Predicting Douglas‐fir Sapling Mortality Following Prescribed Fire in an Encroached Grassland

Tree encroachment in fire‐maintained woodlands and grasslands is a major management concern, yet little information exists regarding the mechanisms of small tree mortality following prescribed burns. We sought to clarify the relative importance of tree size and fire‐induced injury in the post‐fire mortality of encroaching Douglas‐fir trees and to compare results with an existing mortality model for larger Douglas‐fir trees. Crown injury to small Douglas‐fir trees was a significant explanatory variable in post‐fire mortality models, with results suggesting a 20% threshold in crown scorch. Crown injury was strongly related to bole injury, and delayed mortality was important as we documented new mortality 20 months post‐burn. Mortality models for large Douglas‐fir tend to over‐predict small tree mortality, underscoring the need to better understand the mechanisms of fire‐caused mortality for small, encroaching trees.     

Ageing culturally significant relic trees in southeast Queensland to support bushfire management strategies

Appropriate fire management strategies are needed to protect forests and large old ecologically and culturally significant trees in natural landscapes. The aim of this study was to determine the age of large old and relic trees of cultural significance that included Cypress Pine (Callitris columellaris F. Muell.), a species that is sensitive to crown scorching fires in a fire‐prone landscape, and to calibrate a tree‐growth‐rate method for estimating tree age. Twelve large trees were dated using radiocarbon (¹⁴C) dating. The trees are located on North Stradbroke Island (Indigenous name: Minjerribah), southeast Queensland (Australia) in a fire‐prone landscape where recent wildfires have destroyed many large trees. The median tree ages ranged from 155 to 369 years. These results suggest an important role of past Indigenous land management practices in protecting Cypress Pine from crown scorching fires. The tree‐growth‐rate‐based method for estimating tree age generally overestimated the age derived from radiocarbon dating. Bias correction factors were developed for correcting various measures of periodic growth rates. This study provides evidence that appropriate low‐intensity fire strategies have the potential to contribute to the survival of forests and conserve large old trees.     

Enriching small trees with artificial nest boxes cannot mimic the value of large trees for hollow‐nesting birds

Large trees support unique habitat structures (e.g. hollows) that form over centuries and cannot be provided by small trees. Large trees are also declining in human‐modified landscapes worldwide. One restoration strategy gaining popularity involves adding nest boxes to smaller trees to replicate natural hollows. However, limited empirical research has tested how hollow‐nesting fauna responds to the presence of nest boxes. We asked: can the addition of nest boxes increase tree visitation by hollow‐nesting birds? We conducted a before‐after control‐impact (BACI) experiment using 144 nest boxes and 96 sample trees comprised of three sizes (small [20–50 cm dbh], medium [51–80 cm], and large [>80 cm]) and located in four landscape contexts (reserves, pasture, urban parklands, and urban built‐up areas). We recorded a significant increase in hollow‐nesting bird abundance and richness at large trees after nest box additions. However, the same response was not observed at medium, small, or control trees. We also recorded nonsignificant increases in hollow‐nesting bird abundance and richness at trees in modified landscapes after nest box additions compared to trees in reserves and control trees. Our results suggest that adding nest boxes to smaller‐sized trees may not attract hollow‐nesting birds. Therefore, nest box management strategies may require re‐evaluation as it is often assumed that hollow supplementation will attract hollow‐using fauna and sufficiently ameliorate the loss of large, hollow‐bearing trees. We advocate that large tree retention remains crucial and should be prioritized. Large trees could be effective target structures for habitat restoration, especially in modified landscapes.     

Selection of Nest Trees by Cavity‐nesting Birds in the Neotropical Atlantic Forest

One of the five most important global biodiversity hotspots, the Neotropical Atlantic forest supports a diverse community of birds that nest in tree cavities. Cavity‐nesting birds may be particularly sensitive to forestry and agricultural practices that remove potential nest trees; however, there have been few efforts to determine what constitutes a potential nest tree in Neotropical forests. We aimed to determine the characteristics of trees and cavities used in nesting by excavators (species that excavate their own nest cavity) and secondary cavity‐nesters (species that rely on existing cavities), and to identify the characteristics of trees most likely to contain suitable cavities in the Atlantic forest of Argentina. We used univariate analyses and conditional logistic regression models to compare characteristics of nest trees paired with unused trees found over three breeding seasons (2006–2008). Excavators selected dead or unhealthy trees. Secondary cavity‐nesters primarily selected cavities that were deep and high on the tree, using live and dead cavity‐bearing trees in proportion to their availability. Nonexcavated cavities suitable for birds occurred primarily in live trees. They were most likely to develop in large‐diameter trees, especially grapia Apuleia leiocarpa and trees in co‐dominant or suppressed crown classes. To conserve cavity‐nesting birds of the Atlantic forest, we recommend a combination of policies, economic assistance, environmental education, and technical support for forest managers and small‐scale farmers, to maintain large healthy and unhealthy trees in commercial logging operations and on farms.     

Decaying trees improve nesting opportunities for cavity‐nesting birds in temperate and boreal forests: A meta‐analysis and implications for retention forestry

Many studies have dealt with the habitat requirements of cavity‐nesting birds, but there is no meta‐analysis on the subject and individual study results remain vague or contradictory. We conducted a meta‐analysis to increase the available evidence for nest‐site selection of cavity‐nesting birds. Literature was searched in Web of Science and Google Scholar and included studies that provide data on the habitat requirements of cavity‐nesting birds in temperate and boreal forests of varying naturalness. To compare nest and non‐nest‐tree characteristics, the following data were collected from the literature: diameter at breast height (DBH) and its standard deviation (SD), sample size of trees with and without active nest, amount of nest and available trees described as dead or with a broken crown, and amount of nest and available trees that were lacking these characteristics. Further collected data included bird species nesting in the cavities and nest‐building type (nonexcavator/excavator), forest type (coniferous/deciduous/mixed), biome (temperate/boreal), and naturalness (managed/natural). From these data, three effect sizes were calculated that describe potential nest trees in terms of DBH, vital status (dead/alive), and crown status (broken/intact). These tree characteristics can be easily recognized by foresters. The results show that on average large‐diameter trees, dead trees, and trees with broken crowns were selected for nesting. The magnitude of this effect varied depending primarily on bird species and the explanatory variables forest type and naturalness. Biome had lowest influence (indicated by ΔAIC). We conclude that diameter at breast height, vitality, and crown status can be used as tree characteristics for the selection of trees that should be retained in selectively harvested forests.     

Crown dieback events as key processes creating cavity habitat for magellanic woodpeckers

Abstract Woodpeckers are considered keystone species for webs of cavity nesters and habitat and resource specialists that strongly depend on availability of trees suitable for cavity excavation. Most studies carried out in northern hemisphere temperate coniferous forests emphasize the importance of old growth stages of forests or large dead trees as habitat for cavity builders. We present a study of Nothofagus pumilio tree selection by the magellanic woodpecker (Campephilus magellanicus) that incorporates dendroecological data on long‐term growth trends of trees that provides new insights into the processes that create suitable habitat for cavity excavating species. We analysed 351 cavity and neighbouring control trees in terms of age and radial growth patterns, as well as external tree characteristics. In addition, from a subsample of these trees we developed tree‐ring chronologies for each group using standard methods in order to analyse potential differences in radial growth patterns between cavity and non‐cavity trees. Multivariate models that account for differences between paired cavities versus control trees indicated that growth decline and the degree of crown dieback were the primary variables explaining magellanic woodpecker tree selection for cavity building. In contrast to previous work, neither diameter (above a certain threshold) nor age, were important determinants of selection. Furthermore, trees that became present cavity are those that had synchronously declined in radial growth during the 1943–44 and 1956–57 droughts and the 1985–86 massive caterpillar defoliation. Insect outbreaks and extreme climatic events may episodically reduce vigour, induce partial crown mortality, trigger increased fungal attack and heart rot formation at different tree heights on the bole in a group of trees and thus increase availability of soft substrate and their likelihood of cavity excavation by the magellanic woodpecker. These results underscore the importance of drought/biotically‐induced canopy dieback events in creating habitat for woodpeckers and their dependent cavity users.     

Roost tree characteristics determine use by the white‐striped freetail bat (Tadarida australis,Chiroptera: Molossidae) in suburban subtropical Brisbane,Australia

Abstract We examined factors affecting roost tree selection by the white‐striped freetail bat Tadarida australis (Chiroptera: Molossidae), a large insectivorous bat in suburban Brisbane, Australia. We compared biophysical characteristics associated with 34 roost trees and 170 control trees of similar diameter, height and tree senescence characters. Roost trees used by the white‐striped freetail bat had significantly higher numbers of hollows in the trunk and branches (P < 0.003) and were more likely to contain a large trunk cavity with an internal diameter of >30 cm (P < 0.001) than control trees. These trees also accommodated more species of hollow‐using fauna (P = 0.005). When comparing roost trees with control trees of similar diameters and heights, roost trees were on average at a later stage of tree senescence (P < 0.001). None of the roost trees were found in the large forest reserves fringing the Brisbane metropolitan area despite these areas being used for foraging by the white‐striped freetail bat. Although all tree locations in this study were in modified landscapes, roost trees tended to be surrounded by groups of trees and undergrowth. Roost trees provide important habitat requirements for hollow‐using fauna in suburban, rural and forested environments.     

treegraph: automated drawing of complex tree figures using an extensible tree description format

treegraph assists in producing complex ready‐to‐publish figures of phylogenetic trees. The TGF format used by the program automates formatting of several different statistical support value types (confidence estimates) per tree node. Moreover, internal text and graphical labels are automatically arranged at the nodes as are annotations for clades or groups of terminals. treegraph imports nexus trees and related file formats. Beyond common tree edit operations, simultaneous pruning of subtrees (simplification of the tree to higher order clades) and saving of subtrees is possible. treegraph exports to the standard vector graphics formats Scalable Vector Graphics and PostScript.     

Age and Growth Patterns of Brazil Nut Trees (Bertholletia excelsa Bonpl.) in Amazonia,Brazil

Various techniques have been used to estimate the age of Brazil nut trees (Bertholletia excelsa Bonpl.), but these techniques produce large discrepancies. Here, we first verified that two individuals of known ages from a plantation in central Amazonia, Brazil, have a congruent number of growth rings. The indexed average tree‐ring curve was significantly correlated with total precipitation during the rainy season (November–June) over a 50‐yr period, confirming the annual nature of the tree rings. Second, we analyzed Brazil nut trees from two populations in the Trombetas (eastern Amazon) and Purus (central Amazon) regions, performing tree‐ring analysis to estimate tree age and diameter increment rates. We compared age–diameter relationships, mean passage time through 10‐cm diameter size classes, and growth trajectories of individual trees. The maximum age of Brazil nut trees analyzed was 361 yr in the Purus and 401 yr in the Trombetas. Trees at the Purus site had higher mean diameter increment rates and showed more variation compared to trees at the Trombetas site. Individual growth trajectories show that the majority of trees attained the canopy by direct growth, while a smaller number passed through one release or one suppression event before becoming established in the canopy. None of the trees passed through multiple release and suppression events. The age estimations presented here are comparable to previous tree‐ring analyses for the species, and the observed growth patterns support earlier work indicating B. excelsa as a gap‐dependent tree species.     

treespace: Statistical exploration of landscapes of phylogenetic trees

The increasing availability of large genomic data sets as well as the advent of Bayesian phylogenetics facilitates the investigation of phylogenetic incongruence, which can result in the impossibility of representing phylogenetic relationships using a single tree. While sometimes considered as a nuisance, phylogenetic incongruence can also reflect meaningful biological processes as well as relevant statistical uncertainty, both of which can yield valuable insights in evolutionary studies. We introduce a new tool for investigating phylogenetic incongruence through the exploration of phylogenetic tree landscapes. Our approach, implemented in the R package treespace , combines tree metrics and multivariate analysis to provide low‐dimensional representations of the topological variability in a set of trees, which can be used for identifying clusters of similar trees and group‐specific consensus phylogenies. treespace also provides a user‐friendly web interface for interactive data analysis and is integrated alongside existing standards for phylogenetics. It fills a gap in the current phylogenetics toolbox in R and will facilitate the investigation of phylogenetic results.     

Past attacks influence host selection by the solitary bark beetle Dendroctonus micans

1. A spatio‐temporal study of host selection and local spread of a solitary bark beetle attacking live spruce Dendroctonus micans (Kugelann) was carried out using a combination of standard statistical methods, geostatistical analyses, and modelling. The study was based on data from three plots (150–300 trees, 0.3–1 ha) from 1978 to 1993. All trees were mapped and successful and abortive bark‐beetle attacks on each tree were counted annually. Because the attacked trees usually survived, temporal attack patterns as well as spatial patterns could be analysed. 2. The distribution of successful insect attacks on the trees was slightly aggregative, indicating some degree of choice rather than totally random establishment. 3. The level of yearly individual attacks per tree was very stable, suggesting that D. micans usually leave the host in which they develop. 4. The attacked trees were distributed randomly in the plots; at the study's spatial scale, the insects dispersed freely throughout the plot (no spatial dependence). 5. On the other hand, time dependence was strong; some trees were attacked repeatedly while others were left untouched. 6. Among a choice of scenarios (random attack, fixed variability in individual host susceptibility, induced host susceptibility following random attack), the best fit was obtained with the model involving induced individual host susceptibility. This type of relation to the host tree contrasts strongly with patterns generally described in host–plant relationships (including gregarious, tree‐killing bark beetles), where local herbivore damage results in induced resistance. 7. These results suggest that the first attacks in a new stand are made at random, that all or most of the beetles emerging from a tree disperse and resample the stand, and that they settle preferentially on trees that were colonised successfully by previous generations.     

TREEasy: An automated workflow to infer gene trees,species trees,and phylogenetic networks from multilocus data

Multilocus genomic data sets can be used to infer a rich set of information about the evolutionary history of a lineage, including gene trees, species trees, and phylogenetic networks. However, user‐friendly tools to run such integrated analyses are lacking, and workflows often require tedious reformatting and handling time to shepherd data through a series of individual programs. Here, we present a tool written in Python—TREEasy—that performs automated sequence alignment (with MAFFT), gene tree inference (with IQ‐Tree), species inference from concatenated data (with IQ‐Tree and RaxML‐NG), species tree inference from gene trees (with ASTRAL, MP‐EST, and STELLS2), and phylogenetic network inference (with SNaQ and PhyloNet). The tool only requires FASTA files and nine parameters as inputs. The tool can be run as command line or through a Graphical User Interface (GUI). As examples, we reproduced a recent analysis of staghorn coral evolution, and performed a new analysis on the evolution of the “WGD clade” of yeast. The latter revealed novel patterns that were not identified by previous analyses. TREEasy represents a reliable and simple tool to accelerate research in systematic biology ( https://github.com/MaoYafei/TREEasy ).     

Paddock trees, parrots and agricultural production: An urgent need for large-scale, long-term restoration in south-eastern Australia

Summary Scattered trees, or ‘paddock trees’, are keystone structures, which provide multiple ecological values. However, they are in decline in many places. This has serious implications for species that use them, such as the vulnerable Superb Parrot (Polytelis swainsonii) of south‐eastern Australia. We outline three key aspects of the ecology, biology and distribution of the species that illustrate the implications of scattered tree decline. These are that (i) it depends on trees; (ii) it lives across agricultural landscapes; and (iii) it uses scattered tree landscapes dynamically in response to climate variation. We outline the dual challenge of maintaining populations of both scattered trees and the Superb Parrot over large scales and over the long term. Without urgent restoration action, a narrow bottleneck (where there are few mature trees) will make the long‐term future of the Superb Parrot precarious in these landscapes. We outline a vision for future landscapes that addresses this challenge, including the development of a form of Australian ‘wood‐pasture’. We suggest some ways that might be implemented at two scales. At the farm scale, we suggest (i) protecting what remnant vegetation we currently have; (ii) recruiting future large, old trees; (iii) sequentially setting aside land to ensure whole‐of‐farm tree regeneration; (iv) use of incentives to encourage restoration actions; and (v) using a revolving land fund to purchase and reorganize farms into economically and ecologically sustainable units. At the landscape scale, we suggest (i) the need for coordination of long‐term landscape restoration plans; (ii) the possible collaborative management of adjacent farms to ensure economic and ecological sustainability. We conclude that addressing the large‐scale and long‐term challenges of restoring scattered trees in landscapes occupied by the Superb Parrot could restore lost or diminished ecological services. This challenge illustrates the need for action at both the farm and the landscape scale that is planned over the short, medium and long term.     

The ecology,distribution, conservation and management of large old trees

Large old trees are some of the most iconic biota on earth and are integral parts of many terrestrial ecosystems including those in tropical, temperate and boreal forests, deserts, savannas, agro‐ecological areas, and urban environments. In this review, we provide new insights into the ecology, function, evolution and management of large old trees through broad cross‐disciplinary perspectives from literatures in plant physiology, growth and development, evolution, habitat value for fauna and flora, and conservation management. Our review reveals that the diameter, height and longevity of large old trees varies greatly on an inter‐specific basis, thereby creating serious challenges in defining large old trees and demanding an ecosystem‐ and species‐specific definition that will only rarely be readily transferable to other species or ecosystems. Such variation is also manifested by marked inter‐specific differences in the key attributes of large old trees (beyond diameter and height) such as the extent of buttressing, canopy architecture, the extent of bark micro‐environments and the prevalence of cavities. We found that large old trees play an extraordinary range of critical ecological roles including in hydrological regimes, nutrient cycles and numerous ecosystem processes. Large old trees strongly influence the spatial and temporal distribution and abundance of individuals of the same species and populations of numerous other plant and animal species. We suggest many key characteristics of large old trees such as extreme height, prolonged lifespans, and the presence of cavities – which confer competitive and evolutionary advantages in undisturbed environments – can render such trees highly susceptible to a range of human influences. Large old trees are vulnerable to threats ranging from droughts, fire, pests and pathogens, to logging, land clearing, landscape fragmentation and climate change. Tackling such diverse threats is challenging because they often interact and manifest in different ways in different ecosystems, demanding targeted species‐ or ecosystem‐specific responses. We argue that novel management actions will often be required to protect existing large old trees and ensure the recruitment of new cohorts of such trees. For example, fine‐scale tree‐level conservation such as buffering individual stems will be required in many environments such as in agricultural areas and urban environments. Landscape‐level approaches like protecting places where large old trees are most likely to occur will be needed. However, this brings challenges associated with likely changes in tree distributions associated with climate change, because long‐lived trees may presently exist in places unsuitable for the development of new cohorts of the same species. Appropriate future environmental domains for a species could exist in new locations where it has never previously occurred. The future distribution and persistence of large old trees may require controversial responses including assisted migration via seed or seedling establishment in new locales. However, the effectiveness of such approaches may be limited where key ecological features of large old trees (such as cavity presence) depend on other species such as termites, fungi and bacteria. Unless other species with similar ecological roles are present to fulfil these functions, these taxa might need to be moved concurrently with the target tree species.     

Managing mature forest features: The production,accuracy and ecological relevance of a landscape‐scale map

Mature trees and forests contain structural features such as tree hollows, large coarse woody debris and large spreading crowns that provide critical habitat for a wide range of species. These features can take hundreds of years to develop and require careful management to ensure their continued availability. Managing these features requires spatial mapping layers to facilitate landscape‐scale management. This paper outlines how a map of mature forest habitat was developed for Tasmania, Australia. The map was produced using spatial data on vegetation type, mature crown density and senescence, a global layer of forest loss data derived from satellite imagery, a database on timber harvest plans and a spatial layer on the extent of fire. The relationship between mapped mature habitat availability (high, medium, low or negligible) and tree hollow availability in wet forest areas was explored, complementing a similar published study in dry forests. The number of large trees likely to have hollows significantly increased with mapped mature habitat availability, although there was considerable variation and overlap between map categories. Data from a fauna locality database and two radio‐tracking studies showed that three of the vertebrate hollow‐using species examined (Swift Parrot, Common Brushtail Possum and the Tasmanian Long‐eared Bat) and nest records of a species reliant on large tree crowns (the Wedge‐tailed Eagle) were all more likely to occur in areas of higher mapped mature habitat availability. It is concluded that this map reflects the relative availability of tree hollows, is ecologically meaningful and will be useful when managing mature forest habitat at large spatial scales, but the variable accuracy of the map at fine scales needs to be taken into account.     

Age and Long-term Growth of Trees in an Old-growth Tropical Rain Forest, Based on Analyses of Tree Rings and 14C1

In an old‐growth tropical wet forest at La Selva, Costa Rica, we combined radiocarbon (¹⁴C) dating and tree‐ring analysis to estimate the ages of large trees of canopy and emergent species spanning a broad range of wood densities and growth rates. We collected samples from the trunks of 29 fallen, dead individuals. We found that all eight sampled species formed visible growth rings, which varied considerably in distinctiveness. For five of the six species for which we combined wood anatomical studies with ¹⁴C‐dates (ring ages), the analyses demonstrated that growth rings were of annual formation. The oldest tree we found by direct ring counting was a Hymenolobium mesoamericanum Lima (Papilionaceae) specimen, with an age of ca. 530 years at the time of death. All other sampled individuals, including very large trees of slow‐growing species, had died at ages between 200 and 300 years. These results show that, even in an everwet tropical rain forest, tree growth of many species can be rhythmic, with an annual periodicity. This study thus raises the possibility of extending tree‐ring analyses throughout the tropical forest types lacking a strong dry season or annual flooding. Our findings and similar measurements from other tropical forests indicate that the maximum ages of tropical emergent trees are unlikely to be much greater than 600 years, and that these trees often die earlier from various natural causes.     

How do trees die? Mode of death in northern Amazonia

Question: How do trees die in high‐mortality and low‐mortality Amazonian forest regions? Why do trees die in different ways? Location: Humid, lowland forests in Amazonian Peru and Venezuela. Methods: Patterns of multiple treefall and mode of death (standing, broken or uprooted) were recorded for trees ≥10 cm in diameter in permanent plots. Logistic regression was used to relate mode of death to tree diameter, relative growth rate and wood density. Results: Frequency of multiple death events was higher in high‐mortality northwestern (NW) than in low‐mortality northeastern (NE) Amazonia, but these events were small, averaging two trees killed per multiple death event. Breakage was the dominant known mode of death (51±8%) in the NW, with half of fatal breakages caused by other treefalls or breakages. Small and slow‐growing trees were more prone to breaking than uprooting. In NE Amazonia, the dominant known mode of death was standing (48±10%); these trees tended to be relatively large and slow growing. Broken trees in NE forests have a lower wood density than uprooted trees. Conclusions: The major mortality mechanisms differ in the two regions. In the NW it involves an interaction between physiological failure and mechanical failure (small size, slow growth and broken mode). In the NE it is mainly driven by physiological failure (large size, slow growth and standing mode). We propose that by creating different‐sized gaps the different dominant modes of death would favour species from different functional groups and so help to maintain the contrasting functional composition and mortality rates of the two regions.     

No evidence for consistent long‐term growth stimulation of 13 tropical tree species: results from tree‐ring analysis

The important role of tropical forests in the global carbon cycle makes it imperative to assess changes in their carbon dynamics for accurate projections of future climate–vegetation feedbacks. Forest monitoring studies conducted over the past decades have found evidence for both increasing and decreasing growth rates of tropical forest trees. The limited duration of these studies restrained analyses to decadal scales, and it is still unclear whether growth changes occurred over longer time scales, as would be expected if CO₂‐fertilization stimulated tree growth. Furthermore, studies have so far dealt with changes in biomass gain at forest‐stand level, but insights into species‐specific growth changes – that ultimately determine community‐level responses – are lacking. Here, we analyse species‐specific growth changes on a centennial scale, using growth data from tree‐ring analysis for 13 tree species (~1300 trees), from three sites distributed across the tropics. We used an established (regional curve standardization) and a new (size‐class isolation) growth‐trend detection method and explicitly assessed the influence of biases on the trend detection. In addition, we assessed whether aggregated trends were present within and across study sites. We found evidence for decreasing growth rates over time for 8–10 species, whereas increases were noted for two species and one showed no trend. Additionally, we found evidence for weak aggregated growth decreases at the site in Thailand and when analysing all sites simultaneously. The observed growth reductions suggest deteriorating growth conditions, perhaps due to warming. However, other causes cannot be excluded, such as recovery from large‐scale disturbances or changing forest dynamics. Our findings contrast growth patterns that would be expected if elevated CO₂ would stimulate tree growth. These results suggest that commonly assumed growth increases of tropical forests may not occur, which could lead to erroneous predictions of carbon dynamics of tropical forest under climate change.     

Modelling fallen branch volumes in a temperate eucalypt woodland: implications for large senescent trees and benchmark loads of coarse woody debris

Fallen branches are a substantial component of coarse woody debris and a key ecological resource. The depletion of stocks of coarse woody debris since European settlement has contributed to the degradation of Australian grassy box woodlands, including the loss of biodiversity. Restoration options for remnant woodlands include the augmentation of coarse woody debris stocks. However, the extensive modification of grassy box woodlands has left few reference sites for establishing benchmarks to guide such restoration. In this paper we demonstrate a method for predicting fallen branch debris loads in the absence of reference sites, using data from a yellow box–red gum woodland. Our methodology is in two stages: first, the total volume of branch debris under individual trees was modelled; and second, these models were applied to groups of trees to predict stand‐level loads of fallen branch debris. Although the models were developed for yellow box–red gum woodlands, the methodology would be applicable to other communities that lack reference sites. Predicted benchmark loads of fallen branch debris for yellow box–red gum woodland were between 7.0 m³ ha^?1 and 11.9 m³ ha^?1. Large senescing trees contributed the bulk of fallen branch debris. Model predictions indicated a 100‐cm diameter at breast height (dbh) tree was 10 times more likely to produce debris than a 50‐cm dbh tree, and if debris was present a 100‐cm dbh tree produced approximately 10 times the volume of branch debris produced by a 50‐cm dbh tree. These results highlight the importance of large senescing trees for the production of fallen branch debris and support the keystone role of large trees within remnant woodlands, and the need to conserve these structures. Our results also support the active management of regrowth woodland stands to facilitate the progression of individual trees to maturity and senescence. In particular, thinning of regrowth stands may promote the growth of retained trees, ensuring they contribute to fallen branch debris stocks with a minimum time lag.     

Hollow occurrence and abundance varies with tree characteristics and among species in temperate woodland Eucalyptus

Tree hollows are a critical but diminishing resource for a wide range of fauna around the world. Conservation of these fauna depends on sustainable management of tree species that produce the hollows on which they depend. This study addressed the need for empirical data about intraspecific and interspecific variation in hollow occurrence and abundance in woodland trees in Australia. We measured and performed hollow surveys on 1817 trees of seven species of woodland Eucalyptus in central‐western New South Wales, Australia. Trees were surveyed at 51 one‐hectare sites and about 30% of trees surveyed had multiple stems. Generalized linear mixed models that accounted for nestedness of stems within trees and trees within sites detected a significant amount of variation in hollow occurrence and abundance. Models for individual tree stems of live trees showed hollow probability and abundance increased with diameter at breast height (DBH) and with increasing senescence (form). Stems of Eucalyptus microcarpa Maiden had a higher probability of having hollows than similar DBH stems of Eucalyptus camaldulensis Dehnh., Eucalyptus melliodora A.Cunn. ex Schauer or Eucalyptus populnea ssp. bimbil L.A.S.Johnson & K.D.Hill. Dead stems in live trees were more likely to have hollows than live stems of similar DBH. Each stem in a multi‐stemmed tree had a lower probability of hollow occurrence and lower abundance of hollows than single‐stemmed trees of similar DBH. For stems of dead trees, hollow occurrence and abundance increased with DBH and differed depending on stage of senescence. A comparison of our data with other studies indicates regional variation of hollow abundances within tree species.