bluuebunny/crossref_metadata_2025 huggingface dataset:
An experimental investigation of patch use by female monarch butterflies, Danaus plexippus (L.)
Authors: BULL C. M. , ZALUCKI M. P. , SUZUKI Y. , MACKAY D. A. , KITCHING R. L.
Published: July 2006

Monarch butterflies, which breed throughout the year in southeastern Queensland, Australia, were studied in four dense milkweed patches during the winter months (June‐August) 1983. The percentage of marked females recaptured was measured in each of four 15‐day sampling periods. In patches where males were experimentally removed, female recapture rate decreased compared with patches which had the same density reduction but no change in sex ratio. There was a significant correlation between female recapture rate and the proportion of males in samples, but female recapture rate was not correlated with population density, the number of males, the number of females or the proportion of young butterflies in the samples. We propose that females assessed patch quality by the sex ratios, and left a patch sooner if encounter rate with males was low. Since males provide a nutrient ‘reward’ during copulation, they may be a limited resource for females during winter. An alternative interpretation, that females left a patch sooner when female density was higher, was not supported as strongly by the data.
Relationships between litterfall rate, litter mass and decomposition rate in Eucalyptus forests in southeastern Australia
Authors: HUTSON BARRY R. , VEITCH L. G.
Published: July 2006

Measurements of annual litterfall rate and mean annual litter mass for various indigenous open‐forests are listed, along with the consequent decomposition constant (k) and mean annual rainfall.

Using data only from sites considered valid for comparison (i.e. all those with a sclerophyllous plant understorey, not recently burnt, grazed or invaded by an exotic decomposer, and where for accuracy of assessment the litter layer has been sampled on several occasions) a quadratic relationship between litterfall rate and litter mass was significant, with decomposition rates at sites increasing with increasing litterfall rate.

The existence of such a relationship may be useful for future studies: if litter data obtained lie appreciably outside the values on the line of quadratic regression, it would be worthwhile checking the accuracy of litterfall and mass estimates, site past history and the validity of the decomposition constant estimate.

There was a significant positive linear relationship between the decomposition constant and mean annual rainfall at sites where rainfall was within the range 600–1800 mm y‐1, the general limits for open‐forest site development. However, more data are required to increase the predictive value of relationship.
The organization of a honeyeater community in an unpredictable environment
Authors: McFARLAND DAVID C.
Published: July 2006

The honeyeater community of an open‐layered forest was studied in the New England National Park over a 2.5 year period. Various aspects of honeyeater behaviour (aggression, social and foraging) were examined during transects and by use of time‐budgets. Time‐budgets were used to estimate the daily energy requirements for each species. Since nectar availability in the study area was variable, the energy produced per day by the nectar sources was occasionally insufficient to meet the daily energy demands of the honeyeater community. No strong spatial partitioning of the nectar resources by the birds was found. Use of the resources appeared to be based primarily on dominance interactions (interspecific aggression), with the larger species tending to dominate the smaller ones. Smaller species survive in the area because of their behavioural attributes and greater foraging efficiency which enables them to use the sparse supply of nectar on poor days. Temporal gradients in nectar richness may be just as important as spatial gradients in permitting the coexistence of species which use the same resource in the same habitat. Most of the results from this study fail to support the predictions made elsewhere concerning the organization of communities in unpredictable environments.
Soil seed‐bank components of the northern jarrah forest of Western Australia
Authors: VLAHOS STEPHEN , BELL DAVID T.
Published: July 2006

The germinable soil seed‐store of the northern jarrah (Eucalyptus marginata Donn ex Sm.) forest was found to average 767 seeds m−2 (range:377–1579 seeds m−2) over six randomly selected plots within a range of forest sites. A total of 68 different taxa of vascular plants were recognized following heating and glasshouse tray germination tests of field‐collected soils. Both the qualitative and quantitative composition of the soil seed‐bank were dominated by annuals and sub‐shrubs. Because less than 10% of the seed of the soil was from species of the dominant tree and woody shrub strata, there were major floristic differences between the existing flora and the composition of the soil seed‐bank. The influences of the soil seed‐bank on rehabilitation of disturbed jarrah forest lands and current fire management are discussed.
Population dynamics of the shrub Acacia suaveolens (Sm.) Willd.: Seed production and predispersal seed predation
Authors: AULD TONY D. , MYERSCOUGH PETER J.
Published: July 2006

Seed production and predispersal seed predation in the shrub Acacia suaveolens were examined over 3 consecutive years in eight populations in south‐eastern Australia. Seed‐crop sizes varied both between and within populations of different ages. Seed production was maximal in the first one to four flowering seasons after establishment, and then declined with plant age. The size of the annual seed‐crop was also influenced by rainfall for that year.

Predispersal seed predation varies between populations over fruiting seasons with the initial large seed‐crops resulting in predator satiation. Within one fruiting season, no significant variation in the extent of predispersal seed predation was found in any of three populations studied. There were two major forms of predispersal seed loss: toss of whole fruits to Melanterius corosus (Coleoptera: Curculionidae) and external insect seed grazers, and loss of individual seeds within fruits to M. corosus. Exclusion experiments showed that seeds lost to these predispersal seed predators would otherwise have been matured by the parent plant. The effects of predispersal seed predation cannot be directly related to seedling recruitment. Indirectly, such predation may influence the dispersion of seeds in the soil profile and hence, subsequent recruitment.
On comparing herbivore damage in Australian and north temperate systems
Authors: FOX L. R. , MORROW P. A.
Published: July 2006

Two recent reports suggested that Eucalyptus trees in Australia sustain less insect damage than previously reported (Ohmart 1984; Ohmart et al. 1983a). Those conclusions were based partly on new data and partly on a survey of reports describing herbivory in Australian and in northern forest ecosystems. In this paper the present authors argue that the logic and data interpretations in Oh mart (1984) and Ohmart et al. (1983a) are flawed, and a re‐evaluation of arguments and existing data about levels of herbivory is presented.

We also discuss several broader issues raised by this dispute. In particular, we emphasize that the variability that troubles some investigators is a fundamental component of the ecological and evolutionary processes in these systems. This variability generates differences in patterns that are not the result of inaccurate techniques nor of biased observers. It is argued, further, that it is not possible to predict the ecological or management consequences of either large or small amounts of herbivory from assessments of mean levels in natural systems.
Development of a new piosphere in arid chenopod shruhland grazed by sheep. 1. Changes to the soil surface
Authors: ANDREW MARTIN H. , LANGE ROBERT T.
Published: July 2006

Piospheres, that is, zones of attenuating stocking impact extending out from watering places, are a feature of arid pastoral regions. The present authors studied, for the first time, the initial development of a piosphere in respect of a number of variables of the soil surface. The site was near‐pristine chenopod shrubland, part of a paddock of 1340 ha near Whyalla, South Australia, stocked with ca. 200 sheep on a new watering point. Soil features monitored over the first 2.5 years were dung deposition, sheep track development and surface erosion, the soil lichen crust, compaction of the soil surface and dustfall, using fenced plots of at least 550 m2 as controls.

Piosphere patterns (i.e. patterns reflecting the concentricity of stocking pressure around water) were manifest within the first 3 months for sheep dung deposition, sheep track development, and lichen cover. Soil compaction, which was confined to sheep tracks and then largely to the surface 5 cm, displayed a piosphere pattern when it was first recorded 6 months after stocking. Bulk density of this layer was elevated by up to 20%. There was only a weak piosphere pattern in dustfall. The piosphere patterns in sheep track development and destruction of the lichen crust became more pronounced in time. Track direction was near radial. After 2 years the limit of the piosphere pattern ranged from ca. 10 m from the trough for infiltration into dry soil after an abrupt rainstorm, to greater than 800 m for sheep track intensity. These changes occurred at stocking levels amongst the lowest in Australian arid zone pastoral situations.

After the first 9 months of sheep stocking there was no discernible effect of grazing on the density of the short‐lived grasses or on the pattern of kangaroo arid rabbit activity as judged by the pattern of their dung deposition. No discernible erosion of the soil surface other than in sheep tracks occurred during the first 2 years.
Insect herbivory on mangrove leaves in North Queensland*
Authors: ROBERTSON A. I. , DUKE N.C.
Published: July 2006

Estimates of leaf damage by insect herbivores are presented for 25 species of mangrove plants, comprising canopy and understorey species. Leaf area loss was highly variable among the species sampled, with means ranging from 0.3 to 35.0% of expanded leaf area. There was also great variability amongst leaves within species, and the mean coefficient of variation for leaf loss from the 25 species was 266%. Of the 12 species sampled at more than one site in North Queensland, eight exhibited small, but significant, between‐site differences in herbivory. In general, it did not appear that height in the canopy influenced herbivory. For the dominant mangrove forest community type at Missionary Bay, an estimated mean of 2.1% of leaf production, or 11 g m‐2 per year, entered the direct grazing pathway. This very low figure is compared with estimates from other studies on mangrove forests and estimates from a variety of Australian terrestrial forests.
Interrelationships among some ectomycorrhizal trees, hypogeous fungi and small mammals: Western Australian and northwestern American parallels
Authors: MALAJCZUK N. , TRAPPE J. M. , MOLINA R.
Published: July 2006

Species of the hypogeous fungus genus. Mesophellia have been shown to form ectomycorrhiza with Eucalyptus diversicolor and improve seedling growth. Since the morphology of these fungi increases their dependence on animal mycophagy for spore dispersal, these results imply a tripartite interrelationship between eucalypts, hypogeous fungi and marsupials which parallels the North American interrelationship between ectomycorrhizal pine, hypogeous fungi and rodents. An understanding of the independent but analogous interrelationships on the two continents has implications for forest management, especially in regard to the effects of forest conversion on other members of the ecosystem.
A transect study of the Eucalyptus forests and woodlands of a dissected sandstone and laterite plateau near Darwin, Northern Territory
Authors: KIRKPATRICK J. B. , BOWMAN D. M. J. S. , WILSON B. A. , DICKINSON K. J. M.
Published: July 2006

Tabletop Mountain in the Northern Territory is a sandstone plateau topped in part by a residual laterite soil. The vegetation of the plateau was mapped and transects placed to cover the mapping units in which eucalypts were dominant or shared dominance. A polythetic divisive classification of the transect floristic data was largely congruent with the mapping units, which also differentiated the dominants. Topography and soils have an apparently strong influence on the nature of the vegetation through their influence on the periodicity and intensity of drought and Waterlogging. However, differences in soil fertility and understorey flammability are postulated to be important in discriminating several of the mapped vegetation types. The flora of Tabletop more closely resembles that of the Alligator Rivers region than that of the Mitchell Plateau or Weipa. Some of the communities differentiated at Tabletop are related floristically to some of the communities differentiated in the Alligator Rivers region and at Gove.
Flower colour change inBanksia ilicifolia: A signal for pollinators
Authors: B.LAMONT BYRON , COLLINS BRIAN G.
Published: July 2006

Both birds and insects visit yellow flower heads ofBanksia ilicifoliarather than those in the pink or red phases. Birds carry most pollen. Substantial nectar and pollen rewards are present only in the yellow phase. The timing of flower colour change also corresponds to a decline in viability of presented pollen and stigma receptivity. Colour change is age‐dependent rather than pollinator‐induced. Bird visits to yellow or red heads are essentially determined by the availability of nectar in each rather than differences in their visibility. Fruit set is negligible in the absence of pollinators but still < 1% in their presence.

Banksia ilicifoliahas the smallest heads and is the most localized of five co‐occurring and partly co‐floweringBanksiaspecies. It is hypothesized that the restriction of flower colour change toB. ilicifoliaincreases the competitiveness of this species: bird visitors are directed to flower heads with abundant nectar, viable pollen and receptive stigmas, foraging and pollination efficiency thereby being enhanced without a marked reduction in long‐distance attractiveness of the tree to potential pollinators.
Pollination biology in the Snowy Mountains of Australia: Comparisons with montane Colorado, USA
Authors: INOUYE DAVID W. , PYKE GRAHAM H.
Published: July 2006

Various aspects of the pollination biology of the alpine flora of Kosciusko National Park, NSW, were examined from late December 1983 until the end of March 1984, including flowering phenology, corolla tube lengths, flower colour, ultraviolet reflectance patterns, visitation rates to the flowers and proboscis lengths of the flower‐visiting insects. An average of 5.3 species flowered in each of 13, 2 m×2 m montane plots and 5.6 species in the 13 alpine plots. The maximum number in flower simultaneously averaged 4.1 species in the montane and 3.3 in the alpine plots; flowering peaked in mid‐January, Corolla tube lengths of the flora averaged 1.73 mm.

The most common floral colour was white or predominantly white (40 species), followed by yellow (14 species). Only six of the 38 species (16%) examined had some type of reflectance pattern; the remaining species all absobed ultraviolet.

Flies appeared to be the major pollinators. The insects collected in the study area comprised 60 species of Diptera, 33 species of Hymenoptera, and several species each of Lepidoptera and Coleoptera. On average, 14.4% of flowers watched during 379 observation periods (10 min each) were visited. On average, each plant species was visited by 6.4 species of flies, 2.4 species of bees, wasps or sawflies, one species of butterfly or moth and 0.3 species of beetles. Visitation rates increased over the growing season, and were significantly affected by ambient temperature (positively), light levels (positively) and wind speed (negatively).

The maximum proboscis length for the 25 most common species of bees was 2.76 mm, but 18 of 51 species of flies had proboscis lengths longer than this. The mean proboscis length for all 25 species of bees was 1.68 mm, and for 51 species of flies was 2.31 mm. Proboscis lengths for flies were positively correlated with the average corolla length for the plant species they visited. For bees, however, the range in proboscis lengths was relatively small and did not show this pattern.

There appear to be significant differences between the plant‐pollinator community of alpine Australia and other alpine areas where bumblebees are common pollinators. These differences include shorter proboscis and corolla tube lengths, and perhaps an increased diversity and significance of flies as pollinators.
Plant species‐richness and invasion by exotics in relation to disturbance of wetland communities on the Riverine Plain, NSW
Authors: McINTYRE S. , LADIGES P. Y. , ADAMS G.
Published: July 2006

A combination of field surveys and seed‐bank measurements were used to describe the macrophytic vegetation of intermittent wetlands on the Riverine Plain, in New South Wales. Three habitat types were sampled, representing wetland vegetation subjected to varying intensities of exogenous (human‐induced) disturbance: swamps (least disturbed), roadside table drains (moderately disturbed), and rice crops (highly disturbed). Forty‐two plant species were common to all three habitats and 36 species occurred in two of the three habitats. Of the 82 species that were restricted to a single habitat type, 33 were recorded for swamps, 19 for roadsides and 30 for rice fields.

Species‐richness (number of species per 50 m2) was found to be significantly lower in rice fields compared with either roadsides or swamps, which were not significantly different. Richness of native vascular species differed significantly among all habitat types, with swamps > roadsides > rice fields. Richness of exotic species also differed: roadsides > rice fields > swamps. Although the least disturbed habitat (swamps) supported the least number of exotic species, there was no further evidence of a positive relationship between degree of disturbance and degree of invasion. The results provided some support for the hypothesis that maximum species‐richness occurs under conditions of moderate disturbance.

A small negative correlation (r=−0.178, P < 0.01) was found between the number of exotic species and the number of native species occurring at a site. This suggests that, in this case, species‐richness is not an important factor in the resistance of vegetation to invasion by exotic species. The vegetation of intermittent wetlands appears to have a relatively high degree of resistance to invasion. This is attributed to the high level of endogenous disturbance to which the native vegetation is adapted.
The structure of termite communities in the Australian tropics
Authors: BRAITHWAITE R. W. , MILLER L. , WOOD J. T.
Published: July 2006

The distributions of 50 species of termites across five habitat types in Kakadu National Park are described. Open forests are richest in species and monsoon forests are species‐poor. The greatest diversity of termites is associated with infertile soils and is probably related to the enhanced role of termites in these nutrientimpoverished sites. Only the richness of livewood feeders is associated with disturbance in the form of water buffalo impact. Few relationships with physical characteristics of the soil were apparent. Comparisons between continents suggest that lower termites are richer in Australia than on other continents. There are fewer species of soil‐feeding termites, but only two of the four subfamilies of the higher termites (Termitidae) are present in Australia. There appears to be a complementary distribution of areas of high diversity of termites and native herbivorous mammals. This may be due to the ability of termites and other invertebrate groups to exploit low fertility systems and has profound implications for the size structure of the vertebrate community.
A koala (Phascolarctos cinereus Goldfuss) population crash during drought and heatwave conditions in south‐western Queensland
Authors: GORDON G. , BROWN A. S. , PULSFORD T.
Published: July 2006

In the summer of 1979–80, there was a sharp decline in the koala population along Mungalalla Creek in south‐western Queensland. The decline was associated with a heatwave and drought. Live animals and carcasses were counted soon after the decline and at three subsequent periods. It was estimated that more than 63% of the population died. The drought and heatwave caused extensive leaf‐fall and/or browning of the foliage in food trees along stretches of dry creek. The proximate cause of death was thought to be a combination of malnutrition and dehydration. There was evidence, including the differential survival of koalas along the creek, of marked heterogeneity in the quality of the habitat. At sites where the trees were not affected (mainly on large permanent water‐holes) koalas had good body condition and mortality was low, whereas on stretches of dry creek (marginal habitat), koalas were in poor health (poor condition, anaemia, high tick loads) and mortality was very high. Survival of the population was not threatened because many animals survived at the permanent water‐holes. There is evidence that mortality was highest among young animals which may be excluded from optimal sites by older dominant animals. In the years after the crash, continuing drought appeared to prevent recovery of the population. It is thought that such population crashes are rare events as they are apparently caused partly by unusual climatic conditions.
Comparison of crown cover estimates for woody vegetation in arid rangelands
Authors: FRIEDEL M. H. , CHEWINGS V. H.
Published: July 2006

Three methods for estimating crown cover of woody vegetation were compared, in three mapped field sites and one theoretical map of randomly distributed individuals, by computer simulated sampling. The effect of plant size on the performance of the methods was investigated by varying the size of individuals in the theoretical map.

Using the line‐intercept and point‐sampling techniques according to standard procedures, the net crown cover of a species is estimated and overlapping areas are not recognized. The variable plot or Bitterlich gauge technique estimates the total crown cover of individuals, and areas of overlap are thus recorded more than once. Consequently, Bitterlich gauge estimates will always be greater whenever individuals intermingle or overtop one another.

Line‐intercept and point‐sampling techniques produced highly variable estimates when plants were small, but were not prone to greater variability when plant distribution departed from randomness. The Bitterlich gauge estimates were no more variable with small than with large plants, but were affected by the degree of plant aggregation. The problem is overcome by selecting a sample point spacing and a half‐angle for the gauge that optimizes plant counting.

The advantages of the variable plot method over the other two are discussed in terms of speed and operator differences, and it is recommended as a monitoring technique for woody vegetation in arid rangelands.
Response of eucalypt species to drought
Authors: DAVIDSON N. J. , REID J. B.
Published: July 2006

The response of three eucalypt species (Eucalyptus pulchella, Eucalyptus coccifera and Eucalyptus delegatensis) to a severe drought in the summer of 1982/83 was examined at Snug Plains, south‐eastern Tasmania. Few large differences in leaf water potential (Ψl) or stomatal conductance (gs) were apparent even at the height of the drought when both Ψl and soil water potentials (Ψs) reached ca. — 4.5 MPa. However, E. pulchella maintained a higher relative water content (RWC) in its leaves than E. coccifera and E. delegatensis, and showed less severe crown damage. After the first light rains substantial interspecific differences in Ψl and gs occurred. Eucalyptus pulchella restored normal Ψl, gs and RWC more rapidly than the other two species and, even for severely droughted trees, crown growth commenced via epicormic buds near the ends of its branches while for E. delegatensis and E. coccifera crown regeneration was via epicormic buds arising from stems and larger branches. This resulted in a change in dominance in certain stands and showed that E. pulchella was more drought‐resistant than E. coccifera, which was in turn more resistant than E. delegatensis. This conclusion was confirmed during competition experiments using potted seedlings. However, potted seedlings differed from mature field trees by maintaining moderate gs at high vapour pressure deficits and closing stomata at Ψl below ca. — 2.0 MPa.

Substantial variation in the severity of drought symptoms was observed over short distances. This variation appeared to be determined by the moisture‐holding capacity of the soil and the biomass of the stand. Although differences in the rooting patterns of seedlings were evident, field measurements of Ψl and Ψs suggested that all three species were exploiting the same water resource.

In contrast to previous studies, the results suggest that large interspecific differences in tissue hydration and crown damage may be present, even though differences in Ψl, gs and characteristics of the root system may appear small.
The modified primary succession following sand mining: A validation of the use of chronosequence analysis
Authors: TWIGG LAURIE E. , FOX BARRY J. , JIA LUO
Published: July 2006

Changes in small mammal succession along a forested coastal dune system in the Myall Lakes‐National Park, New South Wales, during 15 years of regeneration after sand mining, were determined by surveys in 1982 and 1987. The results clearly demonstrate a wave of succession moving along the mining path, and confirm that over the intervening 5 year period to 1987, small mammal succession has followed a path indicated by that of the 1982 chronosequence. The house mouse, Mus musculus quickly recolonizes disturbed areas, and peak abundance occurred on plots with a regeneration age of 3.7 years in 1982 and 3.4 years in 1987 (i.e. the 3.0–4.5 age class). Colonization by the New Holland mouse. Pseudomys novaehollandiae was first recorded on plots with 4.6 years regeneration in 1982 and 5.4 years in 1987. Peak Pseudomys numbers occurred on plots in the 7.5–9.0 age class in both 1982 and 1987. The common dunnart, Sminthopsis murina appears to be the third species to enter the succession. This modified primary succession closely resembles the mammalian secondary succession following fire where additional evidence suggests that the use of chronosequence analysis may also be appropriate.
Effects of fire on the bird communities of tropical woodlands and open forests in northern Australia
Authors: WOINARSKI J. C. Z.
Published: July 2006

Birds were censused at 24 plots which had been subjected to 14 years of four experimental fire regimes (fire‐exclusion, annual early burn, annual late burn and biennial burn) in Eucalyptus open forest and woodland at Munmarlary, Northern Territory. In addition, short‐term responses of birds to fire at a savannah woodland site near Katherine were examined. At this site patches of the study area were burnt in April, June and August 1987, and birds were censused monthly over the period April to October 1987.

Many bird species were attracted to areas that had been recently burnt. These were mostly granivorous species, and omnivorous and carnivorous species which fed on the ground. Influxes of these species occurred because fires increased accessibility to food by clearing the ground of its previous dense grass layer.

Succession of bird species to long‐unburnt areas was relatively limited, although species which fed or nested in the shrubby understorey occurred at greater densities in such areas. Frugivorous birds may become more common in areas protected from fire, thereby driving succession to monsoon vine forests from Eucalyptus forests, though, in terms of current fire regime, this process may be prohibitively slow.

The hot fires of the mid to late Dry season may be less beneficial to granivores than the cooler fires typical of the early Dry. Accordingly, recent changes in the fire regime may have contributed to the decline of some bird species.
The importance of herbivory in the population dynamics of three sub‐alpine eucalypts in the Brindabella Range, south‐east Australia
Authors: WILLIAMS J. E.
Published: July 2006

it is hypothesized that herbivory plays an important role in limiting the distribution of Eucalyptus pauciflora in sub‐alpine forests. In the Brindabella Range, ACT, E. pauciflora is generally replaced downslope by E. dives and increased herbivory towards its lower distribution may be a factor in this replacement. Further, the co‐occurrence of E. dalrympleana with E. dives and E. pauciflora may be maintained by a density‐dependent stabilizing mechanism based on the impact of leaf parasites.

Mean levels of leaf damage by insects on the lignotuberous seedlings of these three sub‐alpine eucalypts were not consistent with these hypotheses. Seedlings of E. dalrympleana showed significantly lower levels of damage (7.4–9.4%) compared with those of E. pauciflora (13.9–20.2%) and E. dives (19.2–20.7%) but no significant intra‐specific differences in the mean levels of leaf damage with altitude occurred for any of these eucalypts. These results suggest that insect herbivory as a factor regulating the population dynamics of sub‐alpine eucalypts may have been overemphasized.
Differential responses to salinity help explain the replacement of native Juncus kraussii by Typha orientalis in Western Australian salt marshes
Authors: ZEDLER JOY B. , PALING ERIC , McCOMB ARTHUR
Published: July 2006

The influence of salinity on Typha orientalis and Juncus kraussii was documented in experiments on germination of seeds and on growth of seedlings and adult, rhizome‐bearing plants. Juncus was more salt‐tolerant than Typha at all three life‐history stages, but salt tolerance increased with plant age for both species. Although seeds of both species germinated at 0 and 5 ppt, the germination data overestimated salt tolerance for Typha. Only the newly emerged seedlings of Juncus were capable of growth after removal from the 5 ppt NaCl solution to fresh water. Typha seedlings that initiated growth at 0 ppt grew well at 5 ppt but not at 10 ppt, while Juncus seedlings were tolerant of 10 ppt. Although the 20 ppt treatment caused high mortality of Juncus seedlings, the 10 ppt treatment mainly reduced growth. Adult plants of Typha, which were collected from the field, survived the 20 ppt treatment, while adult Juncus survived the 40 ppt treatment. The presence of salt (10–40 ppt) shortened the growing season for adult, rhizome‐bearing plants of both Juncus and Typha, with a lower maximum and earlier peak in total leaf length and maximum leaf number. Thus, the greater biomass in fresh water was achieved primarily through a longer growth period, rather than a greatly accelerated growth rate.

Interactions between the two species were explored in mixed‐species culture of both seedlings and adult rhizome‐bearing plants. Interspecific interactions were present at low salinity, but results differed for seedlings and adult plants. Typha seedlings failed to outgrow Juncus seedlings (at 5 ppt) but adult plants of Typha outgrew Juncus (at 0 ppt). Relative yields (biomass in mixed/pure pots) for Juncus and Typha seedlings were 0.85 and 0.26 at 5 ppt. Relative yields of adult plants were 0.24 for Juncus and 1.20 for Typha at 0 ppt. For both seedlings and adults, the species that ultimately dominated the mixed‐species pots produced just as much total biomass as in pure‐species pots, even though initial planting density was half as high.

Extrapolating findings to the field situation, it appears that Typha has a narrow regeneration niche. The indication is that Typha could invade Juncus stands only following salinity reduction (allowing seed germination and early seedling growth) and after disturbance disrupts the native vegetation. The combined conditions of prolonged low salinity and open habitat occur where street drains are cut through the salt marsh. The probability of Typha becoming established would be highest in such areas. vegetative expansion would follow with continued freshwater influx, as rhizome‐bearing plants gain an interspecific advantage.
Dieback of rural eucalypts: Does insect herbivory relate to dietary quality of tree foliage?
Authors: LANDSBERG JILL
Published: July 2006

Foliar dietary quality, and the damage that insects caused to the foliage of dieback‐affected and healthy Eucalyptus blakelyi trees, were monitored for 3 years, on pastoral properties in the Australian Capital Territory. Compared with healthy trees, the foliage of dieback trees was more heavily grazed by insects, and its dietary quality was generally superior. Some of the differences in dietary quality were related to the average age of the foliage of healthy and dieback trees. But when statistical models were used to equalize the effects of differences in leaf ages, leaves on dieback trees nonetheless tended to have lower specific weights, and were sometimes rounder and contained more nitrogen. Regression analyses of herbivory against each of the dietary quality variables showed that the only significant relationship that was consistent for both of the years monitored was for foliar nitrogen and herbivory for both dieback and healthy trees. In the first year, regressions between herbivory and specific leaf weight, shape, or sugar content were also significant, but only amongst the dieback trees. This may indicate that these relationships were a response to, rather than a primary cause of, the repeated high defoliation of the dieback trees. Multiple regression equations incorporating annual means of several quality variables explained a high proportion of the variance in annual herbivory, but were grossly different between years.
Demography of woody plants in relation to fire: Banksia serrata Lf. and Isopogon anemonifolius (Salisb.) Knight
Authors: BRADSTOCK R. A.
Published: July 2006

Banksia serrata and Isopogon anemonifolius are serotinous resprouters (single‐stemmed tree, multi‐stemmed shrub, respectively) found in forests within the Sydney region. Studies were conducted to predict the population dynamics of these species. Seed production and survival and the accumulation of seed‐bank within cones were estimated in relation to time since fire. Emergence, survival and development of lignotubers were measured in young juveniles and the time taken to reach adulthood was estimated. This information and published data on survival were used to estimate the amount of recruitment of adults and juveniles necessary for stands to remain in a stable state under frequent (<16 years), high and low intensity fire regimes. The effects of longer intervals (up to 80 years) between fires were also estimated. It was predicted that B. serrata populations will decline in numbers when the interval between high intensity fires is <9 years, while under low intensity fires the critical interval was 12–13 years. In I. anemonifolius the predicted intervals were 14 and 16 years, respectively. When fires are timed so that maximum seed‐bank is available (about 30 year interval), it is unlikely that resprouters will dominate communities because the seed‐banks and rates of growth of seedlings of obligate seeder shrubs are greater than these resprouters. Populations of these resprouters may be more able to persist than obligate seeders when the fire frequency is either very high (<6 years) or low (>50years), though the density of resprouter populations may slowly decline under such fire regimes.
Evidence of recent mangrove decline from an archaeological site in Western Australia
Authors: KENDRICK GEORGE W. , MORSE KATE
Published: July 2006

Mangrove‐associated molluscan material predominates in a 7000‐year‐old Aboriginal midden site on the subtropical north‐central coast of Western Australia at a locality now remote from significant modern mangroves. A palaeolagoon, separated from the ocean since about 5000 years bp, is the likely principal source of the shell midden material. An apparent decline of mangroves between Exmouth Gulf and the Gascoyne River delta since the Middle Holocene is attributed primarily to sedimentary processes, which have modified the initial, transgressive shoreline established around 7–6000 years bp, This may reflect similar processes reported from northern Australia.
Experiments in ecology and management: Their logics, functions and interpretations
Authors: UNDERWOOD A. J.
Published: July 2006

Experimental tests of clearly articulated hypotheses are an increasingly widespread feature of modern marine ecology. Increased use of experiments has not, however, been accompanied by increased understanding of the logical structure of falsificationist tests. Most observations can be explained by several different models or theories. To distinguish among these requires demonstration of the falsity of the consequences or predictions of incorrect models. This is best achieved by deriving from each model one or more hypotheses (predictions) about the type, form or nature of observations that should occur in some not‐yet‐examined set of circumstances. Because of logical constraints on the possibility of proving the correctness of such hypotheses, they must be inverted to form logical null hypotheses which comprise all alternative possibilities to those predicted in the hypotheses. Correctness or not of null hypotheses can then be ascertained by an appropriately designed experiment (or test), leading to unambiguous rejection or retention of the null hypotheses. The former corroborates the hypotheses and provides support for the correctness of the explanatory model for the original observations. In contrast, retention of a null hypothesis identifies an incorrect model. The growth of knowledge is thus the elimination of false models, theories and explanations.

Ecological experiments usually require statistical procedures for determining whether or not null hypotheses should be retained. Construction of statistical null hypotheses (i.e. definitions of parameters of frequency distributions of test statistics) sometimes requires that these be identical to logical hypotheses (and not to the logical nulls). This leads to irrational acceptance of hypotheses and the models or theories from which they were derived. It also poses immense problems for determinations of statistical power of experiments.

Ecological experiments are analysed to reveal the nature of, and linkages between, their components in relation to falsificationism, statistical procedures and the logical properties and interpretations of ecological theories.
Physical variability, diversity gradients and the ecology of temperate and tropical reefs
Authors: McGUINNESS KEITH A.
Published: July 2006

Traditionally, compared with the tropics, temperate systems are believed to: (i) have environments which are less favourable (i.e. harsher, more variable and less predictable); and (ii) support communities which are less diverse. Explanations for differences between temperate and tropical communities, including differences in diversity, generally rely on the former notion.

The evidence for these ideas is, at best, equivocal. Organisms are subjected to physical stresses and disturbances on both temperate and tropical reefs. Communities on temperate reefs are not invariably less diverse than those in the tropics, at least at small spatial scales. Finally, there is as yet little evidence of genuine differences between the ecology of temperate and tropical communities.

There is, however, much small‐scale, spatial patchiness in the structure of reef communities and their physical environment. This patchiness in structure may result from patchiness in biological factors (e.g. recruitment) or in the physical environment. This small‐scale variation in environmental factors may prove to be a more important determinant of community structure than the large‐scale, latitudinal trends some ecologists have been obsessed with.
Herbivory and patch dynamics on rocky reefs in temperate Australasia: The roles of fish and sea urchins
Authors: JONES G. P. , ANDREW N. L.
Published: July 2006

Sea urchins are widely considered to be the major grazers in temperate subtidal systems, with herbivorous fish being browsers of minor importance. This paper reviews spatial and temporal patterns in these herbivores on rocky reels in temperate Australasia, with the aim of assessing their relative impacts on patch structure and dynamics. Herbivorous fishes are widespread and make up a significant numerical component the reel fish fauna. Sea urchins are also abundant, but not all geographic locations support actively grazing species.

Both fish and sea urchins exhibit distinct patterns of distribution among depth strata. Within depth strata, all herbivores are restricted to (sea urchins) or forage preferentially in (fish) particular habitat patches, causing a mosaic of different feeding activities. These patches are either related to specific features of the habitat (e.g. Kelp patches, topography) or behavioural interactions. Foraging by sea urchins and demersal‐nesting damselfishes is intense and persistent, whereas in the kelp‐feeding fish Odax cyanomelas, foraging reaches greatest intensity at predictable locations during a few months of every year.

Many fish and sea urchins consume some algae in preference to others. However, feeding preferences may determine the nature of the impact only in fishes. For sea urchins, preference may occasionally determine the order in which algae are consumed, but at high densities they consume all available macroalgae.

Impacts of both types of herbivore on the abundance of algae have been recorded. Some sea urchins (e.g. Evechinus chloroticus, Centrostephanus rodgersii) appear to severely modify biogenic habitat structure by maintaining ‘barrens’ (areas devoid of macroalgae) over long periods. In contrast to this, the effects of fishes may be more transitory (e.g. seasonal impact of Odax cyanomelas on brown algae) or occur at smaller spatial scales (e.g. nest sites maintained by male Parma victoriae) Herbivorous and other fishes appear to respond to spatial patterns in algal distributions, rallier than having it major impact upon them. The relative effects of fish and sea urchins on the long‐term dynamics of kelp forests are unknown, hut temporal patterns in herbivore abundance and behaviour, and algal demography arc urgent targets for research.
Species‐area curves and growth‐form spectra for some herb‐rich woodlands in western Victoria, Australia
Authors: LUNT IAN D.
Published: July 2006

Species‐area curves are presented for three woodlands with herbaceous understoreys in western Victoria. Australia. Up to 93 species of vascular plant were recorded from 128 m2. making these woodlands one of the richest terrestrial vegetations recorded from temperate Australia. Species richness at this scale is comparable with that recorded from kwongan (sclerophyllous shrubland) in south‐western Australia. Up to 45 species were recorded from 10 m2. At this scale the woodlands are the richest terrestrial vegetation recorded from Australia, and among the richest in the world, being comparable with the renowned chalk grasslands of Europe. The growth‐form spectra of these woodlands differ dramatically from those of other species rich communities in temperate Australia due to the abundance of herbs and dearth of woody species. In contrast to species rich woodlands in Israel and California, perennial herbs rather than annuals predominate. Although the woodlands studied are protected in conservation reserves, regional floristic surveys are required to determine the geographic extent, floristic variability and conservation status of herb‐rich woodlands in Victoria.
Sandstone vegetation pattern in the Jim Jim Falls region, Northern Territory, Australia
Authors: BOWMAN D. M. J. S. , WILSON B. A. , FENSHAM R. J.
Published: July 2006

Analysis of 58 floristic quadrats from two areas near Jim Jim Falls on the Arnhem Land Plateau revealed seven plant communities: wetland; monsoon forest; Allosyncarpia forest; broadleaf woodland; shrubby Eucalyptus woodland; Eucalyptus arnhemensis woodland; and sandstone scrub. The communities inter‐grade with each other and form a complex mosaic. The patterning of vegetation is related to topography, rockiness, degree of fire protection and moisture supply. Surface soil nutrient concentrations were similar in all the communities with the exception of the monsoon forest which was substantially more fertile. We suggest that moisture supply is the primary determinant of vegetation and soil fertility patterns. Fire in the preceding dry season stimulated some herbaceous species, while a long unburnt shrubby Eucalyptus woodland was invaded by some monsoon forest seedlings. Conservation of the present mosaic of vegetation presents a major challenge to land managers because of this variable impact of fire.
Woody overstorey impact on herbaceous understorey in Eucalyptus spp. communities in central Queensland
Authors: SCANLAN J. C. , BURROWS W. H.
Published: July 2006

Native pasture yield and species composition within naturally occurring Eucalyptus communities of central Queensland were studied. Within a site, herbaceous yield decreased as tree basal area increased with the greatest relative decrease at sites with low pasture production potential. Mitscherlich regressions between herbaceous yield and tree basal area Y = A + B*e−kx) accounted for >80% of the observed variation at all sites. The absolute value of ‘k’ was greatest for those sites that had the lowest yield in the absence of trees.

Pasture composition in treeless plots varied widely among sites. However, the direction of species compositional change was similar for all sites except one subject to short‐term inundation on a heavy clay soil. Grass tribes differed in their occurrence in areas of high tree basal area. Andropogoneae had lower actual yield and percentage composition (by dry weight) at high tree basal area, while Paniceae showed the reverse trend. Non‐grass herbaceous plants made a greater contribution to pasture composition at higher tree basal area although actual dry matter yield remained relatively constant over a wide range of basal areas.
Dispersal of an introduced shrub (Crataegus monogyna) by the Brush‐tailed Possum (Trichosurus vulpecula)
Authors: BASS DAVID A.
Published: July 2006

The Brush‐tailed possum Trichosurus vulpecula eats the fleshy fruits of the introduced shrub Crataegus monogyna and defaecates intact seeds at least 0–50 m away. Viability of seeds recovered from faeces was >73%. comparable to the viability of fresh seeds (87.6%). Seed dispersal by possums has been largely neglected and may have important implications for invasion by woody weeds in Australasia.
Disturbance regimes in North Queensland rainforests: A re‐evaluation of their relationship to species richness and diversity
Authors: SAXON E. C.
Published: July 2006

Changes in tree species richness and diversity after logging and natural disturbance on small rainforest plots in north Queensland were studied by Nicholson et al. (1988). They found logging had enhanced richness and diversity, which declined in its absence. A re‐evaluation of their data, especially those on the predisturbance condition of these plots, indicates that their conclusions are untenable.