bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractA 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

AbstractThe 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

AbstractIn 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

AbstractThree 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

AbstractThe 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

AbstractChanges 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

Abstract 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

Abstract 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

Abstract 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

Abstract 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

AbstractBanksia 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

AbstractMangrove‐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

AbstractExperimental 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

AbstractTraditionally, 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.