Smooth Bark Research Articles

Phenomorphology and ecomorphological characters of Maytenus senegalensis L. Shrublands in the Iberian Peninsula: A comparison with other Mediterranean plant communities

This work sets out to establish ecomorphological and phenomorphological patterns in the constituent flora of an Iberian Maytenus senegalensis plant community in order to relate it with or separate it from other types of Mediterranean vegetation. This plant community contains tall shrubs, scrubs, palms and vines of a variety of families. Typical ecomorphological adaptations to the Mediterranean climate were observed in the community studied: an abundance of thorny species or species with tomentose leaves and photosynthetic stems, small leaves and a high presence of species with organs capable of post-fire regeneration. However, the community also showed hybrid characteristics between scrubland (predominantly malacophyllous leaves lasting 9 months on average and low biomass) and tall shrubland communities (predominance of phanerophytes up to 3 m in height, predominantly smooth bark, periodical reposition of leaves, mean lifespan of plants 25 years and mainly fleshy fruit). The community also presents an outstanding quantity of amphiphytes (29%). From a phenological point of view, the formation of buds in winter, flowering in spring, summer–autumn seed dispersal and leaf shedding in summer are typical of other Mediterranean communities, while fructification and growth lasting three seasons, as in the case of Maytenus shrubland, is not. The RVA phenophasic index (balance between reproductive and vegetative phenophases) with values of 0.4–2 shows an intermediate value between typical shrubland (0.3–1) and forest community (1–2) values. The APC index (period of phenophasic activity of the community) differentiates it from others, since it remains at 100% for seven months, three of which are winter months. Phenophasic patterns (overlapping, or not, of flower bud formation, flowering and growth) show how similar M. senegalensis shrubland is to forests because of the absence of phenophase pattern type A (characteristic in open-scrublands); in addition, we have detected a new pattern (type G), still regarded as exclusive to M. senegalensis. As regards the existence of coenomorphs (group of species with similar morpho-functional strategies), the studied community showed much greater diversity than other communities studied to date, with an Strategies Richness index (SRi) of 0.79 (11 groups covering the 14 species existing), pointing to the co-existence of a great variety of eco-phenomorphological strategies, each with a successful response to the same ecological conditions. Finally, some of the species in the community, e.g. Asparagus horridus, Chamaerops humilis and M. senegalensis, stand out because of their unique ecomorphological and phenological characteristics.

Interacting effects of tree characteristics on the occurrence of rare epiphytes in a Swedish beech forest area

Many epiphytes in Swedish beech forests are associated with old and damaged trees. In this study we examined the impact of bark, soil and stemflow pH, water-holding capacity and bark structures on this association. We also analyzed whether the influence of these factors differed between species of conservation concern (red-listed and indicator species of woodland key habitats) and species not of conservation concern. One hundred and one age-determined living beech trees (range 58-277 yrs) in 13 beech-dominated stands were surveyed in a forest landscape in southern Sweden. We recorded 119 species in total (76 lichens, 43 bryophytes) of which 21 were red-listed and 17 indicator species (26 lichens, 12 bryophytes). NMS ordination showed that the species composition of lichens changed primarily with tree age and along the gradient of smooth bark versus moss cover. Bark pH and tree vitality were the most important gradients for bryophyte composition. The combination of old damaged beech trees and high bark pH resulted in the highest mean number of species of conservation concern for both lichens and bryophytes. The link between these factors is partly explained by a positive effect of tree age on the stemflow pH. Species number of bryophytes not of conservation concern increased with bark pH, whereas the corresponding group of lichens was favored primarily by increased light availability. Neither the water-holding capacity of bark nor soil pH affected patterns of species number. The results from this study show that old beech trees infected by fungi, with a higher bark pH, are the most valuable trees for epiphytes of conservation concern.

Ecology and web allometry of Clitaetra irenae, an arboricolous African orb-weaving spider (Araneae, Araneoidea, Nephilidae)

Abstract Analysis of ecological data of the arboricolous nephilid spider Clitaetra irenae Kuntner 2006, endemic to Maputaland forests, South Africa, indicates the species' dependence on this highly threatened habitat. We tested C. irenae habitat dependence via GIS analysis by plotting the known distribution against southern African ecoregions. In the southern part of its range, C. irenae inhabits almost exclusively one ecoregion, the Maputaland coastal plain forests; but further north, in tropical southern Africa, it continues inland into Malawi's woodlands. We test and refute the hypotheses that C. irenae inhabits exclusively mature trees, trees of a particular species, trees with a smooth bark, tree habitats at certain height above ground, and only closed canopy forest stands. The ecological niche of C. irenae is flexible as long as suitable trees under at least partially closed canopy are available. We quantify the C. irenae ontogenetic web changes from orb to ladder and the simultaneous hub displaceme...

Commiphora otjihipana (Burseraceae), a new species from the Kaokoveld, Namibia

Commiphora otjihipana Swanepoel, here described as a new species, is only known from the Otjihipa Mountains, Kaokoveld Centre of Endemism, northwestern Namibia. It appears to be most closely related to C. africana (A. Rich.) Engl . Diagnostic morphological characters of C. otjihipana include the often spineless branches, smooth, non-peeling, pale grey, reddish brown or reddish grey bark, usually glabrous leaves and branches, and unisexual or bisexual flowers. Illustrations of the plant and a distribution map are provided.

MIDDLE MIOCENE GLOBAL CHANGE AND PALEOGEOGRAPHY OF PANAMA

Fossil leaves in the middle Miocene Cucaracha Formation along the Panama Canal are 10–15 cm long, thick, and entire-margined; fossil pollen is also dicot dominated, as expected for wet tropical forests. Fossil woods include palms and ring-porous dicots, with smooth bark as is found in weakly seasonal tropical climates. In contrast, late Hemingfordian to early Barstovian mammals of the Cucaracha Formation are the same as those found in Nebraska, Kansas, and Florida, where climate was drier and cooler and vegetation more open. Cucaracha paleosols reconcile these differences as evidence of a mosaic of swamps to mangal (mangrove forests) preserving plants and dry uplands preserving mammals. A dozen pedotypes represent as many vegetation types, including mangrove, fresh-water and marine-influenced swamp, early successional riparian woodland, colonizing forest, dry tropical forest, and woodland. Many paleosols have calcareous nodules, and some have pedogenic barite nodules. Depth to carbonate and paleosol thickness with carbonate indicate mean annual precipitation of 573–916 ± 147 mm and mean annual range of precipitation of 27–65 ± 22 mm. Chemical analyses of paleosol Bt horizons confirm mean annual precipitation of 296–1142 mm and mean annual temperature of 15–16 ± 4.4°C. Low precipitation and temperature estimates imply a rain shadow from a high (1400–4000 m) volcanic mountain range to the west, with continuous land connection to allow immigration of mammals from North America. Partial enclosure of the Caribbean Sea by a mountainous Panama peninsula, as well as by Antillean arcs, initiated high Caribbean marine temperature and salinity well before Pliocene isthmian closure.

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.

Selective bark-stripping of beech, Fagus sylvatica, by free-ranging horses

Incidence and intensity of bark-stripping by horses was surveyed in stands and tree lanes of European beech ( Fagus sylvatica L.) in Veluwezoom National Park, by using transects. Damage was apparent on 38% of beech trees, and 11% were seriously damaged (score 3 or more). Susceptibility to bark-stripping was found to be strongly size dependent, with highest damage rates occurring at the smaller DBH classes (≤40 cm). Another significant factor affecting damage rate was bark structure, albeit this factor was confounded with tree size. Beech trees with a smooth bark were significantly more damaged compared to individuals with a rough bark structure. Occurrence pattern was another significant factor. Stand trees had higher damage rates compared to trees occurring in lanes along roads and paths. Mean rate of fungal infection of bark-stripped beeches was much higher in stands (46%) than in tree lanes (11%), and strongly increased with increasing damage class. We also analysed beech bark for several macronutrients and compared these with those of several other commonly occurring tree species. Macronutrients in bark tissue could not explain horses’ preference for beech.

Stem and leaf gas exchange and their responses to fire in a north Australian tropical savanna

We measured stem CO2 efflux and leaf gas exchange in a tropical savanna ecosystem in northern Australia, and assessed the impact of fire on these processes. Gas exchange of mature leaves that flushed after a fire showed only slight differences from that of mature leaves on unburned trees. Expanding leaves typically showed net losses of CO2 to the atmosphere in both burned and unburned trees, even under saturating irradiance. Fire caused stem CO2 efflux to decline in overstory trees, when measured 8 weeks post-fire. This decline was thought to have resulted from reduced availability of C substrate for respiration, due to reduced canopy photosynthesis caused by leaf scorching, and to priority allocation of fixed C towards reconstruction of a new canopy. At the ecosystem scale, we estimated the annual above-ground woody-tissue CO2 efflux to be 275 g C m(-2) ground area year(-1) in a non-fire year, or approximately 13% of the annual gross primary production. We contrasted the canopy physiology of two co-dominant overstory tree species, one of which has a smooth bark on its branches capable of photosynthetic re-fixation (Eucalyptus miniata), and the other of which has a thick, rough bark incapable of re-fixation (Eucalyptus tetrodonta). Eucalyptus miniata supported a larger branch sapwood cross-sectional area in the crown per unit subtending leaf area, and had higher leaf stomatal conductance and photosynthesis than E. tetrodonta. Re-fixation by photosynthetic bark reduces the C cost of delivering water to evaporative sites in leaves, because it reduces the net C cost of constructing and maintaining sapwood. We suggest that re-fixation allowed leaves of E. miniata to photosynthesize at higher rates than those of E. tetrodonta, while the two invested similar amounts of C in the maintenance of branch sapwood.

Change of interception process due to the succession from Japanese red pine to evergreen oak

Extensive measurements of rainfall, throughfall and stemflow in a forest during succession from Japanese red pine ( Pinus densiflora Sieb. et Zucc.) to a combination of red pine and lower canopy trees—evergreen oak ( Quercus myrsinaefolia Blume) and evergreen theaceous tree ( Eurya japonica Thunb.) allowed the effect of this succession on the interception of rainfall to be evaluated. The measurements were conducted on two occasions: 1984/1985, and 2001/2002 when the lower canopy trees had become dominant. During this period, 75% of the red pines had been removed, and there was a substantial increase in stemflow ( p<0.01), essentially no change in throughfall ( p<0.01), and a substantial decrease in interception ( p<0.01). The increase in stemflow was attributed to the increase in lower canopy trees; trees that have steeply angled branches, smooth bark surfaces and water repellent leaves; all of which enhance stemflow. The decrease in interception was due to the decrease in canopy water storage (2.6–1.1 mm/event) and an increase in evaporation during rainfall event (0.7–1.1 mm/event). The decrease in storage partly resulted from the removal of red pines, the bark of which is thick, flaky, and therefore, very absorptive. It was responsible for 88% of the actual rainfall storage at the beginning of the experiment. During the 17 year-period, the size of the lower canopy trees increased more rapidly than that of red pines. The increase in evaporation was due to the increase in canopy gaps by the removal of 75% of the red pines during the succession, and was a minor factor in affecting interception loss.

Effects of Fragment Size and Habitat Heterogeneity on Cryptogam Diversity in the Low-boreal Forest of Western Canada

The effects of fragmentation of the sub-humid low-boreal forest in agro environments on bryophyte and lichen diversity were analyzed on 44 woodlots in three regions of northern Alberta, Canada. Woodlots were selected to cover a wide variety of shapes and sizes in each area. Several microclimatic variables, which included temperature at three different heights above the forest floor, relative humidity, and the amount of light penetration were measured in five m diameter circular sample plots along transects that covered the length and the width of each fragment. The number of microhabitats that included living trees with creviced and smooth bark, standing dead, different decay classes of downed woody debris, soil and rock were tabulated at each sample plot. Bryophyte and lichen presence was noted for all microhabitats found within each plot. There was a trend of decreasing temperature and light intensity and increasing humidity up to 15 m from the edge of the fragments. A multiple regression analysis revealed that the distance from edge and the habitat heterogeneity were the most important variables affecting bryophyte and lichen species richness. Further analysis indicated that edge effects were significant for bryophytes, but not for lichens. The size and shape of fragments had a significant effect on habitat heterogeneity, and bryophyte and lichen diversity. Although there was a distinction between the floras in each region, the effects of fragment size and habitat heterogeneity were similar. An indicator species analysis selected several indicators of large, medium, and small fragments that were also indicators of habitat heterogeneity and species richness. The presence or absence of several indicator species is used to produce performance benchmarks for habitat heterogeneity and species richness. The use of indicator species offers an inexpensive and relatively easy method to evaluate edge effects and habitat heterogeneity on bryophyte and lichen diversity in woodlots.

The Library of Adventure

I am a fast reader who became a slow reader. I started in the fast-reading lane in the sense that I learned to read unusually young and was treated as a freak show for visitors to the Presentation Convent school in Thurles, where my schooling began. No guest—lay or clerical, church canon or Department of Education inspector—was spared what was no doubt a cringe-making display, as I gave command performances from Pear's Encyclopaedia or a gold-edged Lives of the Saints. My greed for words gathered momentum in secondary school with essay competitions, radio scripts, a verse-speaking medal, slogan and caption entries. I read with the obsession of an addict in the grip of an uncontrollable urge. Whatever had been written, I wanted to read. Whatever there was to read, I wanted to have read. Eventually, what there wasn't to read, I wanted to write. At some point in my childhood, I began to ruefully realize that one book a day—adventure novels, biographies of the great inventors, stories of everyday life in distant lands like Norway and France, heroic accounts of missionaries and lifeboat men—would make only a small dent in the stock of the local library. I therefore resolved to double the dose and increase my intake to two books a day, as though I needed a book for each of my avaricious eyes. My favorite reading position was in a large tea chest propped against the smooth bark of a mature laburnum tree; close enough to the backyard rose beds to catch their wafting scent and near enough to the proliferating blackcurrant bushes to warily monitor their progress. The currants, which seemed to increase and multiply at a prodigious— even promiscuous—pace, would need to be picked for jam-making before their plum-colored skins reached seam-bursting ripeness. My tea chest was rendered comfortable by deft deployment of borrowed cushions and a deaf ear to the demands that I clamber out of my shell and—instead of risking cabin fever—help to weed the long thin lettuce and cauliflower beds. I have never lost my sense of urgency about reading, any more than I have gained a sense of urgency about weeding. I sometimes want to bypass the reading process altogether and—reverting to the metaphor of addiction—simply [End Page 9] inject knowledge into my veins so that they might course with whatever wisdom or insight the reading of Proust or Plato, Maria Edgeworth or William Faulkner would confer. But reading is a gratifying act in itself, and one pleads for more time, more life, to get through everything: Amichai to Zabolotsky, Zozimus to Aristotle. My older brother Frank once remarked that "Whenever someone buys a book, they also imagine they are buying the time to read that book"— a sage insight which encapsulates not only the pleasurable anticipation that accompanies the buying of a book but also the depth of our illusions. We feel more learned simply for having bought Tacitus' Agricola or Juvenal's Satires. The volume is handled and fondled, sniffed and shelved, never again in many instances to be disturbed: a bibliographical example of "dust to dust." If living authors received royalties for books read rather than books bought, they couldn't hope to balance their own books. "A poem is never finished, only abandoned," Paul Valéry famously remarked of the writing process. And—of the reading process—one might similarly claim of our frenzied, distracted age, "No book is ever started, only anticipated. . . ." When I say I was a fast reader, I don't mean that I read carelessly or skipped pages. Skipping was an activity in which my sister and her friends specialized—the metronymic beat of their rhymes and the rhythmic thud of their sandaled feet as much a defining part of summer as hoverfly hums and horsefly bites. As a reader, I absorbed every page, eking out the pleasure; but—displaying a youthful conflict of interests&#x02014...

Preference for habitats with low structural complexity in the praying mantid Ciulfina sp. (Mantidae)

Habitat selection by mobile animals is strongly influenced by habitat characteristics that allow for effective predator avoidance, increased foraging efficiency and reproductive success. Often predator avoidance takes priority; this can be achieved through choosing habitats with high structural complexity. By contrast, the praying mantid Ciulfina inhabits structurally simple tree trunk habitats in woodlands and rainforests of northern Queensland, Australia. Field observations and experiments revealed a strong preference for tree trunks with a smooth bark type and small circumference. Subsequent laboratory experiments supported these field results, and further indicated that the preference for such habitat structures may be associated with a faster running speed across the smooth textured bark and around trunks of a smaller circumference. Ciulfina run to escape predation and actively forage across the open tree trunk habitat. Thus selecting smooth trees with small circumference facilitates increased running speeds and thereby may increase foraging ability and predator avoidance.

Atlantic Hazelwoods – a neglected habitat?

Summary Atlantic Hazelwoods form a distinctive (yet apparently over-looked) habitat that appears to be unique to western Scotland and, to a lesser degree, western Ireland. The origins of this habitat appear to date from the early Holocene, and there is compelling evidence that some stands may have existed in unbroken succession for 10,000 years. Recognition of the potential relict status of some areas of hazel gradually emerged as a result of several decades of study of the lichen flora. The smooth bark of hazel in western Scotland is known to support a species-rich and specialised lichen community (the Graphidion), including rare, endemic and old woodland indicator species. However, the full expression of this community is found to occur only in certain stands: often coastal, with no (or very few) other trees or shrubs present, and with a long history, but with little evidence of intensive exploitation. Seeking further evidence to back up the relic status of these Atlantic Hazelwood stands proved elusive...

Barking up the wrong tree: climbing performance of rat snakes and its implications for depredation of avian nests

Nest depredation is the leading cause of nest failure in Neotropical–Nearctic migratory birds, which are of interest because of their declining populations. In a recent study in a bottomland hardwood forest, Acadian Flycatchers (Empidonax virescens) experienced higher nest success in Nuttall oak (Quercus nuttallii), a tree species with relatively smooth bark at maturity. To determine if variation in bark-surface irregularities may influence the ability of a predator species to access the contents of avian nests, we examined the climbing abilities of rat snakes (Elaphe obsoleta) on trees having three different bark types. None of the subjects was able to ascend large Nuttall oaks in the absence of vines; with vines present, subjects still required more time to climb Nuttall oaks than to climb other species. A few of the subjects successfully climbed smaller Nuttall oaks lacking vines, but ascent time was longer and climbing behavior was modified from that observed in the other trials. Our results indicate that the likelihood of nest predation by rat snakes decreases in this forest when birds nest in trees with smooth bark and without vines. Investigators need to consider differences among nest substrates that are important to both the prey and the predator.

Geographic variation in seedling morphology of Chukrasia species

Seed collected from 23 native provenances of Chukrasia A.Juss. and one Australian land race was used to study geographic variation in seedling morphology under temperature-controlled glasshouse conditions. Twenty-four variates were measured for each seedling and the resultant data subjected to univariate and multivariate analyses. The multivariate analyses effectively separated the Chukrasia genus into three different groups or eco-geographical clusters. The most important characteristics that separated the groups were bark structure, leaf type and midrib colour. The first group, provenances from China, Laos, Malaysia, Vietnam and the Australian land race, is characterised by smooth bark, pinnate or intermediate leaves and reddish-green to greenish-red midrib. The second group, provenances from Myanmar and Thailand, is characterised by rough bark, mainly bipinnate leaves and green midrib. The third group, provenances from Sri Lanka, is characterised by rough bark, bipinnate leaves and red midrib. The study clearly shows Chukrasia to be a polymorphic species comprising at least three ecotypes or possibly three ecospecies. A study of allozyme variation may better reveal the systematics within the genus.

Four Years of Epiphyte Colonization in Douglas-fir Forest Canopies

In 1995, we installed surface-sterilized, rough-barked and smooth-barked tree branches in clearcuts, young forests, and old growth. Half of the experimental branches were inoculated with propagules of the epiphytic cyanolichen, Lobaria oregana. In 1997, we concluded that L. oregana was associated with old-growth Douglas-fir forests because of dispersal limitation; addition of L. oregana propagules resulted in a marked increase in establishment rates. In 1999, we revisited the experiment to determine whether other epiphytes had colonized the tree branches. We also checked to see if the 1997 results of the experiment persisted. A total of 26 epiphyte genera (nine bryophytes and 17 lichens) had colonized the branches. Lichen colonization was generally fastest in clearcuts. Colonization by alectorioid lichens was rapid in both clearcuts and old growth but slow in young forests. In contrast, bryophyte colonization was relatively rapid in all age classes. Epiphyte colonization was generally more rapid on smooth bark than on rough bark, although Cladonia was more frequent on rough-barked branches. Bryophytes, cyanolichens, and Sphaerophorus globosus were more frequent on inoculated branches than on control branches, implying that the L. oregana propagule mixture used in 1995 was contaminated with other epiphytes. Like L. oregana, these species may also be dispersal-limited. The number of established L. oregana thalli in clearcuts and young stands decreased from 1997 to 1999, but the number of thalli remained relatively stable in old growth. After four years, established L. oregana thalli were larger in clearcuts than in either young stands or old growth. Overall, the fourth-year results of our experiment confirm the importance of dispersal limitation as the cause of old-growth association in L. oregana in western Oregon.

DISPERSAL LIMITATIONS OF EPIPHYTIC LICHENS RESULT IN SPECIES DEPENDENT ON OLD-GROWTH FORESTS

Epiphytic lichen biomass accumulates slowly in forest canopies. We evaluated three alternative hypotheses for the slow accumulation of epiphytic lichens, using two experiments in tree crowns from 15 Douglas-fir forest stands representing three age classes: old growth, young, and recent clearcuts. The first experiment evaluated whether forest age, bark roughness, or dispersal rate limits the establishment of the dominant old-growth-associated lichen, Lobaria oregana. Surface-sterilized branches with either rough or smooth bark were repeatedly inoculated with propagules and compared 1 yr after the last inoculation. Dispersal affected rates of establishment: inoculated branches had 27× more newly established thalli than controls. Establishment on smooth bark was highest in clearcuts, intermediate in young forests, and lowest in old growth. There was as much or more establishment of sown propagules on smooth-barked branches as on rough-barked branches in all age classes. In the second, transplant-performance experiment, Lobaria oregana grew as rapidly in young forests as in old growth but lost biomass and suffered more injuries in clearcuts. In contrast, L. pulmonaria performed at least as well in clearcuts as in young forests and old growth. Poor dispersal and establishment limit the development of L. oregana populations in Douglas-fir forests. Particular substrates and microenvironments found only in old growth are not essential for Lobaria establishment and growth. Maximizing the number and dispersion of remnant trees in cutting units should maximize the rate of accumulation of L. oregana biomass in the regenerating forest. The single most important action promoting the accumulation of old-growth-associated epiphytes will be the retention of propagule sources in and near all cutting units.

Selection of hibernation sites by Anthonomus pomorum: preferences and ecological consequences

AbstractThe apple blossom weevil, Anthonomus pomorum (L.) (Coleoptera: Curculionidae), has a long period of aestivo‐hibernation in the adult stage lasting from summer to early spring of the following year. Potential hibernation sites within an apple orchard consist of high‐stem rough‐bark trees or dwarf smooth‐bark trees. Field release‐recapture experiments in 2 consecutive years showed that 64 and 47% of the weevils remained in the vicinity of the release sites in an area of high‐stem trees and dwarf trees, respectively. The dispersing weevils moved over an average distance of 5.5 m in the dwarf tree area, as compared to 3.8 m in the high‐stem tree area. The prevalent direction of dispersal was along tree rows in both areas. Some weevils displayed, after release in mid‐July, a directional dispersal to the adjacent forests. Others, released in the dwarf tree area, dispersed towards the area of high‐stem rough‐bark apple trees. Experiments simulating various hibernation sites demonstrated that the litter of dry leaves was the most preferred overwintering shelter, yielding a relatively high survival rate. Branches with rough bark ranked second, while branches with smooth bark, grass and pure soil were not favourable for overwintering. Flight tendency in newly emerged weevils of summer generation was significantly higher in June/July than in August/September. This corresponds to the dispersal behaviour in the field. The timing of spring colonisation of apple trees was similar for weevils overwintering within the orchard and for those from outside. These results suggest that modern, dwarf apple orchards offer unfavourable conditions for overwintering, but that the relatively small proportion of weevils which manage to reach the adjacent forests find optimal hibernation sites there.

Endothia gyrosa associated with severe stem cankers on plantation grown Eucalyptus nitens in Tasmania, Australia

SummarySevere stem cankers in Eucalyptus nitens, from a 14‐year‐old mixed provenance plantation, were associated with infection by Endothia gyrosa, present in its teleomorph state. Surveys of incidence among canker severity classes were carried out in a thinned and pruned stand and an adjacent unthinned and unpruned stand within the affected plantation. No differences in incidence among the canker severity classes were found between the thinned/pruned and unthinned/unpruned stands or between different crown dominance classes within the unthinned/unpruned stand. However, the incidence among canker severity classes was strongly associated with bark roughness with 97% of rough‐barked trees developing either annual cankers or cankers causing cambial damage. Stem cankers were found on only 11% of trees with smooth bark. Bark roughness in E. nitens was shown to differ significantly between provenances. Deployment of provenances prone to rough bark in routine plantation establishment may pose a risk of damaging stem canker outbreaks.

Some observations on overwintering of spiders (Araneae) in two contrasting orchards in the Czech Republic

Overwintering of spiders was studied by means of cardboard trap bands in two different orchards in the Czech Republic, an apple under integrated pest management (in 1993) and an abandoned pear (in 1995). Twenty-seven species of spiders were found to overwinter on tree trunks. The overwintering composition was not very similar to the composition of arboreal spiders detected during spring and summer by beating tree branches. For example, Clubiona specimens occur on ground and canopy in summer but prefer tree trunks to pass winter. Except Clubionidae, three other families, Philodromidae, Theridiidae and Dictynidae, predominated in trap bands. The two study orchards differed in species composition of overwintering spiders as a result of the orchard type (commercial versus abandoned), temporal variation, and the bark structure (rough in pear and smooth in apple). The commercial apple orchard was predominated by small insecticide-tolerant spiders, Theridiidae and Dictynidae, whereas the abandoned pear orchard was dominated by large susceptible species of Clubionidae and Philodromidae. Installation of cardboard bands on young trees with smooth bark may significantly support overwintering of spiders. Distribution of spiders among trap bands of the IPM orchard showed a clumped pattern. It appeared that populations under pressure are spatially distributed. A significant negative correlation was observed between large spiders (Philodromidae) and small ones (Theridiidae and Dictynidae) resulting presumably from interspecific predation. Non-linear models were fitted to these relationships. The relationship between Philodromidae : Clubionidae, Clubionidae : Theridiidae, and Clubionidae : Dictynidae could not be described by correlation. Thus, it is concluded that Clubionidae do not interact with other spiders at overwintering sites.