M.T. Tanton

The conservation of arboreal marsupials in the montane ash forests of the Central Highlands of Victoria, South-East Australia: III. The habitat requirements of leadbeater's possum Gymnobelideus leadbeateri and models of the diversity and abundance of arboreal marsupials

Factors influencing the presence and abundance of leadbeaters possum Gymnobelideus leadbeateri McCoy and the diversity and abundance of other species of arboreal marsupials in montane ash forests were determined from logistic and Poisson regression analyses. The presence of G. leadbeateri was related to the number of trees with hollows and the basal area of Acacia spp. There was a positive correlation between the abundance of the animal and the number of trees with hollows, the quantity of decorticating bark and a negative correlation with the number of shrubs and the slope of the site. The diversity of arboreal marsupials was greatest on sites with a large number of trees with hollows, a high basal area of Acacia spp., a large quantity of decorticating bark and south- or east-facing sites. A model containing similar variables was developed for the abundance of arboreal marsupials. This model also produced a significant negative correlation with the number of stumps resulting from timber harvesting operations. Our findings highlight the deficiencies of current measures to conserve arboreal marsupials which are dependent on hollows in trees, when these forests are harvested by clear-felling.

Characteristics of hollow-bearing trees occupied by arboreal marsupials in the montane ash forests of the Central Highlands of Victoria, south-east Australia

Abstract A total of 1125 hollow-bearing trees was observed for the presence of arboreal marsupials in the montane ash forests of the Central Highlands of Victoria, south-east Australia. Different species of arboreal marsupials exhibited preferences for hollow-bearing trees with different characteristics. Gymnobelideus leadbeateri (Leadbeaters possum) selected short, fat trees with numerous holes and a large quantity of dense surrounding vegetation. Very large hollow-bearing trees were favoured as nest sites by Petauroides volans. Petaurus breviceps preferred trees with a large number of fissures, whereas trees favoured by Antechinus stuartii were tall and thin. Trees selected as nest sites by Trichosurus caninus were typically short and fat with few holes. Our results provide evidence of resource partitioning of hollow-bearing trees amongst arboreal marsupials. Clear-felling of montane ash forest on an 80–120-year rotation will have a highly detrimental effect on arboreal marsupials by substantially reducing the number and range of types of hollow-bearing trees required to support the complete diversity of species. The 80–120-year interval between logging operations will result in trees being harvested well before they develop characteristics which make them suitable nest sites for arboreal marsupials.

The abundance and development of cavities in Eucalyptus trees: a case study in the montane forests of Victoria, southeastern Australia

Abstract A study of the abundance of cavities in Eucalyptus regnans, Eucalyptus delegatensis, Eucalyptus nitens, Eucalyptus obliqua and Eucalyptus cypellocarpa is described. The investigation used a database of 2315 living and dead trees with cavities, measured on 523 sites each of 3 ha throughout the montane ash forests of the Central Highlands of Victoria, southeastern Australia. Poisson regression analysis was used to examine the relationships between the number and type of cavities and a range of attributes of trees. These analyses demonstrated that, for all species of trees, the abundance of holes, fissures and hollow branches increased with tree diameter. Log-linear analysis of contingency tables demonstrated that various combinations of cavity types typically occur. Patterns of co-occurrence of cavities changed significantly according to the diameter, height and form of trees. The application of restricted maximum likelihood estimation (REML) for examining multi-level data, enabled the relatioships between the number of cavities, tree characteristics and site parameters to be analysed The characteristics of trees that were important were height, diameter and form. Site parameter that had a significant influence on the total number of cavities in trees included slope, latitude and stand age. This highlights the range of factors, at several measured spatial scales, that may influence the development of cavities in Eucalyptus trees. Although the various relationships derived in this study were highly significant, the statistical models had limited predictive ability. Thus for any given tree the development of cavities will be influenced by site and tree attributes as well as highly stochastic episodic events that may occur during its lifetime. The key findings from the study are discussed in terms of their relevance to forest wildlife management.

The conservation of arboreal marsupials in the Montane ash forests of the central highlands of Victoria, Southeast Australia: I. Factors influencing the occupancy of trees with hollows

Abstract A total of 1125 trees with hollows on 152 sites in the montane ash forests of the Central Highlands of Victoria was observed for the presence of arboreal marsupials. One of every 3 trees was occupied by an arboreal marsupial and

The conservation of arboreal marsupials in the montane ash forests of the Central Highlands of Victoria, south-east Australia. II: The loss of trees with hollows and its implications for the conservation of leadbeater's possum Gymnobelideus leadbeateri McCoy (Marsupialia: Petauridae)

Abstract Leadbeaters possum, Gymnobelideus leadbeateri McCoy, a rare and endangered arboreal marsupial inhabiting the montane ash forests of the Central Highlands of Victoria, is dependent on hollows in mature and dead trees. The number of trees with hollows that had collapsed between 1983 and 1988 was assessed at 32 sites located in ash-type forests in the Central Highlands of Victoria, south-eastern Australia. The extent of decay amongst standing trees with hollows was also determined. A simple stochastic model of the decline and collapse of these trees was calculated from the data. The model was applied to data on trees with hollows collected from 497 other sites within the study region to predict their future abundance and availability over the next 75 years. Almost 18% of the total measured population of trees had collapsed in the 5-year interval between assessments. A subjective categorization of the form of the trees was the best predictor of the susceptibility to collapse. More senescent trees were those most vulnerable to collapse and they also exhibited the highest rates of decay. Stochastic models based on transition probabilities of trees with hollows predict that very few of the sites surveyed will support such trees in 50 years time and imply a severe future shortage of trees containing suitable nest hollows for wildlife until at least the end of the next century. Silvicultural practices which result in ash-type forests being clear-felled on a short-term (80–120 year) rotation will further accelerate and exacerbate the anticipated shortage. The implications of these effects for wildlife, particularly G. leadbeateri , are discussed.

Hollow selection by vertebrate fauna in forests of southeastern Australia and implications for forest management

Abstract We examined the types of hollows, and types of hollow-bearing trees, occupied by vertebrate fauna in temperate eucalypt forests in southeastern Australia. Hollow-bearing trees are selected for retention in wood production forests to mitigate the effects of logging on hole-nesting fauna. A total of 471 hollows was examined in 228 trees felled as part of routine logging operations. Fauna had occupied 43% of all hollows (⩾2cm minimum entrance width; ⩾5cm depth). Hollows with small (2–5cm), medium (6–10cm) and large (>10cm) minimum entrance widths had occupancy rates of 29, 44 and 62%, respectively. The internal dimensions of hollows, especially hollow depth, were the best predictors of hollow occupancy, even when variables measured at the tree and site levels were considered. Fauna occupied 57% of all hollow-bearing trees. In a Poisson regression model, the number of hollows in trees that contained evidence of occupancy was positively associated with: (1) the total number of hollows visible in the tree; (2) the proportion of the trees crown that contained dead branches; and (3) tree diameter. The number of different vertebrate species that occupied trees was positively associated with the same explanatory variables except tree diameter. Thus, our results suggest that trees with multiple hollows and dead branches in the crown should be preferentially selected for occupancy by hollow-using fauna. Our results suggest that trees with the largest diameter are not the most suitable for retention. Possibly because they contain proportionally fewer hollows with small entrances, which are favoured by some vertebrate species.

The effects of slash burning on the mortality and collapse of trees retained on logged sites in south-eastern Australia

Abstract Trees may be retained on logged sites in eucalypt forests for a number of reasons, such as to provide wildlife habitat, for future wood production, for aesthetic reasons, to mitigate erosion, or to provide seed for regeneration. These trees may be required to survive for a considerable period to meet these objectives. Logged sites in eucalypt forests are routinely treated with a post-logging slash-burn to reduce fuel loads and facilitate regeneration. We compared rates of mortality and collapse among trees retained on logged sites that were routinely treated with a high-intensity slash-burn with logged sites routinely treated with a low-intensity slash-burn. All observations were made 2–5 years after logging. The proportion of all retained trees that were killed after logging was 37% on sites treated with a high-intensity slash-burn and 14% on sites treated with a low-intensity slash-burn. The rate of collapse among retained trees over the same period was 1.5 and 0.5%, respectively. Results of logistic regression models indicated that trees retained on logged sites were more likely to die and collapse if the site was treated with a high-intensity slash-burn; however, trees were also more likely to die if the basal area of trees retained on the site was relatively low and the site had a northerly aspect. Mortality was similar among all diameter classes on sites treated with a high-intensity slash-burn. Some of the objectives of retaining trees on logged sites, such as perpetuating hollow-bearing trees for wildlife, may be compromised where high-intensity post-logging slash-burns are employed.

Foraging patterns of the long-nosed potoroo (Potorous tridactylus) for hypogeal fungi in mixed-species and regrowth eucalypt forest stands in southeastern Australia

Abstract Foraging activity of the long-nosed potoroo (Potorous tridactylus), a medium-sized ground-dwelling marsupial, was monitored in a multi-aged eucalypt forest site and a regrowth eucalypt forest site in southeastern Australia. The probability of occurrence, abundance and characteristics of diggings left in the soil profile by P. tridactylus while foraging for hypogeal (underground) fungal fruiting bodies, were recorded in relation to topographic location. We simultaneously obtained data on the distribution of animals from trapping records at both sites. In the multi-aged forest site, the probability of occurrence of diggings was higher in midslope-sheltered and gully locations than elsewhere in the catchment. In contrast, the abundance of diggings was similar across most topographic locations, though increasing in late autumn and winter, particularly in gully locations. This was in response to increased production of hypogeal fruiting bodies of some fungi. The depth of digs decreased concomitantly with this shift in foraging pattern. Thus, digs in gully locations were shallower than digs in ridge and midslope locations. At the regrowth forest site, the probability of occurrence and abundance of diggings of P. tridactylus was significantly higher in midslope-sheltered aspects than elsewhere in the catchment. Dig depth was shallower in gully sites than ridge or midslope sites, but did not change over time in any seasonal pattern. Differences in the probability of occurrence, abundance and characteristics of diggings of the two study populations partially reflect differences in the use of hypogeal fungi as a food resource. The distribution of trapped P. tridactylus at both study sites did not entirely reflect patterns of foraging, highlighting the limitations of this type of data in interpreting patterns of resource use by forest-dwelling mammals. The utilisation of different slope and aspect classes by P. tridactylus for foraging has important implications for the management of mycophagous mammals in multiple-use forests.

Within-tree distribution of attack by Hypsipyla robusta Moore (Lepidoptera: Pyralidae) in Australian Red Cedar (Toona australis (F. Muell.) Harmes)

Abstract Field and laboratory evaluations were made of the within-tree distribution of attack of Hypsipyla robusta in Australian Red Cedar (Toona australis). Proportions of shoots attacked by the insect increased with shoot height, relative shoot height, shoot length, shoot basal diameter and shoot slenderness (shoot length/shoot basal diameter). The most significant factor influencing the log-odds of attack of shoots was their relative height. Shoots positioned at above 90% of tree height were attacked twice as often as the lower-positioned shoots. This suggests that terminal shoots would be among the first to be attacked once a tree is attacked. There was a gradual shift of feeding loci with respect to host tissues as the larva aged. Feeding by larvae of the first two instars was found most often in terminal foliage or previously damaged tissues of shoots or tree stems. Pith-feeding (tunnelling) started at the later 2nd instar. On average, a larva initiated feeding in a mean of 5.4 different locations during its life time, with a minimum of three and a maximum of 11. Switching of feeding loci was most frequent during early 1st instar and much of the 3rd and early 4th instars.

Factors affecting population densities of the Common Wombat, Vombatus ursinus, in plantations of Pinus radiata

Abstract Population densities of wombats were estimated in eucalypt forest, and in 1-, 3-, 6-, 10-, 15-, 20- and 25-year-old pine plantations. There was a significant difference in the numbers of wombats inhabiting the different types and ages of forest. Factors contributing to the fluctuating population densities were investigated. There was a strong correlation between the number of wombats and the number of medium and major burrows in an area. Where burrows are not the limiting factor, grass (the dominant food of the wombat) becomes an important requirement. These findings are of particular importance in the management of plantations if the aim is to sustain wombat populations in all stages of pine forest. Management strategies to enhance the multiple use of pine plantations should aim to minimise disturbance of burrows throughout forestry operations. In particular, burrows should be conserved during the initial clearing stages. The timing of thinning of plantations also affects the availability of food in plantations. At present, this is left until the canopy has completely closed over and no grasses are present. This initial thinning could be brought forward.