Tree Hollows Research Articles

Patterns in Tree Cavities (Hollows) in Euphrates Poplar (Populus euphratica, Salicaceae) along the Tarim River in NW China

Populus euphratica Oliv., an indicator species for eco-environmental change in arid areas, plays a key role in maintaining the stability of fragile oasis–desert ecosystems. Owing to human interference as well as to the harshness of the natural environment, P. euphratica forests have suffered severe damage and degradation, with trunk cavities (i.e., hollows) becoming increasingly pronounced, and thus posing a great threat to the growth, health, and survival of the species. Currently, there is a gap in our understanding of cavity formation and its distribution in P. euphratica. Here, cavities in the trunks and branches of a P. euphratica in a typical transect (Arghan) along the lower Tarim River were studied based on field positioning observations combined with laboratory analysis. The results revealed a large number of hollow-bearing P. euphratica stands in the study area; indeed, trees with hollows accounted for 56% of the sampled trees, with approximately 159 trees/ha. Sixty-six percent of hollow trees exhibited large (15 cm ≤ cavity width (CW) < 30 cm) or very large (CW > 30 cm) hollows. The main types of cavities in the trees were trunk main (31.3%), trunk top (20.7%), branch end (19.5%), and branch middle (19.5%). Tree parameters, such as diameter at breast height (DBH), tree height (TH), east–west crown width (EWCW), height under branches (UBH), and crown loss (CL) were significantly different between hollow and non-hollow trees. Both cavity height and width were significantly and positively correlated with DBH and CL, as well as with average crown width (ACW) (p < 0.001) and the distance from the tree to the river. The proportion of P. euphratica trees with cavities showed an overall increasing trend with increasing groundwater depth. Our findings show that cavities in P. euphratica varied with different tree architectural characteristics. Water availability is a major environmental factor influencing the occurrence of hollowing in desert riparian forests. The results provide scientific support for the conservation and sustainable management of existing desert riparian forest ecosystems.

Thinking inside the box: Restoring the propolis envelope facilitates honey bee social immunity.

When wild honey bee colonies (Apis mellifera) nest in hollow tree cavities, they coat the rough cavity walls with a continuous layer of propolis, a substance comprised primarily of plant resins. Studies have shown that the resulting "propolis envelope" leads to both individual- and colony-level health benefits. Unfortunately, the smooth wooden boxes most commonly used in beekeeping do little to stimulate propolis collection. As a result, most managed bees live in hives that are propolis-poor. In this study, we assessed different surface texture treatments (rough wood boxes, boxes outfitted with propolis traps, and standard, smooth wood boxes) in terms of their ability to stimulate propolis collection, and we examined the effect of propolis on colony health, pathogen loads, immune gene expression, bacterial gene expression, survivorship, and honey production in both stationary and migratory beekeeping contexts. We found that rough wood boxes are the most effective box type for stimulating propolis deposition. Although the use of rough wood boxes did not improve colony survivorship overall, Melissococcus plutonius detections via gene expression were significantly lower in rough wood boxes, and viral loads for multiple viruses tended to decrease as propolis deposition increased. By the end of year one, honey bee populations in migratory rough box colonies were also significantly larger than those in migratory control colonies. The use of rough wood boxes did correspond with decreased honey production in year one migratory colonies but had no effect during year two. Finally, in both stationary and migratory operations, propolis deposition was correlated with a seasonal decrease and/or stabilization in the expression of multiple immune and bacterial genes, suggesting that propolis-rich environments contribute to hive homeostasis. These findings provide support for the practical implementation of rough box hives as a means to enhance propolis collection and colony health in multiple beekeeping contexts.

Impacts of changing fire regimes on hollow-bearing trees in south-eastern Australia

Background Many species use hollows or cavities that form in trees. The effect of an increasing fire frequency on hollow-bearing trees is unclear. Aims To predict the effects of increasing fire frequency on the abundance of hollow-bearing trees and identify how to make forests more resilient to these changes. Methods We simulated how increasing fire frequency will affect the abundance of hollow-bearing trees in forests of south-eastern Australia and conducted a sensitivity analysis to identify which variables affect these predictions. Key results Other things being equal, we found a negative relationship between the number of hollow-bearing trees and increasing fire frequency. However, we identified scenarios where the number of hollow-bearing trees remained stable, or increased, with frequent fires. Conclusions Hollow-bearing trees will decline where frequent fires co-occur with high rates at which trees collapse (or are removed) and/or where there are not a sufficient number of suitable mature trees in which new hollows can be excavated by fire. Implications The impact of increasing fire frequency on hollow-dependent fauna is likely to be greatest in forests where regeneration is inhibited, a large number of trees are removed before they form hollows, and/or where rates of collapse among trees is elevated.

Densities of feral honey bee colonies utilising tree hollows in central Perth, Western Australia

Densities of feral honey bee colonies utilising tree hollows in central Perth, Western Australia

Risk assessment of hollow-bearing trees in urban forests

The paper is a study of risk assessment posed by trees in selected urban woodlands (urban forests) of Warsaw. Two groups of trees were analysed and compared: exhibiting signs of maturity and ageing (hollow-bearing trees with open or hidden cavities and/or caries) and with no signs of decay. 373 individual trees growing near routes frequently or continuously used for recreational purposes were examined using Roloff's vitality classification, and tree risk assessment method, complemented by instrumental studies: a resistance resistograph, pulling tests, and sonic tomography (SoT). The collected data was analysed using the Chi-square test. The results indicate that it is not possible to conclude unequivocally that the presence of hollows in aged trees significantly increases the risk of falling. According to the safety factor results from the SoT and pulling tests, no correlation was demonstrated between the presence of hollow trees and an increase in risk class. The highest proportion of hollow trees (89.42%) was in the low risk group for trunk fracture and uprooting. The results also indicate the coherence of the diagnostic methods to be necessary for providing sufficient information to assess the statics and, ultimately, as our study showed, the protection of hollow trees.

Foraging Activities, Environmental Factors, and Increment Weight of Tetragonula biroi Colonies in Beekeeping with Different Hive Materials

Tetragonula biroi is one of the stingless bee species that has many benefits for human life besides producing honey, propolis, and 13 derivative products. Another important service provided by this bee is as a plant pollinator. This research aims to determine the relationship between the foraging activity of T. biroi bees, environmental factors, and colony development in hives made of different materials. The study was conducted in Rompegading Village, Maros Regency. This research method used a completely randomized design consisting of four different hive materials, namely glass, triplex, cement, and tree hollows, and each treatment was repeated three times. Parameters observed were the number of worker bees leaving and entering the hive throughout the day, colony weight gain, and environmental factors (temperature, humidity, and light intensity). The results showed that the highest foraging activity of worker bees and colony weight gain occurred in natural hives (tree hollows) in the fourth week of observation and in artificial hives made from cement materials. The peak of bee activity entering and leaving the hive occurred in the morning from 07:00–10:00 and in the late afternoon from 13:00–16:00. In the morning, more bees leave the hive, while more enter in the afternoon. Factors such as temperature, humidity, and light affect the foraging activity of worker bees.

The breeding biology of the Western Red-tailed Cockatoo Calyptorhynchus escondidus in the wheatbelt of Western Australia

ABSTRACT A breeding population of Western Red-tailed Cockatoos Calyptorhynchus escondidus was studied between July 1974 and December 1981 at Nereeno Hill, in the northern wheatbelt of Western Australia. Egg-laying occurred during two clearly defined periods each year; with peaks mid-March to mid-April (Autumn breeding) and early-August to mid-October (Spring breeding). Thirty-two percent of the 459 eggs laid during the study were laid in Autumn and 68% in Spring. Growth rates of nestling wings and body mass were similar between seasons and years. Nearly one third of breeding attempts failed during incubation and 40.7% successfully fledged a nestling. Fledgling survival in the first year was low (17.5%), however, annual survival was higher after the first year; 80.0% after four years. Birds were killed by Wedge-tailed Eagles Aquila audax, shot by farmers, and drowned in stock troughs. Based on evidence from one individually-marked pair, Western Red-tailed Cockatoos may form long lasting pair bonds. While females breed every 12 months, some have bred in both Autumn and Spring seasons. Young Red-tailed Cockatoos remain with their parents up to two years after fledging, and adults may have young from two breeding seasons accompanying them. The breeding biology of Red-tailed Cockatoos is compared with that of closely related species from the genera Calyptorhynchus and Zanda. Threats to the species are loss of mature hollow-bearing trees and almost complete dependence on the seeds of Double Gee Emex australis, an introduced agricultural weed, for food.

Shell Amebas of the Natural and Historical Park “Bitsevsky Forest”, Moscow

For the first time in protozoology, research was carried out on the fauna of testate amoebae in a city park. One hundred and nine species and infraspecific taxa of this group of free-living protozoa were found in various types of habitats in the Bitsevsky Forest park in Moscow. To assess the species diversity of testate amoebae, samples were taken from tree hollows; small oligo-mesotrophic swamps; epiphytic mosses from tree trunks; mosses on deadwood; bottom samples from reservoirs; soil samples near tree trunks, as well as directly in the area of the Yasenevo park estate. Various ecological groups of testate amoebae have been identified, the richest communities of eurybionts inhabited soils, as well as mosses on deadwood. Bottom sediments of manor ponds were inhabited mainly by hydrophilic species of the genus Difflugia.

Spatio‐temporal species aggregations do not rule out interspecific competition in tree hollow spider assemblages

Abstract A community's biological diversity reflects coexistence between species. This often depends, to some extent, on whether there is competition for resources and how it is dealt with. The nature of old‐growth tree hollows is confined and relatively isolated, which makes them ideal for investigating the competition phenomena between their inhabitants, such as Araneae. The existence of interspecific competition in the structuring of tree hollow spider assemblages in Mediterranean forests was inferred by spatial co‐occurrence pattern analyses with null models at both the community and pairwise levels. The analysis included 36 spider species collected monthly with emergence traps for 1 year. The distribution of four ecological traits, body size and phenology on the resulting pattern type was discussed. The analyses showed spatial segregation at the community level and spatial aggregations between species with different traits predominated at the pairwise level. Hunting strategy and body size were the main differential traits to facilitate these aggregations. In addition, only the aggregations led by Amaurobius scopolii–Scotophaeus scutulatus and Eratigena atrica–Liocranum majus also showed an overlap during their main activity period. Community segregation and spatio‐temporal aggregations of species with differential traits suggest that interspecific competition is a very likely structuring factor of tree hollow spider assemblages. Instead, segregations at the pairwise level seem to result from other factors, for example, habitat preferences.

Why is the hermit beetle so rare in Central European managed forests? Habitat requirements of the forest population of Osmoderma barnabita

In Europe, more than 95% of forests are managed and only 2.2% of forests are undisturbed by man. Therefore, appropriate forest management strategies are crucial to the survival of all forest-dwelling species. Among them are saproxylic beetles, one of the most sensitive to forest management organisms, often treated as important indicators of the degree of transformation of forest ecosystems. The object of our study was the hermit beetle Osmoderma barnabita, so-called primeval forest relict, used as an umbrella species for forest conservation in Central Europe. However, most studies of habitat preferences of this species have been conducted in anthropogenic habitats, and it is not known to what extent they correspond to the habitat requirements of forest populations. The aim of this research was to fill this knowledge gap, as well as to assess differences in characteristics of hollow trees preferred by the hermit beetle between managed and unmanaged forests. Our results indicate that five predictors affect the occurrence of O. barnabita in Central European forests: trunk diameter, tree health, number of entrance holes per tree, size of the entrance hole, and their height above ground, all having positive effect on its presence. The most important predictors were tree health, size of the entrance hole and their height above the ground, while trunk diameter was the least informative variable. Managed and unmanaged forests differed significantly in three out of five characteristics of hollow trees preferred by the species. Unmanaged forests had a greater share of trees with higher trunk diameter, larger hole entrances and poorer health. Therefore, the protection of the species should be based not only on the preservation of hollow trees, but also on maintaining their diversity, ensuring availability of optimal conditions for the local habitat.

Pronounced daily heterothermy in the White-throated Treecreeper Cormobates leucophaea

Torpor, a controlled reduction in metabolism and body temperature, reduces energy expenditure substantially. However, torpor expression in wild passerines is currently understudied. We show that skin temperature (Ts) of resting White-throated Treecreepers (N = 4) fell by ~ 5 °C on average in both summer and winter, independent of ambient temperature, but we could not confirm torpor use (Ts reduction > 5 °C). It is possible that roosting in tree hollows provides sufficient insulation to minimise energy loss, or torpor is used only during extreme conditions. Further studies are needed to characterise the physiological flexibilities of species and, therefore, their capability to cope with changing environmental conditions.

Wildfire and Climate Impacts Tree Hollow Density in a Temperate Australian Forest

Tree hollows are an important landscape resource used by fauna for shelter, nesting, and predator avoidance. In fire-prone landscapes, wildfire and climate may impact hollow dynamics; however, assessments of their concurrent impacts are rare. We conducted a field survey at 80 sites in the Sydney Basin bioregion (Australia) to understand how fire frequency, fire severity, mean annual temperature, and mean annual precipitation concurrently impacted the site-density of small- (<5 cm entry width), medium- (5–10 cm entry width) and large-size (>10 cm entry width) tree hollows and tree basal scars (which mediate hollow formation via invertebrate access to heartwood), when tree-size and dead/live status were considered. A unimodal relationship occurred between medium- and large-sized hollow densities and fire frequency and severity, respectively, with hollow densities greatest at intermediate frequencies/severities. Increases of 1.82, 1.43, and 1.17 hollows per site were observed between the 1 (reference) and 2, 2 and 3, and 3 and >3 fire frequency categories. Increases of 1.26, 1.75 and 0.75 hollows per site were observed between the low (reference) and moderate, moderate and high, and high and very high fire severity categories. Fire severity was also positively associated with basal scar density, with increases of 2.52, 8.15, and 8.47 trees per site between the low (reference) and moderate, moderate and high, and high and very high categories. A weak positive and stronger negative association was observed between mean annual temperature and small-sized hollow and basal scar density, respectively. Dead and medium-sized tree density was positively associated with medium-sized hollow and basal scar tree density, respectively. Collectively, our results suggest that wildfires, and in some cases climate, have diverse and size-specific impacts on tree hollow and basal scar density. Our results imply that fire regimes that allow for moderately severe wildfire will promote larger-sized tree hollows, which are a limiting resource for many fauna species.

When bat eats bat: diet and roosts of the greater broad-nosed bat (Scoteanax rueppellii) across different regions and habitats

Roost selection and diet are fundamentally important to bats and can vary geographically and with habitat. The greater broad-nosed bat (Scoteanax rueppellii) is infrequently captured and poorly known, meaning appropriate conservation actions are difficult to determine. To assess variation across different habitats, we collected faecal samples for dietary analysis and radio-tracked individuals to identify roost trees at four different sites across New South Wales, Australia. Analysis of droppings verified beetles as the main prey in each study area except one dominated by mangroves, and confirmed for the first time carnivory in wild-caught individuals from the presence of hair from other bat species in its droppings. Very large, hollow trees were used as maternity roosts, being typically larger than neighbouring trees. Roosting habitat varied from wet sclerophyll forest in gullies to old-growth mangroves, and tree species used as roosts also varied. Colony size at maternity roosts was often 50–100 bats and fidelity to the maternity roost varied, with some being switched almost daily and others occupied for at least several days. One maternity roost was re-used 2 years later. Both the importance of beetles in the diet and roosts located in more productive landscapes suggest coastal plains and foothills may represent key habitat.

Alien vs. Predator: Impacts of Invasive Species and Native Predators on Urban Nest Box Use by Native Birds.

Many bird species in Australia require tree hollows for breeding. However, assessing the benefits of urban nest boxes to native birds requires frequent monitoring that allows to assess nesting success. To better understand the benefits of nest boxes for native birds, we examined the impact of local habitat characteristics, invasive species (common myna, Acridotheres tristis), and native mammalian predators on urban nest box use and nesting success of native birds. We installed 216 nest boxes across nine locations in southeastern Australia (S.E. Queensland and northern New South Wales) in both long-invaded sites (invaded before 1970) and more recently invaded sites (after 1990). We monitored all boxes weekly over two breeding seasons. We recorded seven bird species and three mammal species using the nest boxes. Weekly box occupancy by all species averaged 8% of all boxes, with the species most frequently recorded in the nest boxes being the common brushtail possum (Trichosurus vulpecula), a native cavity user and nest predator. We recorded 137 nesting attempts in the boxes across all bird species. The most frequent nesting species were the invasive alien common mynas (72 nesting attempts). We recorded an average nesting failure rate of 53.3% for all bird species. We did not record any common mynas evicting other nesting birds, and found that several native species used the same box after the common myna completed its nesting. We recorded native possums in 92% of the boxes, and possum occupancy of boxes per site was negatively correlated with bird nesting success (p = 0.021). These results suggest that when boxes are accessible to invasive species and native predators, they are unlikely to significantly improve nesting opportunities for native birds. To ensure efficient use of limited conservation resources, nest boxes should be designed to target species of high conservation importance and limit other species of both predators and competitors.

La Chine, le Japon et l’« étoffe » de Perse

Abstract in English Pressing past the frameworks of the wa-kan (Japanese-Chinese) and sangoku (“the Three Kingdoms”), this essay explores a border-crossing “geopoetics” in order to espy distant “Persia” in the literary culture of classical Japan. In the “Picture Contest” midway through The Tale of Genji, an illustration supposedly set in far-off Persia is praised not for its exoticism but rather for its adroit synthesis of Japanese and Chinese pictorial elements. It turns out that the Persia made by Japanese persons around the beginning of the eleventh century is connected to the intermixing of all things Chinese and Japanese, especially when it comes to poetry. In other words, the stuff of this artificial Occident is laced through with these twin poetries from Asia’s easternmost extremities. We can see this interlacing in vernacular fictions, such as The Tale of the Tree Hollow (Utsubo monogatari), in which one of the protagonists is a Persian mage reincarnated in Japan obliged to recite passages in bilingual alternation, night by night, before the monarch. Elsewhere, academicians of Chinese “letters” exhibit their boundless knowledge of this “Far West” in such bilingual works as The New Man’yōshū (Shinsen man’yōshū) and The New Collection of Resonant Verse (Shinsen rōeishū). The latter presents itself as a learned sequel to The Collection of Japanese and Chinese Resonant Verse (Wakan rōeishū)—an emblem of the Heian period’s bilingual poetics which, in its turn, attracted the attention of monk-commentators who used the anthology to develop their Indo-Buddhist cosmo-cartography, including Persia. Persia, therefore, gets woven out of this mix of poetry in Chinese and Japanese—a mixed arrangement that enjoys an unparalleled display in the scrolls of the Collection of Resonant Verse. In its turn, The Collection itself begins to appear like an altogether “Persian” kind of terrain : a virtual terrain which belongs neither to China nor to Japan, but which is nonetheless made out of both.

A preliminary catalogue of the Coleoptera (Hexapoda: Insecta) of the Monte Netto Regional Park (Lombardy NE Italy).

The Po Plain (Northern Italy) is one of the most urbanized areas in Europe. In such a territory, where ecosystem degradation reached critical levels and the agricultural matrix is prevailingly intensive, small fragments of hilly oak-hornbeam forests still persist. Examples of well preserved forests of the Po Plain are those of the Monte Netto Regional Park that represents irreplaceable refuges for both sedentary and migratory species. In this paper we present a preliminary list of Coleoptera inhabiting the Park collected during 10 years of field surveys using several sampling techniques (hand netting, beating tray, sight-collecting and collecting under bark; water nets; litter reducers, light traps; aerial sweet-bait trap; cross-vane panel trap, pitfall traps, Malaise traps, window traps, and walking transects). Specific samplings were also made in tree hollows and by car-netting. To date we have identified 834 species belonging to 531 genera and 71 families (several specimens and some families are still undetermined). Among all the species identified, 31 were non-native while 202 were included in the Red List of Italian saproxylic beetles, 12 of which were in threatened category. The high beetle richness and the presence of many endangered species recorded during this survey, emphasises the conservation value of Monte Netto. Moreover, the discovery of species linked to old and stable forest systems, such as Osmoderma eremita, Oxylaemus cylindricus, Pycnomerus terebrans or Xylotrechus antilope suggests how, despite their small size and the fact that they are surrounded by agricultural land, the remaining forest patches of Monte Netto still possess a fair level of naturalness, especially in the internal areas of the larger plots. Future targeted research, also intended to cover other parts of Monte Netto, could increase our present knowledge; however, and at least in the number of families, we do not expect a substantial increase in species richness.

Diurnal tree-roosting by Eastern Horseshoe Bats Rhinolophus megaphyllus

ABSTRACT The Eastern Horseshoe Bat Rhinolophus megaphyllus is known to roost in caves, disused mines, tunnels and old buildings. Other tropical Rhinolophus species are reported to use tree roosts, but this has not been reported for R. megaphyllus. We describe the features of a R. megaphyllus tree roost identified on the mid north coast of NSW. The tree was monitored over a 10-year period before the tree's collapse during the 2019/2020 wildfires. The tree was not observed to be used in the maternity season. The discovery highlights the potential importance of hollow trees as habitat for species not previously recorded as using tree roosts. In addition, the discovery further identifies the need for consideration of changing fire management with the onset of warming and drying as part of climate change. Prevention of future conflagrations, as was witnessed during 2019/2020 fire season, should consider a range of options to help prevent the loss of valuable hollow-bearing habitat trees.

Interaction Networks Help to Infer the Vulnerability of the Saproxylic Beetle Communities That Inhabit Tree Hollows in Mediterranean Forests

Insect communities are facing contrasting responses due to global change. However, knowledge on impacts of communities' reorganizations is scarce. Network approaches could help to envision community changes in different environmental scenarios. Saproxylic beetles were selected to examine long-term variations in insect interaction/diversity patterns and their vulnerability to global change. We evaluated interannual differences in network patterns in the tree hollow-saproxylic beetle interaction using absolute samplings over an 11-year interval in three Mediterranean woodland types. We explored saproxylic communities' vulnerability to microhabitat loss via simulated extinctions and by recreating threat scenarios based on decreasing microhabitat suitability. Although temporal diversity patterns varied between woodland types, network descriptors showed an interaction decline. The temporal beta-diversity of interactions depended more on interaction than on species turnover. Interaction and diversity temporal shifts promoted less specialized and more vulnerable networks, which is particularly worrisome in the riparian woodland. Network procedures evidenced that saproxylic communities are more vulnerable today than 11 years ago irrespective of whether species richness increased or decreased, and the situation could worsen in the future depending on tree hollow suitability. Network approaches were useful for predicting saproxylic communities' vulnerability across temporal scenarios and, thus, for providing valuable information for management and conservation programs.

Restricting living space: Development and larval morphology in sticky frogs (Microhylidae: Kalophrynus) with different reproductive modes

We compare reproductive features, development, and larval morphology in three closely related species of sticky frogs (Kalophrynus Tschudi, 1838) inhabiting the lowland and mountain forests of Vietnam and displaying a variety of reproductive modes. While K. interlineatus breeds in open temporary ponds, K. honbaensis and K. cryptophonus are phytotelm-breeders using tree hollows and bamboo stems for reproduction. Their tadpoles also differ in trophic specialization: larval K. interlineatus are typical suspension-feeders, whereas K. honbaensis and K. cryptophonus are obligatorily oophagous. All three species differ in egg and clutch sizes, duration of embryonal period and hatching stage, and the structure of the larval digestive tract and skeleton. Based on external and internal morphology, we conclude that tadpoles of K. interlineatus and K. cryptophonus represent two “extremes” of the adaptive spectrum of microhylid larvae, while K. honbaensis displays a set of transitory traits. Relying on these new findings in anuran biology, we discuss reproductive, ontogenetic, and morphological rearrangements during the transition from pond breeding to phytotelm breeding and from microphagy to macrophagy as well as the significance of the revealed adaptations to different habitats and larval life modes.

The dendrochronological potential of decayed yew wood

A significant difficulty in the accurate ageing of many of the largest-diameter yew trees (Taxus baccata L.) found in the United Kingdom is their vulnerability to heartwood decay. This has presented a considerable barrier to extending yew chronologies beyond c.330 years into the past. Decayed wood often survives within the sound cylindrical structure of hollow and hollowing yews. Here we present the analysis of such decayed yew wood using a novel wet-scanning technique. Long series for four out of five large hollow yew trees sampled are successfully cross-matched to produce a 374-year-long mean series spanning 1532–1905. These newly dated series extend the previous mean UK yew chronology by 158 years. Although currently undated, the central decayed material from the largest yew at Selborne produces a 196-year series which is likely to include material from the 14th century. Given the number of large hollow yew trees surviving in the UK, this research highlights the potential for using decayed yew wood to improve the ageing of yew trees and extending a regional yew chronology.