bluuebunny/crossref_metadata_2025 huggingface dataset:
Absorption, translocation, and fate of propyzamide in witloof chicory (Cichorium intybus L.) and common amaranth (Amaranthus retroflexus L.)
Authors: MERSIE W.
Published: July 2006

Witloof chicory (Cichorium intybus L.) is tolerant to propyzamide and common amaranth (Amaranthus retroflexus L.) is sensitive. The absorption, translocation, and metabolism of propyzamide was studied in seedlings of witloof chicory and common amaranth to determine if differences in these processes cause the differential sensitivity. At 24,48, and 72 h after root treatment, there was no difference in the concentration of 14C (g−1 plant dry wt) in com‐mon amaranth and witloof chicory. Approximately 50% of the absorbed 14C was translocated out of the roots to shoots of both species at 24 and 48 h after treatment. After 72 h about 55 and 74% of the absorbed 14C was translocated to shoots of witloof chicory and common amaranth, respectively. Distribution of 14C (g−1 plant dry wt) in plant parts of witloof chicory and common amaranth seedlings was similar. Roots of both species accumulated the highest concentration of total 14C, whereas shoots contained the lowest. Thin layer chromatography revealed that the herbicide was metabolized in neither species 48 h after treatment. No differences were found in absorption, translocation, or metabolism between witloof chicory and common amaranth with regard to propyzamide.
Sulfonylurea resistance in Stellaria media [L.] Vill.
Authors: KUDSK P. , MATHIASSEN S. K. , COTTERMAN J. C.
Published: July 2006

A sulfonylurea resistant biotype of common chickweed (Stellaria media L. Vill.) was found in a field treated with chlorsulfuron or metsulfuron for eight consecutive years. In pot experiments the biotype was resistant to postemergence treatments with the following acetolactate synthase (ALS) inhibitors: chlorsulfuron, metsulfuron, tribenuron, triasulfuron, rimsulfuron, sulfometuron, flumetsulam and imazapyr. The level of resistance to chlorsulfuron and sulfometuron was higher than to the other sulfonylurea herbicides. Whereas the level of cross resistance to the triazolopyrimidine herbicide, flumetsulam was comparable to that of metsulfuron, that of imazapyr was significantly lower. In contrast to imazapyr the biotype was not resistant to imazethapyr, an other imidazolinone herbicide. ALS in vitro assays revealed that resistance was due to an ALS enzyme that was less sensitive to ALS inhibiting herbicides. Herbicides with different modes of action were equally effective on the susceptible and resistant biotypes.
Photosynthetic parameters in glyphosate‐treated sugarbeet (Beta vulgaris L.)
Authors: MADSEN K. H. , HEITHOLT J. J. , DUKE S. O. , SMEDA R. J. , STREIBIG J. C.
Published: July 2006

Variable fluorescence and carbon dioxide exchange rate (CER) were measured in intact leaves of glyphosate‐treated sugarbeet plants, to investigate rapid effects on photosynthesis. In one experiment, a significant effect on variable fluorescence and CER was found within 8 h after herbicide application. The effect on stomatal conductance was not significant. In a second experiment, the effects of light or dark conditions during herbicide application and 24 h later were evaluated. Under light conditions glyphosate significantly reduced variable fluorescence after 4 h. However under initial conditions of 24 h darkness, followed by alternating 8 h light/8 h dark, the effect was not significant until 44 h after treatment, by which time the plants had received several hours of light. The eflect on variable fluorescence 8 h after herbidde application correlated positively with plant survival 7 days later.
Profils écologiques et liaisons interspécifiques. Deux approches complémentaires appliquées à l'étude des groupements de mauvaises herbes des cultures du Saïs (Maroc central)
Authors: LOUDYI M. C. , GODRON M. , ELKHYARI D.
Published: July 2006

Résumé: Summary

L'étude présentée est basée sur les données fournies par l'exploitation de 277 relevés réalisés dans les cultures du Saïs entre 1977 et 1987. Les relevés ont été soumis parallélement à deux méthodes d'analyse: la méthode des profils écologiques et l'analyse statistique des liaisons interspécifiques.

Vingt groupes coenologiques de mauvaises herbes ont été mis en évidence par l'analyse statistique des liaisons interspécifiques. Deux groupes, choisis parmi les 20, sont analysés dans cette étude.

Les groupes coenologiques sont interprétés en faisant appel à la lecture des profils écologiques des espéces. L'utilisation conjointe des deux méthodes montre qu'elles sont adaptées à l'étude du milieu cultivé et complémentaires quant à leurs apports, L'interprétation de ces groupes apporte des informations intéressantes concernant la sensibilité des mauvaises herbes aux descripteurs du milieu et la valeur indicatrice des espèces.

En dépit d'une certaine concordance des résultats obtenus par chacune des deux approches, l'étude montre que la méthode analytique des profils écologiques permet une analyse plus détaillée du comportement des mauvaises herbes. Elle offre, en effet, la possibilité de nuancer le comportement de certaines espèces à l'intérieur d'un groupe coenologique donné et de détecter des tendances que l'analyse des liaisons interspéciques ne permet pas, à elle seule, de percevoir.

Ecological profiles and interspecific associations: two complementary approaches to the study of weed associations in arable land in the region of Saïs (Central Morocco)

This study is based on botanical species data obtained from 277 samples taken from the cropped areas of Saïs, Morocco, between 1977 and 1987. Two types of analysis were done: definition of ‘ecological profiles’, and statistical analysis of interspecific associations. Twenty groups of weeds with highly correlated presence or absence ('coenological groups') were detected by statistical analysis of interspecific links. Two of these groups were selected for more detailed analysis in this study. The results demonstrated that both methods of analysis were well suited to the study of weed associations in cultivated areas, and they provided information about the indicator value of species for environmental variables. Although the methods gave similar results, that of ecological profiling allowed a more detailed analysis of weed behaviour as it permitted small variations in behaviour of species within similar coenological groups to be distinguished.
Non‐enzymatic conjugation of fenoxaprop‐ethyl with glutathione and cysteine in several grass species
Authors: TAL J. A. , HALL J. C. , STEPHENSON G. R.
Published: July 2006

Laboratory studies have shown that the amounts of glutathione (GSH) and cysteine are higher in grass species that are moderately tolerant, such as wheat (Triticum aestivum L., cv. Fredrick), and moderately susceptible, such as barley (Hor deum vitlgare L., cv. Legér) and triticale (cv. OAC Trillium), to fenoxaprop‐ethyl (FE) than in species that are very susceptible to the her bicide, such as oat (Avena saliva L., cv. OAC Woodstock), wild oat (Avena fatua L.), yellow foxtail (Setaria glanca (L.) Bcauv.), large crab grass (Digitaria sanguinalis (L.) Scop.) and bar nyard grass (Echinochloa crus‐galli (L.) P.B.). The safener, fenchlorazole‐ethyl (FCE) was found to increase and decrease, respectively, the amounts of GSH and cysteine in the moderately tolerant and moderately susceptible species but had no effect on the susceptible species. It is sug gested that in the moderately tolerant and moderately susceptible species, especially following FCE treatment, more GSH is available to detoxify the herbicide. Glutathione‐S‐tranferase activity (GST) for FE was found to be very low in all of the species tested. In vitro experiments at physio‐logical pH. demonstrated that FE may conjugate with GSH nonenzymatically. Therefore, it is suggested that nonenzymatic conjugation of fenoxaprop‐ethyl with glutathione may be an important mechanism for tolerance of some grasses to this herbicide.
Impact of drilling date on Apera spica‐venti L. and Alopecurus myosuroides Huds, in winter cereals
Authors: MELANDER B.
Published: July 2006

The impact of drilling date on Apera spica‐venti and Alopecurus myosuroides in winter cereals was investigated in field trials in 1991 and 1992. Two drilling dates were considered with an inter val of 14 to 16 days between dates. Generally, drilling date had an inconsistent effect on weed plant populations in spring, but seedling emerg ence of both species appeared to be delayed at the later drilling compared with the earlier date. This delay may partly explain the reduced com petitive ability of A. myosuroides in wheat in 1991 and 1992 and of A. spica‐venti in wheat in 1991 at the later drilling date. The seed popula tion per plant of both species was lower at the later date in some instances, whereas in others drilling date had no effect. Reduced seed produc tion was mainly caused by a reduction of the number of inflorescences per plant. The poten tial of utilizing drilling dates as a cultural control measure against grass weeds is discussed.
Simulation of the persistence of atrazine in soil at different sites in Portugal
Authors: ROCHA F. , WALKER A.
Published: July 2006

The effects of soil temperature and soil moisture content on the rates of degradation of atrazine, were measured in the laboratory in soils from different sites in Portugal. Persistence of atrazine was measured in the same soils in the field during the spring and summer of 1984, 1985, 1986 and 1987. Weather records from the different sites, measured during the periods of the field experi ments, were used in conjunction with appropriate constants derived from the laboratory data in a computer program to simulate persistence in the field. The model generally overestimated the ob served soil residues, particularly during the first 7–14 days after application. The fit from the model was good from day 14 to the end of the experiments.
A simulation of herbicide use based on weed spatial distribution
Authors: JOHNSON G. A. , MORTENSEN D. A. , MARTIN A. R.
Published: July 2006

Intensive field surveys were conducted to deter mine the spatial distribution of composite broad leaf and grass weed seedlings in seven maize and five soybean fields in eastern Nebraska in 1992. Farmer fields where herbicides were applied in a 38‐cm band over 76‐cm spaced rows were chosen for this study. Weed populations were measured in the interrow and in the band‐treated intrarow. Spatial maps constructed for grass or broadleaf weeds revealed that individual species as well as species assemblages are highly aggregated. On average, 30% of the sample area in the 12 fields surveyed was free of broadleaf weeds and 70% free of grass weeds in the interrow area (no her bicide). Where a pre‐emergence herbicide was applied (intrarow), 71% of the sample area was free of broadleaf weeds and 94% free of grass weeds. Increasing the threshold to some value other than zero resulted in a larger field area not requiring a herbicide application. The results of these distribution studies indicate that herbicide use could be substantially reduced if weed dis tribution maps or real‐time plant sensing were available to provide information for intermittent herbicide application systems or refinement of economic thresholds.
Effect of weed position on yield loss in soyabean and a comparison between relative weed cover and other regression models
Authors: BERTI A. , SATTIN M.
Published: July 2006

The importance of the position of weeds with respect to crop rows in the determination of crop yield‐weed density relationships and the usefulness of relative cover (RC) of the weeds as an explanatory variable were studied in soyabean [Glycine max (L.) Merrill] competing with two summer weeds with contrasting canopy structure (Xanthium strumarium L. ssp. italicum and Echinochloa crus‐galli L.). The position of the weeds was of little importance in the relationship between yield loss and weed density. This information is important because published experiments have used different types of weed distribution (e.g. evenly distributed or sown in rows). For both weed species it was possible to obtain a single relationship between yield loss and RC for measurements made from 30 days after crop emergence to soyabean canopy closure. The competitive effect of the weeds appeared to be strictly related to RC, indicating that for weeds growing taller than the crop the main competitive factor may be the shading caused by the leaves of the weeds situated above the crop canopy.
Changes in Pteridium aquilinum growth and phototoxicity following treatments with lime, sulphuric acid, wood ash, glyphosate and ammonium nitrate
Authors: DOLLING A.
Published: July 2006

The comparative effects of lime, sulphuric acid, wood ash, glyphosate and ammonium nitrate on Pteridium aquilinum (L.) Kuhn growth and development were evaluated in a Scots pine (Pinus sylvestris L.) clear‐cut stand in south‐east Sweden over a 4‐year period. P. aquilinum growth was effectively controlled following the application of glyphosate, but the other treatments generally had little effect on growth in terms of shoot density and length. Shoot length was positively related to the number of shoots on plots treated with ammonium nitrate but negatively correlated with the number of P. aquilinum shoots found on wood ash‐treated and control plots. In a bioassay aspen (Populus tremula L.) seedling emergence and pH were significantly lower in humus treated with sulphuric acid, glyphosate, ammonium nitrate and in untreated humus as compared with the humus treated with lime and wood ash. The negative effect of humus on emergence of aspen seedlings may be caused by phytotoxic compounds at a lower pH level. Forest regeneration might be performed with shade‐tolerant species such as Norway spruce (Picea abies (L.) Karst.) planted beneath a thin canopy of trees to prevent the rapid increase of P. aquilinum.
Growth characteristics of spring barley and selected weeds. II. Effect of temperature and irradiance in growth chambers
Authors: SEMB K.
Published: July 2006

As a part of a broader study, two experiments were carried out in growth chambers with three day/night temperature regimes (10/7, 20/14 and 30/21^C) studying growth characteristics of individual seedlings over a four‐week period. Experiment 1 was performed with spring barley (Hordeum vulgare L.), Galeopsis tetrahit L., and Viola Arvensis Murray. Experiment 2, with three irradiance levels at 20/14^C, and one irradiance level at the other temperatures, was performed with spring barley, V. arvensis, Chenopodium album L., Brassica rapa L. sspoleifera (DC.) Metzger, and Stellaria media (L.) Vill. Leaf area, dry weight, relative growth rate, net assimilation rate, and net photosynthetic rate generally showed an optimum at 20/14^C. Increasing irradiance resulted in a decreased specific leaf area. Expressed as fraction of shoot dry weight, green leaves decreased and stems, flowers, and yellow leaves increased with increased time, irradiance, and temperature. At all temperatures, barley, B. rapa and G. tetrahit had the largest dry weights, but at 20/14^C. C album and S. media and at 30/21^C C. album also had large values. Differences in dry weight between species correlated more to morphological features than to assimilation rate.
Modelling the effect of weed‐seed distribution in the soil profile on seedling emergence
Authors: GRUNDY A. C. , MEAD A. , BOND W.
Published: July 2006

Experiments to monitor weed seedling emergence from various soil depths were begun in 1989. Recently shed seeds were buried in either narrow bands at a range of depths in the soil or mixed evenly between the soil surface and each of these depths. Total emergence of Stellaria media (L.) Vill., Matricaria spp., Veronica persica Poiret, Veronica arvensis L. and Polygonum aviculare L., declined with increasing depth of burial. A similar pattern was observed for Chenopodium album L. with the exception of emergence from the surface layer. The reduction in emergence with increasing soil depth was greater for seeds in the narrow‐banded treatments than for those in broad layers. A model was developed using the data from the narrow‐banded treatments to predict emergence from distributions over broad layers. Predictions from the model closely agree with the data from the present broad‐layer treatments and those from a similar experiment made in the 1960s. By including the effects of depth of seed burial on seedling emergence, this model could be combined with models that determine the effects of cultivation on seed distribution, and therefore improve precision of predictions of seedling emergence from the seedbank.
Modelling the economics of herbicide treatment in wheat and barley using data on prevented grain yield losses
Authors: BOURDÔT G. W. , SAVILLE D. J. , HURRELL G. A. , DALY M. J.
Published: July 2006

Losses in grain yield prevented by controlling weeds were measured in 59 fields of (southern hemisphere) spring‐sown wheat (Triticum aestivum L.) (cv, Otane) and 45 fields of spring‐sown barley (Hordeum vulgare L.) (cv. Corniche) in five consecutive growing seasons from 1988/89 until 1992/93 in the Canterbury region of New Zealand. The losses were measured as the differences in yield between weeded and non‐weeded plots located in randomly positioned pairs in the fields. In the first 2 years, the weeding was by push hoe in‘organically grown crops. For the last 3 years, the fields were under prophylactic herbicide regimens with nonweeded plots created by excluding commercial herbicide applications (made mostly in October for wheat and November for barley) with polyethylene sheets placed temporarily over the plots. For each season the distributions of yield losses were modelled using the normal distribution and probabilities of ‘breaking even’ on herbicide use derived by substituting cumulative probability density functions into a simple break‐even model for herbicide use. The model assumed that herbicide application in the current crop has no flow‐on economic effect for succeeding crops. The mean annual yield losses prevented by herbicide application were positively correlated with September and October rainfall for wheat and bailey respectively. As a consequence, the probabilities of breaking even on herbicide use increased with increasing spring rainfall. Using historical rainfall records, probabilities of breaking even were estimated for each of the 48 years from 1947 to 1994. Averaging over these years, the analysis revealed that at current grain prices prophylactic use of the commonly applied herbicides is likely to be uneconomic in 24% (95% confidence limits 6% and 50%) of fields of average‐yielding Otane wheat and in 26% (95% confidence limits 1% and 91 %) of fields of average‐yielding Corniche barley in Canterbury. It was concluded that there is potential for withholding herbicide treatments without jeopardizing profitability in these crops, particularly in seasons with low spring rainfall.
Responses of Abutilon theophrasti to agricultural management systems
Authors: ZHANG J. , HAMILL A. S.
Published: July 2006

Seeds of Abutilon theophrasti Medic., collected from plants growing in a continuous maize or soyabean field subjected to herbicide application, cultivation or no weed management for 10 years, differed significantly in their weight and germinability. The differences in mean weight and germinability of the progeny seeds were maintained when the parent plants were grown in a greenhouse under controlled conditions. The offspring of plants with or without previous exposure to atrazine responded similarly to the herbicide in all the measurements of the growth and development of the plants, except blooms. Significant differences between the two groups of plants were mainly observed in the weight and germinability of their seeds. Although plants with or without previous exposure to atrazine usually did not differ significantly in their response to the herbicide in terms of individual traits, they differed both in the amount and pattern of overall response across all traits. The difference in overall response between plants increased with increasing rate of atrazine. It is possible that previous exposure to the herbicide had caused minor variation in a group of inter‐correlated traits or in the strength or pattern of correlation among traits.
Pathogenicity of fungi collected in northern Ghana to Striga hermonthica
Authors: KROSCHEL J. , HUNDT A. , ABBASHER A.A. , SAUERBORM J.
Published: July 2006

Thirteen fungal species were isolated from diseased plants of Striga hermonthica (Del.) Benth in northern Ghana. The pathogenicity of 12 isolates of the fungal species including Curvularia fallax Boed, Fusarium equiseti (Corda) Sacc., Fusarium equiseti var. bullatum (Sherb.) Wollenw., F. oxysporum Schlecht, F. solani (Mart) Sacc., Macrophonuina phasealina (Tassi) Goidan, and Sclerotium rolfsii (Sacc.) were evaluated against S. hermonthica under controlled environmental conditions. All isolates were pathogenic to S. hermonthica when propagated on wheat (Triticum aestivum L.) grains and incorporated pre‐planting into the soil. However, their virulence differed. Two isolates of F. oxysporum and one isolate of F. solani reduced the emergence of S. hermonthica by 88%, 98%, and 76%, respectively. Sorghum (Sorghum bicolor (L.) Moench) yield was increased by 26% when S. hermonthica was controlled. In contrast, in the control treatment with S. hermonthica no yield could be obtained. The F. oxysporum isolates were not pathogenic on sorghum. Germination tests indicated that the F. oxysporum isolates were highly pathogenic to S. hermonthica seeds. Although the F. solani isolate reduced the emergence of S. hermonthica in the pot experiments, it did not influence germination. This indicates that pathogens may attack different stages in the life cycle of S. hermonthica.
Atrazine soil metabolism in maize fields treated with organic fertilizers
Authors: ROUCHAUD J. , GUSTIN F. , CALLENS D. , BULCKE R.
Published: July 2006

The metabolism of atrazine in soil was studied in two maize fields located in regions with different soil types. Treatments were cow manure or pig slurry (50 tonnes each ha‐1) applied once either in March or in November before sowing, or green manure incorporated in March. Control plots were not treated with organic fertilizers. Atrazine at 0.75 or 1.0 kg a.i. ha‐1 was applied after sowing. In the 0‐12 cm soil layer, the main atrazine metabolites found were deethylatrazine and hydroxyatrazine. Low concentrations of deisopropylatrazine and 6‐chloro‐1, 3, 5‐triazine‐2, 4‐diamine were also observed. During the 4 months after sowing, the organic fertilizers decreased the rate of atrazine degradation, but subsequently there were no differences between treated and control plots. At harvest, the concentrations of atrazine and its metabolites were very low and similar in all plots. The organic fertilizers thus did not cause atrazine metabolites to accumulate in soil. In addition, atrazine and its metabolites were never detected below 12 cm in any of the plots.
The influence of crop rotation and soil tillage on seed population dynamics of A vena sterilis ssp. ludoviciana
Authors: NAVARRETE L. , QUINTANILLA C. FERNANDEZ
Published: July 2006

The dynamics of seed populations of Avena sterilis ssp. ludoviciana (Durieu) Nyman in plots maintained under different crop rotations and tillage systems was studied over a 5‐year period. The seed reserves buried in the soil were practically depleted during this period by using any of the three cropping systems evaluated. No significant differences were found between using a continuous barley rotation with annual application of herbicides and using a barley:fallow rotation with herbicides applied only as needed. The decline in seed populations was not affected by the tiliage system used during the fallow period (ploughing or no tillage). The tillage practices used in the various treatments, combined with the variable seed output from each treatment, resulted in different vertical distribution of the seeds in the soil profile. Shallow cultivation resulted in an accumulation of seeds in the upper soil layers; in contrast, a large proportion of the seeds were buried and maintained below 15 cm in the ploughed treatments. Although the seed distribution patterns produced by the various tillage systems had an effect on seedling recruitment, the largest changes in this parameter were associated with the different cropping sequences. Four times more seedlings were recruited in years under barley cropping than in those under fallow.
Relationships of the macrobenthos of Moreton Bay to prawns and to abiotic factors
Authors: STEPHENSON W.
Published: July 2006

Relationships are established between flux measures in macrobenthos and climatic variables, and between these measures and certain estimates of the catches of penaeid prawns. Cycles in flux do not appear to reflect inherent annual rhythms; positive flux (overall recruitment rates) show strong positive correlations with temperatures of seven months previously; negative flux (overall depletion rates) show strong positive correlations with prawn catches of the same month or a month before.
McArthur's fire‐danger meters expressed as equations
Authors: NOBLE I. R. , GILL A. M. , BARY G. A. V.
Published: July 2006

McArthur's fire‐danger meters for grasslands (Mark 3) and forests (Mark 5) have been widely used in Australia for fire‐danger forecasting and as a guide to fire behaviour. We present a set of equations to describe the data provided on these meters plus equations pertinent to the recently‐produced Mark 5 grassland meter. The equations provide a simple method of describing the forecasting system and are particularly useful for machine processing, and modeling.
The feeding ecology of the dingo II. Dietary and numerical relationships with fluctuating prey populations in south‐eastern Australia
Authors: NEWSOME A. E. , CATLING P. C. , CORBETT L. K.
Published: July 2006

The dietary and predator‐prey relationships of Canis familiaris dingo were studied for 9 yr at a coastal site and for 1.5 yr at a montane site in south‐eastern Australia. The percentage occurrences of items eaten were obtained from faeces, and the abundances of prey by counting water‐birds, trapping small mammals, and tracking large and medium‐sized mammals on specially prepared soil plots. Dingoes were also estimated by tracking.

The diet was broad but predominantly mammalian (23 species). Dietary frequencies were grouped around three weight modes, 0.1, 1.25 and 16 kg, corresponding with bush rat (Rattus fuscipes), ringtail possum (Pseudocheirus peregrinus) and swamp wallaby (Wallabia bicolor). The amplitudes of those frequencies approximately doubled from mode to mode, viz. 4, 13.5 and 28.3%, respectively. Medium‐sized mammals have been recognized as the staple prey because of their dependability. Their density estimates fluctuated least among prey‐groups, and track records of dingoes in the mountains were significantly related to them. Other categories of prey were supplementary (large mammals), opportune (small mammals) and scavenged.

Although there were general tendencies for dietary frequencies to follow prey abundances, significant functional and numerical responses were obtained only for water‐birds (coot and swan). Their super‐abundance in the mid‐years of the coastal study and their highly clumped distribution were the likely causes.

Predation was disproportionately severe on mammalian prey‐classes after an extensive wildfire at the coastal site. Such predation may have suppressed populations of wallabies and kangaroo for 2 yr until the water‐birds became super‐abundant. The prevalence of wombats in the mountains may have induced heavy predation upon other less numerous large prey. Concepts of profitability in feeding appear to apply to the dingo more than those of optimization of time or energy.

The decline in dingoes was correlated most with long‐term declines in water‐birds and medium‐sized mammals. At the time, abundance estimates of wallabies and kangaroos were increasing and those species increasingly predominated in the diet. The ability to hunt co‐operatively was apparently ineffectual in preventing decline in dingo numbers.

It is suggested that pack size is related inversely to the level of temporal instability in the environment. Frequent wildfires may prevent staple (mediumsized) and supplementary (large) prey from being abundant simultaneously, a combination thought necessary for large pack size.
Rabbits and the failure of regeneration in Australian arid zone Acacia
Authors: LANGE R. T. , GRAHAM CLARE R.
Published: July 2006

Three experiments are reported concerning the effect of rabbit grazing (Oryctolagus cuniculus L.) upon the recruitment of Acacia seedlings to populations in the South Australian arid zone.

In western myall woodland (Acacia papyrocaqsa Benth.) under prevailing rabbit and sheep densities, seedlings exposed to grazing by these two herbivores or to rabbits alone were severely pruned, whereas totally protected seedlings grew unchecked.

Seedlings of four Acacia species; A. papyrocarpa, A. oswaldii (F. Muell.), A. kempeana (F. Muell.) and A. burkittii (F. Muell. ex Benth.) were transplanted into four 50 m × 50 m rabbit‐proof enclosures. Six rabbits were introduced into each enclosure and within 24 h half of the total seedling population had been grazed. This was at a seedling dry weight ratio of 1|150 000 of the total fodder on offer. In one of the enclosures no seedlings were eaten and there is evidence to suggest that a dense patch of grass had a buffering effect, reducing grazing pressure.

Small shoots cut from old Acacia and transferred to the ground throughout 1000 ha of western myall woodland were grazed rapidly near rabbit warrens and progressively less rapidly with increased distance from warrens.

The experiments demonstrated that even with the lowered post‐myxomatosis population densities, rabbit grazing pressure would significantly affect recruitment in arid zone Acacia populations in the absence of stock.
Foliage projective covers of overstorey and understorey strata of mature vegetation in Australia
Authors: SPECHT R. L.
Published: July 2006

At maturity, both overstorey and understorey foliage projective covers (FPC) tend to reach steady‐state values which are correlated with the evaporative coefficient (k) in the water balance equation of the soil‐plant‐atmosphere continuum.

Overstorey FPCs of mature communities increase linearly from 20 to 85% along the moisture gradient from arid to humid regions. Understorey FPCs in mature communities are relatively constant along the same moisture gradient, increasing only slightly from 40 to 47%.

Plant communities which have overstorey FPCs different from the norm, appear to show a compensatory decrease or increase in understorey FPC so that the sum of the FPCs of overstorey and understorey is equal to that predicted for the region.
The epifauna of megaripples: species' adaptations and population responses to disturbance
Authors: SHEPHERD S. A.
Published: July 2006

Strong tidal currents flowing over mobile sediment give rise to migrating bedforms termed megaripples and sandwaves. For colonizing epifauna a megaripple field is a habitat subject to repeated disturbance as advancing megaripples bury all epifauna in their path. Eight epifaunal species occur in a megaripple field in tipper Spencer Gulf, South Australia. The stalked bryozoan Lanceopora obliqua is an r‐strategist and occurs patchily in high densities. An ascidian Polycarpa pedunculata, probably a K‐strategist, and a group of four species of articulated bryozoans, have much lower population densities which are predictable according to the frequency of disturbance. Other species occur in low, but variable densities. Some species show adaptations in morphology, behaviour or life history patterns which favour survival in this unusual environment.
Seasonal changes in characteristics of cattle dung as a resource for an insect in southwestern Australia
Authors: MATTHIESSEN J. N. , HAYLES L.
Published: July 2006

The value of cattle dung as a food resource for the bush fly Musca vetustissima (Walker) in the winter rainfall agricultural region of southwestern Australia was assessed by bioassay in the laboratory. The size (headwidth) of adult females was measured from flies reared on different samples of dung. Variation in size correlated with seasonal patterns of pasture growth, larger flies being produced during the growing season from autumn to spring. Size declined with senescence of annual pastures in late spring and early summer, occurring later in southern areas where the growing season was longer. After pasture senescence, dung from shorter growing season areas usually produced larger flies, apparently a result of the inverse relationship between digestibility of feed and length of growing season. Dung from irrigated perennial pastures never produced flies as large as that from annual pastures but generally high values were sustained during summer. Grazing of cereal stubble and feeding of hay in annual pasture areas during summer usually caused some increase in fly size. A spontaneous resurgence in the size of flies often occurred several weeks after pasture senescence and was attributed to more thorough digestion as a result of reduced intake of less palatable dry pasture.
Variation in leaf toughness and phenolic content among five species of Australian rain forest trees
Authors: LOWMAN M. D. , BOX J. D.
Published: July 2006

Several leaf characteristics, including toughness and total phenols and condensed tannins, were measured in Australian rain forest leaves of different ages and related to observed herbivory rates. In most cases, toughness and chemical toxicity increased as leaves aged, and corresponding insect grazing decreased. Herbivory losses ranged from 4.8% to 32.5% leaf area losses, and were more positively correlated with toughness than with phenolics. It is suggested that a suite of factors, including physical and chemical characteristics of leaves as well as spatial and temporal factors, interact to create variation in grazing intensities.
Effects of urban development and habitat alterations on the distribution and abundance of native and exotic freshwater fish in the Brisbane region, Queensland
Authors: ARTHINGTON A. H. , MILTON DA. , McKAY R. J.
Published: July 2006

The distribution of freshwater fish in creeks throughout the Brisbane region was determined by a survey carried out in 1977–78. Seventeen native and six exotic species were recorded in 55 creeks. Sixteen native and four exotic species were collected in a more restricted survey of central Brisbane in 1981. Urban development and the establishment of exotic plants have resulted in substantial changes to the aquatic environment in many of the creeks surveyed. Exotic grasses, especially para grass (Brachiaria mutica) have reduced the extent of free water by growing partly into stream channels. Floating exotic plants blanketed some stream reaches. Native aquatic macrophytes have declined, apparently due to dredging, siltation and other disturbances. These changes have affected the distribution and abundance of native and exotic fish. Native species with a preference for open water and beds of aquatic plants have declined in creeks overgrown by para grass and floating plants. Melanotaenia fluviatilis, Retropinna semoni, Pseudomugil signifer, Craterocephalus stercusmuscarum and Ambassis nigripinnis have been affected. Para grass and floating plants have not affected the range or abundance of Hypseleotris galii, H. compressus and Mogurnda adspersa. Gambusia affinis and Xiphophorus helleri have been advantaged by expansion of their preferred habitat type ‐ the edges of pools where exotic grasses have grown partly into the water. The effect of exotic fish on native species is unclear. There was a correlation between large numbers of G. affinis and small numbers of H. galii and M. fluviatilis. Correlations could result from predatory or competitive interactions between species. Alternatively, correlations could be due entirely to the effects of habitat alterations on exotic and native species. However, H. galii was evidently not disadvantaged by the habitat alterations studied. Thus there may be a complex interaction between this species and G. affinis. There was no evidence that X. helleri had affected the range or abundance of native species.
Species diversity and temporal distribution of ants in the semi‐arid mallee region of northwestern Victoria
Authors: ANDERSEN ALAN N.
Published: July 2006

The ant communities of two adjacent sites bearing markedly different vegetation (heath and mallee) were studied using quadrat counts and pitfall traps in semi‐arid northwestern Victoria. The ants were extremely abundant and rich in species (86 species from 27 genera were recorded from two 50 m × 25 m plots within 25 m of each other) and were dominated by species ofMonomorium and Iridomyrmex. Pronounced site differences in species composition were found, with 73% of the most abundant species showing a strong site preference. The ants exhibited marked seasonality: activity was highest in summer and lowest in winter and this was accompanied by a high turnover of species in time, resulting in pronounced seasonal differences in species composition. Most foraging was nocturnal during summer but was almost exclusively diurnal during winter, and individual species displayed distinctive patterns of diet foraging activity. Although the overall temporal distribution of the communities were apparently controlled by temperature, interspecific competition may also be an important factor influencing the seasonal and diel distributions of individual species, resulting in their high degree of temporal separation. The overall consequence is that although the study area contains many abundant species with similar ecological requirements, few of these are active in the same place at the same time.
Estimates of damage by herbivorous insects onEucalyptustrees
Authors: FOX L. R. , MORROW P. A.
Published: July 2006

High levels of insect damage on Eucalyptus have been noted but not quantified in previous literature. We present estimates of leaf damage for 44 Eucalyptus species from a variety of habitats. Overall, an average of 15% of expanded leaf area was missing. While some species were generally lightly grazed, others, especially those in more mesic. higher altitude communities, usually sustained much heavier leaf damage. In the age and size classes, communities and years that we sampled, the overall levels of damage to eucalypts were higher than chronic damage levels reported for north temperate communities. We also suggest a simple method for rapidly estimating the proportion of leaf area missing from trees.
Altitudinal distribution of several eucalypt species in relation to other environmental factors in southern New South Wales
Authors: AUSTIN M. P. , CUNNINGHAM R. B. , GOOD R. B.
Published: July 2006

Four problems associated with studying the altitudinal distribution of eucalypt species are examined: the lack of specific physiological relationship between altitude and plant growth, the influence of other environmental factors, the availability of suitable data and the need for statistical analysis. Presence/absence data for eucalypt species were obtained from several sources. Probability of occurrence in 100 m zones is determined for E. maculata, E. muellerana, E. fastigata, E. sieberi, E. dalrympleana and E. pauciflora. The influence of other factors is demonstrated for several species using direct gradient analysis. Aspect is important for E. fastigata and E. rossii in addition to altitude and rainfall.

The statisical model used was the logit‐linear model: log (p/I– p) = linear function of environmental variables where p is the expected probability of being present for a given combination of environmental variables. Two examples are presented. E. dalrympleana can be predicted from altitude, rainfall, radiation index (measure of aspect) and an interaction term between altitude and aspect. E. rossii presence is predicted by altitude, rainfall, radiation index and geology. Altitude is transformed into an estimate of mean annual temperature which is shown to clarify some overlaps of species distribution.

It is concluded that use of data collected for other purposes can be used in a generalized linear model for presence data to show the complex correlations which exist between the altitudinal distribution of some eucalypts and other environmental factors.
Scale problem in classification: an application of a stochastic method to evaluate the relative homogeneity of sample units
Authors: DALE P. E. R.
Published: July 2006

A basic problem in experimental design is to select a sample unit at a scale appropriate to the variables being observed and to the nature of the topic. Where hierarchical classification procedures are used it is important that the scale of the basic units is such that any variation found within the sample is small relative to that between the groups formed. In this paper a method is applied to evaluate the relative homogeneity of sample units. Replicates from each sample are classified hierarchically. The method of Sandland & Young (1979a, b) is used to determine the probability at division of the number of replicates assigned at a division to the same group occurring by chance. A high probability indicates relative heterogeneity of the samples from which replicates are drawn; a low probability suggests relative homogeneity. An example from the area of urban ecology illustrates an application of the method. It is used to evaluate the relative homogeneity of spatial units (Census Collectors Districts) with respect to dwelling characteristics in inner city Brisbane. Possible applications in other areas of ecology are briefly considered.
Banksia ericifolia transgresses the self‐thinning boundary
Authors: MORRIS E. C , MYERSCOUGH P. J.
Published: July 2006

Self‐thinning B. ericifolia stands were observed to have high mean plant weights for their density, exceeding the upper boundary of the (log mean plant weight = 4.4–1.5 log mean plant density) line of White (1980) by approximately 0.5 units on the y scale (log mean weight per plant (g)). While proportion of shoot as stem and leaf area indices were similar in thinning stands of B. ericifolia and other species, specific leaf area was six to eight times less in the Banksia populations.
Short note Report of diurnal acid metabolism in two aquatic Australian species of Isoetes
Authors: KEELEY JON E.
Published: July 2006

Previous studies have demonstrated the presence of crassulacean acid metabolism in the North American submerged aquatic Isoetes howellii (Isoetaceae). Diurnal changes in titratable acidity and malic acid levels indicate the presence of this pathway in two Australian species of Isoetes.
Changes in Melaleuca forest density on the Magela floodplain, Northern Territory, between 1950 and 1975
Authors: WILLIAMS ALEXANDER R.
Published: July 2006

The stability of the Magela floodplain prior to the development of uranium mining at Ranger, in the Magela catchment, was estimated by comparing aerial photographs taken in 1950 and 1975, using the density of Melaleuca swamp forest as an index of change. The 1975 photographs were interpreted in the light of a ground survey carried out in the dry season of 1976. There was no increase in the area occupied by Melaleuca trees, indicating that infilling of perennial swamp and plant succession were not significant agents of change in this period. Thirty‐eight per cent of the forested area suffered a significant decrease in tree density: fire, wind and buffalo are among the probable causes, and these hazards should be taken into account in monitoring the effects of the uranium mining.
Altitudinal variation in Leptospermum flavescens Sm. (Myrtaceae)
Authors: MORRISON DAVID A.
Published: July 2006

Correlation of altitude with morphological data from herbarium specimens of two taxa within the Leptospermum flavescens group indicates that, in the Sydney region, there is a convergence of leaf and flower size at higher altitudes. There are also altitudinal differences in germination ability, growth rate and leaf chemistry. Experimental evidence suggests that at least some of this altitudinal variation is genetically fixed within the populations.
Experimental confirmation of interspecific competition between native and introduced mice
Authors: FOX BARRY J. , POPLE ANTHONY R.
Published: July 2006

This paper tests the hypothesis that Pseudomys novaehollandiae shows competitive superiority over Mus musculus. Experimental removals of P. novaehollandiae on four I ha treatment plots and additions on a further four I ha plots show significant effects of interspecific competition when compared to two I ha unmanipulated control plots. Significant effects of P. novachollandiae populations on the abundance of M. musculus populations were observed for number of captures/day, abundance/trapping session and for the recruitment of new individuals over the post‐removal period, thus allowing rejection of the null hypothesis in each case. There was an apparent ceiling on the total rodent abundance which is indicative of a resource limitation. The resource in short supply appears to be space, but it is not clear if the competition is for food or shelter resources contained within such space or for the space per se, but the latter seems less likely.

The confirmation of this interspecific competition supports the inferences drawn from a considerable amount of indirect evidence, largely descriptive, obtained from previous studies in the Myall Lakes National Park. This study also shows that competition is one of the mechanisms controlling the replacement of species in the succession following disturbance and lends support to the habitat accommodation model proposed for such succession. These points support previous statements on the importance of interspecific competition as a determinant of the structure of these small‐mammal communities.
Nectar utilization and pollination by Australian honeyeaters and insects visitingCalothamnus quadrifidus(Myrtaceae)
Authors: COLLINS BRIAN G. , NEWLAND CHARLES , BRIFFA PETER
Published: July 2006

Nectar availability inCalothamnus quadrifidusflowers was studied at Wongamine Nature Reserve in late spring (November). Despite some overnight depletion by moths and other invertebrates, more nectar was present in flowers at dawn than at the preceding dusk. Significant nectar depletion occurred within a few hours after dawn, mainly due to foraging by two honeyeater species.Lichmera indistinctaandPhylidonyris nigra. Thereafter, nectar availability was maintained at relatively low levels, principally because of foraging by honeyeaters and honey bees.Apis mellifera, that became active during the warmer part of the day. Although individual honeyeaters consumed more nectar than A.mellifera, honey bees were so abundant that their total impact was greater than that of either honeyeater species for much of the day. Transfer ofC. quadrifiduspollen between flowers is necessary in order to achieve a high level of seed set, as the flowers appear to be protandrous. Honeyeaters appeared to be considerably more significant pollen vectors thanA. mellifera.
Effects of fire on central Australian rangelands. I Fire and fuel characteristics and changes in herbage and nutrients
Authors: GRIFFIN G. F , FRIEDEL M. H.
Published: July 2006

Results of fire experiments in two important rangeland types in central Australia showed that a winter fire was effective in reducing fuel and was easily controlled. Composition of pasture plants palatable to cattle was either maintained or improved. A summer fire significantly decreased the grass component white increasing the proportion of forbs, particularly unpalatable species. Rainfall, season of burning and reduction of cover appeared to be important factors in controlling the composition of post‐fire herbage. There was no important effect of fire on nutrients in either season of burning.