Eucalypt Woodland Research Articles

The effects of grazing and fire on vegetation and the vertebrate assemblage in a tropical savanna woodland in north-eastern Australia

We studied the response of vegetation and vertebrate assemblages to fire and grazing, and their interacting effects, in Eucalyptus woodland in north-eastern Australia. In this vegetation type, many pastures remain free of cattle grazing due to the occurrence of a native shrub poisonous to livestock. Vegetation (floristic data and 22 habitat variables) and vertebrate fauna (birds, mammals, reptiles) were sampled in 29 standardized 50 × 50-m quadrats in the 2001 wet season, representing four treatments: sites burnt recently (within 2 y) and grazed by cattle (4–8 ha per livestock unit); sites unburnt (last burnt >2 y ago) and grazed; sites burnt recently and ungrazed; and unburnt and ungrazed sites. Fire and grazing had a significant influence on vegetation: both grazing and fire reduced ground cover (fire in grazed sites 51–23%, fire in ungrazed sites 68–39%) and increased the cover of forbs (8% in burnt and grazed sites, 3% if ungrazed) and tussock grasses (20% in grazed and unburnt sites and 5% when ungrazed). Grazing caused a shift in floristic composition from the perennial hummock grass Trioda pungens to tussock grasses (e.g. Aristida spp., Enneapogon spp.), forbs (e.g. Phyllanthus spp.) and shrubs (e.g. Acacia spp.). Of the vertebrate groups, birds responded more to fire effects (9 species), reptiles to grazing effects (6 species) and mammals to the interaction (2 species). Species reacted to increases in bare ground (e.g. crested pigeon Ocyphaps lophotes, hooded robin Melanodryas cucullatus, Ctenophorus nuchalis) and to the dominant ground cover (e.g. Ctenotus pantherinus) or change in vegetation architecture (e.g. singing honeyeater Lichenostomus virescens, variegated fairy-wren Malurus lamberti). The clearest example of an interacting effect was the cycle of complementary dominance between the rodents Pseudomys delicatulus and P. desertor, the latter's post-fire recovery becoming more muted in sites where cattle grazed (modelled time for population recovery twice as long as in ungrazed sites).

Faecal near infrared reflectance spectroscopy (F.NIRS) measurements of non-grass proportions in the diet of cattle grazing tropical rangelands

Frequent faecal near infrared reflectance spectroscopy (F.NIRS) analyses of faeces from cattle grazing a range of tropical pastures were used to measure the non-grass component, and other aspects, of their diets. Seasonal profiles of non-grass and crude protein in the diet are presented for nine sites from the speargrass, Aristida–Bothriochloa, and Mitchell grass dominated pasture regions, and for three shrubland sites where browse was plentiful. In grass-dominated native pastures of the speargrass and Aristida–Bothriochloa pasture regions of Queensland where little browse was available, non-grass was usually only 5–15% of the diet. Diet non-grass was even lower for a buffel grass pasture. In uncleared eucalypt woodland in the speargrass region, browse may have contributed up to 20% of the diet in the late dry season when grasses were senesced. In regions with abundant browse (e.g. mulga lands and desert upland systems) cattle preferentially selected actively growing grasses and forbs when they were available. With diminishing availability or declining quality of the forbs and grass due to grazing selection and dry conditions, browse increasingly contributed to intake. In Mitchell grass dominated pastures forbs often comprised more than 50% of the diet, and there appeared to be strong selection for forbs during the dry season. Where browse was available in association with Mitchell grass dominated pastures, it appeared to contribute to intake only in the late dry season. Dry season sampling in monsoonal tallgrass and Mitchell grass dominated pastures indicated dietary crude protein to be linearly correlated with diet non-grass, demonstrating the importance of non-grass in the prevention or alleviation of dry season protein deficiency in cattle. Changes in diet selected by cattle in relation to season and rainfall were generally in accord with the previous limited information, largely with sheep, in comparable vegetation systems. The results demonstrate the value of F.NIRS technology to assist understanding of diet selection by grazing cattle in northern Australia.

Relating pine-litter intrusion to plant-community structure in native eucalypt woodland adjacent to Pinus radiata (Pinaceae) plantations

Radiata pine (Pinus radiata D.Don) plantations are often found in close proximity to vegetation set aside for biodiversity conservation. We examined the intrusive effects of radiata pine beyond the confines of plantations by quantifying the penetration of pine litter (needles, cones, twigs and seeds) and wildings from plantations into adjacent eucalypt woodland in the Jenolan Caves Karst Conservation Reserve (south-eastern Australia). We then investigated the relationship between pine-litter intrusion and plant-community structure in adjacent woodland vegetation. We found significantly higher quantities of pine litter and wildings at all sites adjacent to plantations than at reference woodland sites that were not adjacent to plantations. At adjacent sites, pine litter decreased significantly with increasing distance from plantations. Alarmingly, native plant species richness declined and exotic plant species richness increased with increasing quantities of pine litter. Thus, there were fewer native plant species and more exotics in areas bordering pine plantations. Our findings suggest a potentially important link between the intrusion of pine litter and a loss of native biodiversity and facilitation of exotic-species invasion. We suggest the provision of a buffer zone around plantations in order to minimise intrusive impacts of plantations on native biodiversity.

Harnessing nature to improve sustainability

Harnessing nature to improve sustainability

Fungi in Agricultural Landscapes: Implications for Eucalypt Woodland Revegetation

Fungi in Agricultural Landscapes: Implications for Eucalypt Woodland Revegetation

Prescribed burning in a Eucalyptus woodland suppresses fruiting of hypogeous fungi, an important food source for mammals

Fruit bodies of hypogeous fungi are an important food source for many small mammals and are consumed by larger mammals as well. A controversial hypothesis that prescribed burning increases fruiting of certain hypogeous fungi based on observations in Tasmania was tested in the Australian Capital Territory to determine if it applied in a quite different habitat. Ten pairs of plots, burnt and nonburnt, were established at each of two sites prescribe-burnt in May 1999. When sampled in early July, after autumn rains had initiated the fungal fruiting season, species richness and numbers of fruit bodies on the burnt plots were extremely low: most plots produced none at all. Both species richness and fruit body numbers were simultaneously high on nonburnt plots. One of the sites was resampled a year after the initial sampling. At that time species richness and fruit body abundance were still significantly less on burnt plots than on nonburnt, but a strong trend towards fungal recovery on the burnt plots was evident. This was particularly so when numbers of fruit bodies of one species, the hypogeous agaric Dermocybe globuliformis, were removed from the analysis. This species strongly dominated the nonburnt plots but was absent from burnt plots in both years. The trend towards recovery of fruit body abundance in the burnt plots one year after the burn was much more pronounced with exclusion of the Dermocybe data. The Tasmanian-based hypothesis was based mostly on the fruiting of two fire-adapted species in the Mesophelliaceae. Neither species occurred on our plots. Accordingly, the results and conclusions of the Tasmanian study cannot be extrapolated to other habitats without extensive additional study. Implications for management of habitat for fungi and the animals that rely on the fungi as a food source are discussed.

A hypothesis to explain why the south-western subspecies of the Crested Shrike-tit (Falcunculus frontatus leucogaster) is rare and declining

The south-western subspecies of the Crested Shrike-tit (Falcunculus frontatus leucogaster) is uncommon and declining in abundance. Moreover, populations fail to persist in even large remnants of native vegetation within agricultural areas. Reasons for the scarcity of Shrike-tits in south-western Australia, their decline, and their failure to survive in fragmented habitats are unclear, but are possibly related to the scarcity of persistent decorticating bark on south-western Australian eucalypts relative to eucalypts in habitats where the species is abundant in eastern Australia. At two widely separated areas of eucalypt forest and woodland in eastern Australia, where Shrike-tits have been studied and appear relatively abundant, they take most of their prey from bark, particularly loose and decorticating bark. By contrast, in woodlands of south-western Australia, most prey appears to be obtained by foliage gleaning. I suggest that bark substrates provide a richer food resource for Shrike-tits than foliage, and that Shrike-tits in south-western Australia must forage over much larger areas to obtain adequate food than those that have been studied in the east. Other studies have shown that canopy arthropods are less abundant on eucalypts in south-western than in eastern Australia. Thus, as a result of both differences in foraging substrate availability and lower arthropod abundances, Shrike-tit population densities are lower in south-western Australia than much of eastern Australia. Low population densities and the need for large home-ranges typify organisms sensitive to habitat fragmentation. It is therefore hypothesised that both low numbers and a failure to persist in habitat fragments by Shrike-tits in southwestern Australia are a consequence of the limited abundance of suitable bark substrates for foraging, a reliance on foliage gleaning, and lower arthropod abundances. Conservation of this species in south-western Australia therefore requires protection of large contiguous areas of eucalypt woodlands and forests.

Redistribution of soil water by lateral roots mediated by stem tissues

Evidence is increasing to suggest that a major activity of roots is to redistribute soil water. Roots in hydraulic contact with soil generally either absorb or lose water, depending on the direction of the gradient in water potential between root and soil. This leads to phenomena such as "hydraulic lift" where dry upper soil layers drive water transfer from deep moist layers to the shallow rhizosphere and, after rain or surface irrigation, an opposite, downward water transfer. These transport processes appear important in environments where rainfall is strongly seasonal (e.g. Mediterranean-type climates). Irrigation can also induce horizontal transfers of water between lateral roots. Compared with transpiration, the magnitudes, pathways, and resistances of these redistribution processes are poorly understood. Field evidence from semi-arid eucalyptus woodlands is presented to show: (i) water is rapidly exchanged among lateral roots following rain events, at rates much faster than previously described for other types of hydraulic redistribution using sap flow methods; (ii) large axial flows moving vertically up or down the stem are associated with the horizontal transfer of water between roots on opposite sides of the stem. It appears that considerable portions of the stem axis become involved in the redistribution of water between lateral roots because of partial sectoring of the xylem around the circumference of these trees.

Evaluation of aerial photography for predicting trends in structural attributes of Australian woodland including comparison with ground-based monitoring data

The accurate assessment of trends in the woody structure of savannas has important implications for greenhouse accounting and land-use industries such as pastoralism. Two recent assessments of live woody biomass change from north-east Australian eucalypt woodland between the 1980s and 1990s present divergent results. The first estimate is derived from a network of permanent monitoring plots and the second from woody cover assessments from aerial photography. The differences between the studies are reviewed and include sample density, spatial scale and design. Further analyses targeting potential biases in the indirect aerial photography technique are conducted including a comparison of basal area estimates derived from 28 permanent monitoring sites with basal area estimates derived by the aerial photography technique. It is concluded that the effect of photo-scale; or the failure to include appropriate back-transformation of biomass estimates in the aerial photography study are not likely to have contributed significantly to the discrepancy. However, temporal changes in the structure of woodlands, for example, woodlands maturing from many smaller trees to fewer larger trees or seasonal changes, which affect the relationship between cover and basal area could impact on the detection of trends using the aerial photography technique. It is also possible that issues concerning photo-quality may bias assessments through time, and that the limited sample of the permanent monitoring network may inadequately represent change at regional scales.

Generalised regressions provide good estimates of insect and spider biomass in the monsoonal tropics of Australia

Abstract The estimation of arthropod biomass is often important in studies of terrestrial ecosystem structure and function, including analyses of the relative importance of different arthropod taxa in the diet of insectivorous animals. In order to estimate arthropod biomass in eucalypt woodlands and rehabilitated mine‐land in the monsoonal tropics of northern Australia, insect morpho‐species (n = 693) and spider morpho‐species (n = 100) were collected, sorted, then weighed and measured. Body length–weight regressions were determined for spiders, nine insect orders and all insects combined. There was a significant relationship between body length and weight for all taxonomic groups, with the power model being a better predictor than linear or exponential models for all groups except Diptera (which was best predicted by the linear model). Whilst Schoener (1980) found that the length–weight regression slopes of neotropical insects (all orders combined, as well as several individual orders) differed from those of their temperate North American counterparts, our comparisons between monsoon‐tropical and temperate Australian arthropods suggested differences among Dipterans and spiders only. We conclude that generalised regressions provide adequate estimates of arthropod biomass across Australia, providing that the body proportions of the dominant taxa do not vary substantively.

Habitat selection in two Australasian treecreepers: what cues should they use?

When habitats differ in quality, individuals may attempt to maximise fitness through habitat selection. However, complete tests of habitat selection are rare, in part because many studies fail to quantify fitness consequences of habitat choice. We studied habitat selection of Australasian treecreepers (Passeriformes: Climacteridae) in temperate eucalypt woodland by examining the influence of habitat characteristics and confounding factors on annual reproductive success. In the pair-breeding White-throated Treecreeper (Cormobates leucophaeus), older females and territories with fewer stumps and less woody debris produced more young, possibly because these habitat characteristics lead to reduced conflict with Brown Treecreepers (Climacteris picumnus). In the cooperatively breeding Brown Treecreeper, larger groups and territories with lower densities of shrub, moderate levels of ground cover, and greater amounts of foraging substrate produced more fledglings, whereas territories with greater invertebrate biomass produced more independent young. Predicted annual reproductive success in the best territory was up to two offspring more than predicted success in the worst territory; thus, treecreepers would benefit from selecting good quality habitat. However, complete tests of habitat selection need to evaluate whether dispersers actively sample multiple habitats and choose the best available, and thus whether individual-level processes determine large-scale patterns of distribution and abundance. These results also suggest that current conservation efforts to exclude grazing from remnant patches of eucalypt woodland may be inappropriate if not used in conjunction with other management actions, because such exclusion may dramatically increase shrub density and ground cover. Alternative management tools need to be investigated that will maintain a mosaic of microhabitat types and thus protect the eucalypt woodland ecosystem, not just a few of its species.

Diversity and Abundance of Biological Soil Crust Taxa in Relation to Fine and Coarse-Scale Disturbances in a Grassy Eucalypt Woodland in Eastern Australia

Over the last 200 years the box woodlands of eastern Australia have been considerably altered by European farming practices. These changes have been accompanied by a reduction in the size and number of patches of vegetation as well as the quality of the understorey vegetation and underlying soil surface. We measured diversity and abundance of soil crust taxa in relation to habitat complexity, remnant area and width, diversity of vascular plants as well as the number, size and separation of patches of vegetation and grass butts (coarsescale patchiness), and an index of surface stability derived from measures of seven soil surface features of small microsites (patches of bare/crusted, litter- or grass-covered soil; micro-scale) on both coarse- and fine-textured soils at 35 sites in south-eastern Australia. Fifty taxa were recorded from the 35 sites, and there were more taxa from sites with fine-textured soils (12.7) compared with coarse-textured soils (4.4). The soil crust community was dominated by a few relatively common species, with many species occurring at only a few sites. Half the number of species accounting for <1% of total abundance. Bare and crusted microsites supported more species and greater cover compared with grassy microsites. Crust diversity declined with increasing coarselevel disturbances (i.e. declines in habitat complexity, remnant area and width, and diversity of vascular plants) but the results were not consistent between soil types. No measures of fine-scale disturbance were related significantly to any of the crust diversity or abundance measures, and there was no evidence of a recent grazing effect on crust composition. The fact that few sites had many species (and visa versa) suggests to us that many sites are probably required to conserve soil crust taxa in these highly fragmented landscapes

Changes in soil water repellence and its distribution in relation to surface microtopographic units after a low severity fire in eucalypt woodland, Sydney, Australia

The distribution and persistence of water repellence was altered by low severity fire and subsequent rain in soil supporting eucalypt woodland on sandstone terrain in Sydney, south-eastern Australia. Water drop penetration times were recorded to depths of 0.08 m in situ 9 months before the experimental fire, immediately after fire, 4 weeks later when rainfall had modified the soil surface but the soil was dry, and 5 weeks after the fire when the soil was moist. Spatial variation in water repellence was high in all cases except immediately after the fire, when soil was almost uniformly strongly repellent to 0.03 m depth, and less uniformly repellent at 0.04–0.06 m depth. Heavy rain moved litter, ash, and mineral soil, modifying the soil surface into microtopographic units including litter dams, microterraces, and other areas with differing proportions of litter, bare soil, and gravel. Post-rain water drop penetration measurements were taken on and beneath these different surface conditions, in order to investigate the possible contribution of water repellence to the formation and maintenance of litter dams and microterraces characteristic of this terrain after fire. Water repellence did not appear to be directly correlated with the presence or absence of surface litter. Results suggest the long-term and spatially variable water repellence found in soils associated with vegetation dominated by eucalypts in Australia is maintained by factors different from those causing extreme and uniform water repellence after fire. Variable water repellence at the soil surface and within the profile may contribute to differential survival of seedlings after fire. The possible breakdown of water repellent compounds formed after fire and the distribution and development of hydrophobic biotic structures including fungal hyphae and proteoid roots need to be investigated.

Diet and feeding selectivity of common wombats

The seasonal diets and feeding selectivity of common wombats (Vombatus ursinus) in mountainous eucalypt forest, eucalypt woodland and pasture were determined using faecal analysis. Grass species contributed the largest proportion (95%) of epidermal fragment area in faecal pellets, with at least 20 species being eaten. The most abundant grasses in pellets in all seasons were the tough, wiry snow grasses (Poa sieberiana and P. labillardieri), with Microlaena stipoides comprising a substantial proportion of the diet in summer and autumn. Grass leaf was the most abundant plant part in pellets (81%), with grass stem and grass sheath comprising 11%. The seasonal proportion of grass seedhead in pellets varied from just traces during autumn and winter to a substantial component of the diet during summer (21% of epidermal fragments in pellets). Forbs comprised less than 1% of pellet material, and tree or shrub species were not detected in the diet. Feeding selectivity (and hence dietary niche breadth) varied seasonally; wombats become less selective in their feeding as plant diversity and abundance decreased. Positive selection was shown for monocots and negative selection for forbs. Grass species were eaten in broadly similar proportions to their abundances in the field, but with moderate to strong selection or rejection of a few species.

In situ symbiotic seed germination and propagation of terrestrial orchid seedlings for establishment at field sites

The establishment of five species of temperate terrestrial orchids (Caladenia arenicola Hopper &amp; A.P.Brown, Diuris magnifica D.L.Jones, D. micrantha D.L.Jones, Pterostylis sanginea D.LJones &amp; M.A.Clem. and Thelymitra manginiorum ms) in natural habitat through in situ seed sowing, or by planting of seedlings and dormant tubers, was evaluated. Seed of the Western Australian temperate terrestrial taxa, Caladenia arenicola and Pterostylis sanguinea germinated best when sown into soil inoculated with mycorrhizal fungi at field sites but failed to develop the tubers necessary for surviving summer dormancy. However, seedling survival improved when actively growing symbiotic seedlings were transferred to natural habitat during the growing season. Caladenia arenicola and P. sanguinea seedlings survived the initial transfer to field sites but only P. sanguinea survived into the second growing season. Highest survival was obtained by translocating dormant tubers of C. arenicola and Diuris magnifica, with D. magnifica persisting at the site 5 years after translocation. However, outplanted C. arenicola survived for only 2 years. In another trial, where seedlings and dormant tubers of a rare orchid Thelymitra manginiorum were translocated into eucalypt woodland, 18% persisted after 5 years. The rare orchid D. micrantha exhibited the highest survival rates, with greater than 80% of tubers surviving 5 years after transfer of mature dormant tubers to field sites. This study highlights the benefit of using optimised methods for seedling production by symbiotic germination and nursery growth to produce advanced seedlings or dormant tubers to maximise the survival of translocated plants. It also demonstrates the need to consider different strategies when dealing with individual species.

Capture success and population density of the northern bettong Bettongia tropica in northeastern Queensland.

The population density of the northern bettong (Bettongia tropica), an endangered potoroid restricted to northeastern Australia, was estimated using minimum known-to-be-alive (MKTBA) and Jolly-Seber estimates derived from mark-recapture data. At Davies Creek in the north of the bettong's current range, bettong population densities were significantly lower in Allocasuarina forest (1.5 bettongs km-2) that in Eucalyptus woodland (3.7 - 7.5 bettongs km-2). At Eucalyptus woodland sites south and west of Davies Creek, population density was up to twice as great as it was at Davies Creek, while at sites north of Davies Creek, population densities were very low. Capture success was variable, ranging between 5 and 21%. Our data support previous research that suggested B. tropica density on the Lamb Range was correlated with latitude and moisture. Despite the restricted distribution of the northern bettong, our data indicate that populations on the Lamb Range, the species' stronghold, are generally healthy.

A burning issue: using fire to accelerate tree hollow formation in Eucalyptus species

Summary The importance of hollows to many species of arboreal mammals and birds in Australia has been clearly established, as has the significance of large, old trees in providing hollows. Since European settlement, considerable areas of eucalypt forests and woodlands have been cleared, resulting in significant loss of habitat, including hollow-bearing trees. Recruiting and retaining large, old trees is important to the ongoing survival of hollow—dependent fauna. However, in wood production areas maintaining sufficient numbers of hollows is problematic, since the age at which trees become economically mature is considerably less than that at which they become hollow-bearing. Management strategies aimed at retaining some hollow-bearing trees can assist, but many forests and woodlands are immature and contain too few of these trees. The ability to accelerate hollow formation where hollow-bearing trees are lacking is crucial, but cost—effective methods suitable for use on a large scale are seemingly few. The use of fire to accelerate hollow formation in Eucalyptus trees is one option.

Bird communities in remnant woodland on the New England Tablelands, New South Wales

We provide a geographic and landscape context for ongoing studies on bird communities in eucalypt woodland remnants on the New England Tablelands, New South Wales. We draw together several surveys that have not been published in the scientific literature, and integrate them with previously published material. A total of 142 woodland bird species, including 12 threatened species, was recorded in remnant woodland in the area above 900 m elevation from 50 km SSE to 100 km NNW of Armidals. There was a positive relationship between remnant size and bird species richness. Woodland reserves &gt;300 ha supported significantly more species than remnants &lt;100 ha on private land. Intensively surveyed reserves also had more species than remnants surveyed more casually. Threatened and other declining species occurred mainly in medium-sized (100-300 ha) and large reserves; foraging guilds of small to medium-sized, ground and above-ground insectivores were impoverished in degraded medium-sized and small remnants on private land. Almost the full range of woodland bird species was found at one or more sites, indicating their conservation value. However, some species were found in few sites or were only vagrants at a site. Active management will be needed to retain the current diversity of bird species in such heavily cleared landscapes.

The role of intense nest predation in the decline of Scarlet Robins and Eastern Yellow Robins in remnant woodland near Armidale, New South Wales

A study of open-nesting Eastern Yellow Robins Eopsaltria australis and Scarlet Robins Petroica multicolor, on the New England Tablelands of New South Wales in 2000?02, found low breeding success typical of eucalypt woodland birds. The role of intense nest predation in the loss of birds from woodland fragments was investigated by means of predator-exclusion cages at robin nests, culling of Pied Currawongs Strepera graculina, and monitoring of fledging and recruitment in the robins. Nest-cages significantly improved nest success (86% vs 20%) and fledging rate (1.6 vs 0.3 fledglings per attempt) for both robin species combined (n = 7 caged, 20 uncaged). For both robin species combined, culling of currawongs produced a twofold difference in nest success (33% vs 14%), a higher fledging rate (0.5 vs 0.3 per attempt), and a five-day difference in mean nest survival (18 vs 13 days) (n = 62 nests), although sample sizes for nests in the cull treatment (n = 18) were small and nest predation continued. Although the robin breeding population had not increased one year after the cull, the pool of Yellow Robin recruits in 2001?03, after enhanced fledging success, produced two emigrants to a patch where Yellow Robins had become extinct. Management to assist the conservation of open-nesting woodland birds should address control of currawongs.

Distribution, habitat and conservation status ofLeggadina lakedownensis(Rodentia: Muridae) in Queensland

The Lakeland Downs Mouse Leggadina lakedownensis is one of two species of short-tailed mice endemic to Australia. In Queensland there have been only very few recent sightings, and the species was thought to be restricted to parts of northern Cape York Peninsula. Five new localities are reported, including range extensions to central Queensland. Habitat for the species varies from chenopod to spinifex grasslands, Melaleuca woodlands and open savanna Eucalyptus woodlands, ranging from tropical coastal esplanades to sub-tropical rangelands. Trap localities encompass altitude from sea level to over 1000 m, and annual rainfall from 600-1800 mm, but are unified by a dense ground cover and waterlogging red or white sandy clays. Some potential threats to these rodent's populations are postulated including loss of ground cover and clearing of habitat in coastal regions. Despite contentions of a plaguing species, this rodent was rarely encountered in areas extensive sampled within its range. Notwithstanding the spa...