Wet Eucalypt Forest Research Articles

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

Summary 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.

Distribution and conservation status of the Mt Mangana stag beetle, Lissotes menalcas (Coleoptera: Lucanidae)

Lissotes menalcas (the Mt Mangana Stag Beetle) is an obligate log dwelling beetle and is presently classified as vulnerable under the Tasmanian Threatened Species Protection Act 1995. The distribution, habitat and conservation status of this species were investigated through a combination of collation of known locations and searches for the in decaying logs across likely areas of occurrence. L. menalcas was found to have a wide distribution in south eastern Tasmania and is now recorded from 34 localities. The species was found in a variety of wet forest habitats from old-growth mixed forest through to 23-year-old wet eucalypt silvicultural regrowth. About 12% of wet eucalypt forest within the predicted range of L. menalcas is formally reserved, and another 14% on Crown land is unlikely to be subject to logging. L. menalcas appears to tolerate both wildfire and clear felling with regeneration burning. Because the species depends on an ongoing supply of rotting logs for its long-term survival, plantation development will probably lead to the elimination of the species from such areas. Analysis of the likely impact of plantation establishment within its range over the next ten years indicates that it will not reach levels that would lead it to be considered as vulnerable. Thus, it is recommended that the status of the species be changed from vulnerable to rare. However, there is a need to determine the ecological sustainability of present forest management practices in relation to the decaying-log habitat and to continue to monitor the extent of clearing and modification of the species' habitat.

Fire history of the tall wet eucalypt forests of the Warra ecological research site, Tamania

Summary Fire history since 1850 was reconstructed by analysing tall wet eucalypt forest stands in the Warra long-term ecological research (LTER) site in southern Tasmania. Major fires occurred in 1898, 1906, 1914 and 1934. Fifty-seven percent of the forest has remained unburnt since 1850. Sixty percent of the forest burnt since 1850 occurs as mixed age stands, while 40 percent is pure regrowth. Ring counts of stumps of three veteran eucalypt trees indicated that the mature and oldgrowth forests of the Warra site represent a number of pre-1850 fires. One extant oldgrowth eucalypt stand was estimated to be over 450 years old. The common occurrence of multi-aged wet eucalypt stands has silvicultural implications where a management objective is to emulate pre-existing stand structures. While the fire history reported here is limited mainly to the period since 1850, it provides a good basis for understanding the current stand structures of the tall wet eucalypt forests of the Warra site. Such an understanding is essential to interpret results from current and planned ecological studies associated with the LTER program at Warra.

Seasonal patterns of activity in geometrid moths (Lepidoptera: Geometridae) from a lowland and highland eucalypt forest in Tasmania

Activity patterns of geometrid moths were compared in two areas, one in wet eucalypt forest at high altitude and the other in mainly dry forest at low altitude in Tasmania. One hundred and twenty‐six species were able to be grouped into six distinct groups (i.e. spring, spring and summer, summer, autumn, autumn and winter, all year) in terms of their patterns of seasonal occurrence. Three of the 16 species common to the two sites differed in their seasonality of occurrence, with their length of occurrence being extended at Old Chum Dam compared with Central Plateau. Moth numbers strongly reflected monthly changes in minimum temperature, with moth activity being greater at the high altitude site than at the low altitude site for an equivalent temperature. However, a given change in minimum temperature led to an equivalent change in the magnitude of moth numbers at both sites. These seasonal patterns of occurrence must be considered in the planning of biodiversity surveys.

Managing native forest for Blackwood (Acacia melanoxylon) production in north western Tasmania

Summary Blackwood is a common species in the native forests of north western Tasmania where over 70% of Tasmania's blackwood is cut. It occurs in significant volumes in swamp forests, riverine rainforests and as an understorey component of wet eucalypt forests. The biggest asset for native forest blackwood establishment is the ground-stored seed resource which germinates after disturbances, including logging. Other important silvicultural considerations are form and browsing. The blackwood swamps were logged selectively until the 1970s when patch clearfelling and burning was introduced, with fencing of the regeneration to prevent browsing. This has subsequently been refined so that swamp forests with a high component of rainforest species are logged selectively to conserve these late successional species, and the use of fire is now minimised. Poisoning with 1080 is used as an alternative to fencing to reduce the level of browsing. Some riverine rainforest is selectively logged for blackwood although many areas are unavailable due to Forest Practices Code requirements. Retained rainforest trees provide lower branch suppression although myrtle density can be reduced by the myrtle wilt disease. Adequate browsing protection and good form are difficult to achieve in riverine environments. Selected areas of wet eucalypt forest with a high blackwood density are clearfelled, burnt, sown with eucalypts and fenced to protect the abundant blackwood regeneration resulting from ground-stored seed. Costs of $270 ha−1 were estimated for the fencing. A comparison of eucalypt and blackwood stocking in similar fenced and unfenced coupes up to 11 years old showed the fenced coupes had a mean blackwood density of 2500 stems ha−1 while unfenced coupes averaged 70 stems ha−1. There was no significant difference in the eucalypt stocking between fenced and unfenced areas. Development of blackwood prescriptions continues, with further work in the blackwood swamps to reduce or eliminate the use of 1080 poison, while the emphasis in wet eucalypt forests is towards cheaper fencing.

The impact of forest harvesting on water yield: modelling hydrological changes detected by pollen analysis

Abstract Forest harvesting practices have been shown to have a hydrological impact that is akin to bushfire regeneration. Fine resolution fossil pollen studies in the upper Delegate River basin, East Gippsland, Australia, have revealed large changes in the reproductive activity of aquatic plants synchronous with the onset of harvesting activities. This paper seeks to establish an explanation for these changes by applying a 2-parameter regional bushfire yield trend model to the wet eucalypt forests above the pollen core site. Using histories of piecemeal coupe (harvesting plot) development, the model was used to reconstruct annual runoff yields between 1970 and 1991 assuming zero harvesting. The results indicated a progressive reduction in simulated annual yields (relative to the zero disturbance scenario) attaining between 20 and 55% loss by 1987/1988. Given the historic rate of harvesting, over a 50% reduction of water yield is expected to occur by 2005 due to factors including enhanced forest transpiration. Such hydrological changes would have significant implications for downstream fauna and flora and for stream dynamics.

A Floristic Comparison of Vascular Species in Tasmanian Oldgrowth Mixed Forest With Regeneration Resulting From Logging and Wildfire

About 20% of Tasmania's wet eucalypt forest is mixed forest, i.e. having a rainforest understorey and a eucalypt overstorey. While one-third of the mixed forest is formally reserved, much of the remainder is subject to logging on an 80-100 year rotation which is insufficient for the redevelopment of mature mixed forest. The routine silvicultural regeneration treatment for wet eucalypt forests is to clearfell, burn and sow with eucalypt seed. A comparison of the Vascular floristics of 20-30-year-old silvicultural and wildfire regeneration with oldgrowth mixed forest showed that most species common in oldgrowth mixed forest were represented in approximately similar frequencies in silvicultural regeneration and wildfire regeneration. The major floristic difference between the two regeneration types was the much lower frequency of oldgrowth epiphytic fern species in silvicultural regeneration and a higher frequency of a sedge species often associated with disturbed areas. However, after a single logging treatment, the vascular plant floristics of silvicultural regeneration were sufficiently similar to wildfire regeneration to assume that, in the absence of further logging or fires, the silvicultural regeneration could become mature mixed forest and eventually rainforest. Further work is required to determine whether regrowth mixed forest can be logged at 80-100 years and still retain sufficient rainforest elements to eventually return to mixed forest within the life span of the dominant eucalypts. The critical factor in the silvicultural perpetuation of mixed forest may be rotation length rather than regeneration treatment.

The phytosociology and synecology of Tasmanian vegetation with Callitris

Eleven discernible floristic plant communities were identified in vegetatlon containing Callitris in Tasmania. C.rhomboidea and C. oblonga largely segregate into two sets of communities. These sets occupy distinctly different parts of the environmental range of Callitris in Tasmania. Callitris co-occurs with at least 14% of the Tasmanian native higher plant flora in rainforest, wet eucalypt forest, dry eucalypt forest, grassy woodland, scrub and heath, and is dominant in some quadrats of most communities. The major measured correlates of floristic variation in the data set were temperature and precipitation conditions. The combination of the wide ecological range demonstrated by the data set and the highly restricted nature of Callitris distribution suggests that the taxon has a range much diminished by shorterm perturbation. Callitris may have been part of an extensive dry rainforest formation in eastern Tasmania before people invaded the area.

Book reviews

Books Reviewed in this Article: Environment and Resource Economics: An Introduction M. Common The Wet Eucalypt Forests of Tasmania J. G. Kirkpatrick, R. J. Peacock, P. J, Cullen and M. G. Neyland Coastal‐Offshore Ecosystem Interactions (Lecture Notes on Coastal and Estuarine Studies 22) B. O. Jansson Hotting Up Brian Mathew Crowley Ecology of Birds: An Australian Perspective H. Ford

Holocene Forest and Wetland Vegetation Dynamics at Barrington Tops, New South Wales

Pollen analyses from eight sites and fifty-seven radiocarbon analyses from nine sites are described to give a vegetation history and chronology across the Barrington Tops Plateau. It is shown that sites record local plant community history, and that between-site comparisons enable identification of vegetation change across the Plateau. At present, the area above 1000 m supports a mosaic of sub-alpine grasslands, montane eucalypt forests, wet eucalypt formations, cool-temperate rainforests and wetland communities. By 9000 BP these had all been well established but there have been changes in the contributions of each vegetation type to the mosaic. In the period from 6500 to 3500 BP, cool temperate rainforest covered a larger area of the Plateau in the east, while wet eucalypt forests were more extensive in the west than at the present. This could have resulted from an increase in temperature and in summer rain-bearing winds from the south and east. Retreat of these forest types began around 5000 BP and by 1600 BP large areas on the west were replaced by montane eucalypts with a sub-alpine grassland understorey. Some expansion of cool-temperate rainforest began in the same region from about 1500 BP, although this was mainly restricted to sheltered localities. In the wetland areas there was a general trend from open water with aquatics to higher productivity with sedges and Sphagnum-forming hummock/hollow communities around 3500 BP. Peat formation then became widespread and expanded within the last few centuries when further wetland areas became established, particularly in the Gloucester Tops

Genotypes of Armillaria hinnulea in wet sclerophyll Eucalypt forest in Tasmania

Forty six genotypes of Armillaria hinnulea were detected in 1.1 ha of wet sclerophyll eucalypt forest in southern Tasmania. Many genotypes were restricted to individual or adjacent host trees although a few had a wider distribution. The number of genotypes per unit area was much greater than for Armillaria luteobubalina a species which occurs in dry sclerophyll eucalypt forests.

Vegetation and Modern Pollen Rain From the Barrington Tops and Upper Hunter River Regions of New South Wales

Vegetation was mapped using existing maps, Landsat interpretation, aerial photograph interpretation and some verification by ground surveys. Twenty-five moss cushions were collected to identify pollen rain and pollen indicators of vegetation for use in fossil pollen interpretation. Eucalyptus (10%), Poaceae (4-10%), Casuarina (4-5%), Asteraceae (Tubuliflorae) (0-4%) and Cyperaceae (0-2%) were the general components in the pollen rain of the region. Subtropical rain forest was characterized by Backhousia and low values of a wide range of taxa. Cool temperate rain forest had Nothofagus values above 40% and Eucalyptus values below 20%. Subalpine grasslands had Poaceae values above 45%, Eucalyptus values below 15% and small quantities of Epacridaceae and Goodeniaceae pollen. Subalpine forest and wet eucalypt forest formations had very similar pollen representation and could be confused in pollen spectra. However, Monotoca, Banksia, Leptospermum pollen and fern spores were more common in the wet eucalypt forests. Dry eucalypt formations were characterized by 2-20% values of Bursaria, Callitris and Dodonaea as well as eucalypt values.