Wet Eucalypt Forest Research Articles

Site effects outweigh riparian influences on ground-dwelling beetles adjacent to first order streams in wet eucalypt forest

In wet eucalypt forest with a rainforest understorey the vegetation adjacent to first order streams does not form a distinct riparian strip. This study investigated the riparian response of terrestrial ground-dwelling beetles adjacent to four such streams in Tasmania, Australia. Beetle assemblages varied more between the four sites than they did with distance from stream within sites, where they exhibited a measurable but subtle riparian response. The extent of the riparian zone varied between the four study sites, with a 1-5 m riparian zone at three sites and a gradually changing community up to 50-100 m upslope at one site. There was a trend for greater between plot variability immediately adjacent to the streams, possibly because this is a more highly disturbed environment. None of the habitat variables measured were consistently associated with riparian or upslope assem- blages of beetles, probably explaining the subtlety of the beetles' riparian response. Forest conservation efforts for terrestrial species should not necessarily be focused on the riparian zone in preference to upslope areas.

Why conservation reserves should not always be concentrated in riparian areas: A study of ground-dwelling beetles in wet eucalypt forest

Reserve corridors in production forestry landscapes are frequently concentrated in riparian areas. This study describes the numerical response of ground-dwelling beetles to increasing distance from streams, with the aim of evaluating the effectiveness of such a bias in reserve allocation. Patterns in abundance and diversity of epigaeic beetles were quantified at four first order streams in wet eucalypt forest in Tasmania, Australia. The depth and pattern of beetles’ riparian response varied between streams. Commonly trapped beetles were less abundant near to three of the four streams, and the numerical response model differed in each case. Species richness of common beetles was also lower near one of the streams. Pooled abundance and richness of rare species did not vary in response to the riparian–upslope transition. No riparian or upslope specialist species were identified among the most commonly collected species. Compared to upslope habitat, the riparian–upslope transition encompassed greater variability in species composition without actually increasing overall richness. The study findings demonstrate the need for ecosystem-specific data to optimize reserve placement, since the results were not predicted from general vegetation patterns, ecological theory, or the widely held assumption that riparian areas support greater abundance and diversity of organisms than adjacent upslope areas. Reserves encompassing more upslope habitat are recommended to complement those located in riparian areas.

Recovery of lichens after logging: preliminary results from Tasmania's wet forests

Logging in Tasmania's wet eucalypt forests has traditionally been based on a clearfell, burn and sow regime, a process that has become increasingly controversial in recent years. The managing authority for these forests, Forestry Tasmania, has designed a Silvicultural Systems Trial in Tasmania's Southern Forests to explore alternative methods for harvesting and regenerating eucalypts. One of the components of this Trial is a study of lichens and bryophytes. Pre-logging surveys revealed a diverse flora comprising 134 lichen and 144 bryophyte taxa. Logging and regeneration produces a suite of new microhabitats for colonization by lichens and bryophytes. After three years, 51 lichens have been recorded in the plots. Twenty-eight were recorded in the unlogged forest, and represent recolonizers; lichen survivors after logging and regeneration treatment are very few. The remaining 23 lichens represent some transient weedy species as well as some that are typical of more open, drier conditions. A feature of the post-logging flora is the high proportion of species also found in the Northern Hemisphere. Re-establishment of the pre-logging flora is limited by habitat and will depend on the re-establishment of pre-logging habitats such as mature dominant trees and understorey trees and shrubs.

A comparison of litter beetle assemblages (Coleoptera) in mature and recently clearfelled Eucalyptus obliqua forest

Abstract This study compares litter‐dwelling beetles in mature wet eucalypt forest with those in young forest regenerated following clearfelling. The aims of the study were to determine the extent to which these forest ages support differing litter beetle assemblages, and to identify species characteristic of each age. Beetles were collected with pitfall traps in a spatially replicated study design to avoid confounding forest age and site differences. Three transects of traps were located in each of mature and young forest stands at four study sites. Beetle abundance was greatest in young forest, and young and mature forest supported distinctly different beetle assemblages. Of 37 commonly collected species, an indicator species analysis found 9 species characteristic of young logging regeneration, and 7 species characteristic of mature unlogged forest. These species could be useful in other Tasmanian studies concerning forest management impacts. Only two significant indicator species were carabids, suggesting that focusing only on carabids as indicators of forest management may be undesirable.

The role of fire and nutrient loss in the genesis of the forest soils of Tasmania and southern New Zealand

The dominant soil patterns in forested or previously forested landscapes in southern New Zealand and Tasmania are described. Soil properties on adjacent sunny and shady aspects in hill country of the South Island of New Zealand are compared to soil properties under adjacent ‘dry’ and ‘wet’ eucalypt forest in Tasmania. A soil contrast index or SCI is defined for comparing soil contrasts on parent materials of different absolute nutrient contents. Three soil groups are defined using the SCI. Group 1 soil pairs are stable New Zealand soils in which exchangeable Ca + Mg + K values are higher on drier sunny aspects than on moister shady aspects. Group 2 soil pairs are New Zealand soils in which soils on sunny aspects display evidence of topsoil erosion by wind; consequently some soil pairs on dry (sunny) aspects have lower levels of exchangeable Ca + Mg + K than soils on moister (shady) aspects. Group 3 soil pairs are Tasmanian. Soils on drier sites (under dry eucalypt forest) invariably have lower exchangeable Ca + Mg + K values than soils on moister sites (under wet eucalypt forest), which is the reverse of the pattern in SCI Group 1 soils in New Zealand. Except on clay-rich parent materials, Tasmanian soils under dry forest generally have texture-contrast profiles and a mean C/N ratio in topsoils (A1 horizons) of 29. Soils under wet forest generally have uniform or gradational texture profiles and a mean topsoil C/N ratio of 15. The texture-contrast soils show strong clay eluviation with sand or sandy loam textures in upper horizons and clayey textures in lower horizons. However, in New Zealand texture-contrast soils are all but absent, and do not occur in the previously forested areas described in this paper. Topsoils (Ah horizons and soils sampled to 7.5 cm depth) in New Zealand areas sampled in this study have a mean C/N ratio of 15, regardless of whether they occur on sunny or shady aspects. We propose that the frequency and spatial occurrence of fire are the dominant processes causing: (1) the marked difference in levels of nutrients and different topsoil C/N ratios in soils of Tasmania; (2) the development of texture-contrast soils under dry forests in Tasmania; and (3) the difference between soil patterns in New Zealand and Tasmania. Fire depletes nutrients in forests by causing losses to the atmosphere, losses by runoff, and losses by leaching. Nutrient loss by fire encourages fire-tolerant vegetation adapted to lower soil nutrient status, so frequent fire is a feedback mechanism that causes progressive soil nutrient depletion. By destroying organic matter and diminishing organic matter supply to the soil surface fire inhibits clay–organic matter linkages and soil faunal mixing and promotes clay eluviation. Fire frequency is likely to have increased markedly with the arrival of humans at ca. 34 000 years B.P. in Tasmania and ca. 800 years B.P. in New Zealand. We argue that texture-contrast soils have not formed in New Zealand because of the short history of frequent fires in that country. A corollary of this conclusion is that texture-contrast soils in Tasmania are, at least in part, anthropogenic in origin.

Effects of trap position, trap history, microhabitat and season on capture probabilities of small mammals in a wet eucalypt forest

In this study, we use data drawn from a series of trapping events on four 0.5-ha trapping grids surveyed in the wet eucalypt forests of central Victoria, south-eastern Australia, to identify relationships between capture probabilities and several factors of interest for three species of small mammals that are common throughout the forests of this region: the agile antechinus (Antechinus agilis), the dusky antechinus (Antechinus swainsonii) and the bush rat (Rattus fuscipes). The design of our study – four regular trapping grids – generated spatio-temporal data with binary responses and many covariates. We used powerful and relatively new statistical methodology to deal with the spatio-temporal dependence patterns in the data – analytical problems that are common in trapping data such as these modelled here. Although A. agilis, A. swainsonii and R. fuscipes are among the best studied mammals in Australia, our data analysis produced new perspectives on their probability of being captured. In particular, we quantified how capture probability is affected by trap position within a trapping grid, day of capture in a sequence of trapping days, history of trap occupancy over time by different species and sexes of those species, time of the year or season, and microhabitat attributes. Our insights are discussed in terms of their consequences for trapping protocols that might be applied in the field.

Distribution, habitat and conservation of two threatened stag beetles, Hoplogonus bornemisszai and H. vanderschoori (Coleoptera: Lucanidae) in north-east Tasmania

The distribution and habitat of two stag beetles, Hoplogonus bornemisszai and H. vanderschoori (Coleoptera: Lucanidae) listed under the Tasmanian Threatened Species Protection Act 1995 were investigated. The number of sites of occurrence for H. bornemisszai was increased from 4 to 28 and its extent of occurrence was calculated to be 1,200 ha (12 km2). The number of sites of occurrence for H. vanderschoori was increased from 3 to 22 and its extent of occurrence was 9,510 ha (95 km2). Both species appeared to have patchy distributions and occurred at variable population densities. H. vanderschoori was found predominantly in wetter forest types than H.bornemisszai including rainforest and mixed forest types, but was not found in regenerating wet eucalypt forest. The ranges of the two species did not overlap. However, the range of H. bornemisszai is contiguous with that of another threatened stag beetle, H. simsoni. Together, the ranges of the three species indicate the presence of a biogeographical mosaic. Only 20% of potential habitat for H. bornemisszai, and 30% for H. vanderschoori, occurs in reserves or areas bound by a conservation covenant. Conservation measures are recommended for the maintenance of populations of these species in areas subject to forestry activities.

Impact of major snig tracks on the productivity of wet eucalypt forest in Tasmania measured 17–23 years after harvesting

Summary During ground-based harvesting operations the passage of machinery leads to the formation of a mosaic of major and minor snig tracks from tree stumps to the landing. The impact of heavy traffic can lead to significant changes in the underlying soil physical properties and potentially in long-term growth of trees on these tracks. This study examined the impact of major snig tracks on the productivity of wet eucalypt forest in Tasmania. The three stands studied were dominated by Eucalyptus obliqua that regenerated from clearfelling, slash burning and aerial sowing 17–23 y earlier. Accumulated tree growth and soil physical and chemical properties were measured in three zones: snig tracks, transitional zone (edge of snig tracks), and control. There was a dramatic decline of 52– 80% in the accumulated tree volume in snig track zones when compared to the control zones. This was accompanied by a significant increase in the soil bulk density of 20–23%, and measured changes in a number of soil properties including 22– 33% decrease in organic carbon, 28–32% decrease in total N, and 3–11% decrease in total P on the snig track zones. There was no significant difference in either the soil physical or chemical properties of the transitional zones compared to the control zones, but there was a significant increase in tree growth in the transitional zones, ranging from 30% to 100%. An increase in stand density was the major factor contributing to improved growth in transitional zones, with increases in average diameter and average height having minimal effect. After 17–23 y the increase in stand productivity in the transitional zone compensated for much of the productivity lost due to poor growth on the snig tracks. The overall negative impact of snig tracks on stand productivity was calculated to be of the order of 2–3%.

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.

Development and evaluation of predictive habitat models to assist the conservation planning of a threatened lucanid beetle, Hoplogonus simsoni, in north-east Tasmania

The use of predictive habitat distribution models by land managers in the conservation management of threatened species is increasing. Few models, however, are subsequently field-checked and evaluated. This study evaluates the statistical strength and usefulness for conservation purposes of three predictive habitat models developed for a threatened stag beetle, Hoplogonus simsoni, found in the wet eucalypt forests and mixed/rainforests of north-east Tasmania. The relationship between various environmental variables for which spatial (GIS) information was available and the density, frequency of occurrence and presence/absence of the species was investigated using generalised linear modelling. Models developed were coupled with the GIS data to develop maps of predicted occurrence within the species’ range, grouped into categories of habitat quality. The models found that altitude, aspect, slope, distance to nearest stream and overstorey tree height were significantly associated with the occurrence of the species. Evaluation of the statistical strength of the models with independent data of species’ occurrence collected at 95 sites found that the density model performed poorly with little correlation between predicted and observed densities of the species. The frequency of occurrence model, however, showed a moderate ability to predict both species’ abundance and presence/absence. The presence/absence model had a similar discriminatory ability in predicting presence or absence of H. simsoni, but also showed some potential as an indirect predictor of species’ abundance. Assuming a correlation between relative abundance and habitat quality, the frequency of occurrence predictive model appeared to be the better and more direct discriminator of high quality habitat relative to the other models. The value of species’ habitat models and the need to evaluate their utility in the development of conservation strategies are discussed.

The distribution and habitat characteristics of a threatened lucanid beetle Hoplogonus simsoni in north-east Tasmania

The distribution and characteristics of habitat utilized by a threatened species of stag beetle in north-east Tasmania Hoplogonus simsoni (Coleoptera: Lucanidae), were examined as a first step in the development of conservation management objectives for the species. The beetle was found to have a restricted distribution of 250 km2 and its regional distribution appeared to be related to the occurrence of granitic geology and a moderately high rainfall at low elevations. The species was patchily distributed across its range. High-density populations of the species were restricted to the eastern part of its distribution, but over most of its range it occurred at very low densities. Relative abundances of H. simsoni were greatest in wet eucalypt forest, with significantly fewer beetles found in mixed forest and rainforest. Dry eucalypt forest was found to be unsuitaole habitat although the beetle was found to occur in the ecotone between wet and dry eucalypt forest Potential wet forest habitat for the species is estimated to encompass 18 200 ha or 72% of its range. The species was not found in areas of wet eucalypt forest that had been converted to pine plantation. However, H. simsoni was found to occur in wet eucalypt forest regenerating after clearfelling and some of the highest density populations of the species occurred in 70 year old wet eucalypt forest regenerating following a wildfire. The relationship between various habitat variables and the occurrence of the beetle was investigated using Generalized Additive Modelling and robust regression. The presence of wet eucalypt forest below 300 m altitude; slope less than 5�; a deep leaf litter layer; and a forest structure with a well-developed canopy best explained the occurrence of the beetle. These habitat characteristics probably relate to a requirement for a cool, moist, stable microclimate and an absence of wildfire for some time. The potential habitat of H. simsoni as identified in this study is poorly reserved across its range and a high percentage has been identified by the forest industry as having potential for conversion to pine plantation. This highlights the importance of having mechanisms for "off-reserve" conservation of threatened species. like H. simsoni, which are often poorly represented in or completely absent from formal reserves.

Distribution, habitat characteristics and conservation requirements of a forest-dependent threatened invertebrate Lissotes latidens (Coleoptera: Lucanidae)

The distribution, habitat and conservation requirements of an endangered stag beetle, Lissotes latidens (Coleoptera: Lucanidae), in south-east Tasmania were investigated. This study trebled the known range of the species to 280 km2, of which 15% constituted potential habitat. The beetle was found to inhabit a range of wet forest types including damp eucalypt forest, wet eucalypt forest, rainforest and riparian areas amongst drier forest types. Relative to other Tasmanian lucanids, L. latidens was found to occur at quite low population densities. The species had a preference for forest with a well-developed overstorey and greater than 10% ground cover of coarse woody debris (CWD). Although L. latidens is soil-dwelling throughout its life-cycle, it has a close association with CWD, occurring under logs at the interface of soil and CWD. Suitable forest habitat for L. latidens is poorly reserved, with 48% managed under clearfell, burn and sow forestry regimes; a practice that is likely to lead to the depletion of CWD over successive harvesting rotations. Recommendations are made for the conservation management of habitat utilised by L. latidens in ‘off-reserve’ areas. The need for conservation strategies to incorporate the temporal dynamics of habitat important to forest-dependent threatened species is discussed.

Coarse woody debris, biodiversity and management: a review with particular reference to Tasmanian wet eucalypt forests

Summary This paper reviews the biodiversity conservation issues relating to management of coarse woody debris (CWD) in the wet eucalypt production forests of Tasmania, with particular emphasis on clearfell, burn and sow (CBS) silviculture and on fuelwood harvesting. CBS is the standard silvicultural system in these forests, while fuelwood harvesting, as currently proposed, would involve the recovery of a higher proportion of felled biomass than standard CBS, as well as some pre-existing CWD. Studies and practices from around the world are considered that have relevance to the temperate Australian forestry situation in general, and the Tasmanian situation in particular. The paper considers the ecological roles of CWD in natural forest ecosystems, emphasising its value as a key structural component and as habitat for biodiversity (especially invertebrates). Temporal continuity and spatial connectivity in supply of CWD, and presence of larger-diameter CWD, emerge as key factors determining community richness and composition. Whilst levels of CWD naturally fluctuate spatially and temporally in wet eucalypt forests, studies from northern temperate and boreal forests with similar dynamics demonstrate that, historically, management of native forests has tended to result in a gradual diminution of the CWD resource. Larger-diameter material is readily diminished through management, with potential consequences for dependent biodiversity. Suggested mitigation measures (landscape-level and coupe-level), to accommodate biodiversity concerns and avoid a long-term conservation management problem for forest managers in Tasmania, centre on two main concerns. One is the likelihood that current standard rotation lengths used in CBS are probably too short to allow for the recruitment of sufficient CWD to replace that which is lost through harvesting, regeneration burning and natural decomposition. The other concern is that fuelwood harvesting may significantly increase the impacts of CBS on biodiversity in general and on threatened species in particular.

Shedding some light on Thismia rodwayi F. Muell. (fairy lanterns) in Tasmania: distribution, habitat and conservation status

Thismia rodwayi is a seldom-seen, subterranean plant that occurs in Tasmania, the eastern states of the Australian mainland and New Zealand. Surveys for the species were prompted by a new record from Archers Sugarloaf near Meander in Tasmania's central north. Several new populations of the species were subsequently discovered in wet eucalypt forests dominated by Eucalyptus obliqua, E. regnans, E. delegatensis or E. viminalis, with an understorey dominated by Pomaderris apetala, Bedfordia salicina and/or Olearia argophylla. The species is now known from the Meander, Glen Huon, Little Denison River, Mount Field, Mount Wellington and Ben Lomond areas. Analysis of current information suggests that the listing of T. rodwayi under Schedule 5 (Rare) of the Tasmanian Threatened Species Protection Act 1995 is appropriate.

Macrofungal diversity and community ecology in mature and regrowth wet eucalypt forest in Tasmania: A multivariate study

Abstract The biodiversity of macrofungi in mature and young regrowth Tasmanian wet forests is described at the species level and at the community level. The macrofungal communities studied were much more species‐rich than their vascular plant counterparts, with the total number of macrofungal taxa outnumbering vascular plants by four to one. This ratio applied in both mature and young regrowth forest sites. Some 242 taxa of macrofungi were recorded, of which 132 were identified to species level, the remainder to species groups or higher taxa. Distinct communities could be discerned from multivariate analysis (ordination and classification) of vascular plant and macrofungal data from the mature and regrowth sites. The two vascular plant communities had different fire histories, and this difference is also assumed to account for the separation of the macrofungal communities of the two forest types. There was generally a high level of congruence between the vascular plant and the macrofungal communities. However, one young regrowth site, which was relatively close to the mature sites in the ordination space for the analysis of vascular plants, was distant from the mature forest sites for the analysis of macrofungi. Another regrowth site, which had experienced wildfire rather than silvicultural regeneration, clustered with mature sites for some analyses of the macrofungal assemblage. Variation in the macrofungal communities was correlated with a different set of the measured environmental variables than was variation in the vascular plant communities. Mature and young regrowth forests were found to have distinctly different macrofungal floras, with approximately 40% of the taxa in each forest type being restricted to that type of site. Suitable indicator taxa (restricted or preferential to particular forest types) for use in further studies are suggested.

The spatial distribution of non-native plant invaders in a pine–eucalypt landscape mosaic in south-eastern Australia

Factors influencing the spatial distribution of two major species of non-native plants, blackberry ( Rubus fruticosus) and radiata pine ( Pinus radiata) wildlings in a fragmented forest landscape in south-eastern Australia were quantified. A total of 1067 plots within three broad groups of sites was surveyed for these two non-native plant species. The sites were in large continuous areas of native eucalypt forest, an extensive plantation of P. radiata, and sites in patches of remnant eucalypt forest embedded within the pine plantation. In the case of the 507 plots located within patches of remnant eucalypt forest, an array of variables (e.g. distance to surrounding pine plantation, and floristic and structural attributes) was measured and used in statistical analyses of non-native plant occurrence. P. radiata wildlings were totally absent from plots in large continuous areas of native eucalypt forest, but present at 5% of plots within patches of eucalypt remnants embedded within the pine plantation. Logistic regression showed that the occurrence of P. radiata wildlings in the eucalypt remnants was significantly higher in plots where the neighbouring pine plantation had been established for a long time, plots that were dominated by dry eucalypt forest types, and plots with a limited cover of ground vegetation. The occurrence of R. fruticosus differed significantly ( P<0.001) between the groups of sites; 59% of plots in the pine plantation, 41% in the eucalypt remnants, and 7% in continuous areas of native forest were invaded. For the eucalypt remnants, the occurrence of this species was significantly greater in plots close to the surrounding pine plantation, with fewer species of native shrubs, in wet eucalypt forest types, and with low values for both eucalypt basal area and rock cover. The results of this study indicate that even though non-native plant invasion is already relatively extensive in the study area, it is likely to further increase. The array of factors influencing the spread and establishment of P. radiata wildlings and R. fruticosus indicate that the control of these non-native plants will be extremely difficult in the existing plantation estate. However, the adoption of some simple protocols could make it feasible to limit their spread to newly established areas of the pine plantation estate.

Impacts on soils from cable-logging steep slopes in northeastern Tasmania, Australia

Cable-logging is a method commonly used to harvest native forests on steep slopes in Tasmania, Australia. A study was carried out to determine impacts on site disturbance and selected soil properties resulting from cable-logging wet eucalypt forest developed on granite substrates in northeastern Tasmania. The results show that both the area and depth of soil surface disturbance are relatively minor, with ca. 11% of the study coupe affected by moderate (litter and part topsoil removed) or severe (subsoil exposed) disturbance. Cable draglines accounted for just over 7% of the soil disturbance (7% moderate and 0.2% severe), whereas tree uprooting associated with the logging accounted for a further 3% moderate disturbance and 1% severe disturbance. Measurements of soil properties in the surface layer (0–10 cm) show that bulk density is ca. 20% higher and organic carbon content (kg/ha) is 15% lower on cable draglines compared to undisturbed sites. However, the dominant type of soil disturbance caused by cable-logging appears to have been displacement of the upper 10 cm of topsoil from the centre to the outside edges of draglines rather than compaction in situ. Comparison of the data with studies of ground-based logging of wet native forests elsewhere in southeastern Australia shows that cable-logging has resulted in significantly less impact on both area of soil disturbed and soil properties. The results are also discussed in relation to relevant sustainability indicators (soil erosion, organic matter and compaction) specified in Criterion 4 of the Montreal Process together with recently proposed threshold values.

Occurrence of pygmy possums, Cercartetus lepidus and C. nanus, and their nest sites in logged and unlogged dry and wet eucalypt forest in Tasmania

Summary Occurrence and nest site use by pygmy possums were investigated in dry and wet sclerophyll forest in Tasmania. There were four silvicultural treatments in the dry sclerophyll forest (a clearfelled coupe with 17-year-old regrowth, two partially logged coupes and old-growth forest) and four in the wet sclerophyll forest (4- and 20-year-old regrowth resulting from clearfelling, 80-year-old natural regrowth and old-growth forest). Cercartetus lepidus was captured in all ages of regrowth and in both partially logged and old-growth forest. C. nanus was captured only in 20- and 80-year-old regrowth in wet sclerophyll forest. Partially decayed logs were important nest sites for C. lepidus. Fissures in live trees associated with fire scars and hollows in stumps were also used as nests. All three nests of C. nanus were located in stumps. The amount of suitable nesting substrate did not appear to be a factor limiting populations in either the dry or wet sclerophyll forest.

Spatial Variability in Species Composition in Birds and Insects

If spatial patterns of change within a habitat were similar for both vertebrates and insects, then vertebrates would provide useful surrogates for designing reserves for the conservation of invertebrates. Data from two eucalypt habitats were analysed to determine levels of habitat richness, site richness and species turnover in birds and insects. For birds the relatively low species richness and turnover indicated that sites within the habitat were similar in composition. In wet eucalypt forests Diptera were very speciose with over 1,000 morphospecies sorted. Species turnover was slightly higher than for birds, indicating a large number of species change from site to site. In dry eucalypt woodland, insects trapped through the winter months were not speciose but turnover between sites was very large. This suggests reserves designed to conserve insects may need to be larger than for birds in order to include the high site variability and richness of insect communities. Spatial patterns of birds and insects were investigated further, to determine if sites that were closer together were more similar for both birds and insects. No patterns were found for birds in either habitat suggesting birds are not responding to changes in the environment at this scale. Diptera in wet eucalypt forest showed higher similarity between close sites than distant sites, while for winter insects in dry eucalypt woodland the relationship was significant when two outlier points were removed. Overall, birds are not good surrogates for insects in either habitat as no relationship between birds and insects in site-to-site similarity was found.

The development and current implementation of silvicultural pratices in native forests in Tasmania

Summary The historical development of silvicultural practices in Tasmania is reviewed for eucalypt forests, rainforests and blackwood forests. The silviculture of eucalypt forests prior to the 1950s was characterised by selective logging without any planned regeneration treatment. By the 1960s extensive research in the wet eucalypt forests resulted in the systematic application of silvicultural regimes based on clearfelling, slash burning and regeneration from seed trees or artificial sowing. This regime was extended to most eucalypt forest types throughout the 1970s with mixed results. Partial harvesting techniques were developed and introduced in the 1980s for multi-aged forests with sparse understoreys. Clearfelling remains the predominant regime in lowland wet eucalypt forests with a dense understorey. A range of partial logging methods are used for most drier and highland eucalypt forests. Over the last decade, 45% of native forest coupes on State forest had partial harvesting, 39% were clearfelled, burnt and sown and 16% were converted to plantations. On private land, 44% of native forest coupes had partial harvesting, 9% were clearfelled, burnt and sown, 28% were converted to plantations and 19% were converted to non-forest uses such as agricultural grazing. Silvicultural techniques for rainforest and blackwood swamps have been relatively recently developed, primarily to supply special timbers for furniture and craftwork. The implementation of native forest silviculture is guided by a series of Native Forest Technical Bulletins which specify silvicultural prescriptions for commercial forest types. Some future directions for native forest silviculture are discussed.