Northeast Queensland Research Articles

Kin recognition in rainbowfish ( Melanotaenia eachamensis ): sex, sibs and shoaling

Living with relatives can be beneficial to individuals via the evolution of kin-directed altruism, but this is tempered by the increased risk of inbreeding. Therefore, in social species, the ability to recognise relatives can be highly advantageous. This study focuses on kin discrimination in the Lake Eacham rainbowfish, Melanotaenia eachamensis, an endangered freshwater species from north-east Queensland, Australia. First, I examined kin recognition abilities when a combination of both chemical and visual recognition cues was available. When given a choice of shoaling with same-sex groups, females spent significantly longer with full-sibs rather than half-sibs, full-sibs rather than non-relatives and half-sibs rather than non-relatives. Males spent significantly longer shoaling with full-brothers versus half-brothers, but showed no other shoalmate preferences. Second, in the presence of only chemical cues, females did not discriminate among groups of different levels of relatedness, but males showed a non-significant tendency to associate with full-sibs rather than non-relatives. Male shoaling behaviour seemed to be more influenced by factors other than relatedness, e.g. intra-sexual competition. Finally, I found that the shoaling preferences of females changed when exposed to groups of males. Females preferred to associate with non-relatives rather than half-brothers and non-relatives rather than full-brothers. There was no significant difference in the time spent with half-brothers versus full-brothers. Taken together, my results suggest that females have very good kin recognition abilities. They prefer to shoal with female relatives but avoid male relatives, and so are able to balance the benefits of nepotism and the costs of incest.

The Application of Synoptic Stratification to Precipitation Forecasting in the Trade Wind Regime

Abstract A 1129-day high quality rainfall dataset was collated, from the months of March to November 1993–97, where trade wind flow predominates across the northeast Queensland tropical coast. This dataset was matched with numerical model fields from the Australian regional limited area model. Synoptic precipitation regimes were identified by subjective classification of a major portion of the development data utilizing radar, surface, and upper-air data. With the aid of classification trees, a series of objective sorting criteria were developed to stratify the numerical model dataset into weather regimes prior to the development of a series of predictive equations for rainfall through screening regression. In addition to raw numerical model output, potential predictors with established links to trade wind precipitation were offered to the regression procedure. Rainfall equations were also developed by seasonal stratification of the development data. Further comparison was made with rainfall occurrence ou...

Land Cover Change and its Environmental Significance in the Herbert River Catchment, North-east Queensland

There has been considerable recent concern over the amount of vegetation clearance in the wet tropics of northern Australia. This paper reports on the results of a case study undertaken in the lower Herbert River catchment in north-east Queensland, which utilised remote sensing and Geographic Information Systems (GIS) to assess both spatial and temporal changes in land cover since European settlement in the mid-nineteenth century. We demonstrate that since European settlement there has been a substantial reduction in the area of Melaleuca, rainforest, and eucalyptus-dominated land-cover patterns. We also provide a range of quantitative measures to show that the landscape diversity, integrity and quality of these ecosystems have also declined between the 1860s and 1996. We conclude that reform is required at policy, planning and enterprise levels if the ecological, economic and social values of these systems are to be maintained in the future.

In Search of Australia’s Highest Waterfalls

Wollomombi Falls in northeast New South Wales and Wallaman Falls in northeast Queensland have for many years vied for the title of Australia's greatest single drop waterfall. Recently, however, that rank has been passed to Ellenborough Falls in northeast New South Wales (Australian Geographic, 1998; AUSLIG, 1999). This paper examines the various claims, and suggests the most likely candidate for the title.

Regional and Landscape-scale Patterns of Shrub Invasion in Tropical Savannas

The shrubby vine Cryptostegia grandiflora and the shrub Ziziphus mauritiana were both introduced to northern Australia over 100 years ago and have become invasive in savanna woodland environments. Data from a land resource survey were used to examine regional- and landscape-scale distribution patterns of these species in the Dalrymple Shire, an area of over 6 1/2 million hectares in northeast Queensland. Each species was present at 10% of the 2362 sites examined and most frequent and abundant close to Charters Towers, the major settlement of the regions. C. grandiflora was recorded at 50 % of sites within 20 km of the town and in 14 out of 21 of the region's major sub-catchments. Z. mauritiana was recorded at 32 % of sites within 20km of Charters Towers, but in only three sub-catchments. Little of the variation in frequency and abundance of C. grandiflora and Z. mauritiana was accounted for by landscape factors, including geology, soils, or vegetation. While survey results do not absolutely distinguish between history, habitat and disturbance in explaining the weed's current distributions within the region, a strong influence of historical factors is suggested. Both exotic species were much less abundant than Carissa spp., a native taxon that has purportedly increased in the region in recent decades. In spite of their current prominence as weeds, there is potential for further increase by both C. grandiflora and Z. mauritiana. This increase could include expansion from the zone of high abundance and proliferation within that zone. While the results of such surveys must be interpreted with caution, they can yield useful information about regional patterns of plant invasion.

Foraging ecology of three species of hipposiderid bats in tropical rainforest in north-east Australia

We studied the foraging ecology of three species of hipposiderid bats – Hipposideros diadema (mean forearm length: 82 mm), H. cervinus (47 mm) and H. ater (41 mm) – in tropical, lowland rainforest in north-east Queensland, Australia. H. diadema foraged by perching within gaps and flying out to intercept slow-flying insects. The two smaller species typically foraged during flight, in undisturbed forest and gaps, and captured insects by aerial hawking. Seven arthropod taxa were identified in faeces of H. cervinus, with Coleoptera and Lepidoptera being present in most faeces. Percentage volume of moth scales was generally low: 35 of 60 faeces had a volume of <10%, whereas all faeces (n = 60) of H. ater had a moth scale volume of >90%. No other taxa were frequently present in faeces of H. ater. Differences in foraging ecology between H. diadema and the smaller species were related to its large size and low manoeuvrability. The dietary differences we found between H. ater and H. cervinus were unexpected, because both species have high-frequency echolocation calls (160–164 and 144–145 kHz, respectively), which suggested that both would capture predominantly moths. Our data show that pairs of hipposiderid species with only small differences in call frequencies may consume different prey taxa; however, we contend that dietary variation is more likely to result from differences in body size, wing morphology, and tooth, jaw, and cranial morphology.

Quantifying Inputs of Pesticides to the Great Barrier Reef Marine Park – A Case Study in the Herbert River Catchment of North-East Queensland

The Great Barrier Reef Marine Park (GBRMP) is an ecosystem whose ecological features are recognized internationally. There is a need to evaluate the impacts of historical and contemporary changes in land use on the GBRMP. This paper quantifies pesticide inputs in the Herbert River catchment of North Queensland in the context of changes in land use over the last 100 years. We show that three major phases of rural land use and land cover change have occurred, with large areas of native vegetation converted to agricultural production. The increase in agricultural land has seen a corresponding increase in the area receiving pesticides. We present data showing application histories for organochlorine, organophosphate, phenoxy, triazine, urea, mercurial and azole group pesticides. While the fate of these pesticides in aquatic and marine systems is largely unknown, these trends pose a significant challenge for agricultural industries in complying with the principles of ecologically sustainable development (ESD).

Management of exotic pine plantations in northeast Queensland for goshawks

Summary As a compromise between forestry and wildlife needs, it has been recommended that a mix of native forest and plantation in various stages of succession be integrated to form a mosaic of different forest types. However, lack of detailed biological data on species dependent upon native forest has hampered the development of such an approach. Between 1987 and 1990, we monitored breeding and foraging activity of the Grey Goshawk Accipiter novaehollandiae and Brown Goshawk A. fasciatus in a North Queensland State Forest converted to exotic softwood Pinus caribaea production. Fifty per cent of the area was planted with pine aged between 1 and 9 years old, intermixed with native forest and woodland. The area supported several pairs of goshawks that bred only in large mature trees within native forest or woodland, but often used plantations for hunting where these formed ecotones with other habitats. Based on the results of this study we make the following preliminary recommendations for the conservation of goshawks in areas of managed plantation: (1) forest maintenance should be avoided, particularly around active goshawk nests, during the breeding season, from August to December; (2) an area of 20 ha of native forest should be retained as a buffer zone around any active goshawk nest; (3) woodland and forest along watercourses is particularly important goshawk habitat and a minimum width for riparian buffer zones is considered to be 200 m from the watercourse to the edge of P. caribaea plantations; (4) the ecotone between tall open forest and tall woodland that occurs adjacent to riparian closed forest is an important habitat for breeding goshawks and should be conserved wherever possible; and (5) the 50–50 mix of native woodland/forest and plantation, as at Abergowrie, appears able to sustain viable populations of goshawks, at least in the short-term.

The last glacial cycle from the humid tropics of northeastern Australia: comparison of a terrestrial and a marine record

A detailed pollen record from the Ocean Drilling Program Site 820 core, located on the upper part of the continental slope off the coast of northeast Queensland, was constructed to compare with the existing pollen record from Lynch's Crater on the adjacent Atherton Tableland and allow the production of a regional picture of vegetation and environmental change through the last glacial cycle. Some broad similarities in patterns of vegetation change are revealed, despite the differences between sites and their pollen catchments, which can be related largely to global climate and sea-level changes. The original estimated time scale of the Lynch's Crater record is largely confirmed from comparison with the more thoroughly dated ODP record. Conversely, the Lynch's Crater pollen record has assisted in dating problematic parts of the ODP record. In contrast to Lynch's Crater, which reveals a sharp and sustained reduction in drier araucarian forest around 38,000 yrs BP, considered to have been the result of burning by Aboriginal people, the ODP record indicates, most likely, a stepwise reduction, dating from 140,000 yrs BP or beyond. The earliest reduction shows lack of a clear connection between Araucaria decline and increased burning and suggests that people may not have been involved at this stage. However, a further decline in araucarian forest, possibly around 45,000 yrs BP, which has a more substantial environmental impact and is not related to a time of major climate change, is likely, at least partially, the result of human burning. The suggestion, from the ODP core oxygen isotope record, of a regional sea-surface temperature increase of around 4°C between about 400,000 and 250,000 yrs BP, may have had some influence on the overall decline in Araucaria and its replacement by sclerophyll vegetation.

Dry-Season Bird Diversity in Tropical Rainforest and Surrounding Habitats in North-east Australia

SummaryA quantitative analysis of bird species richness and abundance in habitats in and adjacent to rainforest in north-east Queensland, Australia, is presented. Bird assemblages in five habitats surrounding tropical rainforest were compared using line transects over a six-week period in the winter dry-season, between July and September 1995. Data were analysed using the Shannon—Weaver index of biodiversity and by a rarefaction method. Avian biodiversity was more variable between sites than between habitat types. While no habitat stood out at either extreme, diversity was highest in an area of riverine rainforest. Rainforest interior proved one of the poorest habitats for bird diversity. However, species assemblages were different among habitats, with 38% of species being found in only one habitat type.

Sap Suckers: A Novel Bird ‘Guild’ in Wet Sclerophyll Forests of Tropical North Queensland

[Extract] The sap of the Red Stringybark or Red Mahogany Eucalyptus resinifera is an important dietary component for the northern race of the Yellow-bellied Glider Petaurus australis reginae, locally named the Fluffy Glider (Quin 1996). In north-east Queensland, Yellow-bellied Gliders are classified as vulnerable, with a distribution limited to the wet sclerophyll forests at the western edge of the rainforest, between Daintree and Cardwell (Maxwell et al.1996). Harrington & Sanderson (1994) have shown that these wet sclerophyll forests have contracted by more than 50% in the past 50 years due to logging and invasion by rainforest. Yellow-bellied Gliders emerge at night to forage on sap, which is obtained by biting out small patches of bark from the trunk or main branches. Only E.resinifera is exploited in this way in north-east Queensland whereas a number of species of eucalypt are used in other parts of Australia (Russell 1995). Sap continues to exude during the day and birds regularly feed at the active sap-scars, an event that has been reported only by Russell (1981) in north-east Queensland. Goldingay (1996) briefly mentions diurnal use of the sap-feeding wounds but provides no details. This paper reports our observations of the species of bird using sap-scars; we discuss this behaviour and the factors influencing its occurrence.

Air mass and dynamic parameters affecting trade wind precipitation on the northeast Queensland tropical coast

Daily precipitation data for 21 rainfall reporting stations along the northeast Queensland tropical coast were collated for a period of 168 days during periods of sustained trade wind flow. Parameters that may influence precipitation were classified as either characteristic of the prevailing air mass or dynamic in nature. Parameters that displayed a high correlation with daily precipitation were derived by combining air mass and dynamic parameters. Dynamic parameters displayed stronger relationships with trade flow rainfall than upstream air mass indicators, with synoptic scale coastal forcing predominating. Derived parameters involving a combination of air mass and dynamic parameters provided the best individual indicators of daily precipitation with a linear correlation of up to 0.74 and 0.70 for regionalized and individual station daily rainfall, respectively. Linear regression techniques are used to develop five-parameter multivariate equations sourced from 1525 potential parameters. For the developmental data, the resulting equations account for 65 and up to 58% of the variance of regionalized and individual station daily rainfall, respectively. A 53 day trial test, using these equations on independent data produced a linear correlation of 0.83 and 0.68 for regionalized and individual station daily rainfall, respectively. © 1998 Royal Meteorological Society

Redefining the ecological niche of a tropical rain forest canopy tree species using airborne imagery: long-term crown dynamics of Toona ciliata

Past controlled growth experiments indicate that the seedling and sapling responses of the tropical rainforest canopy tree species Toona ciliata are most consistent with a light-demanding, early successional pioneer. This ecological niche assignment was tested in the mature stage of its life cycle after it achieves a position in the upper canopy. Mortality, survivorship and crown growth rates over the 18-y period 1976–1994 were measured using co-registered repeat airborne stereophotographic coverage of a representative forest stand in northeast Queensland, Australia, where T. ciliata had the fourth highest relative importance in a population of 46 co-occurring canopy tree species. The airborne re-inventory was conducted in a 3.6-ha sample area and limited to only canopy trees. The results were compared with a ground-based inventory of both canopy and subcanopy trees ≥10 cm dbh in a 0.5-ha permanent plot. Over the period 1976–1994, there was no mortality and no evidence of decline among T. ciliata conspecifics having crown areas >60 m2 and trunk diameters >30 cm. In the 3.6-ha airborne sample area, more than 85% of T. ciliata survivors experienced positive crown growth, in contrast to only 57% of the other co-occurring canopy trees. Toona ciliata's crown growth rates were highest in the 60–80-m2 crown size class. Upon reaching an upper canopy position, T. ciliata not only persisted as a dominant canopy tree species, but it also achieved some of the largest crown areas (>100 m2). Toona ciliata mortality in the ground-based plot involved mainly subcanopy trees of 10 – 30 cm dbh that had not yet assumed a canopy position and were not detectable in the aerial stereopairs. Both the crown and dbh growth rates of T. ciliata indicate enhanced vigour in the later stage of its life cycle. Its long-term survivorship and growth patterns are indicative of a persistent canopy tree species that fits the niche of a long-lived, shade-intolerant pioneer. These results demonstrate the usefulness of a long-term airborne database on the life-histories of canopy tree crowns for more clearly defining their ecological niches.

Pasture management in semi‐arid tropical woodlands: Effects on species diversity

Abstract The effects of pasture management options (sowing introduced legumes and grasses, timber treatment, applying fertilizer, cultivation before sowing, and stocking rate) on species diversity were measured at two experimental sites (Hillgrove and Cardigan) near Charters Towers, northeast Queensland. Species were divided into three groups (sown, native and exotic) and diversity was measured as species density (number of species recorded in each plot and number of species/quadrat) annually from 1982 to 1992. The responses of individual native and naturalized species to treatment were also determined. All management options affected diversity but the responses varied with site and season, and with the different measurement scales. The density of sown species either increased or was unaffected by all the management options; there were no significant decreases. The density of native species showed both positive and negative responses; it increased at high stocking rates and with tree killing at Hillgrove, and decreased with pasture sowing and cultivation. The density of exotic species increased as stocking rate was increased and decreased when pastures were sown (although not at the quadrat scale at Hillgrove). Overall the most diverse vegetation was on plots grazed at high stocking rates; at the plot scale these were native pastures but at the quadrat scale the sown pastures had more species. Among the native and naturalized species, only Portulaca spp. were more frequent on the oversown plots than the native pasture plots; 48% (Hillgrove) and 68% (Cardigan) of the species were less frequent on the oversown plots. Fertilizer application had little effect on species frequencies, while timber treatment resulted in both increases and decreases in frequency of a small number of species. The species were divided into four groups on the basis of their responses to stocking rate: a grazing‐sensitive group (e.g. Themeda triandra), two grazing‐tolerant groups which either slightly decreased (e.g. Chrysopogon fallax) or slightly increased (e.g. Sida spinosa) in frequency as stocking rate increased, and a fourth group of species which were frequent only at high stocking rates (e.g. Bothriochloa pertusa). There were no close relationships between herbage yield and species density.

Permo‐Carboniferous gold epoch of northeast Queensland*

The 40Ar/39Ar and U‐Pb methods of isotopic dating have been used to determine the age of alteration minerals and host rocks from a number of Permo‐Carboniferous Au deposits in the Tasman Fold Belt system of northeast Queensland. There was a continuum in porphyry‐style Au mineralisation from ca 330 to 290 Ma, which post‐dates epithermal Au in the Eastern Basin sequence of the Drummond Basin. Porphyry‐style Au at Kidston, and the Buck Reef, Ravenswood, formed at ca 330 Ma. The Red Dome and Mungana skarns were deposited at ca 320–310 Ma and ca 310 Ma, respectively. The Au mineralisation at Mt Wright, and in the quartz‐sulfide veins, Ravenswood, was emplaced at ca 310–305 Ma. The youngest porphyry‐style Au deposit is Mt Leyshon, which probably formed at ca 290 Ma. Where high‐level intrusions are associated with Au, magmatism and mineralisation are, in general, essentially coeval. The age of the host rocks to the Permo‐Carboniferous Au deposits is variable, and may be more than 150 million years older than the mineralisation. The plutonic‐style Au deposit at Charters Towers is significantly older than the porphyry systems, and formed at ca 414Ma.

The Abundance of the Rufous Owl Ninox rufa in Upland and Highland Rainforests of North-east Queensland

The Abundance of the Rufous Owl Ninox rufa in Upland and Highland Rainforests of North-east Queensland

Evolutionary Distinctiveness and Status of the Endangered Lake Eacham Rainbowfish (Melanotaenia eachamensis)

The Lake Eacham rainbowfish (Melanotaenia eachamensis) was declared extinct in the wild in the late 1980s after it disappeared from its only known locality, an isolated crater lake in northeast Queensland. Doubts have been raised about whether this taxon is distinct from surrounding populations of the eastern rainbowfish (Melanotaenia splendida splendida). We examined the evolutionary distinctiveness of M. eachamensis, obtained from captive stocks, relative to M. s. splendida through analysis of variation in mtDNA sequences, nuclear microsatellites, and morphometric characters. Captive M. eachamensis had mtDNAs that were highly divergent from those in most populations of M. s. splendida. A broader geographic survey using RFLPs revealed some populations, initially identified as M. s. splendida, that carried eachamensis mtDNA, whereas some others had mixtures of eachamensis and splendida mtDNA. The presence of eachamensis‐like mtDNA in these populations could in principle be due to (1) sorting of ancestral polymorphisms, (2) introgression of M. eachamensis mtDNA into M. s. splendida, or (3) incorrect species boundaries, such that some populations currently assigned to M. s. splendida are M. eachamensis or are mixtures of the two species. These alternative hypotheses were evaluated through comparisons of four nuclear microsatellite loci and morphometrics and meristics. In analyses of both data sets, populations of M. s. splendida with eachamensis mtDNA were more similar to captive M. eachamensis than to M. s. splendida with splendida mtDNA, supporting hypothesis 3. These results are significant for the management of M. eachamensis in several respects. First, the combined molecular and morphological evidence indicates that M. eachamensis is a distinct species and a discrete evolutionarily significant unit worthy of conservation effort. Second, it appears that the species boundary between M. eachamensis and M. s. splendida has been misdiagnosed, such that there are extant populations on the Atherton Tableland as well as areas where both forms coexist. Accordingly, we suggest that M. eachamensis be listed as vulnerable, rather than critical (or extinct in the wild). Third, the discovery of extant but genetically divergent populations of M. eachamensis on the Atherton Tableland broadens the options for future reintroductions to Lake Eacham.Distintividad Evolutiva y Estatus del Amenazado Pez Arcoíris (Melanotaenia eachamensis) del lago EachamEl pez acoíris del lago Eacham (Melanotaenia eachamensis) fue declarado extinto de poblaciones silvestres a finales de los 80’s después de su desaparición de la única localidad conocida, un cráter aislado en el noreste de Queensland. Se han incrementado las dudas acerca de si este taxón es distinto de las poblaciones circunvecinas del pez arcoiris del este (Melanotaenia spendida splendida). Examinamos la difernciación evolutiva de M. eachamensis, obtenida de stocks cautivos, en relación con M. s. splendida mediante un análisis de variación en secuencias de ADNmt, nuclear, microsatélites y caracteres morfométricos. M. eachamensis cautivos tuvieron ADNmt que difirió grandemente de aquellos provenientes de la mayoría de las poblaciones de M. s. splendida. Un estudio geográfico mas amplio usando RFLPs reveló que algunas poblaciones inicialmente identificados como M. s. splendida, contenían ADNmt de eachamensis, mientras que otros presentaron mezclas de DNAmt de eachamensis y splendida. La presencia de DNAmt del tipo de eachamensis en estas poblaciones, podría en principio, deberse a 1) una forma de polimorfismos ancestrales, 2) Introgresión del ADNmt de M. eachamensis hacia M. s. splendida o 3) límites incorrectos para las especies, tal como que algunas poblaciones actualmente asignadas al ADNmt de M. s. splendida son M. eachamensis o son una mezcla de las dos especies. Estas hipótesis alternativas fueron evaluadas mediante comparaciones de cuatro loci microsatélites nucleares y datos morfométricos y merísticos. En el análisis de ambas bases de datos, las poblaciones de M. s. splendida con DNAmt de M. eachamensis fueron mas similares a M. eachamensis cautivos que a M. s. splendida con ADNmt de splendida, esto soporta la hipótesis 3. Estos resultados son significativos para el manejo de M. eachamensis en diversos aspectos. Primero, las evidencias moleculares y morfológicas indican que M. eachamensis es una especie distintiva y una unidad evolutiva significante, lo suficientemente valiosa como para un esfuerzo conservacionista. Segundo, si parece que los limites de especies entre M. eachamensis y M. s. splendida han sido mal diagnosticados, a tal grado que hay poblaciones existentes en el altiplano de Atherton, asi como en áreas donde ambas formas coexisten. De acuerdo con esto, sugerimos que M. eachamensis debe ser enlistada como vulnerable, en lugar de crítica (o extinta). Tercero, el descubrimiento de poblaciones existentes, pero genéricamente divergentes de M. eachamensis en el altiplano de Atherton amplía las opciones para futuras reintroducciones en el lago Eacham. X775047

Learning From History to Survive in the Future: Management Evolution on Trafalgar Station, North-East Queensland.

Managing rangeland enterprises requires balancing socio-economic goals within a production environment characterised by ecological complexity and large climatic variability. Trafalgar Station in north-east Queensland, has been trying to maintain this balance over a period of 80 years and three generations of the one family. This paper explores how management on Trafalgar Station has gone through four evolutionary phases and examines the advantages and disadvantages of each of these stages of development. The first 50 years of management was a technologically constrained era of low stock numbers and poor productivity but there were few resource management problems. Next followed a 20 year period of production maximisation which was made possible by improved cattle genetics and nutritional technologies. With drought feeding occurring more frequently and loss of perennial grasses and soil becoming more evident, there came the realisation that this high stocking strategy was unsustainable. The management of Trafalgar then embarked on a new philosophy based on conservative stocking (similar to historical levels) and increased emphasis on herd, pasture and financial management. This new management philosophy required a transitional phase where stock numbers. and income, were very low to allow pasture condition to improve. Current herd management focuses on maintaining quality rather than quantity, strategic use of supplements for production, and developing a diverse range of markets for sale cattle. Conservative stock numbers have increased opportunities in pasture management with 15 to 20% of the property now annually rested from grazing. Fire has been reintroduced to restrict "thickening" of native woody plants and to control exotic woody weeds. Together with long-term financial planning, these improvements in management are reducing economic risk. The perceived benefits of the current management philosophy are supported by simulation modelling studies of pasture and animal production and analyses of property economics.

Tree-grass relationships in open eucalypt woodlands of northeastern Australia: influence of trees on pasture productivity, forage quality and species distribution

Pasture yield, quality and species distributions were compared between zones around live and killed eucalypt trees at two woodland sites in northeast Queensland which differed markedly in soil fertility. Trees affected pasture quality and yield on an individual tree basis: N concentration and dry matter digestibility tended to be higher under trees than in inter-tree areas at both sites and pasture yields declined with distance from killed trees at the lower fertility site. However, the distribution of individual species did not vary markedly with distance from trees. Trees also affected pasture yield on a woodland basis: yields were greater where the trees were killed than under intact woodland. Soil under trees had higher levels of organic carbon and greater litter cover than soil in inter-tree areas. However, pasture yields did not generally reflect this fertility gradient since growth was limited by moisture availability due to drought conditions during the study period. Pasture N concentration was higher under trees that in inter-tree areas since plants under trees produced a similar amount of biomass as plants in inter-tree areas, but had access to higher nutrient levels. Trees appeared to have a greater effect on soil nutrient availability at the low fertility site. Live trees depressed pasture yields to a lesser degree at the low fertility site, demonstrating that the effects of trees on soil water availability (on a woodland scale) are less important when soil nutrients are more limiting to growth. These results indicate that, while removing trees may enhance pasture productivity, this benefit may be offset by a reduction in pasture quality. Given the beneficial effect of trees on soil nutrients, tree removal may also have longer term implications for soil nutrient dynamics.

Responses by birds to fire regime and vegetation at the wet sclerophyll/tropical rainforest boundary

Changes in fire regime have been identified as the cause of the loss of nearly 50% of wet sclerophyll forest in north Queensland in the last 50 years. In the absence of fire, rainforest invades and eventually eliminates the specialized wet sclerophyll forest biota. Bird populations and foraging behaviour were monitored in areas selected to encompass both recent and advanced rainforest invasion. Foraging guilds are discussed in relation to increasing rainforest biomass. Some species, such as the Pale Yellow Robin Tregallasia capito nana were advantaged by the expansion of rainforest. Other species, such as the Golden Whistler Pachycephala pectoralis showed no significant response, whereas the endemic subspecies of the Eastern Yellow Robin Eopsaltria australis magnirostris was clearly disadvantaged. The latter species is of particular concern because in north-east Queensland it is dependent upon wet areas adjacent to rainforest and requires open ground in which to forage. Over the longer term the White-naped Melithreptus lunatus and White-cheeked Phylidonyris nigra Honeyeaters are also threatened by habitat loss. These honeyeaters favour the wetter areas adjacent to the rainforest which are gradually being lost to the invasive process. To maximize biological diversity in the wet tropics of north Queensland, it is necessary to maintain the full spectrum of natural habitats. Fire management is therefore required to maintain the wet sclerophyll forest and its dependent fauna.