bluuebunny/crossref_metadata_2025 huggingface dataset:
Nutrient changes in surface soils after an intense fire in jarrah (Eucalyptus marginata Donn ex Sm.) forest
Authors: GROVE T. S. , O'CONNELL A. M. , DIMMOCK G. M.
Published: July 2006

The effects of an intense fire on the nutrient status of jarrah(Eucalyptus marginata Donn ex Sm.) forest soils were investigated. At seven experimental sites, representing a range of soil and vegetation types, surface soils were sampled to a maximum depth of 20 cm before, immediately after, and 1 year after the fire.

Immediately after the fire, concentrations of total and extracted nutrients in surface (0–3 cm) soils increased markedly. One year later, concentrations of extracted nutrients in surface soils had returned to levels close to pre‐burn concentrations. During this period, some properties of sub‐surface (3–20 cm) soils also changed: Bray‐extractable phosphorus and electrolytic conductivity decreased, whereas ex‐tractable potassium and pH increased relative to pre‐burn concentrations. Initial increases in concentrations of extractable forms of nutrients were determined largely by the amounts of nutrients deposited in fine ash, whereas the changes after 1 year depended more on the leaching of ions and their reactions with the mineral soil.

Increases in total amounts of major nutrients in surface soils arising from additions of fine ash were generally well correlated with amounts in pre‐burn litter and with amounts in the components of organic matter likely to be consumed in the fire. Significant quantities of all nutrients are redistributed from aboveground sources to the soil surface during intense fires, including nutrients which are most susceptible to losses through volatilization. This redistribution of nutrients is discussed in relation to short‐term and long‐term effects on plant growth and functioning of the jarrah ecosystem.
The composition, structure and distribution of heathland and grassland communities in the subalpine tract of the Bogong High Plains, Victoria
Authors: WILLIAMS R. J. , ASHTON D. H.
Published: July 2006

In the subalpine tract of the Bogong High Plains (37°S, 147°E; altitude 1600–1800 m a.s.l.) the vegetation consists of a mosaic of snow gum (Eucalyptus pauciflora) woodland, heathland, grassland and wetland communities. Classification (polythetic‐agglomerative) and ordination (principal co‐ordinates analysis) of quadrat data from heathlands and grasslands on relatively well drained sites allowed the identification of four main heathland and grassland vegetation units. These units may be ranked in a structural and floristic continuum, from closed heath variously dominated by Prostanthera cuneata, Orites lancifolia and Phebalium squamulosum to closed heath dominated by P. squamulosum and Grevillea australis, open grassy heath of G. australis and Poa hiemata. and grassland of P. hiemata. The transition from Prostanthera closed heath to Poa grassland is correlated with gradients of decreasing steepness and rockiness of terrain, and increasing exposure and frost.
Bushfire incidence, fire hazard and fuel reduction burning
Authors: GILL A. M. , CHRISTIAN K. R. , MOORE P. H. R. , FORRESTER R. I.
Published: July 2006

Daily routine 3 p.m. meteorological data for Melbourne, Victoria, were processed to provide estimates of maximum forest fire danger index (including soil‐water deficit), potential number of days for failure of fire suppression for given quantities of fuel, and potential number of days for optimal prescribed fuel reduction burning in eucalypt forests given the same quantities of fuel. Although two models for estimating soil dryness gave widely different results, the effect of these differences on the value of the McArthur forest fire danger index (FFDI) was relatively small overall. However, over the 28 years of record, the number of ‘extreme’ days given using the Mount dryness index was 50% greater than that given by the Keetch‐Byram index.

The number of forest fires in Victoria (as a whole) was found to be related to 3 p.m. FFDI (for Melbourne) and to the incidence of weekends or public holidays. Potentially, bushfires near Melbourne would be ‘uncontrollable’; that is, with an intensity greater than 4000 kW m‐1 on level ground, on an average of about 100 days per year (at 3 p.m.) if ignition were to occur where litter fuel weights were about 301 ha‐1. However, if fuel weights were less than 81 ha‐1, the potential number of ‘uncontrollable’ fires would be near zero. Using equations to predict conditions ideally suited to safe fuel reduction burning at 3 p.m. the average number of appropriate days per year increased from zero at a fuel weight of near 71 ha‐1 to a maximum of 14 at 15 t ha‐1. The extent to which the models used in this study are accurate is arguable so further work is needed.
Factors influencing the maintenance of an inverted Eucalyptus coccifera tree‐line on the Mt Wellington Plateau, Tasmania
Authors: GILFEDDER L.
Published: July 2006

The Tasmanian snow gum, Eucalyptus coccifera Hook.f., forms low‐open woodlands on the dolerite plateau of Mt Wellington, Tasmania. The species occurs at the inverted and upper slope tree‐lines, and its spatial distribution appears to be strongly influenced by soil drainage characteristics. Both experimental work and field observations indicate that water‐logging is the principal agent determining the inverted tree‐line limits of E. coccifera on Mt Wellington. However, deficiencies of moisture also play a role in limiting the distribution of snow gums. There was no evidence to indicate that frost influences the lower tree‐line limits of the species, despite the genetic variation shown in the frost resistance of trees from various provenances. Strong ice‐bearing winds influenced the morphology of E. coccifera individuals, but was not a factor in limiting the distribution of the species.
Demography of woody plants in relation to fire: Banksia ericifolia L.f. and Petrophile pulchella (Schrad) R.Br.
Authors: BRADSTOCK R. A. , O'CONNELL M. A.
Published: July 2006

Plants of Banksia ericifolia and Petrophile pulchella are sensitive to fire. Changes in population size under different fire regimes were estimated, based on measurements of post‐fire seedling emergence, seedling survival, survival and seed production in established plants of differing ages, survival of seeds held in serotinous cones and seed‐release in the periods between fire.

Seeds were first available at 5 years in P. pulchella and 6 years in B. ericifolia. Exact replacement would be possible when burnt at these ages, if seedling establishment were very high. Low establishment would delay replacement to 13 years of age in both species. Late summer/autumn fires of high intensity favour high establishment. Such fires at 8–10 year intervals would be tolerated without any sustained decline in numbers. Fires at 10–15 year intervals could occur regardless of season or intensity with little risk of a population decline. Large increases in numbers and density would follow fires spaced at 15–30 years. Enough seeds would be available for replacement up to about 50 years in both species. Viable seed‐release in unburnt conditions was sufficient to compensate for deaths in stands over 20 years old, even with very low levels of establishment.

Two variables accounted for the biggest changes in numbers and density between generations interspersed by fires; namely the age at which a stand is burned and the proportion of seeds which emerge as seedlings. A comparison with other similar species showed similarities in controls on emergence and establishment, lengths of primary juvenile periods and life spans.
Holocene vegetation, fire and environmental history of the Discovery Bay region, south‐western Victoria
Authors: HEAD LESLEY
Published: July 2006

The results of pollen, sedimentary and charcoal analyses of four cores and three peat profiles are presented. Casuarina woodland dominated the dryland vegetation over at least the past 6000 years, with a Melaleuca lanceolata‐composite scrub association on the dunes. There is no evidence of higher sea levels in the area in the past 6000 years, with the present freshwater backdune swamp and lake systems being maintained or expanded. After a period of regional dune building between about 6000 and 4000 years BP, dune mobilization and advance in the last 4000 years or so overrode seaward brackish and fresh swamp systems. This dune advance severed Long Swamp from the Glenelg River estuary and precipitated the development of freshwater swamp conditions there. Burning of the swamp surface, often associated with the presence of Typha, is evident in a number of peat samples and is probably primarily anthropogenic. Continuous low‐level burning occurred throughout the dryland vegetation of the region but is not associated with any long‐term or widespread vegetation change. None of the environmental changes identified require a purely climatic explanation, and all have relevance for discussions of the regional prehistory.
Volume and activity of micro‐organisms in litter from native and sown temperate pasture species
Authors: HUTCHINSON K. J. , KING K. L.
Published: July 2006

A serial extraction method was developed to estimate microbial volume in pasture plant litter. Litter from six species was evaluated over four seasons and a five fold range in microbial volume per unit mass was established in the descending order of: Trifolium repens, Lolium perenne, Festuca arundinacea, Phalaris aquatica, Poa sieberana and Themeda australis. The ranking among litter sources was the same for both fungi (F) and bacteria (B) and the ratio F/B ranged from 4 to 10. Accompanying respiration measurements (O2) were made over a range of litter moisture and at temperatures which represented field conditions. Maximum responses of respiration to moisture were estimated for each source and season, along with the Q10 temperature effects between 5, 15 and 25°C.

Potential microbial production and generation times were calculated for the six litters. Differences between litters were associated with microbial standing crops rather than turnover times. However, moisture and temperature appeared to be the major determinants of seasonal responses, for example, Q10 effects. Microbial parameters calculated for Phalaris aquatica. in the field environment, were in substantial agreement with those from Eriophorum sp. in a tundra site (Flanagan & Bunnell 1976). Residues quality, as reflected by the amount and activity of microbial colonizers, is discussed in relation to the potential of management to enhance biological mineralization of pasture residues.
Consequences of differences in body mass, wing length and leg morphology for nectar‐feeding birds
Authors: COLLINS BRIAN G. , PATON DAVID C.
Published: July 2006

Nectar‐feeding birds are prominent in many parts of the world, and vary with respect to body size. Despite the availability of considerable morphometric data, few concerted efforts have been made to assess the influence of attributes such as mass, wing length and leg morphology upon the speed, acceleration, mode and energetic cost of movement by birds between flowers when foraging for nectar. This review attempts to consolidate and interpret available data and highlight areas where further investigations appear warranted. Australian honeyeaters are generally larger, and American hummingbirds smaller, than Hawaiian honeycreepers and sunbirds of Africa or Asia. Sunbirds, honeyeaters and honeycreepers generally perch while extracting nectar from flowers. Hummingbirds usually hover, apparently because suitable perches close to flowers are lacking, and not because hovering increases the speed at which flowers can be visited. Honeyeaters move from one flower to another at speeds that are at least as great as those for hummingbirds. Most passerine nectarivores need to ingest more nectar per day than hummingbirds in order to maintain energy balance, some species devoting more than 60% of the day to foraging. The major consequence of reduced foraging activity by hummingbirds, which spend only 5–30% of the day in this manner, appears to be male emancipation from nest construction and care of offspring. Large nectarivores have a greater capacity to store surplus food and to fast than smaller birds, and so can take advantage of short‐lived peaks in nectar abundance. Nectarivores such as honeyeaters should therefore be favoured by the rapid diurnal changes in nectar availability which are characteristic of many Australian and African habitats. Body mass also determines the likely access to rich sources of nectar through size‐related interspecific dominance hierarchies. In all families, larger species tend to monopolize the most rewarding nectar supplies, forcing smaller subordinate species to use poorer, more scattered sources. Within particular species, males usually have longer wings and greater masses than females. These variations imply that the two sexes differ with regard to their foraging ecology, although few supporting data are currently available.
Interspecific competition between mice: A reciprocal field manipulation experiment
Authors: FOX BARRY J. , GULLICK GRAEME
Published: July 2006

Previous studies have demonstrated a species replacement sequence in disturbed forest and heathland, with the native New Holland mouse (Pseudomys novaehollandiae) replacing the introduced house mouse (Mus musculus) in the earliest part of the succession. The replacement appeared to be competitive displacement and this has been confirmed by controlled experimental removal of P. novaehollandiae from field sites, which produced significant increases in the abundance and habitat use of Mus musculus. This paper reports the results of the controlled reciprocal manipulation experiment in the field. A pulsed addition of M. musculus to three treatment plots produced significant reductions in the abundance and habitat use of P. novaehollandiae, when compared with control plots with no addition of M. musculus. This effect was observed only at high M. musculus densities, and the return to the control conditions within 3 months of the pulsed addition is consistent with asymmetric interspecific competition from competitively superior P. novaehollandiae. The importance of considering the regional abundance of M. musculus in relation to its competitive ability is stressed, as at high densities M. musculus is able to create its own ecological space contrary to its more usual competitively submissive status.
A comparison of methods for assessing defoliation, tested on eucalypt trees
Authors: LANDSBERG JILL
Published: July 2006

Little is known of the extent to which differences in methodology contribute to differences in reported levels of tree defoliation. In this study several common methods of assessing defoliation were compared on Eucalyptus blakelyi Maiden trees growing in a stand known to sustain a range of defoliation levels. Assessments were made of whole trees and of individual leaves collected at discrete intervals as well as of tagged samples of leaves that were monitored over a year. Despite fortnightly monitoring intervals, I was not able to identify with certainty any specific cause of loss of whole leaves other than senescence. Annual defoliation assessed on discrete samples of leaves was higher than annual defoliation assessed on monitored samples, presumably because the age of leaves in the discrete samples was sometimes underestimated. Leaf‐level defoliation assessed from visual estimates was consistently higher than digitizer measurements of leaf areas, but calibration of estimates resulted in similar values. Values derived for tree‐level defoliation from leaf‐level measurements differed widely. depending on the method of calculation. For the samples collected from trees in this study, mean percentage defoliation per leaf was not an adequate descriptor of defoliation for the samples, since the frequency distributions of defoliation per leaf were markedly non‐normal. This problem was avoided by using the samples, rather than the individual leaves, as the basic unit of expression of defoliation, with the total percentage defoliation per sample calculated from the ratio of total area of damage to total potential area, summed for all the leaves in the sample. For expanding leaves, the percentage of area damaged was not equivalent to the percentage of area missing from the expanded leaves, because of differences in the relative rates of growth of holes and leaves.
Seasonal foraging activity and microhabitat selection by echidnas (Tachyglossus aculeatus) on the New England Tablelands
Authors: SMITH A. P. , WELLHAM G. S. , GREEN S. W.
Published: July 2006

Seasonal foraging activity and microhabitat selection by echidnas on the New England Tablelands was determined by monitoring the number and relative predominance of different types of digging activity on a 2 km × 50 m transect over a 12 month period. Digging was classified into four basic types: those into the soil surface (SOILDIGS); those at the base of logs, stumps or trees (LOGDIGS); those at the base of termite mounds; and those in the litter. SOILDIGS were most prevalent, accounting for 490 (74%) of the total 666 digging records. The number of SOILDIGS correlated with season and temperature, reaching a maximum of 11 ha−1 per month in late spring and a minimum of zero in winter. SOILDIGS were attributed to searches for ants and scarab beetle larvae. Approximately half of the SOILDIGS exposed ant nests or galleries, while the remainder were presumed to result from searches for the larvae of pasture dwelling scarab beetles, particularly Sericesthis spp. Scarab beetle larvae were absent from echidna scats collected during winter but occurred in 20% of scats collected during summer, LOGDIGS accounted for 157 digging records (24%) and were attributed to searches for ants and termites, LOGDIGS did not vary with season or climate, but the proportion of LOGDIGS that exposed ant or termite nests or galleries changed from 48% in winter to 5% in summer. The distribution and density of SOILDIGS and LOGDIGS along the transect correlated significantly with the availability of echidna shelter (or refuge) sites, in all seasons Some residual variation in digging activity was explained by the number and biomass of ants active on the soil surface, but not with any other direct or indirect measures of food availability. Seasonal changes in foraging activity by echidnas, and their apparent dependence on shelters, are interpreted in an energetic context as strategies for reducing predation and overcoming a period of increased energy demand and decreased food availability experienced during winter.
Light environments within montane tropical rainforest, Mt Bellenden Ker, North Queensland
Authors: TURTON S. M.
Published: July 2006

Irradiance and photosynthetic photon flux density (PPFD) at five sites within a montane tropical rainforest were compared to test for differences among characteristic environments within the same forest type. The five habitats investigated were a large clearing (800 m2). a small gap (150 m2), the lower canopy, and two shaded understorey sites. Daily average irradiance ranged from 32.3 W m‐2 in the heavily shaded understorey to over 400 W m‐2 in the large clearing. Similarly, daily average PPFD ranged from 10.2 to over 800 μmol m‐2 s‐1 at corresponding sites, respectively. Daily total irradiation in the understorey, small gap, and lower canopy were 7.9–8.8%, 11.8% and 11.5%, respectively, of irradiation in the large clearing. For daily total PPFD, relative values for the same sites were 1.3–3.8%, 6.0% and 10.3%, respectively. Comparisons of frequency distributions for irradiance showed that the only significant difference was between the large clearing and the four forest sites. Comparisons of frequency distributions for PPFD showed significant differences among all five sites. Median PPFDs were always above the range of known light compensation points for rainforest plants even in the heavily shaded understorey, and usually above the known light saturation levels of canopy members. These results indicate that the reduction in PPFD by cloud cover does not limit the rates of photosynthesis.
The roles of floristics and physiognomy in avian community composition
Authors: MACNALLY RALPH C.
Published: July 2006

There has been debate as to whether the composition of avifaunas is determined primarily by responses of species to the floristic composition of habitats or to the structural features of habitats (viz. physiognomy). Some evidence suggests that the effects of geographic scale may be the source of this dispute. The present analysis demonstrated that the influence of both floristics and physiognomy could be detected at the regional level for avifaunas of south‐eastern Australian woodlands. The impact of floristics often may be obscured by patchiness and relatively rapid rates of spatial change in the phytosociology of habitats relative to those of avian species, even at the local scale (say 10 km). Such potential occlusion of the importance of floristics to avifaunas may be overcome by using floristic similarity indices that are based on plant taxonomic representations at both the specific and subfamilial levels. Both floristics and physiognomy are likely to affect avifaunal composition, although the perceived significance of each factor may vary with the scale of observation.
Larval predation by epifauna on temperate reefs: scale, power and the scarcity of measurable effects
Authors: YOUNG CRAIG M.
Published: July 2006

Benthic suspension feeders often occur at high densities on temperate reefs and other hard bottoms. Beeause many such organisms hayc prodigious feeding rates in the laboratory, it has often been predicted that established epifauna would deplete larval populations, thereby influencing density, spatial distribution and species eomposition at settlement. Most field manipulations of filter‐feeder density have not controlled for faetors other than larval predation that could produce the same pattern. In controlled experiments, larval predation effects are seldom observed. Intermittent feeding and small radii of predator influenee present many more opportunities for settlement than has generally been assumed. Two important faetors often foil attempts to measure predation effeets: low statistieal power due to small effect sizes, and choice of spatial scales larger than thdse where predation effeets oeeur.
Palynology of a Holocene marine transgressive sequence, lower Mulgrave River valley, north‐east Queensland
Authors: CROWLEY G. M. , ANDERSON P. , KERSHAW A. P. , GRINDROD J.
Published: July 2006

A sediment core from the lower Mulgrave River flood plain in north‐east Queensland was examined using standard pollen analysis techniques to investigate vegetation and sea level changes during and since the Holocene marine transgression. Saltwater penetrated the Mulgrave River to the core site in the early Holocene, with the consequent development of riverside mangrove forests dominated by Sonneratia lanceolata, a community not previously recorded in Australian pollen sequences. From about 7000 to 6000 years ago, Rhizophora forest was the dominant vegetation community around the site. During this period, vertical sedimentation kept pace with, or at times exceeded, the rate of sea level rise. As sea level stabilized, about 6000 years ago, continued sediment accumulation led to the development of upper‐intertidal Ceriops/Bruguiera forest and then freshwater swamp forest. The vegetation changes in this latter part of the sequence reflect the present seaward to landward vegetation zonation in the area.
Experimental transplants of mice (Pseudomys and Mus) on to early stages of post‐mining regeneration in open forest
Authors: FOX BARRY J. , TWIGG LAURIE E.
Published: July 2006

Results are presented for three controlled replicated experiments in which mice were transplanted onto the early successional stages of two regenerating mining paths. Naive house mice (Mus musculus) were successfully introduced on to sites regenerating for 8 years, with 56% remaining after 3 days and 2% still present after 69 days. Naive New Holland mice (Pseudomys novaehollandiae) had marginal establishment success on sites regenerating for 4.9 years, with 21% remaining after 3 days and 3% still present after 22 days. However, on sites regenerating for 3.9 years and 4.4 years, all 17 transplanted New Holland mice had dispersed from the treatment plots after 3 days. New Holland mice have been shown to be competitively dominant to house mice. Hence, we conclude that the reason New Holland mice do not colonize mining paths regenerating for less than 4.9 years is the unsuitability of the habitat rather than their exclusion by house mice. These results are consistent with the early stages of the mammalian succession following sand mining and fit the same habitat accommodation model proposed for post‐fire mammalian succession.
Fish larvae settling in seagrass: Effects of leaf density and an epiphytic alga
Authors: WORTHINGTON D. G. , WESTOBY M. , BELL J. D.
Published: July 2006

Settlement of fish to seagrass with low leaf densities was investigated by a field experiment in Botany Bay, NSW. Artificial seagrass units (ASU) were used to simulate isolated seagrass habitats of 0, 25, 50, 100, 200 and 400 leaves m‐2. A total of 369 fish of 21 species settled in the experimental units during a 6 week period. The labrid, Achoerodus viridis, made up almost 70% of these individuals. The abundance of recently settled A. viridis increased greatly between 0 and 25 leaves m ‐2, At more than 25 leaves m‐2, A. viridis settled in approximately equal numbers. Patterns of settlement for all other species combined were similar to those for A. viridis. During the experiment, an epiphytic alga. Giffordia mitchellae, colonized and grew on the ASU. The alga increased the structure associated with the experimental units. Treatment leaf densities could thus be regarded only as relative measures of shelter. At low leaf densities, fish settlement increased with increasing algal cover; at higher leaf densities, the opposite occurred. The rapid increase in abundance of recently settled fish over a relatively narrow range of leaf densities above zero implies that small increases in shelter can have large effects on settlement of larval fish.
Energy dynamics of grasshopper populations in a temperate grassland community in India
Authors: KAUSHAL B. R. , JOSHI P. C.
Published: July 2006

Population dynamics, biomass and secondary net production of orthopterans, particularly acridids, were studied in a temperate grassland at Naukuchiatal, India, from February 1986 to January 1988. A total of 38 plant species were recorded in the grassland and mean aboveground net primary production was 6760 kJ m‐2 per year. Thirteen orthopteran species occurred in the grassland. Most individuals were acridids, followed by tettigonids and gryllids; acridids were dominant both in density and biomass. The maximum population density was 5 m‐2 and the maximum biomass was 275 mg m‐2. Mean secondary net production was 10 kJ m‐2 per year. Acridids consumed an average of 2.3% of the above‐ground primary production.
Effects of fuel reduction burning on epigeal arthropods and earthworms in dry sclerophyll eucalypt forest of west‐central Victoria
Authors: NEUMANN F. G. , TOLHURST K.
Published: July 2006

The effects of prescribed low‐intensity burning during spring and autumn on invertebrates in litter/upper soil were assessed in dry sclerophyll mixed eucalypt forest near Daylesford, west–central Victoria. The 4‐year study was based on 68 848 arthropod specimens representing 29 ordinal or lower level taxa contained in 1980 pitfall trap samples, and on in situ counts of earthworms (Annelida) in 2220 litter/upper soils samples.

The spring bum caused short‐term reductions in activity among the common ‘major’ taxa Collembola (springtails) and Diptera (flies), and among the rarely trapped ‘minor’ taxa Opilionida (harvestmen), Lepidoptera (moths) and Apocrita (parasitic wasps) for up to one year. These reductions were associated with low fine fuel loads in the first year after the fire. Populations of earthworms also declined substantially, but recovered within 3 years of the burn. The autumn burn suppressed the Collembola and the ‘minor’ taxa Blattodea, Polydesmida, Thysanura and Tettigoniidae for up to 10 months. Earthworms were not affected. Very dry soil conditions were associated with depressed collembolan activity at study sites irrespective of burning.

Given the importance of Collembola, larval Diptera and earthworms among decomposers in forest litter, it appears that the spring burn, and to a lesser extent the autumn burn, may have temporarily reduced the decomposer cycle. Further research on individual species is required to substantiate this conclusion, and also on the effects of high frequency burning. In the interim, any broadscale fuel reduction burning in forest ecosystems similar to that studied here should be scheduled for autumn rather than spring to protect earthworms and no burning should be permitted during drought periods, to minimize adverse impacts on the overall invertebrate fauna inhabiting litter/upper soil.
Seasonal changes in activity of subterranean termite species (Isoptera) in Western Australian wheatbelt habitats
Authors: ABENSPERG‐TRAUN MAX
Published: July 2006

Subterranean termite assemblages in woodland, mallee and heath habitats of the Western Australian wheatbelt were sampled for seasonal changes in species richness and species abundance. The study was carried out in Durokoppin and Kodj Kodjin Nature Reserves between January and November 1988, and a trench method was used to sample termites. Species richness changed over time, with monthy means of: woodland 10 species (range: 5–15), mallee 8 species (range: 4–15), heath 8 species (range: 5–15). Species richness was highest in autumn and spring when termite activity in the soil was also highest due to favourable soil moisture.Amitermes neogermanusandTumulitermes petiluswere the most abundant species in woodland and mallee in all seasons. During summer, the pooled observations of these two species accounted for 50% (woodland) and 82% (mallee) of all observations. Their predominance may be due to greater tolerance of low soil moisture and a more diverse diet than obligate wood‐feeders (e.g. Rhinotermitidae). The latter were generally absent near the soil surface in summer, possibly because food sources deeper within the soil were utilized. Four species were abundant in heath:Tumulitermes dalbiensis(monthly mean 20% of all species observations),T. comatus(13%),Amitermes. sp.‘R’ (18%)andDrepanotermes rubriceps(12%). These four species showed no seasonal change in their relative abundance, possibly because their diet restricted them to surface‐foraging.
Changes in subtidal habitat following mass mortality of sea urchins in Botany Bay, New South Wales
Authors: ANDREW N. L.
Published: July 2006

On two occasions, between June and October 1986 and April/May 1988, mass mortality of the sea urchin Centrostephanus rodgersii occurred at Bare Island in Botany Bay, New South Wales. Following the widespread disappearance of C. rodgersii in August 1986, the abundance of filamentous and foliose algae increased and crustose corallines declined. There was also a large, but shortlived, increase in the density of limpets, particularly Patelloida alticostata, which then fell to nearly zero after 15 months. In October 1986, the habitat found at other sites in Botany Bay was consistent with a recent disappearance of C. rodgersii. At all sites a complex assemblage of non‐crustose algae developed, the species composition of which differed among sites. A large recruitment of C. rodgersii was observed at all affected sites in February 1987 and January 1988. These individuals grew quickly and reached a mean size of approximately 35 mm test diameter at the end of their first year.
Fungal pathogens as selective forces in plant populations and communities*
Authors: BURDON J. J.
Published: July 2006

Pathogens are potent selective forces whose importance in shaping the size and structure of individual plant populations and whole communities has been underestimated. Even in situations where host and pathogen have been associated over long periods of time, pathogens regularly affect host fitness by reducing fecundity and increasing mortality either directly or indirectly through reductions in competitive ability.

The genetic consequences of such disease‐induced reductions in fitness are profound. On a broad geographic scale, race‐specific resistance generally occurs more frequently in regions characterized by environments favourable for disease development. Within such areas, however, the distribution of resistant plant genotypes is often very patchy. This probably reflects the importance of extinction and colonization events in the continuing co‐evolutionary dynamics of host‐pathogen associations.

At a demographic level, pathogen‐induced reductions in host fitness may lead to changes in the size of populations. In turn, this may lead to changes in the relative diversity of whole communities. Documentation of this scale of interaction is poor, but the devastating consequences of the introduction of pathogens into alien environments provides a salutary reminder of their power to change plant communities radically.
The effects of ants on herbivory and herbivore numbers on foliage of the mallee eucalypt,Eucalyptus incrassataLabill.*
Authors: MACKAY DUNCAN A.
Published: July 2006

Although there has been much recent interest in ant‐plant mutualisms, few data are available on the effects of foraging ants on herbivore numbers and levels of herbivory on plants that do not offer specific inducements to attract ant visitation. In forestry plantations and tropical crops, ants have erratic but sometimes dramatic effects on the numbers of insect herbivores but, in more natural habitats, their effects on levels of herbivory appear to be largely unknown. In Australia, where ants andEucalyptuswoodlands are ubiquitous and abundant and where considerable debate has occurred regarding levels of herbivory inEucalyptusforests, very little work has been done to examine the effects of ants on densities of insect herbivores on eucalypts.

In this study, ants were experimentally excluded from mature and immature foliage of saplings of the malleeEucalyptus incrassatain South Australia, and herbivore numbers and levels of leaf herbivory were assessed during the next 6 months. No significant differences in herbivory were found between ant‐access and ant‐exclusion treatments. In spring and early summer, ants were found in associations with aggregations of eurymelid bugs on young foliage, and the effects of ants on bug densities were experimentally investigated. Bug densities decreased rapidly in ant‐exclusion treatments compared with ant‐access controls. Ants also quickly removed seeds ofE. incrassatafrom experimental caches.

The potential of ants to limit the numbers of insect herbivores on eucalypts seems limited given their tendency to form mutualistic associations with sap‐feeding Homopterans and because of a lack of other herbivores that are particularly vulnerable to ant predation.
Colonization of pasture by Kunzea ericoides in the Tidbinbilla Valley, ACT, Australia
Authors: KIRSCHBAUM SARAH B. , WILLIAMS DAVID G.
Published: July 2006

Stand morphometry and age structure were analysed for populations of burgan, Kunzea ericoides, which were colonizing pastoral land in the Tidbinbilla Valley, Australian Capital Territory. Three types of stands, (i) closed burgan‐dominated; (ii) open burgan‐dominated; and (iii) mixed burgan and eucalypts, were compared at each of two locations. Burgan ages were determined from growth ring counts cross‐correlated with seasonal rainfall and annual increments in Pinus radiata. Burgan stands have developed from windblown seed coming from nearby forest margins and drainage‐lines. The species colonized rural lands in the Tidbinbilla Valley rapidly from the early 1960s, when changes in land use practices occurred which enabled sparse colonists to contribute to rapid population expansion. Colonization was initially slow, but recruitment increased dramatically in the early 1960s in closed and open stands when densities were between 0.01 and 0.03 plants m‐2. These stands did not follow classic secondary succession, as the differences between stands sampled were largely the result of differences in burgan density and floristic composition of the sites at the time of change in land use practices. These differences in turn influenced the phenotypic response of individual plants and the ensuing stand structures. A closed shrub canopy of burgan, together with the species self‐replacement strategies, is likely to prevent other species from entering the closed burgan sites and becoming dominant. Where the objective is to limit the spread of burgan, isolated plants, which act as foci for spread, would be the primary target for control.
Predicting the abundance of hollow‐bearing trees in montane forests of southeastern Australia
Authors: LINDENMAYER D. B. , CUNNINGHAM R. B. , NIX H. A. , TANTON M. T. , SMITH A. P.
Published: July 2006

Poisson regression analyses were used to relate the number of hollow‐bearing trees on 523 sites in the montane ash forests of the Central Highlands of Victoria to a range of environmental variables. Region, logging history, the dominant species of eucalypt, slope angle, topographic position and the age of the stand influenced significantly the number of hollow‐bearing trees. A simple predictive model containing these factors has possible application in geographic information systems and may assist in the assessment of wildlife habitat.

The number of multi‐aged stands and living trees with fire scars indicates that some individuals of ‘fire‐sensitive’ montane ash eucalypts appear to survive intense wildfire.
Nectar depletion and its implications for honeyeaters in heathland near Sydney
Authors: ARMSTRONG DOUG P.
Published: July 2006

Several researchers have attempted to calculate whether depression of nectar resources by Australian honeyeaters is likely to limit their densities. Such calculations can be misleading, however, and do not directly test whether birds depress nectar availability. I monitored changes in nectar availability during the 8–9 months that honeyeaters bred in heathland near Sydney, and caged inflorescences to test whether nectar availability was being depressed by birds.

There were pronounced seasonal changes in nectar availability in each of 2 years, and caging substantially increased the amounts of nectar in inflorescences during months when nectar production was low. The effects of caging must have resulted from exclusion of honeyeaters, as: (i) open‐ended cage controls showed that the effects of caging resulted from exclusion of foragers, not from artifacts of caging; (ii) day‐only and night‐only caging showed that nectar was depleted only during the day: and (iii) observations showed that cages did not exclude any diurnal foragers other than honeyeaters. Resident honeyeaters spent more time foraging during months when nectar was scarce, implying that the rates at which they could obtain nectar were affected by changes in nectar availability. It is therefore possible that the depletion of nectar by honeyeaters could have limited their densities. However. I argue that such limitation could only be inferred safely if nectar‐supplementation experiments showed survival and/or reproduction to be limited by nectar availability.
Response of a monsoon forest‐savanna boundary to fire protection, Weipa, northern Australia
Authors: BOWMAN D. M. J. S. , FENSHAM R. J.
Published: July 2006

A numerical floristic analysis of samples across a monsoon forest‐savanna boundary, from an area that had been actively protected from fire for 15 years, at Weipa, northern Australia, revealed three communities: (i) a monsoon forest with a low closed canopy composed mainly of tree species with extra‐Australian tropical affinities and a sparse ground layer; (ii) an ecotone with a distinct closed microphyll shrub layer beneath the open canopy of savanna trees; and (iii) a savanna dominated by Eucalyptus tetrodonta. The development of the ecotone has occurred since fire protection and is of limited extent within the fire protected block. The monsoon forest occurred on soils with significantly higher concentrations of bauxitic pisoliths than the other two communities. Soils under the monsoon forest had significantly higher concentrations of total K, S, C, N, exchangeable K and Ca, and higher pH and electrical conductivity than for soils of either of the other communities. A positive relationship between woody basal area and concentrations of surface soil total P, N, C, exchangeable Ca, CEC and gravel was detected across a 20 m transect from the ecotone community into the savanna. The invasion of monsoon forest seedlings was greatest in the ecotone, with few occurring in the savanna. It appears that the expansion of the monsoon forest requires the development of a layer of shrubs. The mechanism of this facilitation is unclear, although the possible role of nutrient enrichment by the shrubs requires further investigation.
Spread and potential distribution of Senecio madagascariensis Poir. (fireweed) in Australia
Authors: SINDEL B. M. , MICHAEL P. W.
Published: July 2006

Abstract
The potential distribution of the herbaceous weed Senecio madagascariensis Poir. (fireweed) in Australia was estimated using the Bioclimate Prediction System, BIOCLIM. Climate profiles for S. madagascariensis predicted that suitable areas occurred only in the south‐eastern region of Australia. Its potential to spread outside these areas was assessed by comparing the present African and South American distributions of this species with that observed in Australia. The rate of spread of S. madagascariensis in New South Wales was exponential, although in some regions, such as the Gloucester River Valley, the rates had decreased because all farms had become infested. The results indicate that S. madagascariensis may spread and increase in abundance along the far south coast of New South Wales and in south‐eastern Queensland. Coastal areas in eastern Victoria and as far north in Queensland as the Tropic of Capricorn may be invaded.
Soil salinity is correlated with a decline in 13C discrimination in leaves of Atriplex species
Authors: WALKER C. D. , Sinclair R.
Published: July 2006

Abstract
A dune‐swale‐dune transect in north‐eastern South Australia with a regular covering of saltbush (Atriplex vesicaria and Atriplex stipitata) was studied. The transect topography was surveyed, as were the Δ (discrimination against 13C in CO2) of the saltbush plants, and the electrical conductivity and chloride profiles of the soil. Increasing soil salinity, surveyed as electromagnetic (EM) soil conductivity, correlated with a decrease in A composition in the leaves of the C4 Atriplex species. No such correlation occurred with the whole plant. Further, the Δ of foliage was more variable than the Δ of whole plants. The Δ of foliage was higher than that of corresponding stems. We suggest that soil conductivity measured in this way is a meaningful assessment of plant growth conditions, and that further study will demonstrate its scope for incorporation into field studies of native plants at a quantitative level.
Herbivorous arthropods on bracken (Pteridium aquilinum (L.) Khun) in Australia compared with elsewhere
Authors: SHUTER E. , Westoby M.
Published: July 2006

Abstract
The herbivorous arthropod fauna of bracken fern (Pteridium aquilinum (L.) Khun), at a site near Sydney, Australia, is described and compared with previously reported bracken faunas in other geographic regions. Monthly sampling over 18 months found 17 species of herbivorous arthropods (15 insect and two mite species) from five orders. At the ordinal level, the mixture differed substantially from the bracken faunas of sites in Britain and Papua New Guinea. Notable was the presence of Thysanoptera and Acari, and the absence of Coleoptera and Hymenoptera. The mixtures of orders/families represented in the site bracken faunas in Britain, and less so in Australia, resembled those in the pool of herbivorous arthropods in those regions. Further, the mixture of orders on bracken was more similar to the mixture of orders on other ferns than to the mixture of orders among herbivorous insects on all plants; such similarity was not evident at family level. Compared with sites in other regions, the Sydney site had an abundance of pinna‐sucking species and a dearth of mining species. Differences between regions in feeding niches most occupied tended to correspond with the differences in orders represented. Not all features of the fauna of bracken near Sydney reflected differences in the general herbivorous arthropod fauna of Australia compared with other regions, or differences between the herbivore faunas of ferns and seed plants. Its composition must be attributed in part to stochastic aspects of the speciation of herbivorous arthropods onto host plants.
Germination biology of selected central Australian plants
Authors: JURADO E. , Westoby M.
Published: July 2006

Abstract
Risk spreading of germination may be particularly common in environments with unpredictable climates. Germinability, propensity to germinate at different temperatures and germination speed were classified for seeds of 105 species from the central Australian arid zone, and related to plant growth form, perenniality, seed size and seed dispersal mode. Almost all species had at least some seeds which were dormant, consistent with the idea that risk spreading is important in arid zones. Dispersal mode and plant perenniality were not found to be associated with germinability. Seeds of most species germinated rapidly relative to what has been recorded from higher‐rainfall environments, as might be expected in an environment where wet soils are usually temporary. Faster germination tended to be associated with low germinability, suggesting a spectrum of strategies from species that risk a small number of their seeds in many rainfall events, to those that germinate only in large rainfall events but then risk large numbers of seeds.
Tree invasion of an intermittent wetland in relation to changes in the flooding frequency of the River Murray, Australia
Authors: BREN L. J.
Published: July 2006

Abstract
Aerial photographs taken in 1945, 1957, 1970, and 1985 were used to examine the invasion of red gum (Eucalyptus camaldulensis Dehn.) into an extensive, natural grassland. This grassland occupied a high flood frequency site adjacent to the major River Murray, Australia. Photogrammetric techniques were used to provide information on the successive states of 200 m × 200 m grid cells covering the wetland. The information collected was then assembled into a Markov Chain model of change in the wetland. Prior to 1945 the tree‐plain boundary appears to have been stable. The model, extrapolated into the future, showed the almost complete extinction of extensive grass plains, although small‐scale intimate mixtures of plain and red gum will exist as a stable form. Analysis of hydroperiods suggested that a major factor in this is the increased summertime levels and reduced winter‐spring levels of the River Murray as a consequence of the need for downstream transmission of irrigation water. The affected areas tend to lie between the summertime heights of the river in the pre‐regulation and post‐regulation days. Although there are few water management options for this particular wetland, it is likely that other riverine wetlands have suffered similar changes but could be managed to avoid some of the adverse effects of such changes in hydroperiodicity.