STEM DISTRIBUTION IN IRREGULAR FORESTS

The author outlines the fifty years history of national professional forestry education in Canberra by the Australian Forestry School and its successor the Australian National University Department of Forestry.     

Silvicultural impacts in jarrah forest of Western Australia: synthesis,evaluation, and policy implications of the Forestcheck monitoring project of 2001–2006

This paper, the final in a series of ten papers that report the impact of silvicultural treatments (harvesting and associated burning) in jarrah (Eucalyptus marginata) forest, reviews these papers and explores similarities and disparities. More than 2500 species were processed, dominated by macro-invertebrates, vascular flora and macrofungi. Few significant impacts were evident, and most species groups were resilient to the disturbances imposed. Regeneration stocking did not meet specified standards on two gap release and seven shelterwood grids subjected to silvicultural treatment in the period 1988–2002. Six treated grids had a retained basal area of more than 18 m² ha^?1, which obviated the need for further regeneration. More than 50 y may be needed for biological processes to reverse the increase in bulk density of soil caused during harvesting. Cryptogams (especially lichens) were the species group most sensitive to disturbance, although recovery of species richness was nearly complete 10 y after disturbance. For cryptogams and vascular flora, species recorded in only one grid (singletons) were more likely to occur on reference grids than on silviculturally treated grids. For all species groups studied, the imprint of harvesting 40 or more years earlier on species composition had become indistinguishable from that on grids never harvested. Soil nutrient status correlated with species richness for fungi on wood (negatively), light-trapped invertebrates (positively), birds (positively) and terrestrial vertebrates (frogs, reptiles and mammals, negatively). Silvicultural disturbance (timber harvesting and associated burning) correlated with species richness for fungi on wood (positively), terrestrial vertebrates (positively) and cryptogams (negatively). Time since the last (prescribed) fire did not correlate with any species group. Plant disease decreased species richness of light-trapped invertebrates by about 35%. Very few taxa were sufficiently widespread or sufficiently responsive to silvicultural disturbance to be of value as bio-indicators, demonstrating the superiority of biodiversity monitoring over bio-indicator monitoring. It is recommended that FORESTCHECK be expanded into a biological survey of the lower south-west of Western Australia.     

A refined method for estimating capsule crops in individual jarrah (Eucalyptus marginata) crowns

An accurate measure of the number of capsules in the crowns of jarrah (Eucalyptus marginata) trees is needed to assess the potential for seedling regeneration prior to silvicultural treatment in jarrah forests. The current method of estimating capsule crops on jarrah trees uses stem diameter and estimates of capsule density in the crown, but has not been fully validated. In this study, we sought to develop an accurate and practical method of assessing capsule crops in the crowns of individual jarrah trees. We did this by measuring a number of tree characteristics prior to felling them. A total of 24 trees were selected, spanning a range of sizes and crown conditions, and the total number of capsules was counted for each tree. Multiple linear regression was used to model capsule number against various combinations of eight different tree/crown variables, with model fit compared using an adjusted coefficient of determination (adjR²). The final model recommended for field use included three easily measured variables (stem diameter, subjective assessment of capsule density, and subjective assessment of capsule clump distribution in the crown) and had a high degree of predictability (adjR² = 0.83), which was the same as that of the full model. This method substantially improved estimates of crown capsule numbers compared with the method currently used (adjR² increased from 0.29 to 0.83), which tended to underestimate canopy capsule numbers.     

Thoughts towards a forest wildlife management strategy

Wildlife management is becoming increasingly important in Australian forestry and this paper presents the conceptual framework for a relevant wildlife management strategy. Wildlife management in Australian forests might best be co-ordinated nationally. Because of the changing public perceptions of the role forestry must play in wildlife management in native forest, suggestions are made for the modification of present practice which will benefit both timber and wildlife management. The paper also reviews information requirements, the issues and the concerns important in the determination of such a strategy. Information bases are necessary for sound forest wildlife management. The concepts of minimum viable population and optimum habitat are discussed as well as wildlife management design in terms of zoning and the two integrated methods of core population and dispersed population techniques. It is argued that the standards of forest management have to improve to achieve the necessary balance between timber production and wildlife management. This will require an understanding of the aforementioned two concepts and the options available for integrating wildlife and timber management. Priority should be given to the determination of optimum habitat of species, forest site classification and the ranking of wildlife species according to management need.     

Tree Decline and Mortality in Selectively Logged Eucalypt Forests in Central Victoria

The occurrence, symptoms and impact of a dieback disease in selectively logged, mixed species eucalypt forests in central Victoria are described. E. obliqua E. viminalis and E. globulus subsp. bicostata are the main species affected, although a range of other eucalypt and some Acacia species are also killed. Dieback affects trees at all stages of growth and it is estimated that 1400 ha of high quality production forest are severely affected, with a further 600 ha moderately affected, Stands with severe and moderate dieback are estimated to have respective sawlog volume increments of about one half and two thirds that of an average healthy stand. An unidentified species of A miliaria is consistently associated with dead or dying trees. Disease development is associated with selective cutting in pole stage or mature stands, but no consistent associations between site, other silvicultural factors or disease have yet been established. Past drought stress may have influenced disease development in some areas.     

Tree hollow development in wet and dry sclerophyll eucalypt forest in south-east Queensland,Australia

Tree hollow development was studied in Eucalyptus pilularis (blackbutt) and Eucalyptus microcorys (tallowwood) in wet sclerophyll forests, and Eucalyptus signata (scribbly gum) in dry sclerophyll forest in south-east Queensland, Australia. In all three tree species hollow development appeared to be primarily initiated by fungal infection entering trees through dead branches and/or branch stubs rather than from fire scars. The process of hollow development appeared to commence when the trees were around 100 years old.

The size and abundance of hollows increased with the size and age of the tree but there were apparent differences between species. Hollows were found in the majority (>50%) of E. pilularis trees above 100 cm dbh. By contrast most E. microcorys and E. signata larger than 80 cm dbh had hollows. There was a similar difference between species in the numbers of hollows present in trees of different size. E. pilularis trees 100–110 cm dbh had two hollows per tree but this number were present in much smaller E. microcorys or E. signata trees. The rate of growth of E. pilularis is faster than either E. microcorys or E. signata and the rate of hollow formation appears to be dependent on the growth rate of the species. This suggests that hollows begin to develop after comparable times in the different species although the time taken for large hollow development differs between the species.

The analyses suggest that the smallest arboreal marsupials and hollow dependent birds could recolonise regrowth E. pilularis trees after about 165 years but hollows suitable for larger animals would not be available for around 210 years. This time frame would be longer for slower growing species of trees. Some of the implications of this work in connection with management practices that aim to ensure the maintenance of hollow-dependent fauna in these forests are discussed.