bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of nitrogen, plant density and competition between Bromus sterilis and three perennial grasses: the implications for boundary strip management
Authors: REW L.J. , FROUD–WILLIAMS R.J. , BOATMAN N.D.
Published: July 2006

The competitive ability of Festuca rubra L., Hoicus lanatus L. and Poa trivialis L. when grown from seed, in monoculture and in 1:1 additive mixtures with Bromus sterilis L. was studied. B. sterilis was more aggressive when grown in additive mixtures with F. rubra than P. trivialis or H. lanatus. H. lanatus was less dominated by B. sterilis at the second harvest; visual observations suggested that this dichotomy was due to its slower initial growth rate, and its subsequent dense vegetative growth habit. There was no statistically significant difference between the Relative Yield Total (RYT) of B. sterilis in additive mixtures with F. rubra, H. lanatus or P. trivialis, indicating that they were competing for the same resources. B. sterilis produced significantly more reproductive tillers and seeds as a result of nitrogen application, and such production was accentuated in the absence of interspecific competition. The implications of sown grass strips for field margin management are discussed.
Competition between Ridolfia segetum and sunflower
Authors: CARRANZA P. , SAAVEDRA M. , GARCIA–TORRES L.
Published: July 2006

Studies on competition between Ridolfia segetum Maris, and sunflower (Helianthemum annuus L.) were conducted at eight locations in southern Spain in 1990 and 1991. in order to define competition models and to estimate from these economic thresholds as affected by crop inputs and potential yields. Competition losses in sunflower crops ranged from 19% to 56% of weed–free yields. There were slightly better correlations between percentage sunflower reduction and weed density than with weed dry weight, (−0.66 and −0.59, respectively). The weed competitive index, or sunflower crop dry weight reduction per unit dry weight of R. segetum, was 1.09. The percentage yield losses due to weed density (NPRt) were fitted to multiple linear, quadratic, exponential and hyperbolic models. The hyperbolic equation, %RSY=100 (1+1/b*NPRt)−1, where b=0.14 and is the R. segetum competitive ability index, had the lowest error sum of squares (SSE), and gave the best biological explanation for the competition response. Early emergence (before mid–March) made weeds about 1.5 times more competitive than late emergence. The economic threshold to offset the cost of a shallow post–emergence tillage, assuming 70% control efficiency, ranged from about 2.5 plants m −2 for low–yielding crops(1200kgha−1) to less than one plant m−2 for higher–yielding crops (2800 kg ha−1).
Foliar absorption and translocation of nicosulfuron and rimsulfuron in five annual weed species
Authors: MEKKI M. , LEROUX G. D.
Published: July 2006

Ambrosia artemisüfolia L. (common ragweed) and Digitaria ischaemum Schreb. (smooth crabgrass) are not controlled by nicosulfuron and rimsulfuron at the highest recommended application rates, whereas Panicum miliaceum L. (wild proso millet), Amaranthus retroflexus L. (redroot pigweed) and Avena fatua L. (wild oat) are susceptible. The foliar absorption and translocation of 14C‐nicosulfuron and 14C‐rimsulf uron were studied in these weed species up to 48 h after treatment (HAT). Differences in herbicide uptake and translocation were not correlated with the species susceptibility. By 48 HAT, more than 50% of both herbicides remained on the treated leaf surface. Foliar absorption of rimsulfuron was greater than that of nicosulfuron in A. retroflexus, P. miliaceum and A. artemisüfolia. Most of the absorbed herbicide remained in the treated leaf of each weed species. Export of 14C–nicosulfuron ranged from 28 to 54% of that absorbed, in contrast to 15 to 39% for 14C–rimsulfuron. The absorption and translocation rates of both herbicides were highest within the initial 6 HAT, and decreased thereafter. Both herbicides showed approximately the same distribution pattern within each weed species.
Geographical differentiation in allozyme variation in Rumex acetosella subspecies acetosella and angiocarpus
Authors: KORPELAINEN H.
Published: July 2006

Electrophoretic examination of the hexaploid Rumex acetosella L. revealed a substantial amount of genetic variation. Both the genotype frequencies and the distribution of genotypes varied greatly between populations. The North American populations of ssp. angiocarpus possessed less genetic variation than did the European populations of ssp. acetosella or angiocarpus, which may be due to the history of the species. The European populations of ssp. acetosella and angiocarpus appeared to be genetically more similar than the angiocarpus populations from different continents. It is likely that these two subspecies do hybridize when their populations are sympatric. The results do not confirm the presence of an association between morphometric and allozyme variation in R. acetosella.
Evaluation of three empirical models depicting Ambrosia artemisiifolia competition in white bean
Authors: CHIKOYE D. , SWANTON C. J.
Published: July 2006

The performance of three empirical models describing white bean yield loss (YL) from common ragweed competition was compared using field experiments from Staffa and Woodstock, both in Ontario, Canada, in 1991 and 1992. One model was based upon both weed density and relative time of emergence. The other two models described yield loss as a function of weed leaf area relative to the crop. The model based on both weed density and relative time of emergence best described the data sets. The predicted maximum yield loss (A) and the parameter for relative time of weed emergence (C) varied across locations and years whereas the yield loss at low weed density (I) was relatively more consistent across locations and years. Use of thermal time (base temperature=10oC) rather than calendar days did not change the overall fit of the model, but reduced the value of the parameter for the relative time of weed emergence (C). The two parameter leaf area model accounting for maximum yield loss (m) gave a better fit to the data compared with the one parameter model. The relative damage coefficient (q) varied with time of leaf area assessment, location and year. Values of q calculated from relative leaf area growth rates of the crop and weed were similar to observed values.

The relationship between q and accumulated thermal time was linear but varied with location and year. As management tools, models based upon relative leaf area have advantages over models based on density and relative time of emergence since the level of weed infestation needs only to be assessed once, whereas density and emergence time require frequent observations. The ability to assess accurately and quickly both the crop and weed leaf area, however, may limit the practical application of models based on leaf area. The inability of empirical models to account for year–to–year variation in environmental conditions was observed.
Seasonal emergence of weeds in cultivated soil in New Zealand
Authors: POPAY A. I. , COX T. I. , INGLE A. , KERR R.
Published: July 2006

Patterns of seedling emergence of ten weed species from soil cultivated at intervals of approximately one month are described. All species examined showed clearly defined emergence patterns. Polygonum persicaria L. seedlings emerged in spring and early summer. Seedlings of Chenopodium album agg., Portulaca oleracea L. and Solanum nigrum L. emerged in late spring, summer and early autumn.Plantago major L., Rumex spp. (mostly R. obtusifolius L.) and Trifolium spp. (mostly T. repens L.) emerged mostly in spring and early summer. Coronopus didymus (L.) Sm. and Juncus bufonius L. tended to emerge in both autumn and spring.Veronica persica Poir. emerged in spring, summer and autumn. Close similarity between emergence patterns in New Zealand and northern Europe, despite differences in rainfall and temperature, suggests that annual dormancy:nondormancy cycles of seeds buried in the soil are largely responsible for seedling emergence patterns. In New Zealand, seedling emergence tended to be more spread out than in Europe, although seasonal patterns were still distinct. Further work on dormancy cycles in these species would be useful, as would a comparison of the factors inducing and breaking dormancy of comparable seed populations in northern and southern Europe and New Zealand. When seeds were left buried for several years before being encouraged to germinate, seedling emergence patterns tended to be of smaller amplitude, although the overall patterns were still very similar.
Effects of dose and application timing on the seed production of three weed species treated with MCPA or tribenuron‐methyl
Authors: ANDERSSON L.
Published: July 2006

The seed production of Fallopia convolvulus (L.) A. Love, Galium spurium L, and Thlaspi arvense L., treated with MCPA or tribenuron‐methyl, was studied in a pot experiment. The herbicides were applied in doses from 1/16 to 1/l of a full dose at five different growth stages. The largest reduction of seed production was observed on plants treated when one true leaf had developed (F. convolvulus, both herbicides) or at the beginning of the generative phase (G. spurium treated with tribenuron‐methyl and T. arvense treated with either herbicide). Tribenuron‐methyl (0.375 g a.i. ha−1) or MCPA (0.1875 kg a.i. ha−1) applied at bolting stage was enough to reduce the seed production of T. arvense by 83% and 100%, respectively. The seed production of F. convolvulus, treated with 0.75 kg MCPA at the cotyledon stage, was reduced by 70%. Plants of G. spurium with 5–9 axillary shoots, treated with 3 g tribenuron‐methyl, produced 45% fewer seeds than the control. Both herbicides (at least at the highest doses) reduced seed production of all three species more than shoot dry matter.
Influence of herbicide application rate and timings for post‐emergence control of Sorghum halepense (L.) Pers. maize
Authors: ELEFTHEROHORINOS I. G. , KOTOULA‐SYKA E.
Published: July 2006

Field experiments were carried out in Greece from 1990 to 1992 to study the effect of application timing and rate of nicosulfuron and rimsulfuron on Sorghum halepense (L.) Pers. control and maize yield. All herbicide rates are given in terms of active ingredient (a.i.). Nicosulfuron applied at 22.5, 30.0 and 37.5 g ha−1 to S. halepense at height 20–35 cm provided greater than 93% control 90 days after treatment, while rimsulfuron applied at 7.5,10.0 and 12.5 g ha−1 resulted in 81–91% control. Split applications of nicosulfuron and rimsulfuron, as well as tank‐mixtures of nicosulfuron+rimsulfuron, gave 91–94% control. Maize yield in all herbicide treatments was greater than that of the weed‐infested control and similar to that of the hand‐weeded control. S. halepense control with nicosulfuron and rimsulfuron applied to plants 20–35 cm tall was greater than that obtained with their application to plants 5–15, 10–20 or 35–60 cm tall. Rates of 10 and 20 g ha−1 of rimsulfuron provided control of S. halepense similar to or significantly lower than that achieved with 30 and 60 g ha−1 of nicosulfuron, respectively. Maize yield produced by all herbicide treatments applied at any time was significantly greater than that of the weed‐infested control.
Clonal growth and fragment regeneration of Rumex obtusifolius L.
Authors: PINO J. , HAGGAR R. J. , SANS F. X. , MASALLES R. M. , HAMILTON R. N. SACKVILLE
Published: July 2006

Clonal growth and fragment regeneration of Rumex obtusifolius L. were analysed in two dif ferent studies. Clonal growth system was des cribed by a morphological study of underground structure of different‐aged individuals, using maximal branching order in the stem system as an age estimator. Glasshouse experiments were conducted, testing the regenerative capacity of different below‐ground parts and the estab lishment of above root‐collar fragments planted at different depths under contrasting water regimes. Results showed the presence of a ‘phalanx’ type clonal growth system in grassland populations of Rumex. The main structure in volved in clonal growth proved to be the stem system; the region above the root collar was also the only part able to regrow after damage. Stem fragment regeneration occurred to depths of 15 cm, but was prevented in soils maintained at waterlogging and field capacity. The significance of these results in relation to nonchemical con trol of Rumex populations in grasslands is discussed.
Biology of Striga hermonthica (Scrophulariaceae) in Sahelian Mali: effects on pearl millet yield and prospects of control
Authors: WEBB M. , SMITH M C.
Published: July 2006

Aspects of the population: dynamics of Striga hermonthica (Del.) Benth. on pearl millet (Pennisetum americanum (L.) K. Schum.) were studied in Sahelian Mali. Seasonal development was recorded and density‐dependent mortality and fecundity in post‐emergent populations investigated. An attempt was also made to assess yield loss due to S. hermonthica attack using a regression approach. The first S. hermonthica plants emerged 42 days after crop germination, and the minimum time to complete the life cycle from emergence was 56 days. Results indicated a premature mortality of 66% in emerged populations. The growth stage reached by the time of host plant death appeared to be important in determining survival to maturity, premature mortality being greatest in plants that had not reached flowering by this time. The potential seed output per plant was estimated at 10 985. There was no evidence that the fecundity of S. hermonthica was affected by the density of emerged populations. Regression models showed a significant relationship between millet yield and emerged S. hermonthica density. The results suggest that lower densities give a relatively larger decrease in yield per S. hermonthica plant. The results of the study are discussed in relation to their implications for control.
Modelling the effect of duration of weed competition, weed density and weed competitiveness on seeded, irrigated onion
Authors: DUNAN C. M. , WESTRA P. , MOORE F. , CHAPMAN P.
Published: July 2006

Weed removal experiments were conducted in growers' fields in northern Colorado to assess the effect of duration of competition, weed density, weed competitiveness and crop density on irrigated seeded onion (Allium cepa L.). Duration of competition, expressed in thermal time units (TTUs) with a base of 7.2^C, explained 65% of the variation in the reduction of onion relative yield. The first significant reduction in onion relative yield was at 90 TTUs, averaged over weed load (weed density adjusted by competitiveness) and onion density. A polynomial multiple regression model, accounting for duration of competition and weed load, explained 75% of the variation in onion relative yield. A non‐linear multiple regression model, combining a gamma function response of relative yield to duration of competition plus a hyperbolic response of relative yield to weed load, was as good a predictor and a better description of the system. Onion relative yield was more sensitive to the duration of weed competition than to weed load. Bulb size class distribution and the resulting average onion price were affected by weed competition. Polynomial models were used to describe changes in bulb size class proportions as a function of duration of competition, weed load and onion density.
A technique for mapping the spatial distribution of Elymus repots, with estimates of the potential reduction in herbicide usage from patch spraying
Authors: REW L. J. , CUSSANS G. W. , MUGGLESTONE M. A. , MILLER P. C. H.
Published: July 2006

The spatial distribution of Elymus repens L. was mapped in five cereal fields during the 1994 season. Weed maps were created using a semi‐automated system mounted on a vehicle that travelled up the tramlines, centred on a 12‐m‐wide spray boom. Two operators detected weeds visually and recorded their presence and density by means of a simple push‐button system that recorded data from (2 × 1) m2 areas, or cells, across the boom section on a portable computer. The position of the vehicle along the tramline was monitored by integrating output from a wheel sensor. Eight tramlines of one field were mapped three times consecutively, to assess detection and navigational error. Pair‐wise comparisons of the three runs gave approximately 85% repeatability on presence/ absence data, 80% on zero/low‐ or high‐density data and 85% on low/high‐density data when weeds were definitely present. Simultaneous comparisons of all three runs gave 78%, 69% and 75% respectively. Repeated runs of tramlines up to 550 m long recorded mean differences of approximately 2 m with a maximum error of 14 m (2.5%). The spatial distribution of E. repens within the five fields was visibly patchy, but the size and morphology of patches varied both within and between fields. Thus, the potential reduction in herbicide usage as a result of patch spraying varied with patch morphology and infestation level. The effect of lowering the resolution from six (2 × 1) m2 cells to three (4 × 1) m2 cells across the 12‐m boom width showed little change in potential reduction in herbicide usage.
Growth and competitiveness of paraquat‐resistant and ‐susceptible biotypes of Hordeum leporinum
Authors: PURBA E. , PRESTON C. , POWLES S. B.
Published: July 2006

Growth, competitiveness and seed characteristics were compared in paraquat‐resistant and ‐susceptible biotypes of Hordeum leporinum Link collected from neighbouring fields. Dry weight and tiller production were greater in the susceptible biotype as compared with the resistant biotype in the absence of competition, however, the reproductive output was the same. Competitiveness in the field was estimated using a replacement series design that showed only slight differences between the two biotypes. There were no differences in seed weight, number of seeds per head, seed viability or seedling establishment between the two biotypes. When grown in pots in monoculture, the production of tillers was the same throughout the growing season, but inflorescences appeared on the resistant biotype earlier and matured earlier than did those of the susceptible biotype. We conclude that under field conditions the resistant biotype does not show a reduction in fitness as compared with the susceptible biotype.
Seasonal changes in germination responses of buried seeds of the weedy summer annual grass Setaria glauca
Authors: BASKIN G C. , BASKIN J. M. , EL‐MOURSEY S. A.
Published: July 2006

Seeds of Setaria glauca (L.) Beauv. buried in soil and exposed to natural temperature cycles exhibited seasonal changes in temperature, but generally not light; dark requirements for germination. Seeds were dormant at maturity in late September and October (autumn), and during burial from October to January they entered conditional dormancy, germinating up to ≥60% in light and darkness at daily thermoperiods of 25/15,30/15 and 35/20^C by January. During burial from February to May or June, seeds became non‐dormant and germinated up to 68–100% in light and darkness at 15/6,20/10,25/15,30/15 and 35/20^C in May or June. At maximum yearly temperatures in June or July–August, 65–89% of the seeds entered conditional dormancy (germinating at 30/15 and 35/20, but not at 15/6,20/10 and 25/15^C), and the others entered dormancy (not germinating at any thermoperiod). Thus, most buried seeds had an annual conditional dormancy/non‐dormancy cycle, but some had an annual dormancy/non‐dormancy cycle. Except for seeds buried in 1990 that lost the ability to germinate in darkness at all thermoperiods the first summer of burial, seeds incubated in light and in darkness exhibited the same patterns of seasonal changes in germination responses. Although conditionally dormant and non‐dormant seeds germinated to high percentages in darkness in Petri dishes, seedlings were found only in bags of seeds exhumed in April and May 1983, indicating that some factor(s) associated with the burial environment other than darkness prevented germination of buried seeds.
Synergistic joint action of MCPA ester and metsulfuron‐methyl
Authors: HOLLAWAY K. L. , HALLAM N. D. , FLYNN A.G.
Published: July 2006

MCPA is antagonistic to a range of herbicides but there is limited research on its compatibility with other broad‐leaved weed herbicides. In this study we assessed the joint action of MCPA ester and metsulfuron‐methyl on Brassica napus L. using the additive dose model (ADM). The fresh weight responses for selected ratios of the mixture were plotted on the ADM and compared to the predicted mixture response at three assessment levels ‐ 50, 75 and 90% control. The mixture demonstrated increasing synergism as the response level increased from 50 to 90%. This result for MCPA ester is in marked contrast to that of the MCPA amine formulation, which was shown in previous studies to be antagonistic towards sulfonylurea herbicides. Formulation is the major deciding factor in determining the compatability of phenoxy herbicides with other herbicides.
Prediction of the competitive effects of weeds on crop yields based on the relative leaf area of weeds
Authors: LOTZ L. A. P. , CHRISTENSEN S. , CLOUTIER D. , QUINTANILLA C. FERNANDEZ , LEGERE A. , LEMIEUX C. , LUTMAN P. J. W. , IGLESIAS A. PARDO , SALONEN J. , SATTIN M. , STIGLIANI L. , TEI F.
Published: July 2006

For implementation of simple yield loss models into threshold‐based weed management systems, a thorough validation is needed over a great diversity of sites. Yield losses by competition wsth Sinapis alba L. (white mustard) as a model weed, were studied in 12 experiments in sugar beet (Beta vulgaris L.) and in 11 experiments in spring wheat (Triticum aestivum L.). Most data sets were heller described by a model based on the relative leaf area of the weed than by a hyperbolic model based on weed density. This leaf area model accounted for (part of) the effect of different emerging times of the S. alba whereas the density model did not. A parameter that allows the maximum yield loss to be smaller than 100% was mostly not needed to describe the effects of weed competition. The parameter that denotes the competitiveness of the weed species with respect to the crop decreased the later the relative leaf area of the mustard was determined. This decrease could be estimated from the differences in relative growth rate of the leaf area of crop and S. alba. However, the accuracy of this estimation was poor. The parameter value of the leaf area model varied considerably between sites and years. The results strongly suggest that the predictive ability of the leaf area model needs to be improved before it can be applied in weed management systems. Such improvement would require additional information about effects of abiotic factors on plant development and morphology and the definition of a time window for predictions with an acceptable level of error.
Flowering phenology, seed set and bird pollination of five Western Australian Banksia species
Authors: WHELAN ROBERT J. , BURBIDGE ALLAN H.
Published: July 2006

Flowering phenology and seed set characteristics of five species of Banksia were studied in relation to the nectarivorous birds which feed at their inflorescences. Within the Banksia woodland at the study site near Perth, the flowering seasons of the Banksia species were sequential and only slightly overlapping, providing a year‐round nectar source. Although honeyeaters visited alt five species, seed set was very low in each case. Caging experiments indicated that, in B. attenuata at least, alternative pollinators may play a more important role in pollination than do nectar‐feeding birds. It is suggested that non‐avian pollinators, predatory insects, and characteristics of the breeding system may also have been important in the evolution of the observed flowering phenology and patterns of seed set.
Post‐fire succession in the northern jarrah forest of Western Australia
Authors: BELL DAVID T. , KOCH JOHN M.
Published: July 2006

Post‐fire species changes were documented over a portion of the northern section of the jarrah forest of Western Australia from a series of sites of known age since last fire. Species richness and species diversity were observed to increase following fire for several years, followed by a gradual decline. Dominance‐diversity curves indicated that maximum diversity occurred from 3 to 5 years following fire. The species composition of sites of different regions was more similar than sites of similar time since burn. The significance of the results to the programme of controlled burns is discussed.
Composition, spatial and temporal variability of the soil seed pool in a Eucalyptus populnea shrub woodland in central New South Wales
Authors: HODGKINSON KEN C. , HARRINGTON GRAHAM N. , MILES GRAEME E.
Published: July 2006

Three sites in a Eucalyptus populnea woodland in central New South Wales were sampled for the number and composition of seed in the surface cm of soil. There was a total of 3200 seeds/m2 beneath eucalypt canopy, 13800 seeds/m2 in grassy inter‐tree areas and 4000 seeds/m2 in bare inter‐tree areas in April, 1975. These numbers were reduced by 23, 73 and 66% respectively during the subsequent 10 months, when there was no addition of seed. This decline was thought to be mainly due to predation, with germination as a secondary factor. Species composition of the seed pool differed between the three sites with seed of some species being only found beneath the eucalypt canopy or in the inter‐tree areas. There were no seeds that were not present as plants in the community. Any attempts to restore this woodland to its former grassy nature should take into account the low seed population of many of the formerly common grass species and the high number of shrub seeds (>200/m2). Species distribution of seed was highly heterogeneous making adequate sampling very difficult. Extracting and identifying the seed took 8 to 12 man‐h per 100 g sample.
The formal definition of the environment of an animal
Authors: NIVEN B. S.
Published: July 2006

The article describes the first step in the formalization of the theory of animal ecology developed by H.G. Andrewartha, L.C. Birch, T.O. Browning, D.A. Maelzer and their students. The classification of the environment given by H.G. Andrewartha in Introduction to the Study of Animal Populations (1971) is formalized, with the exclusion of the component ‘weather’. In addition, the notion due to D. A. Maelzer that certain objects ‘only modified the value of some resource or other component of environment’ is also formalized and extended. The class of malentities is enlarged to include the case of an animal eating a poisonous animal. This enlarged class includes some animals formally classified as ‘aggressors’. Symbiosis is also discussed.
The light‐brown apple moth, Epiphyas postvittana (Walker): 4. Studies on population dynamics and injuriousness to apples in the Australian Capital Territory
Authors: GEIER P. W. , BRIESE D. T.
Published: July 2006

A population study of the light‐brown apple moth (LBAM), Epiphyas postvittana (Walker), was pursued from 1963–64 to 1966–67 in a naturally‐infested, unsprayed apple plantation near Canberra. The investigation covered the period of tree development leading up to and including, the production of the first substantial crop.

The life history of LBAM and the occurrence of natural enemies were examined. The species did not produce seasonal series of identifiable generations, but individuals in all development stages tended to co‐exist as cohorts of uncertain generation status.

Whereas numbers of LBAM decreased gradually from 1963–64 to 1965–66, they rose again markedly in 1966–67, following the release in the study area of about 3,000 laboratory‐reared moths. From periodic field surveys and complementary experiments, it was inferred that the population dynamics of LBAM in the study area consisted essentially in the production of excessive numbers of immature stages, which were reduced by natural enemies to much smaller cohorts of mature stages, determined by the ability of fruit trees to supply the LBAM's requisite food and shelter. It is argued that this ability, i.e. the carrying capacity for LBAM, decreased as the trees matured, and that the damage of LBAM in the crops of fully‐bearing trees would have been negligible under the conditions prevailing in the study area.

The probability of damage to fruits was directly proportional to the numbers of larvae and of fruits present, indicating that, unlike codling moth for instance, LBAM did not seek out fruits for attack, but struck them by chance encounter.

The results of this life‐system analysis are discussed in the light of Southwood & Comins’(1976) and Southwood's (1977a, b) generalizations on population dynamics, ecological strategies, and the status of pests. LBAM is believed to display all the characteristic features of an ‘intermediate strategist’ and an ‘intermediate pest’.
Productivity and nutrient content of Juncus kraussii in an estuarine marsh in south‐western Australia
Authors: CONGDON R. A. , McCOMB A. J.
Published: July 2006

Juncus kraussii, which is the dominant emergent macrophyte in the marshes of the Blackwood River Estuary, has an estimated net above‐ground production there of 0.3 to 1.3 kg dry weight m‐2 yr‐1. A high standing crop of live culms is present throughout the year and dead material generally exceeds live. New culms are produced throughout the year, but especially during the warm season. Growth and senescence of culms also occurs throughout the year although there is evidence for increased growth in the warm season.

Concentrations of nitrogen and phosphorus are given on a per g dry weight and per m2 basis. Some 60% of the nitrogen and 50% of the phosphorus remain in the dead culm material, the remainder being retranslocated. Sodium and, especially, potassium are readily retranslocated during senescence, but calcium and magnesium are much less mobile.
Species associations in a grassland on a heavy cracking clay soil in north‐west Queensland: their structure, soil associations and effects of flooding
Authors: HALL T. J.
Published: July 2006

Four plant associations were separated on the basis of relative abundance of species in an ungrazed area of open grassland on a heavy cracking clay soil in north‐west Queensland. They were correlated with soil pH, exchangeable potassium, available phosphorus, moisture content and particle size. Two associations were characterized by Iseilema spp., Astrebla spp. and Cyperus spp. and two by Eulalia fulva and Dichanthium fecundum.

Flooding caused a significant decline in the relative abundance of all major perennial grasses except Eulalia fulva, an increase in Cyperus spp., a reduction in legumes, establishment of previously unrecorded forbs, and a reduction in the basal cover of all associations. Heavy grazing by cattle prior to flooding increased the proporton of particular forbs, almost eliminated Astrebla squarrosa and resulted in a basal cover of 1.8% compared with 4.4% in an adjacent exclosure.
Partitioning of resources amongst seed‐harvesters in an ant community in semi‐arid Australia
Authors: BRIESE D. T.
Published: July 2006

Resource partitioning among five species of seed‐harvesting ants in a semi‐arid saltbush and adjacent grassland habitat of southwestern New South Wales is analysed. While habitat differences between species were only slight, the utilization of two resource dimensions, food type and time available for activity by them, varied markedly in response to environmental changes. The degree to which species overlapped in their use of these resources also fluctuated as conditions varied. Thus, both the manner and extent to which the harvester ant species interact is rapidly and continually changing in response to environmental fluctuations. The results suggest that, at most times, there is very little pressure due to exploitative competition within the harvester ant community.
Rainforest invasion onto Tasmanian old‐fields
Authors: READ JENNIFER , HILL ROBERTS
Published: July 2006

The regeneration of rainforest onto land cleared for grazing early this century was studied on several sites in northern Tasmania. Drimys lanceolata, a bird‐dispersed species, was the main invader. The climax forest species. Nothofagus cunninghamii and Atherosperma moschatum were invading slowly from the forest edge with occasional trees established in the field. Woody plants in the old‐field were clumped around logs. This was related to the role of logs in attracting seed and to possible roles as competition‐free sites and sites safe from browsing and climatic stresses. Changes in dominance by particular life forms appeared to be related to dispersal events, environmental modification by the developing vegetation and life history characteristics. The extremely slow invasion by climax species is due to the absence of bare mineral soil as well as to dispersal characteristics, browsing and possibly exposure to climatic stresses.
Microhabitat selection by two reptile ticks at their parapatric boundary
Authors: PETNEY T. N. , BULL C. M.
Published: July 2006

The parapatric boundary between the reptile ticks. Aponomma hydrosauri and Amblyomma limbatum, near Mt Mary, South Australia, coincides with a vegetational ecotone. Samples of litter from each side of the tick boundary showed considerable heterogeneity, but there were consistent differences in the composition and quantity of litter. North of the boundary, where Amb. limbatum is found, there is less litter and an absence of Eucalyptus leaves in the litter. Since the litter retards evaporative water loss, and Ap. hydrosauri is less tolerant of dehydration, reduced litter quantity may reduce the fitness of colonizing Ap. hydrosauri. In laboratory and field trials, larvae and nymphs of both tick species chose litter microhabitats in preference to bare soil, with the exception of fed Ap. hydrosauri larvae which, in trials with litter from north of the boundary, rarely moved from the bare soil. This behaviour may also reduce the fitness of colonizing Ap. hydrosauri.

The two species adopted different positions in the litter. Ap. hydrosauri were predominantly found on the surface, at the interface between soil and litter as fed larvae, and on or under the surface as nymphs. Amb. limbatum larvae were more often buried under the surface, while nymphs were found mostly in the litter above the soil surface. Hypotheses to explain the maintenance of the parapatric boundary are discussed in the light of these results.
Small‐mammal recolonization of open‐forest following sand mining
Authors: FOX BARRY J. , FOX MARILYN D.
Published: July 2006

Changes during regeneration after sand mining for heavy minerals were studied on an area that previously supported open‐forest on the Holocene high dune system in Myall Lakes National Park. Sixteen study areas, on which topsoil was replaced 0.5–10 yr ago, provided information on changes to be expected on any one site over that time period. A number of environmental variables was used in a linear multiple regression analysis to determine which of them is important in accounting for the variance and patterns observed in the biomass of two rodent species colonizing the regenerating areas.

The first small‐mammal colonist is the introduced house mouse (Mus musculus), an opportunistic species present on all sites. Its population density increases rapidly to a maximum at 3 yr after which it declines. Three environmental variables: percentage of bare sand, hardness of the soil in the first 30 cm, and a vegetation structure variable, account for 73% of the variance in M. musculus biomass.

The native New Holland mouse (Pseudomys novaehollandiae) first appears between 4 yr and 5 yr after topsoil replacement and peaks between 8 yr and 9 yr, after which it also declines. A highly significant multiple regression accounts for 69% of the variance in P. novaehollandiae biomass using five significant variables: the proportíon of heath plants present, two vegetation structure variables, the amount of dead plant cover, and the topsoil depth. The species replacement observed confirms the succession indicated by previous work and suggests competitive interaction between these species.

This study confirms the seral positions of rodent species in successions following both mining or fire. There is a stretched time axis for the mining succession following the more complete disruption of the substrate so regeneration more closely approximates primary rather than secondary succession. The non‐linearity of the parameters makes it impossible to predict a recovery time and verifies our previous prediction that recovery estimates from heathland should not be extrapolated to forest.
Detection of transoceanic migration of insects to a remote island in the Coral Sea, Willis Island
Authors: FARROW R. A.
Published: July 2006

Potential insect migrants were sampled by light‐trap at a remote island in the Coral Sea from 15 December 1977 to 30 November 1978 (351 nights). Breeding requirements, seasonal abundance and frequency, wind trajectory relationships, and known migratory tendencies of the 115 taxa collected, were analysed to detect those species migrating overseas from distant land sources. Thirteen influxes were detected from Queensland (minimum crossing 450 km) and one possible influx from Papua (600 km), involving 24 species (83 individuals) unable to reproduce on the island, and up to a further 27 species (73 individuals) among which there was a strong circumstantial evidence of immigration and little or no local reproduction. Sixty seven species (including three of the above putative immigrants) bred on the island and 45 of these were very abundant (99.7% of the total catch of 105480). Long‐range migration is known to occur in most of the latter 45 species, but could not be detected in this study because of the extent of local flight activity. Such activity probably led to a substantial emigration of insects from the island. To sustain the observed rates of colonization, large numbers of migrants, representing most insect orders, must be leaving potential source areas in northern Australia and New Guinea during periods of off‐shore winds.
Influence of sampling strategy on the relationships between fauna and vegetation structure, plant lifeform and floristics
Authors: TAYLOR J. A. , FRIEND G. R. , DUDZIŃSKI M. L.
Published: July 2006

The effect of sampling strategy on animal‐habitat relationships was evaluated with data collected from a 50 ha area containing a sequence of tropical vegetation types.

Sampling sites were located randomly within defined habitat types (i.e. stratified random sampling) and systematically irrespective of habitat type. At each site the fauna, comprising birds (63 species), reptiles (15 species), amphibia (13 species) and grasshoppers (32 species) were sampled for the abundance of species. Simultaneously, vegetation and related data, comprising vertical structure (52 attributes), ground surface condition (18 attributes), plant lifeform (18 attributes) and the abundance of plant species (200) were recorded.

Random and systematic data matrices, comprising sites defined by animal or vegetation attributes, were reduced dimensionally by correspondence analysis. Animal first dimension vectors were then regressed on the first dimension vectors of vegetation structure, lifeform and floristics, respectively.

With stratified random sampling, vegetation structure (comprising vertical and ground attributes) and lifeform explained most of the variation in the fauna; floristics were not a significant factor. On the other hand with the systematic data, fioristics explained almost all of the variation in animal abundance and distribution. By removing the ecotonal sites from the systematic data set and recalculating vectors, the animal—vegetation relationships became similar to those generated from the stratified random sampling data.

Clearly, the sampling strategy employed in a faunal survey has a major influence on the inventory of species, and on the relative importance of vegetation structure, lifeform and floristics in explaining animal distribution. The presence of ecotones in the systematic data set was highlighted as the key to the difference between the sampling strategies.
Flammable infructescences in Banksia: a fruit‐opening mechanism
Authors: LAMONT BYRON B. , COWLING RICHARD M.
Published: July 2006

There is a strong correlation between serotiny and persistent florets in the genus Banksia. Momentary application of flame is sufficient to ignite infructescences retaining a mantle of floral remnants and induce opening of most of the follicles. Prior removal of the florets or tests on species with deciduous florets resulted in no combustion and no follicle opening.
Vegetation and nesting preferences of black noddies at Masthead Island, Great Barrier Reef. II Patterns at the micro‐scale
Authors: HULSMAN K. , DALE P. , JAHNKE B. R.
Published: July 2006

Distribution and abundance of black noddy Anous minutus nests in relation to vegetation were studied at Masthead Island, Great Barrier Reef. Methods used included mapping, correlation and regression analyses.

Number of nests varied significantly with height and species of tree. Taller trees contained more nests per tree than did smatter trees. Most nests occurred in Pisonia but the highest nesting densities occurred in Ficus and Celtis. There were significant positive correlations between treephxsiognomy (d.b.h. etc.) and number of nests in Pisonia, Ficus and Celtis but noddies may avoid nesting in senile trees.

Noddies preferred to nest in some species of tree rather than others, e.g. Ficus and Celtis were apparently preferred to Pisonia. The sparse fotiage of Ficus and Celtis may facilitate access of noddies to their nests and therefore be preferred to the more densely foliaged Pisonia.
The ground parrot (Pezoporus wallicusKerr) in south‐eastern Australia: a fire‐adapted species?
Authors: MEREDITH CHARLES W. , GILMORE ALEXANDER M. , ISLES ANDREW C.
Published: July 2006

The ground parrot(Pezoporus wallicus)has a coastal distribution in Victoria and has declined in range since European colonization. Its habitat consists of two major vegetation communities: coastal heathland and sedgeland. These are further divided into various sub‐communities. These habitats contained high densities of cyperaceous and restionaceous plants, the seeds of which form the bulk of the bird's diet. Seeds and small fruits of some dicotyledonous plants and grasses are also eaten. Seed production by sedges remains fairly constant over time in sedgelands but varies in heathland, depending on time since burning. This variation is reflected by parallel changes in ground parrot population density. Both long unburnt and very frequently burnt heathlands are unsuitable for ground parrots. The birds also require dense vegetation cover.

Ground parrots appear to live in territorial breeding pairs with enforced natal dispersal. This is an adaptation to an environment where habitat is patchily distributed in space and variable in quality over time.
The interaction of density and resource levels in monospecific stands of plants: a review of hypotheses and evidence
Authors: MORRIS E. C. , MYERSCOUGH P. J.
Published: July 2006

The series of asymptotic yield‐density curves traversed by even‐aged monospecific stands of plants at the same resource level is described by the function f(wmax y max), where wmax= spaced plant weight and ymax= maximum yield possible at high densities. If the resource level at which the stands are grown is reduced, two sets of outcomes are possible. The stands at the decreased resource level may show essentially the same crowding effects as the control stands, but at a slower rate (altered‐speed hypothesis). This hypothesis implies a common family of yield‐density curves and a common thinning line for stands at different resource level may occur not only at a different rate at a harvest in the stands of higher growth. Alternatively, crowding effects at a reduced resource level may not only occur at a different rate to the controls but take a different course, leading to more intense crowding effects at a harvest being observed in the stands of lower growth (altered‐form hypothesis). Thus a different family of yield‐density curves and different thinning lines would apply at each resource level. For yield‐density curves, the altered‐speed hypothesis applied if f(wmax, ymax) is the same at each resource level. If this function differs with resource level, the altered‐form hypothesis applies at a harvest provided the ratio ymax/wmax is less at the low resource level. Cases intermediate between these two hypotheses may occur. For thinning lines differences in the position of the non‐thinning/self‐thinning boundary and in f(wmax, ymax) can affect the intercept and slope of thinning lines. The theoretical magnitude of these differences are discussed. Examples of both hypotheses are reviewed. For the altered form cases differences in non‐thinning crowding effects between resource levels are capable of causing significant differences in thinning lines.
Acari and Collembola in the litter and soil of three north Queensland rainforests
Authors: HOLT J. A.
Published: July 2006

The population changes, distribution and composition of litter and soil Acari and Collembola from three north Queensland rainforests are described based on samples collected on six occasions at approximately 3‐monthly intervals. Numbers of Acari and Collembola collected from litter were lower in the north Queensland rainforests than those reported from rainforests outside Australia: however, numbers of Acari and Collembola in the soil were similar to numbers in rainforest soils elsewhere.

Cryptostigmata were the most abundant group of Acari in the litter and 0–4 cm soil layer, comprising 41–55% and 42–55% of the total Acari in the litter and 0–4 cm soil layers respectively. Most of the Acari and Collembola are located in the 0–4 cm soil layer at each site (53–75%), with the litter layer containing the smallest proportion (3–20%). Most of the groups of Acari and Collembola examined show little evidence of seasonal vertical migration between the litter and soil to 8 cm. Minimum numbers of Acari and Collembola in the litter occurred in the dry season and maximum numbers occurred in the wet season. Seasonal fluctuations in numbers of Cryptostigmata appear to be influenced by the periodic saturation of the soil during the wet season.
Seasonality of insect abundance in an Australian upland tropical rainforest
Authors: FRITH CLIFFORD B. , FRITH DAWN W.
Published: July 2006

Monthly light and Malaise trap catches, taken over 31 months, were used to examine seasonal and annual changes in the abundance of predominant orders of upland tropical rainforest insects. Insect numbers and biomass increased during the late dry season, reached a peak during the wetter months, and declined during the early dry period. Fluctuations in insect abundance appeared to relate to (1) climatic factors such as length and severity of the dry season, or amount and period of rainfall; and (2) food availability such as an increase in the production of new leaves, or flowering and fruiting periodicity.
The relationships among eucalypt forest, grassland and rainforest in a highland area in north‐eastern Tasmania
Authors: ELLIS R. C.
Published: July 2006

Changes in the vegetation of a highland area of north‐eastern Tasmania are described and related to a change 150 years ago from Aboriginal to settled land use. Expansion of rainforest dominated byNothofagusinto areas previously dominated byEucalyptus, and ofEucalyptusforest on to grassland that occupied former rain ‐ forest areas is accounted for by local differences in frequency and severity of fires since about 1835.

Successional relationships amongst 12 vegetation types are defined, and discussed in relation to three models of vegetational succession.
Towards a definition of ecological disturbance
Authors: RYKIEL EDWARD J.
Published: July 2006

The terms disturbance, perturbation, and stress have been used in various ecological contexts, often synonymously, inconsistently and ambiguously. Consequently, the meaning of these terms lack any ecological rigor upon which to construct a coherent theory of ecosystem response to disturbance. Herein are some of the semantic and conceptual problems involved in defining disturbance, perturbation and stress, and proposals of working definitions as a basis for further discussion.