bluuebunny/crossref_metadata_2025 huggingface dataset:
Patterns of tree species richness in relation to environment in southeastern New South Wales, Australia
Authors: AUSTIN M. P. , PAUSAS J. G. , NICHOLLS A. O.
Published: July 2006

Abstract
We present regression models of species richness for total tree species, two growth forms, rainforest trees (broadleaf evergreens) and eucalypts (sclerophylls), and two large subgenera of Eucalyptus. The correlative models are based on a data set of 166 tree species from 7208 plots in an area of southeastern New South Wales, Australia. Eight environmental variables are used to model the patterns of species richness, four continuous variables (mean annual temperature, rainfall, radiation and plot size), plus four categorical factors (topographic position, lithology, soil nutrient level and rainfall seasonality). Generalized linear modelling with curvilinear and interaction terms, is used to derive the models. Each model shows a significant and differing response to the environmental predictors. Maximum species richness of eucalypts occurs at high temperatures, and intermediate rainfall and radiation conditions on ridges with aseasonal rainfall and intermediate nutrient levels. Maximum richness of rainforest species occurs at high temperatures, intermediate rainfall and low radiation in gullies with summer rainfall and high nutrient levels. The eucalypt subgenera models differ in ways consistent with experimental studies of habitat preferences of the subgenera. Curvilinear and interaction terms are necessary for adequate modelling. Patterns of richness vary widely with taxonomic rank and growth form. Any theories of species diversity should be consistent with these correlative models. The models are consistent with an available energy hypothesis based on actual evapotranspiration. We conclude that studies of species richness patterns should include local (e.g. soil nutrients, topographic position) and regional (e.g. mean annual temperature, annual rainfall) environmental variables before invoking concepts such as niche saturation.
Competition between red kangaroos (Macropus rufus) and sheep (Ovis aries) in the arid rangelands of Australia
Authors: EDWARDS G. P. , CROFT D. B. , DAWSON T. J.
Published: July 2006

Abstract
Competition between red kangaroos and sheep in the more arid areas of Australia was examined by means of a large‐scale manipulative experiment incorporating two replicates of each of three treatments: sheep‐only, kangaroo‐only and a sheepAangaroo mixture. The study was conducted over two years during which time pasture conditions varied markedly. Competition was intermittent, occurring only during a period of climatically related food depletion (semi‐drought). At this time there was a large increase in kangaroo densities due to an influx of kangaroos from neighbouring areas. Competition reduced live‐weight in sheep but had no significant impact on wool production. This effect was linked to diet selection. Competition caused red kangaroos to favour paddocks destocked of sheep but had no detectable effect on the condition of kangaroos.
Environmental gradients across four rainforest‐open forest boundaries in northeastern Queensland
Authors: TURTON S. M. , SEXTON G. J.
Published: July 2006

AbstractThis paper examines gradients and correlations among nine environmental factors across four contrasting rainforest‐open forest boundaries at Skull Pocket in northeastern Queensland. With few exceptions, the environmental factors formed significant gradients across all four boundaries. Gradients were most pronounced for canopy openness, depth of leaf litter, soil pH, soil temperature and understorey solar radiation, and least pronounced or non‐existent for total nitrogen and organic carbon. Boundary site location was shown to have some influence on the degree of change in environmental factors across the rainforest‐open forest boundary, with depth of leaf litter, organic carbon, soil temperatures in March and June, and understorey solar radiation in June being significantly different among the four boundary sites. The number of significant correlations among the nine environmental factors was also affected by boundary site location.
Fish and decapod crustaceans inhabiting drifting algae in Jervis Bay, New South Wales
Authors: LANGTRY SCOTT K. , JACOBY CHARLES A.
Published: July 2006

Abstract
This study documents the fish and decapod crustaceans inhabiting a bed of Gracilaria verrucosa that was drifting on the bottom of a temperate marine embayment in relatively deep water (15‐ 18m) during autumn 1991. Fauna were sampled with diver‐operated enclosure nets. Relatively few species inhabited the algae at this time, and the assemblage was primarily a subset of that in adjacent Posidonia australis beds. Three fish species [Neoodax balteatus (Odacidae), Cristiceps australis (Clinidae), Siphamia cephalotes (Apogonidae)] and one species of crab [Nectocarcinus tuberculosus (Portunidae)] dominated the catches numerically. A further 14 fish and decapod species were relatively rare. Neoodax balteatus, C. australis and N. tuberculosus were caught at all life stages and appeared to be permanent residents of the Gracilaria. Few juveniles of other species were captured, which indicates that these algal wracks may not be an important nursery habitat for seasonally resident fish species. Trachurus novaezelandiae and a number of other fish species that associate with a variety of benthic habitats appeared to be transient visitors. The biomass of algae varied significantly within the bed, but algal biomass was not a good indicator of faunal abundances. The low species richness of the fish and decapod crustacean assemblage may be related to both lower recruitment in deeper water and to unfavourable characteristics of the alga.
The abundance and growth of Avicennia marina and Rhizophora stylosa in the low shore zone of Darwin Harbour, Northern Territory
Authors: O'GRADY A. P. , MCGUINNESS K. A. , EAMUS D.
Published: July 2006

Abstract
The growth and distribution of the two mangrove seedling species, Avicennia marina (Forsk.) Vierh. and Rhizophora stylosa Griff., were studied in the low‐shore zone at three locations along two estuaries of Darwin Harbour to determine how growth varied along the estuary and within the habitats of the low shore zone. The low shore environment was heterogenous for factors such as salinity and light, with substantial variation within and between locations. Seedlings of Avicennia were in higher densities in light gaps than in the adjacent forest, and density in both habitats decreased towards the mouth of the estuary. Growth of Avicennia seedlings, as measured through in situ growth trials and plant harvests, increased towards the mouth of the estuary. Results for Rhizophora seedlings were more complex although some similar trends were evident. This may have been due to the greater early survival of Rhizophora seedlings compared to Avicennia seedlings. The importance of propagule origin was investigated, for Rhizophora, by transplanting propagules between locations along one estuary. Increased seedling survival was observed at the propagule source site; however, this effect was subtle and probably not the most important factor affecting seedling survival at a site.
Littoral benthos of a Victorian lake and its outlet stream: Spatial and temporal variation
Authors: QUINN G. P. , LAKE P. S. , SCHREIBER E. S. G.
Published: July 2006

Abstract
There have been few comparative studies of the fauna in the two major types of freshwater systems, lakes and streams, in the one locality. This study compared the faunal assemblages at two times of the year (summer and winter) on stones in three locations: the littoral zone of two shores in Lake Purrumbete (one wave‐exposed and one sheltered) and riffles in the Curdies River, which flows out of the lake. The lake fauna was dominated by crustaceans, gastropods and planarians, whereas the stream fauna was dominated by insects. The most abundant lake taxa were also present, but much less abundant, in the stream. The total number of species and individuals and densities of some common species varied between the three locations and between seasons. However, no consistent pattern reflecting a difference between the two lake shores was evident. Interpretation of MDS ordinations of the lake fauna was dependent on the data standardizations applied, with increased separation of the season‐location combinations when species were standardized to equal total abundances; the seasonal difference was always greatest for the exposed (cliff) shore. In contrast, MDS on the stream fauna showed seasonal differences under all standardizations. This was consistent with the high seasonal turnover of species in the stream compared with the lake. These results demonstrate that, even within a local area with similar geology and connected water bodies, lake and stream fauna from the same substratum (stones) can be markedly different. Taxa that occurred in both were more abundant in the lake, whereas seasonal differences in abundance were much greater in the stream.
Fire weather in the wet‐dry tropics of the World Heritage Kakadu National Park, Australia
Authors: GILL A. M. , MOORE P. H. R. , WILLIAMS R. J.
Published: July 2006

Abstract
Seasonal changes of weather and fuels in the wet‐dry tropics are dramatic; fires follow suit. In this paper, we examine quantitatively rainfall, evaporation, wind, temperature and humidity information, and indices derived from them, for Kapalga Research Station and nearby Jabiru in World Heritage Kakadu National Park, Northern Australia. At Kapalga, the average annual rainfall of about 1200mm mostly falls during a 6 month wet season. Grasses, green in the wet, begin to desiccate during the early dry season. Perennial grasses cure more slowly than the annuals, and grasses in drainages cure later than those on ridges. Fire weather is usually most severe in September‐October (late dry season) and least severe in January‐February (late wet season). As the dry season progresses to its peak, daily wind patterns change, daily maximum temperatures increase to an average of 36°C, dew points drop to a minimum, and soil moisture is severely depleted. In the early dry season (cf. later), fires have a greater tendency to go out at night compared with later perhaps because winds then are calmer, fuels are more discontinuous, and relights from burning logs are less likely to occur. Fire weather in the north of Australia appears less severe than that in the southeast of the continent where socially disastrous fires occur periodically.
The effect of the taxon and geographic range size of host eucalypt species on the species richness of gall‐forming insects
Authors: BLANCHE K. ROSALIND , WESTOBY MARK
Published: July 2006

Abstract
This field study was designed to test whether the taxonomic group and geographic range size of a host plant species, usually found to influence insect species richness in other parts of the world, affected the number of gall species on Australian eucalypts. We assessed the local and regional species richness of gall‐forming insects on five pairs of closely related eucalypt species. One pair belonged to the subgenus Corymbia, one to Monocalyptus, and three to different sections of Symphyomyrtus. Each eucalypt pair comprised a large and a small geographic range species. Species pairs were from coastal or inland regions of eastern Australia. The total number of gall species on eucalypt species with large geographic ranges was greater than on eucalypt species with small ranges, but only after the strong effect of eucalypt taxonomic grouping was taken into account. There was no relationship between the geographic range size of eucalypt species and the size of local assemblages of gall species, but the variation in insect species composition between local sites was higher on eucalypt species with large ranges than on those with small ranges. Thus the effect of host plant range size on insect species richness was due to greater differentiation between more widespread locations, rather than to greater local species richness. This study confirms the role of the geographic range size of a host plant in the determination of insect species richness and provides evidence for the importance of the taxon of a host plant.
Natural 15N abundance of vegetation and soil in the Kapalga savanna, Australia
Authors: MORDELET PATRICK , COOK GARRY , ABBADIE LUC , GRABLY MICHELINE , MARIOTTP ANDRÉ
Published: July 2006

Abstract
The natural abundance of the stable isotope 15N was measured in different vegetation components and in the soil of a northern Australian savanna. Most of the vegetation was found to be 15N‐depleted compared to atmospheric N2. Herbaceous legumes, perennial grasses, tree legumes, non‐legume trees and annual grasses exhibited mean δ15N of − 1.7, − 0.8, − 0.7, 0.0 and + 0.3‰, respectively. These results are in good agreement with previous studies. Legumes exhibit slightly negative values, indicating that they are likely to be nitrogen‐fixing plants. Non‐legume plants have a δ15N close to zero, which could equally result from non‐symbiotic fixation, soil organic matter mineralization, or fresh root litter mineralization. In contrast, soil organic matter was 15N‐enriched. Values of δ15N increased with depth and were + 2.5, + 5.2 and +6.1‰ in the 0–10, 10–20 and 20–40cm layers, respectively. Soil organic matter δ15N shows a typical profile of mature soils.
Nest predation in Australian urban environments and the role of the pied currawong, Strepera graculina
Authors: MAJOR RICHARD E. , GOWING GREG , KENDAL CAITLIN E.
Published: July 2006

Abstract
An experiment, involving 2000 members of the public, determined the identity of nest predators in urban environments. Experimental nests of halved tennis balls covered with coconut fibre and wool were manufactured to resemble the nests of willie wagtails, Rhipidura leucophrys. The identity of predators was determined by analysis of imprints left in artificial eggs made of coloured modelling clay. Sixty‐four per cent of nests were preyed upon, with most predation being the result of large birds. Direct observations of predation (n = 134) indicated that pied currawongs were the most common large bird, accounting for 52% of all predation. Predation incidence was higher in gardens with more trees and in which kookaburras, Dacelo novaeguineae, were fed frequently. Among nests placed in trees, nest predation was correlated with nest height. Eggs camouflaged by speckling experienced a similar incidence of predation to plain eggs. This study provides evidence to support the contention that pied currawongs are a major threat to the persistence of small birds in Australian urban environments.
Foraging strategies in orb‐spinning spiders: Ambient light and silk decorations in Argiope aetherea Walckenaer (Araneae: Araneoidea)
Authors: ELGAR M. A. , ALLAN R. A. , EVANS T. A.
Published: July 2006

Abstract
Many species of orb‐spinning spiders construct silk decorations within the structure of the orb‐web. The evolutionary significance of these decorations is poorly understood, but the silk decorations of many species reflect UV light, suggesting that they may function to attract insects. In these species, relatively more silk decoration may be required under dimmer light conditions in order to maintain a constant UV‐reflecting signal, and hence level of insect attraction. We investigated experimentally whether the orb‐spinning spider Argiope aetherea adjusts the amount of silk decoration added to the web according to light conditions. Consistent with the prey‐attracting function, we found that spiders adjusted the quantity of silk decoration to their webs, adding more silk decoration when the web was located in dim light rather than bright light.
The distribution and abundance of barnacles in a mangrove forest
Authors: ROSS P. M. , UNDERWOOD A. J.
Published: July 2006

Abstract
The grey mangrove tree, Avicennia marina, forms a hard substratum in an area otherwise dominated by soft‐sediment. Various intertidal organisms attach to and move about on the trees. The abundant barnacles Elminius covenus, Hexaminius popeiana and Hexaminius foliorum live on a variety of substrata in mangrove forests. Their patterns of distribution and abundance were recorded and models proposed to explain these patterns. Densities of barnacles on bark, leaves and twigs of A. marina were estimated in a locality near Sydney. Elminius covenus were more abundant on bark than on leaves or twigs of A. marina. Hexaminius popeiana, although less abundant on bark than E. covenus, were not found on twigs or leaves. In contrast, H. foliorum were more abundant on twigs than leaves and were not found on the bark of A. marina. Densities of barnacles were greater in the seaward than in landward parts of the forest. Elminius covenus were the most abundant barnacles, H. foliorum were less abundant and H. popeiana were virtually absent in the landward zone. Barnacles in the seaward zone were most abundant at mid‐tidal levels, less at high and low tidal levels of trunks and more abundant on lower than upper surfaces of trunks and leaves. The densities of barnacles differed according to the orientation of the bark or leaf.

Models are proposed to explain the patterns of distribution and abundance of these barnacles. Each involves larval supply, settlement and post‐settlement mortality. It is concluded that similar processes determining patterns of distribution and abundance for sessile organisms living on rock platforms may be applicable to sessile organisms living in the very different habitats of mangrove forests.
Post‐fire regrowth and survival of the invasive tropical shrubs Cryptostegia grandiflora and Ziziphus mauritiana
Authors: GRICE A. C.
Published: July 2006

Abstract
Exotic shrubs are significant invaders of the tropical woodlands of northern Australia. They cause problems for pastoral industries and are likely to induce significant change in woodland communities. A single fire in the middle of the dry season affected the survival and vegetative growth of two important shrub species, Cryptostegia grandiflora and Ziziphus mauritiana. The fire killed about 96% of small plants (height < 100cm), 80% of medium‐sized plants and 45% of large plants (height > 200cm) of C. grandiflora. However, only about 10% of small Z. mauritiana were killed. Most plants of Z. mauritiana resprouted vigorously within three months of the fire. Effects on the vegetative phenology of C. grandiflora persisted until 10 months after the fire, but by four months after the fire, burnt and unburnt Z. mauritiana were similar as regards the distribution of individuals between phenological categories. Changed fire regimes may partially explain the colonization of northern and northeastern Queensland by C. grandiflora but probably had little effect on Z. mauritiana. Fire has significant potential as a tool in the management of C. grandiflora wherever adequate grass fuel can be attained. The use of fire will be particularly valuable for preventing range expansion, for situations where the species is in the early stages of invasion and in parts of the landscape where densities are relatively low.
The independent effects of heat, smoke and ash on emergence of seedlings from the soil seed bank of a heathy Eucalyptus woodland in Grampians (Gariwerd) National Park, western Victoria
Authors: ENRIGHT N. J. , GOLDBLUM D. , ATA P. , ASHTON D. H.
Published: July 2006

Abstract
The independent effects of smoke, ash, and wet and dry heat treatments on seedling emergence from the soil seed bank were tested for soils from fire‐prone heathy woodlands in western Victoria. A total of 763 individuals from 56 species were recorded from the surface soil samples (which covered a total area of 1 m2). Both species richness and density of seedlings was greater for smoke‐ and heat‐treated samples than for controls and ash‐treated samples. However, only the density differences were significant. Mean seed bank densities for the smoke and heat treatments ranged from 855 ± 70m−2 to 1080 ± 58 m−2 and are similar to estimates obtained elsewhere in Australia for heat‐treated soils from dry sclerophyll communities. Of the 56 species recorded, 46 occurred in the smoke and heat treatments but only 33 in the control and ash treatments. The sudden increase in surface soil pH, exchangeable cations and extractable phosphorus which was associated with the ash treatment did not act as a trigger for germination in any of the species recorded here. Chemical constituents from smoke do appear to provide a stimulus separate from the effects of heat, but were not identified with any particular taxa.
Fire and habitat management for a mycophagous marsupial, the Tasmanian bettong Bettongia gaimardi
Authors: JOHNSON C. N.
Published: July 2006

Abstract
The Tasmanian bettong, Bettongia gaimardi, is a mycophagous marsupial that occurs in fire‐prone dry sclerophyll forests. Previous studies have demonstrated that some of the hypogeous fungi on which it feeds become abundant soon after fire, and have suggested that it might depend on regular burning of its habitat. The longer‐term effects of burning on B. gaimardi and its food supply were evaluated by comparing six sites, matched for soil, vegetation and climate, in southeastern Tasmania that had been left unburnt for periods ranging from 1 to 50 years. At each site, the density of B. gaimardi diggings was measured and sporocarps of hypogeous fungi were surveyed. Abundance of hypogeous sporo‐carps was low at sites 2 years or less post‐fire, but was high at sites 4 years and more post‐fire. Species richness was similarly low at recently burnt sites, an effect that was due to the absence of many shallow‐fruiting taxa. All species (with one exception) present at recently burnt sites were also present in long‐unburnt sites. Densities of B. gaimardi diggings were highest at a very recently burnt (<1 year) site and at a site left unburnt for 10 years. These trends suggest that a high frequency of burning may be unfavourable to B. gaimardi in the forest type investigated in this study.
Resilience of an Australian savanna grassland to selective and non‐selective perturbations
Authors: WALKER B. H. , LANGRIDGE J. L. , McFARLANE F.
Published: July 2006

Abstract
Using a randomized experimental design, plots of a savanna grassland were subjected to two levels of grass tuft removal (50% and 90%) in two ways; non‐selective (all species removed in proportion to abundance) and selective (tufts of the most palatable species removed first, then the next most palatable, etc.). The plots were maintained in their cleared states for three years, then monitored for the next five. In general, the sward was resilient to the disturbance except for the 90% selectively cleared treatment, in which a dominant, palatable species (Themeda triandra) failed to recover (though die most palatable species, Sorghum plumosum, did recover). The recovery patterns were dependent on post‐disturbance conditions, and markedly influenced by a particular rainy season and a fire during one of the dry seasons. In addition to species effects, the treatments induced changes in spatial patterning and associated micro‐scale hydrology. These effects persisted in the 90% removal treatment. In this regard the results are scale‐dependent, and the same percentage removals at different scales (e. g. 5 × 5 m patches rather than tuft × tuft scale) would lead to differences in ability to recover. In terms of value to livestock the selective 90% removal treatment was in a poor state at the end of die experiment.

In all treatments die trajectory of species changes was back towards the controls, but the selective 90% plots were fully re‐vegetated before this could be achieved. In these plots, the final steps to complete recovery will occur only after death of established new tufts.
Rapid invasion of a sponge‐dominated deep‐reef by Caulerpa scalpelliformis (Chlorophyta) in Botany Bay, New South Wales
Authors: DAVIS A. R. , ROBERTS D. E. , CUMMINS S. P.
Published: July 2006

Abstract
We document the rapid spread of the green alga Caulerpa scalpelliformis (R. Brown ex Turner) C. Agardh following its establishment in Botany Bay. In February 1996 we estimated that this alga occupied at least 0. 35 hectares of the substratum within the Bay. Coincident with the increase in algal cover on the deep‐reef habitat has been a substantial decline in the cover of sessile invertebrates, predominantly sponges, colonial ascidians and bryozoans. Within 12 months of the appearance of the alga at Inscription Point, random photoquadrats (n= 15) revealed that it had reached an average cover of 56 ± 11% with an estimated average fresh biomass of 5.2 ± 1.1 kg m−2 (±sem). Over the same period the average cover of sessile invertebrates declined from 48 to 23%; a significant change by mixed‐model nested ANOVA. No such decline was observed in reference sites at Henry Head at the northern entrance to the Bay. Within 12 months, the alga had spread to an additional location some 300 m to the east of the originally monitored location, underscoring its ability to rapidly expand across continuous reef. Moreover, the appearance of small isolated plants at the northern entrance to the Bay, indicates that it is also capable of establishing on non‐continuous reef.
Ecological aspects of soil seed‐banks in relation to bauxite mining. I. Unmined jarrah forest
Authors: WARD S. C. , KOCH J. M. , GRANT C. D.
Published: July 2006

Abstract
Germinable seed stores were measured in jarrah forest soils at six sites during one year. The overall mean seed content to a depth of 5 cm was 292 seeds m−2. There was a significant seasonal difference, with a maximum of 435 seeds m−2 in summer, after the majority of species in this Mediterranean ecosystem had flowered and set seed, and a minimum of 207 seeds m−2 in winter. There were also large site differences in both the densities of seed present and the species represented in the soil seed store. More than 85 species were represented in the germinable seed store from a total sampling area of 17.28 m2. The germination of Acacia drummondii, Acacia pulchella, Bossiaea aquifolium, Kennedia coccinea, Lasiopeialum floribundum and Trymalium ledifolium were significantly increased by heating the soil. Smoke produced a significant positive germination response in one species (Trymalium ledifolium). To maximize the contribution of the soil seed store to mine rehabilitation, the ideal revegetation sequence is to collect the topsoil immediately after clearing the vegetation in summer, immediately return the soil to an area to be revegetated, and carry out all earthmoving, landscaping and seedbed preparations prior to the onset of the autumn rains.
Amphibian communities associated with billabong habitats on the Murrumbidgee floodplain, Australia
Authors: HEALEY MICHAEL , THOMPSON DAVID , ROBERTSON ALISTAR
Published: July 2006

Abstract
A study of frog species richness and abundance at four permanent billabongs located in and around the city of Wagga Wagga, southern New South Wales, was carried out from the spring of 1991 to the autumn of 1992. During the sampling period a total of 404 individual adult frogs from six species were recorded. No egg masses or tadpoles were detected during a total of 32 survey hours. Four species of the Family Myobatrachidae represented 81% of the total number of adult individuals sampled, the remaining species belonging to the Family Hylidae. There were significant differences in the mean species richness and mean total number of adult individuals among billabongs. Significant positive correlations were recorded between total adult individuals, total frog species richness and the number of riparian plant species recorded at all billabongs. There were no significant correlations between adult frog numbers and meteorological and water quality parameters. The adults of the four most abundant frog species exhibited significant association with particular microhabitats surrounding billabongs; Crinia parinsignifera was associated with the creeping grass Paspalum distichum, Limnodynastes fletcheri with the rush Eleocharis sphacelata, L. tasmaniensis with sedges Cyperus spp. and the grass P. distichum and Litoria peronii with red gum Eucalyptus camaldulensis and introduced tree species. Differences in adult frog abundance between billabongs appears to be related to the disturbance of riparian vegetation by domestic stock, while the absence of eggs and tadpoles from these permanent billabongs may be explained by the presence of abundant exotic fish species in the billabongs.
The impact of experimental fire regimes on seed production in two tropical eucalypt species in northern Australia
Authors: SETTERFIELD SAMANTHA A.
Published: July 2006

Abstract
This study investigated the effect of three experimental fire regimes on the fecundity, ovule development and seedfall of two common wet‐dry tropical savanna eucalypts, Eucalyptus minima and Eucalyptus tetrodonta, in northern Australia. Both species flower early in the dry season and ovule development occurs during the dry season. This coincides with a period of frequent fires. The three fire regimes considered were applied for four years between 1990 and 1994. These regimes were (i) Unburnt, (ii) Early, fires lit early in the dry season, and (iii) Late, fires lit late in the dry season. The treatments were applied to nine catchments (15–20 km2) with each fire regime replicated three times. Fire intensity typically increases as the dry season proceeds. Therefore, early dry season fires generally differ from late dry season fires in both their intensity and their timing in relation to the reproductive phenology of the eucalypts. Late dry season burning significantly reduced the fecundity of both species, whereas Early burning had no significant effect. Ovule success was significantly reduced by the Early burning for both species. The Late burning significantly reduced ovule success in E. tetrodonta, but not in E. miniata. The results suggest that fire intensity and fire timing may both be important determinants of seed supply. Fire intensity may be a determinant of fecundity, whereas fire timing in relation to the reproduction phenology may have a significant impact on ovule survival. Both fire regimes resulted in a substantial reduction in seed supply compared with the Unburnt treatment. This may have a significant impact on seedling regeneration of these tropical savanna eucalypts.
A method of selecting data points for fitting the maximum biomass‐density line for stands undergoing self‐thinning
Authors: BI HUIQUAN , TURVEY NIGEL D.
Published: July 2006

Abstract
A problem that has always existed in self‐thinning studies is the lack of objectivity in determining which data points to include when fitting the maximum biomass‐density line. This paper demonstrates a more objective method of selecting data points using data from 12 even‐aged Pinus radiata stands undergoing self‐thinning. The method involves the division of a cluster of data points into a specified number of intervals. From each interval, that point having the maximum stand biomass is selected to contribute to the fitting process. This process is repeated a specified number of times using an increasing number of intervals. Each time an estimate of the line is obtained. From these estimates, one can be chosen to represent the maximum biomass‐density line. The method may also be useful in other areas involving the definition of a boundary condition.
Functional importance vs keystoneness: Reformulating some questions in theoretical biocenology
Authors: HURLBERT STUART H.
Published: July 2006

Abstract
Two concepts relating to the influence of individual species on the biocenoses in which they occur are reviewed. The first, the general functional importance of a species, is denned as the sum, over all species, of the changes (sign ignored) in productivity which would occur on removal of the particular species from the biocenosis. General functional importance is calculated as:
image

where Pj is the productivity of the jth species before (t= 0) and after (t= 1) removal of the particular (ith) species being evaluated. Though Ii values cannot be determined empirically, this concept raises provocative questions for theoretical biocenology. The second concept reviewed is that of the keystone species. Never having been precisely or operationally defined,‘keystone’ has come to mean little more than ‘important for something.’ Moreover, there is no empirical or theoretical foundation for the idea that there exists in any biocenosis a natural dichotomy corresponding to the verbal one of keystone and non‐keystone species. Some investigators have implied that such a dichotomy is suggested by the frequency distributions of experimentally determined values of interaction strength. The patterns they refer to are, however, artifacts resulting from small sample sizes and the plotting of frequency distributions on arithmetic rather than logarithmic scales. As a casual metaphor ‘keystone species’ was appealing and harmless; but the pretence that it is a well‐defined concept or phenomenon has had a stultifying effect on ecological thought and argument.
Ecological and economic analysis of lake eutrophication by nonpoint pollution
Authors: CARPENTER STEPHEN R. , BOLGRIEN DAVID , LATHROP RICHARD C. , STOW CRAIG A. , REED TARA , WILSON MATTHEW A.
Published: July 2006

Abstract
The hypothesis that economic damage due to nonpoint pollution exceeds costs of mitigation can be tested by ecologists, economists, and resource managers working at the spatial scale of watersheds for periods of years to decades. We present a framework for combining ecological and economic information to compare management scenarios for nonpoint pollution. Eutrophication of lakes caused by nonpoint phosphorus pollution, a common environmental problem, is the focus of our approach. Economic advantages of mitigating nonpoint pollution increase as the uncertainty of ecological predictions decreases. Uncertainty is measured by the prediction variance of nonpoint pollution models. A major source of variance in nonpoint pollution predictions is the effect of land use change on phosphorus transport. This variance is often large because calibration data sets do not have sufficiently wide ranges of land use variables. Ecological predictions and the resulting economic assessments could be improved by comparative studies of watersheds with contrasting land uses, and by viewing nonpoint pollution management as a large‐scale experiment.
Spatial scales in the study of reef fishes: A theoretical perspective
Authors: CHESSON PETER
Published: July 2006

Abstract Theoretical models imply that spatial scale derives its greatest importance through interactions between density‐dependent processes and spatial variation in population densities and environmental variables. Such interactions cause population dynamics on large spatial scales to differ in important ways from predictions based on measurements of population dynamics at smaller scales, a phenomenon called the scale transition. These differences can account for large‐scale population stability and species coexistence. The interactions between density dependence and spatial variation that lead to the scale transition can be understood by the process of non‐linear averaging, which shows how variance originating on various spatial scales contributes to large‐scale population dynamics. Variance originating below the scale of density dependence contributes less to the scale transition as the spatial scale of the variation declines, while variation originating on or above the scale of density dependence contributes independently of the spatial scale of the variation.
Implications of body size for interspecific interactions and assemblage organization among coral‐reef fishes
Authors: ROBERTSON D. ROSS
Published: July 2006

Abstract Population size‐structure is often ignored in assemblage‐level studies of reef fishes, which usually rely on static and dynamic patterns of relative total abundance to infer what mechanisms organize those assemblages. However, body size has substantial effects on processes that affect competitive relationships between species: (i) small, recently recruited fish, which usually(?) suffer high mortality, can dominate total abundance and strongly influence the dynamics of the relative total abundances of different species, while having little effect on interspecific biomass relations; (ii) numeric abundance and biomass of a species can vary independently, due to habitat variation in population size‐structure resulting from variation in mortality and growth, as well as habitat selection; and (iii) population size‐structure affects the potential for and outcome of interspecific competition due to (a) ontogenetic change in types of resources used, (b) levels of resource needs being dependent on individual and species biomass rather than numbers, (c) advantages due to large size in behavioural contests, (d) variation in population size‐structure being linked to habitat preference, which affects expression of competitive dominance, and (e) size dependency in the development of interspecific resource‐sharing relationships. Assemblage‐level analyses that ignore such size effects may fail to detect important effects of interspecific interactions.
Spatial subdivision within a population of tropical pythons (Liasis fuscus) in a superficially homogeneous habitat
Authors: MADSEN THOMAS , SHINE RICHARD
Published: July 2006

Abstract Based on 10 years of intensive fieldwork, we describe the spatial and temporal distribution of water pythons (Liasis fuscus) on the Adelaide River floodplain, Northern Territory, Australia. Our study provides a cautionary tale, because it was only after several years’ work that we realized that our apparently panmictic study ‘population’ in fact consisted of three subpopulations that were separated during breeding activities although they intermingled for most of the year. The partitioning of the populations is due to the restricted availability and spatial separation of suitable nest‐sites (varanid burrows vs root complexes of paperbark trees). Groups of snakes using each type of nest‐site comprise quite separate breeding populations, because females move to these sites prior to mating. Snakes return to the same breeding sites year after year, with little dispersal between populations (even though snakes from each population often move through other breeding sites during the non‐breeding period). The three subpopulations differed in many traits, including body‐size distributions, age structures, the proportions of reproductive animals, survival rates, timing of reproduction, and reproductive frequencies. Thus, if our study had involved only one of the subpopulations (as would typically be the case with studies of this kind), we would have obtained a misleading view of the ‘real’ (i.e. average) ecological characteristics of our study organisms.
Soil seed bank dynamics in the rare obligate seeding shrub, Grevillea barklyana (Proteaceae)
Authors: VAUGHTON GLENDA
Published: July 2006

Abstract Grevillea barklyana is a rare, obligate seeding shrub that occurs in fire‐prone heath and woodland in southeastern Australia. The size and dynamics of the soil seed bank were investigated in populations 2–29 years after fire in order to identify fire frequencies that would threaten population survival. Plants began flowering 2 years after fire (16%), but maximum inflorescence and seed production did not occur until 15–16 years after fire when plants were full size. Seed production declined in older populations. Fruit:flower ratios were very low (0.1–5.3%). Most flowers (> 95%) failed to initiate fruits. Of the initiated fruits, about 60% aborted, 27% were attacked by parrots and 13% matured. An exclusion experiment showed that fruits attacked by parrots would have otherwise matured. Seeds were consumed on the soil surface by mammals, particularly rodents. Post‐dispersal seed losses were consistently high in all months and in all populations (78–100%). Mortality of adult plants increased with time since fire. In the 29‐year‐old population, 30% of plants were dead and 33% were senescent. Recruitment was negligible in the absence of fire, but following fire the seedling to parent ratio was 20:1. Seedling survival was high (90%) following two years of above‐average rainfall. The observed seed bank was small (3–16 seeds irr) and increased during the first 16 years after fire before declining in the 21‐ and 26‐year‐old populations. The size and dynamics of the seed bank may limit population numbers, especially if the intervals between fires are less than 10 years or greater than 25 years.
Requirement of vegetation gaps for seedling establishment of two unpalatable grasses in a native grassland of central Argentina
Authors: MORETTO ALICIA S. , DISTEL ROBERTO A.
Published: July 2006

Abstract The objective was to determine the effects of root and shoot competition on seedling establishment of the unpalatable grasses Stipa gynerioides and S. tenuissima in a native grassland of central Argentina dominated by the palatable grass S. clarazii. Seeds of the two unpalatable species were sown in natural occurring microsites with shoot and root competition from the palatable species, and in artificially created microsites without either shoot competition or shoot and root competition. In addition, fresh seeds of the unpalatable species were subjected to daily alternating temperatures under laboratory and field conditions to determine the effect on seed dormancy and germination. Seedling establishment of S. gynerioides and S. tenuissima occurred only in microsites without shoot and root competition. Also, the fluctuation of temperature near the soil surface in these microsites reduced dormancy and promoted rapid germination in both species. Our results support the hypothesis that, in swards dominated by palatable grasses, vegetation gaps of low competitive pressure favour seedling establishment of unpalatable grasses. It is suggested that the creation of these gaps by overgrazing can be an important mechanism in the process of species replacement in native grasslands.
An analysis of diet specialization in frugivorous Pteropus poliocephalus (Megachiroptera) in Australian subtropical rainforest
Authors: EBY PEGGY
Published: July 2006

Abstract The Grey‐headed flying fox Pteropus poliocephalus Temminck 1825 is the only mammalian frugivore to occupy substantial areas of the subtropical rainforests of eastern Australia. The composition of the P. poliocephalus diet and diet specialization in the species are therefore pertinent to studies of trophic structure, seed dispersal and evolutionary processes in these forests. During a three‐year diet study, P. poliocephalus used fruits from 44 species of canopy and edge plants. Their taxonomically diverse diet was dominated by the Myrtaceae and Moraceae. Dietary specialization by P. poliocephalus was examined using two criteria: the influence of fruit morphology on diet choice and dietary overlap with sympatric avian frugivores. There was no evidence from either approach that they were specialist feeders. Initial analyses comparing the morphological characters of diet fruits with fruits available to P. poliocephalus during the study period showed a preference for white fruits, berries, syconia and fruits with multiple seeds, and avoidance of black fruits and drupes. However, these significant results were not sustained when the confounding effects of correlations between fruit morphology and other traits were considered. All, except the response to berries, could be attributed to either avoidance by P. poliocephalus of secondary compounds in the Lauraceae or selection for the beneficial phenology of Ficus. Dietary overlap with frugivorous birds was notably high and the fruit diet of P. poliocephalus formed a subset of the avian diet. Associations between fruit colour, size and protective mechanisms have been documented in other rainforest areas and have been proposed as indicators of coadaptive relationships between vertebrate frugivores and their diet plants. However, these associations were not apparent in the morphological characters of fleshy fruits from Australian subtropical rainforest trees. An explanatory hypothesis of primarily avian influence on fruit traits is presented.
Direct and indirect effects of predation on tadpole community structure in the Amazon rainforest
Authors: HERO JEAN‐MARC , GASCON CLAUDE , MAGNUSSON WILLIAM E.
Published: July 2006

Abstract The relationship between the distribution of predators (fish, odonates and water beetles) and prey assemblages (amphibian larvae) was investigated in the tropical rainforest of central Amazonas, Brasil. The anuran community uses a variety of waterbodies for reproduction, ranging from streams and streamside ponds to isolated forest ponds. Predators in this system include fish in streams and streamside ponds, and invertebrates (primarily odonate naiads and beetles) in forest ponds. Tadpole species richness and assemblage structure were related to fish density and species richness. No relationships between tadpole assemblages and abiotic pond characteristics were detected. The presence offish explained much of the variation in both species composition and species richness within and among ponds. Some species of tadpole were consistently found to coexist with high densities of fish. Path analyses suggest that while fish have a strong direct effect on tadpole associations and species richness, they also have an indirect effect through invertebrate predators (odonate larvae and coleopteran beetles). Prey survival‐strategies such as palatability and behaviour may explain how tadpole species composition is affected by predators at the community level. These findings suggest that the observed patterns of habitat use by larval anurans may be structured in response to the distribution of key predators (fish) in this system.
The effects of water on patch use by two Simpson Desert granivores (Corvus coronoides and Pseudomys hermannsburgensis)
Authors: KOTLER BURT P. , DICKMAN CHRISTOPHER R. , BROWN JOEL S.
Published: July 2006

Abstract Water loss while foraging may affect the overall value of food to desert animals. When water is scarce, foragers may alter activity and shun certain types of food due to elevated water loss. When water is abundant, foragers can exploit food patches more thoroughly and remain active over a broader range of ambient conditions. In short, food and water may be complementary resources. The presence of water raises the marginal value of food, particularly those foods low in water content. We tested for the complementarity of food and water to foragers at a sand dune site in the Simpson Desert of arid Australia. To do so, we quantified patch exploitation of foragers in the presence or absence of bowls filled with water. In order to quantify patch use, we provisioned feeding trays with granulated peanuts mixed into a sand substrate. In these trays we measured giving‐up densities (GUD; the amount of food left in a tray after a foraging bout) of diurnal (mostly Australian ravens, Corvus coronoides) and nocturnal foragers (mostly sandy inland mouse, Pseudomys hermannsburgensis). The presence of water affected the GUD of ravens but not of rodents. For the ravens, GUD dropped about 50% in response to added water. For ravens, water and food are strongly complementary. In addition, ravens had lower GUD in the open than the bush microhabitat, and lower GUD at the bottom than the tops of sand dunes.