously‐infested trees, and was observed to peak at smaller stem diameters and bark thicknesses than in previously‐infested trees. 6 Survey teams would increase their probability of detecting new A. planipennis infestations by initiating searches for exit holes and feeding galleries in trunk sections and branches of approximately 7 cm in diameter.     

Male Blue Tits Cyanistes caeruleus choose early-leafing tree species during spring dawn chorus

Capsule Blue Tits sang their dawn song in trees that provided greater concealment.

Aims To determine if dawn singing Blue Tits select trees that increase their concealment.

Methods We compared the timing of leaf growth initiation in Blue Tit song-post trees to the average timing of leaf growth initiation for other tree species within 25 m of the song-post.

Results Most Blue Tits (96%, n = 23) sang from tree species that begin leaf growth earlier than the average tree available within 25 m. If males singing in Hawthorns Crataegus monogyna were excluded, 92% (n = 13) sang from earlier leafing trees.

Conclusion Dawn singing Blue Tits select perches that offer greater concealment.     

Using wavelet analysis to examine bark microrelief

Key Message

An improved quantification of variations in bark microrelief is presented that uses wavelets on a circular domain from data acquired using the LaserBark? automated tree measurement system.

Abstract

An important metric of canopy structure, bark microrelief affects both the hydrology and biogeochemistry of forests. Increased bark microrelief leads to reduced stemflow volumes and higher concentrations of stemflow leachates and nutrient-ions. Consequently, an improved representation of bark microrelief would be useful to describe the influence of various tree species on water and solute contributions to the forest floor. Most existing methods to quantify bark microrelief are ‘global’ measures; that is, they provide a single number that represents the overall bark microrelief of the entire perimeter of the tree. To remedy this, wavelet analysis of LaserBark? automated tree measurement system data is proposed and described to quantify variations in bark microrelief around the perimeter of the tree. This measure describes the spatial differences in bark microrelief and allows representation of trees that exhibit directional variability in bark microrelief due to natural or anthropogenic effects. The results show that wavelet analysis is effective in quantifying both bark microrelief and large-scale tree asymmetry. The radial component highlights changes in the depth of bark microrelief while the tangential component relates to the distance between bark furrows in the bark cross section. Thus, wavelet analysis may be a useful tool for comparing bark structure that varies, for example, within- and between-tree species, at different stages of tree growth, and among trees grown under different environmental conditions.     

A study of a population of birches in Glen Gairn

Summary

A small population of birches was studied with a view to measuring the rangeof morphological variation in Betula pendula Roth, and B. pubescens Ehrh. The general morphological features of crown and bark of trees in the area indicated that both species were present. A more detailed study was made of leaf and fruit characters, accepted by other investigators as being useful in discriminating between the species. It was shown that such characters varied continuously throughout the population and no tree was wholly pubescens- like or pendula-like in all characters.

The implications of these results are discussed in relation to the situation in Glen Gairn and to the general taxonomic situation of the British birches.