Forests Of South-eastern Australia Research Articles

Impact threshold for an alien plant invader, Lantana camara L., on native plant communities

Alien plant invaders significantly threaten native community diversity, although it is poorly understood whether invasion initiates a linear or non-linear loss of resident species. Where low abundances of an invader have little impact on native species diversity, then a threshold level may exist, above which native communities rapidly decline. Our aim was to assess the broadscale effects of an alien thicket-forming shrub, lantana ( Lantana camara L.), on wet sclerophyll forest in southeastern Australia. Vascular plant species richness, abundance and composition were measured and compared along a gradient of lantana invasion. There was a strong negative non-linear relationship between native species richness and lantana cover, indicative of an impact threshold. Native species richness remained stable below 75% lantana cover, but declined rapidly above this threshold level, leading to compositional change. Thus, sparse lantana infestations had evidently little effect on the resident community, with impacts elicited at an advanced stage of invasion. The impact of lantana was pervasive, with all major structural groups (i.e. ferns, herbs, shrubs, trees and vines) exhibiting significant species losses; however, the rate of species loss was relatively greater for tree and shrub species, signalling a shift in vegetation structure from tall open forest to low, dense lantana-dominated shrubland. Potentially, broadscale conservation of species diversity could be achieved by maintaining lantana infestations below the 75% cover impact threshold at sites containing regionally common species that are also widely represented in non-invaded vegetation. This would enable targeted invader eradication at sites of high conservation value (i.e. those containing regionally rare species or endangered ecological communities).

Designing old forest for the future: Old trees as habitat for birds in forests of Mountain Ash Eucalyptus regnans

Old trees are one of many habitat attributes associated with old forests. They are known to be required by many wildlife species including cavity-dependent birds. Forest managers need to select strategies for retaining and regrowing old trees to maintain suitable numbers over time at appropriate configurations in the forest landscape. This paper presents data from wet forests in south-eastern Australia to help elucidate the effects of different strategies on forest birds as one element of biodiversity that needs to be conserved in these forests. Bird abundance was assessed by standard area search at 117 sites in forests of Mountain Ash Eucalyptus regnans in the Victorian Central Highlands, over the course of two spring-summer breeding seasons from 1996 to 1998. The sites contained 60-year regrowth from extensive wildfires in 1939, along with varying numbers of older trees that had survived the fire. Some of the old trees were dead and at varying stages of decay. Numbers of old trees were counted at each site and a range of other habitat measurements taken. Birds were considered by species or guilds of species (feeding and nesting guilds). Bird abundance data were regressed against numbers of old trees and other relevant habitat data. Cavity-nesting birds were positively related to numbers of old trees, and especially to those that remained alive. Bird species that nest in longitudinal cavities in small branches (spouts) were rare at sites that lacked old trees, and were related strongly to numbers of live old trees. Large cavity-nesters were related to numbers of live old trees or all old trees. Treecreepers correlated less strongly, perhaps because they use cavities in decaying snags and stumps as well as large old trees. Honeyeaters and Mistletoe birds were also positively associated with numbers of live old trees, although they do not need cavities. Total bird abundance was positively related to live, dead or all old trees. Several other relationships were found. For example, shrub foragers were related positively to abundance of tall shrubs but not low shrubs; wattle foragers were related positively to abundance of wattles (especially Silver Wattles Acacia dealbata); and Eastern Spinebills Acanthorhynchus tenuirostris were positively associated with abundance of Mountain Correa Correa lawrenciana (the flowers of which provide a major source of nectar). Non-linear relationships between bird abundance and densities of old trees were found for at least two cavity-nesting bird species. The relationship was convex for Striated Pardalote Pardalotus striatus (optimum density 5–12 live old trees/ha) and mildly concave for Crimson Rosella Platycercus elegans. This suggests that the former would benefit from strategies to disperse old trees among regrowth at suitable scales whereas the latter would benefit from strategies to produce clumped distributions of old trees. However, Striated Pardalotes showed a strong preference for live old trees, which cannot easily be kept alive among regrowth after logging or fire, suggesting clumped retention may be more practical for that species too. Three other species showed weak evidence of non-linear responses, but most species showed no significant evidence of departure from linearity. No species or guild showed strong evidence of a threshold level of old tree density (above ∼1 ha −1) below which those birds would not occur. Hence for most of the diurnal birds considered in this study, old trees appear to be useful in proportion to the overall number of suitable old trees that can be retained and regrown (rather than their spatial pattern), and especially the number that can be kept alive. Clumped retention strategies give the best chance of keeping many retained trees alive in retained patches. Otherwise, spacing patterns should be a secondary consideration, except where they are known to be important for species such as owls and arboreal mammals.

The Turbulent Lagrangian Time Scale in Forest Canopies Constrained by Fluxes, Concentrations and Source Distributions

One-dimensional Lagrangian dispersion models, frequently used to relate in-canopy source/sink distributions of energy, water and trace gases to vertical concentration profiles, require estimates of the standard deviation of the vertical wind speed, which can be measured, and the Lagrangian time scale, T L , which cannot. In this work we use non-linear parameter estimation to determine the vertical profile of the Lagrangian time scale that simultaneously optimises agreement between modelled and measured vertical profiles of temperature, water vapour and carbon dioxide concentrations within a 40-m tall temperate Eucalyptus forest in south-eastern Australia. Modelled temperature and concentration profiles are generated using Lagrangian dispersion theory combined with source/sink distributions of sensible heat, water vapour and CO2. These distributions are derived from a multilayer Soil-Vegetation-Atmospheric-Transfer model subject to multiple constraints: (1) daytime eddy flux measurements of sensible heat, latent heat, and CO2 above the canopy, (2) in-canopy lidar measurements of leaf area density distribution, and (3) chamber measurements of CO2 ground fluxes. The resulting estimate of Lagrangian time scale within the canopy under near-neutral conditions is about 1.7 times higher than previous estimates and decreases towards zero at the ground. It represents an advance over previous estimates of T L , which are largely unconstrained by measurements.

Small mammal populations in a eucalypt forest affected by fire and drought. I. Long-term patterns in an era of climate change

This paper reports a study of ground-dwelling, small mammals in coastal eucalypt forest in south-eastern Australia from 1970 through 2005. During this time, the study area burnt in an intense fire in December 1972 and was partially burnt in November 1980. Both fires were associated with prolonged drought. The mammals studied comprised two dasyurid marsupials, Antechinus agilis and A. swainsonii, two native murid rodents, Rattus fuscipes and R. lutreolus, and the introduced house mouse Mus musculus. After intensive sampling throughout the year from 1970 through 1972 to establish basic ecological and population parameters of the small mammal community, populations were sampled annually during late autumn and early winter before the onset of breeding. There were marked differences in the annual (autumn/winter) abundances of all species; numbers of A. agilis ranged from 4 to 142 individuals; A. swainsonii 0 to 43; R. fuscipes 4 to 54; R. lutreolus 0 to 11; M. musculus 0 to 23. Following the 1972 fire, numbers fell to the lowest level recorded during the study and each population subsequently disappeared from the plot between the 1973 and 1974 winter censuses. The less intense 1980 fire did not lead to extirpation, but numbers of A. agilis, A. swainsonii and R. fuscipes declined as drought conditions persisted through 1983. R. lutreolus occurred consistently only following the fires, when a grassy ground vegetation favoured by this species developed. Similarly, M. musculus colonised within two years of the fires and persisted on the plot for 3–4 years before disappearing. Following the fires, populations of the omnivorous R. fuscipes recovered first followed by the scansorial, insectivorous A. agilis and last by the fossorial, insectivorous A. swainsonii. Two primary conclusions emerged from this study. First, the intense fire of 1972 did not kill all the animals immediately, but led to the disappearance of each species from the plot over 18 months. Thus, intense fire had a delayed but catastrophic impact on small ground-dwelling mammals. The fluctuations in population levels, covering more than an order of magnitude, demonstrate that factors other than fire, such as rainfall and drought, drive the population dynamics of these small mammals. As stability and recovery are not features of local populations, long-term studies of benchmark populations are necessary to manage forest biodiversity.

Invasion and management of a woody plant, Lantana camara L., alters vegetation diversity within wet sclerophyll forest in southeastern Australia

Plant invasions of natural communities are commonly associated with reduced species diversity and altered ecosystem structure and function. This study investigated the effects of invasion and management of the woody shrub Lantana camara (lantana) in wet sclerophyll forest on the south-east coast of Australia. The effects of L. camara invasion and management on resident vegetation diversity and recruitment were determined as well as if invader management initiated community recovery. Vascular plant species richness, abundance and composition were surveyed and compared across L. camara invaded, non-invaded and managed sites following L. camara removal during a previous control event by land managers. Native tree juvenile and adult densities were compared between sites to investigate the potential effects of L. camara on species recruitment. Invasion of L. camara led to a reduction in species richness and compositions that diverged from non-invaded vegetation. Species richness was lower for fern, herb, tree and vine species, highlighting the pervasive threat of L. camara. For many common tree species, juvenile densities were lower within invaded sites than non-invaded sites, yet adult densities were similar across all invasion categories. This indicates that reduced species diversity is driven in part by recruitment limitation mechanisms, which may include allelopathy and resource competition, rather than displacement of adult vegetation. Management of L. camara initiated community recovery by increasing species richness, abundance and recruitment. While community composition following L. camara management diverged from non-invaded vegetation, vigorous tree and shrub recruitment signals that long-term community reinstatement will occur. However, secondary weed invasion occurred following L. camara control. Follow-up weed control may be necessary to prevent secondary plant invasion following invader management and facilitate long-term community recovery.

Soil–atmosphere greenhouse gas exchange in a cool, temperate Eucalyptus delegatensis forest in south-eastern Australia

Forests are the largest C sink (vegetation and soil) in the terrestrial biosphere and may additionally provide an important soil methane (CH 4) sink, whilst producing little nitrous oxide (N 2O) when nutrients are tightly cycled. In this study, we determine the magnitude and spatial variation of soil–atmosphere N 2O, CH 4 and CO 2 exchange in a Eucalyptus delegatensis forest in New South Wales, Australia, and investigate how the magnitude of the fluxes depends on the presence of N 2-fixing tree species ( Acacia dealbata), the proximity of creeks, and changing environmental conditions. Soil trace gas exchange was measured along replicated transects and in forest plots with and without presence of A. dealbata using static manual chambers and an automated trace gas measurement system for 2 weeks next to an eddy covariance tower measuring net ecosystem CO 2 exchange. CH 4 was taken up by the forest soil (−51.8 μg CH 4-C m −2 h −1) and was significantly correlated with relative saturation ( S r) of the soil. The soil within creek lines was a net CH 4 source (up to 33.5 μg CH 4-C m −2 h −1), whereas the wider forest soil was a CH 4 sink regardless of distance from the creek line. Soil N 2O emissions were small (<3.3 μg N 2O-N m −2 h −1) throughout the 2-week period, despite major rain and snowfall. Soil N 2O emissions only correlated with soil and air temperature. The presence of A. dealbata in the understorey had no influence on the magnitude of CH 4 uptake, N 2O emission or soil N parameters. N 2O production increased with increasing soil moisture (up to 50% S r) in laboratory incubations and gross nitrification was negative or negligible as measured through 15N isotope pool dilution. The small N 2O emissions are probably due to the limited capacity for nitrification in this late successional forest soil with C:N ratios >20. Soil–atmosphere exchange of CO 2 was several orders of magnitude greater (88.8 mg CO 2-C m −2 h −1) than CH 4 and N 2O, and represented 43% of total ecosystem respiration. The forest was a net greenhouse gas sink (126.22 kg CO 2-equivalents ha −1 d −1) during the 2-week measurement period, of which soil CH 4 uptake contributed only 0.3% and N 2O emissions offset only 0.3%.

Habitat requirements of the yellow-footed antechinus (Antechinus flavipes) in box - ironbark forest, Victoria, Australia

Understanding the habitat requirements of a species is critical for effective conservation-based management. In this study, we investigated the influence of forest structure on the distribution of the yellow-footed antechinus (Antechinus flavipes), a small dasyurid marsupial characteristic of dry forests on the inland side of the Great Dividing Range, Australia. Hair-sampling tubes were used to determine the occurrence of A. flavipes at 60 sites stratified across one of the largest remaining tracts of dry box–ironbark forest in south-eastern Australia. We considered the role of six potential explanatory variables: large trees, hollow-bearing trees, coppice hollows, logs, rock cover and litter. Logistic regression models were examined using an information-theoretic approach to determine the variables that best explained the presence or absence of the species. Hierarchical partitioning was employed to further explore relationships between occurrence of A. flavipes and explanatory variables. Forest structure accounted for a substantial proportion of the variation in occurrence of A. flavipes between sites. The strongest influence on the presence of A. flavipes was the cover of litter at survey sites. The density of hollow-bearing trees and rock cover were also positive influences. The conservation of A. flavipes will be enhanced by retention of habitat components that ensure a structurally complex environment in box–ironbark forests. This will also benefit the conservation of several threatened species in this dry forest ecosystem.

Patchiness of prescribed burns in dry sclerophyll eucalypt forests in South-eastern Australia

Prescribed burning is commonly used in eucalypt forests to reduce fire risk and minimize damage to people and property in the event of a wildfire. The dry sclerophyll forests of south-eastern Australia are naturally fire-prone. Little is known about the heterogeneity of prescribed fires in these forests. This paper reports on the spatial variability of repeated low intensity fires under two burning regimes, in both logged and unlogged forests, for a 17-year period from 1988 to 2005. Prescribed burns were extremely patchy at both the coupe and the plot scale for all treatments. Burns implemented soon after logging covered significantly greater areas than the standard prescribed burns. On the coupe scale, the extent of the burn was influenced by the average aspect of the coupe and the percent of the coupe burnt in the last fire. At the smaller plot scale, the extent of the burn was influenced by the neighbourhood burn patterns, the distance the plot was from the nearest drainage line, the time since the last fire and the percentage of the plot that was burnt in the last fire. Under operational conditions, sites on ridges are likely to burn approximately every 11 years and sites in gullies approximately every 20 years. Patchy burns achieved in this study will provide refuges for fire sensitive species and newly burnt areas for colonizing species and are therefore likely to have significantly lower ecological impacts than homogenous burns.

Regeneration after 8 years in artificial canopy gaps in Mountain Ash ( Eucalyptus regnans F. Muell.) forest in south-eastern Australia

We report on a study of regeneration of Mountain Ash ( Eucalyptus regnans) forest in S.E. Australia in artificially created canopy gaps (0.01–2 ha) and clearfelled coupes (4–27 ha) with different seedbed treatments. Treatments were applied in 1988, 1989, and 1990. Our results are based on measurements 8 years after harvesting. Gap size had a significant influence on sapling height and diameter growth. The effect was substantial for the canopy openings larger than 2 ha, but inconsistent across the smaller gap sizes. Mean height of the largest diameter saplings was significantly greater in the clearfells (13.2 m) than in the 2 ha gaps (10.7 m), while mean heights in the smaller gaps ranged from 6 to 8.8 m. Mean sapling diameters (at 1.3 m) in clearfells and 2 ha gaps were 9.6 and 7.9 cm respectively compared with 3.8–5.8 cm for the smaller gaps. There was lower stocking in all treatments for the third regeneration year (1990), when regeneration operations were delayed by high summer and autumn rainfall. Stocking ranged from 12 to 33% for the smallest gaps, increasing with increasing gap size to 34–64% for 2 ha gaps and 48–76% for clearfells. Results were consistent with a previous study 3 years after treatment, indicating that stocking at 8 years is still dominated by initial stand establishment rather than by stand development processes. There was no significant influence of seedbed preparation on any of the variables tested at year 8; this was in contrast with earlier findings at year 3 when seedling height was significantly higher on burnt sites compared with mechanically disturbed sites. The growth of non-eucalypt competitors was also influenced by gap size and year of regeneration treatment. The main competitor species differed between larger and smaller clearings and between sites. Results indicate that using a silvicultural system based on smaller gaps (<2 ha) in this forest type is likely to result in reduced timber production potential compared with clearfelling.

Do terrestrial invertebrates experience floodplains as landscape mosaics? Immediate and longer-term effects of flooding on ant assemblages in a floodplain forest

Considering the floodplain landscape as a mosaic of habitat patches at different successional stages is useful for understanding (1) the processes associated with individual floods and (2) the legacy of flood history. Here, we investigate the applicability of the mosaic model to opportunistic ant species inhabiting the floodplain. Ground-active ant assemblages in river red gum (Eucalyptus camaldulensis) floodplain forest in south-eastern Australia were sampled before and for two years after a major flood in 2000-2001 at 24 sites with different inundation histories. Despite the mobility and opportunistic life history traits of floodplain ants, flood history appeared to impose a persistent mosaic structure on ant assemblages. Increasing duration of inundation of the forest floor was associated with decreasing species richness. beta-diversity was low, with the ant species at the most inundation-prone sites being a subset of those at drier sites. Less extensive flooding occurred in 2002-2003, enabling the consistency of short-term responses to inundation to be assessed. Flooding acts as a resetting mechanism, creating a characteristic ant assemblage. After floodwaters receded, there was little evidence of convergence in the structure of ant assemblages through time between sites flooded for different durations. The persistence of dissimilarities in ant assemblages suggests that succession towards terrestrialization was either not occurring or that it was operating at a rate that was too slow to be detected.

Occurrence of Angiostrongylus species (Nematoda) in populations of Rattus rattus and Rattus fuscipes in coastal forests of south-eastern Australia

The distributions of the introduced nematode parasite, Angiostrongylus cantonensis, and the native Angiostrongylus mackerrasae in Australia are poorly understood. We sampled rodents and/or their faeces, and intermediate gastropod hosts for the presence of Angiostrongylus species in coastal forests surrounding Jervis Bay in south-eastern Australia. We found A. cantonensis in populations of introduced Rattus rattus in forests to the north of Jervis Bay, and A. mackerrasae in native Rattus fuscipes in forests to the south of Jervis Bay. The apparent geographical separation of these lungworm species may be a consequence of host specificity and negative associations between R. rattus and R. fuscipes that results from interspecific competition. A. cantonensis was regularly found in R. rattus or their faeces across 9 of 12 study sites north of Jervis Bay, and three species of snail common to the area were suitable intermediate hosts. This has potential negative implications for native wildlife and human visitors to these forests, because A. cantonensis infection causes zoonotic disease (neuro-angiostrongyliasis) in humans and a wide range of bird and mammal hosts. Management of pest rodents in the study area is warranted.

Land-use history, forest conversion, and soil organic carbon in pine plantations and native forests of south eastern Australia

Land-use history – the number, type, and duration of previous land uses – is relevant to many questions regarding land-use effects on soil carbon, but is infrequently reported. We examine the importance of land-use history variables, as well as topographic and edaphic variables, on soil C in a range of forest types – native forest, pine plantations, secondary forest and rehabilitated forest – at three contrasting locations in south eastern Australia. Our comparisons include a novel forest conversion of exotic pine plantations to native, broadleaf forest. Using nested ANOVAs, we detected few differences in soil C concentration indices (total C, microbial biomass C, K 2SO 4–C) and C content among eucalypt-dominated vegetation and pine plantations within each location (0–10 cm depth). However, planned contrasts indicated a 30% decrease in soil C content with conversion of native forest to pine plantation of age 37 years. The reverse land-use change – pine plantation to native, broadleaf forest – was associated with a decrease in soil C concentration and content at one location (40%; age 12–13 years) and no detectable changes at another (to age 7 years). Variable effect between locations of this novel land-use change on soil C could be due to differences in potential productivity, conifer species, and plantation age. We used correlation coefficients and general linear models to identify widely applicable variables for predicting soil C concentration and content at local scales (≤ 20 km 2). Within-location relationships with topographic variables were weak and infrequent relative to those with edaphic and land-use history variables. Soil texture was strongly correlated with soil C at each location, although the relative significance of different particle size fractions differed among locations. Electrical conductivity appeared more widely applicable since it was included in C models at two locations. Combining land-use history and edaphic variables produced strong predictive models for soil C concentrations and content at two locations (total r 2 0.83 to 0.95). Positive relationships were indicated between soil C and ‘age of current vegetation’ at one location, and negative relationships were indicated with ‘number of land uses’ at another. These data highlight a potential predictive role for land-use history variables in local-scale assessments of soil C in forested landscapes.

Longer-term response to experimental manipulation of fallen timber on forest floors of floodplain forest in south-eastern Australia

There often are substantial accumulations of fallen timber (logs, large boughs) in many woodlands and forests around the world. However, fallen timber has become a target for removal for use as fuel or for management actions, such as fuel-reduction burning. Many silvicultural practices, such as fast harvesting rotations, coppicing and debris burning prior to re-sowing/re-planting, lead to much reduced fallen-timber loads. Many studies show the ecologically important role fallen timber plays, so its removal is likely to have adverse ecological outcomes. It has previously been shown that a specialized forager on fallen timber, the brown treecreeper Climacteris picumnus, responded strongly over a short-term (20 mo) to a meso-scale (34 ha) manipulation of fallen-timber loads in river red gum Eucalyptus camaldulensis forest in northern Victoria, Australia [Mac Nally, R., Horrocks, G., Pettifer, L., 2002a. Experimental evidence for beneficial effects of fallen timber in forests. Ecol. Appl. 12, 1588–1594]. There were substantially more birds in all treatments in which loads were increased to 40 Mg/ha or more, elevated from averages of ca. 20 Mg/ha across the southern Murray-Darling Basin. Sites were revisited 3 years after the manipulation was conducted and I show here that the changes in density have been sustained. These results suggest that increased fallen-timber loads ≥40 Mg/ha are preferred by the vulnerable treecreeper, and that the bird's responses reported previously were not transient. These elevated densities may translate into increased reproductive success of the treecreepers because larger groupings in this and related cooperative breeders produce more young. I conclude by outlining options for management of fallen timber to provide greater chances of viability for the species.

Carbon and nitrogen in forest soils: Potential indicators for sustainable management of eucalypt forests in south-eastern Australia

Soil organic matter (SOM) has been adopted as an indicator of soil fertility based on the rationale that SOM contributes significantly to soil physical, chemical, and biological properties that affect vital ecosystem processes of forests in Australia. A study was undertaken to evaluate the utility of SOM as an indicator of SFM at two long-term experimental sites in native eucalypt forests, including Silvertop Ash ( E. sieberi L. Johnson) and Mountain Ash ( E. regnans F. Muell.) in Victoria. This study examines the relative contributions made by various sources of carbon in soil profiles (0–30 cm) of forest soils, viz. mineral soil (<2 mm), plant residues, charcoal (>2 mm), and rock fragments (>2 mm). The long-term changes in these fractions in response to management-induced soil physical disturbance and fire (unburnt, moderate and high intensity) were evaluated. After 10 years, carbon levels in the fine soil fraction (soil <2 mm including fine charcoal) were similar across the range of fire disturbance classes in Mountain Ash forest (20–25 kg/m 2) and Silvertop Ash forest (7–8 kg/m 2). Likewise differences in carbon associated with other fractions, viz. microbial biomass, labile carbon, plant residues and rock fragments were comparatively small and could not be attributed to fire disturbance. Burning increased the charcoal carbon fraction from 5 to 23 kg/m 2 in Mountain Ash forest and from 1 to 3 kg/m 2 in Silvertop Ash forest. Taking into account, the percentage area affected by fire, increases in total soil carbon in these forests were estimated at 25 and 7 t/ha, respectively. The effects of physical disturbance of soils were examined at one site in Mountain Ash forest where soil cultivation was used as site preparation rather than the standard practice of burning of logging residues. Total carbon in soil profiles decreased from 29 to 21 kg/m 2 where soil disturbance was severe, i.e. topsoil removed and subsoil disturbed. This was mainly due to a decrease in charcoal carbon from 6.8 to 1.7 kg/m 2 but severe soil disturbance also increased the amount of carbon associated with rock fragments from 1.6 to 3.5 kg/m 2. Management-induced fire increased the coarse charcoal content of soil profiles substantially, thus increasing total carbon content as well as the proportion of recalcitrant carbon in SOM. In contrast, there was little change in the carbon content of the fine soil fraction including the labile and biologically active fractions indicating that these SOM fractions most relevant to ecosystem processes showed little long-term impact from soil disturbance and fire. Conventional sampling of the fine soil fraction (<2 mm) only represented between 50% and 70% of total carbon in the soil profiles. In contrast, total nitrogen in this fraction represented between 75% and 90% of the nitrogen in soil profiles and was less affected by changes in the contributions of N made by coarse fractions. Monitoring of soil N rather than C as an indicator of soil fertility and SFM may be more appropriate for forest soils with significant charcoal content.

Herbivore damage, resource richness and putative defences in juvenile versus adult Eucalyptus leaves

Eucalyptus species often show marked differences in morphology and ecophysiology between adult and juvenile leaves. Given these differences, it was hypothesised that juvenile and adult leaves would present different levels of resources to a herbivore, and potentially different levels of putative anti-herbivore defences. This hypothesis was tested in some eucalypts growing in native forest in south-eastern Australia. There were no significant differences in levels of water, protein or carbohydrates (per unit dry weight) between mature adult and juvenile leaves. No difference was recorded in concentration of total phenolics between leaf forms, but more protein was precipitated (an estimate of tannin activity) in extracts from juvenile leaves. Cyanogenic glycosides were absent from mature leaves, but present in young leaves of both leaf forms in E. polyanthemos. No significant difference in concentration of any terpene was recorded between adult and juvenile leaves in E. nitens and E. regnans. Specific leaf area was lower in adult leaves, and fibre concentration was higher in adult leaves of some species, suggesting that resources in the adult leaf may be less accessible to a herbivore. However, there was no difference in leaf toughness between leaf forms, even though toughness per unit leaf thickness was higher in juvenile leaves. Hence, no major trends in resource concentration were apparent between the leaf forms, and of the defences investigated, only tannin activity varied significantly between the leaf forms.

Salvage harvesting fire-damaged wet eucalypt forests in south-eastern Australia: some ecological perspectives

Summary Recent wildfires burned large areas of native forest in south-eastern Australia. Salvage harvesting will inevitably occur in some areas of burned forest to recover timber and pulpwood, but serious consideration should be given to the intensity of salvage harvesting. In order to provide for forest biodiversity, salvage logging operations must retain sufficient numbers of biological legacies such as living and dead trees that remain in fire-damaged stands and landscapes. Such retention is a critical part of sound forest stewardship which considers both ecological and economic issues, and is consistent with the overarching (and agreed) principles of Ecologically Sustainable Forest Management (ESFM). Retaining biological legacies like living trees, large dead hollow trees, large fallen logs and islands of unburned vegetation is critical for maintaining key ecological processes and creating suitable future habitat for a range of elements of forest biodiversity as stand recovery takes place. Planning where to salvage log, which and how many biological legacies to retain, and where and how to burn slash after salvage logging, will influence the structure of forests and the fate of many forest species for the next several centuries.

Biology of Chrysophtharta agricola (Coleoptera, Chrysomelidae), a pest of Eucalyptus plantations in south-eastern Australia

Summary Chrysophtharta agricola (Chapuis) (Coleoptera: Chrysomelidae) is a pest of eucalypt production forests in south-eastern Australia. Biological characteristics including high fecundity and adult longevity result in the production of large numbers of offspring, despite high levels of offspring mortality from natural enemies. Collection records for C. agricola indicate a host range of over 20 eucalypt species and a geographic distribution from northern New South Wales to southern Tasmania. This paper provides estimates of foliage consumption by larvae and reviews the biology of C. agricola, including its phenology, life stages and natural enemies. Each larva eats about 347 ± 20 mm3 of juvenile E. nitens foliage during its lifetime, with the fourth instar consuming more than half of this. Predators and parasitoids can cause significant mortality in C. agricola populations in the field.

Nematode assemblages from Avicennia marina leaf litter in a temperate mangrove forest in south-eastern Australia

Meiofauna from Avicenniamarina leaf litter in a temperate mangrove forest was enumerated, and the nematode assemblages compared on the bases of leaf colour (used as a guide to leaf age) and shore horizon where samples were collected. Twenty-one putative nematode species were collected from 48 leaf litter samples. Univariate analyses indicated that neither the colour of the leaf nor the shore horizon significantly affected abundance of nematodes. However, of the four (2×2) treatment groups, rarefaction curves revealed highest diversity on brown leaves from under the shade of the tree canopy (H′=0.751±0.126 SE, n=17). Species diversity of leaf litter nematodes was lower in this temperate mangrove system than reported from tropical mangrove studies. ANOSIM tests confirmed a significant effect of shore horizon on nematode assemblages. The dominant feeding group among nematodes was non-selective deposit feeders (7/21 species, but 77% of all nematodes). Epigrowth grazers were represented by 8/21 species of nematodes, but only 19% of the total number. Excised leaves became skeletonised by about 15 weeks. Shorter temporal scales of life cycles of nematodes compared with leaf degradation, and the dynamic nature of epibiontic assemblages, probably explain the similar assemblage structure on yellow and brown leaves.

Transport of leaf litter in upland streams of Eucalyptus and Nothofagus forests in south-eastern Australia

Leaf transport - especially differences among species from diverse taxonomic groups - is generally less well understood than are the other phenomena that influence the fate of leaves in streams, such as conditioning by bacteria and fungi and fragmentation and consumption by invertebrates. To address this topic, we compared the transport behaviour of entire leaves from five indigenous species of tree in a naturally forested, upland stream in south-eastern Australia: two cool temperate rainforest taxa (Nothofagus cunninghamii (HOOK) OERST. and Atherosperma moschatum LABIL.), two sclerophyllous taxa (Acacia melanoxylon R. BR. and Eucalyptus regnans F. MUELL.) and one taxon from the ecotone between the two forest types (Lomatia fraseri R. BR.). Laboratory experiments indicated that, irrespective of flow regime, rainforest leaves sank markedly more slowly than did sclerophyllous leaves. Eucalyptus regnans leaves, for example, in moving water typically sank within 2 days of immersion, whereas Nothofagus cunninghamii leaves in moving water had a mean time before sinking of 8 to 67 days. These differences in flotation behaviour were reflected in field experiments that used marked leaves to quantify transport down a first-order stream in the study area. The field experiments showed the stream to be highly retentive, with leaves from no taxon travelling more than 100m in six hours. Leaves from rainforest taxa, however, were transported longer distances in a given time than were sclerophyllous leaves, and in some of the latter cases (e.g., Acacia melanoxylon) retention commenced in distances as short as 5 m. There was some evidence that small leaves were transported greater distances than were large leaves; leaf texture and flexibility (a reflection of leaf morphology) also influenced transport distance, but the characteristics of the leaf margins seemingly did not. The ecological significance of these findings is that differential transport will influence the relative contribution made by various species to the pool of coarse particular leaf matter occurring in a given reach of a stream. It will also influence the amount of material available to downstream ecosystems and the formation of allochthonous fossil leaf assemblages.

Modelling light penetration edge effects for stream buffer design in mountain ash forest in southeastern Australia

In this paper, we develop models to describe light environment edge effects in retained mountain ash/riparian forest in southeastern Australia following edge creation by clearfell logging. The models are then used in the design of functional buffers whose objective is light environment protection. The study uses hemispherical photographs taken before and after logging at distances from the cut edge ranging from 0–108 m and at heights above ground of 1, 3.4 and 6.8 m. Non-linear regression was used to develop relationships between the change in light penetration due to edge creation and distance from the edge. Vegetation and topographic variables were evaluated as additional explanatory variables. The study indicates that in this vegetation type the factors with the greatest influence on light alteration following edge creation are edge orientation, distance from the edge and height in the canopy. Light penetration edge effects were greatest at north-facing (toward the equator) edges and minimal at south-facing edges, where diffuse light increases due to increased sky view were the only additional light. On north-, east- and west-facing edges light penetration attenuated rapidly over the first 10–30 m of retained forest and reduced gradually thereafter. Light penetration was generally greater higher in the canopy. The regression models for relative change in light penetration, which weights the change in light by the pre-logging light environment, were used to develop a set of depth of edge influence indices for each edge orientation and height above ground. These indices can be used to prescribe buffer widths to achieve specific light environment protection objectives.