bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil moisture relations and critical period of Cynodon dactylon (L.) Pers. (coastal bermudagrass) competition in conservation‐tillage cotton (Gossypium hirsutum L.)
Authors: VENCILL W. K. , GIRAUDO L. J. , LANGDALE G. W.
Published: July 2006

Summary: Résumé: Zusammenfassung

Field experiments were established at the Southern Piedmont Research facility near Watkinsville, GA during 1989 and 1990 to assess the critical period of interspecific interference between different Cynodon dactylon (coastal bermudagrass) densities and cotton (Gossypium hirsutum) in a conservation‐tillage system. Cotton was exposed to coastal bermudagrass for 0, 4, 7, 10 and 25 weeks. Cotton height, yield, and soil volumetric water content were examined. Volumetric water content was determined by time domain reflectometry. Cotton height and yields were significantly reduced by exposure to coastal bermudagrass and reduction in cotton productivity increased with increasing coastal bermudagrass density. Soil volumetric water content decreased in the upper 30 cm of soil with increasing coastal bermudagrass density. The critical period of coastal bermudagrass in cotton was determined to be 4 to 7 weeks after planting.

Relations entre l'humidite su sol et la periode critique de competition de Cynodon dactylon (L.) dans du coton en systeme de labour (Gossypium hirsutum L.)

Des essais de plein champ ont été mis en place sur le centre de recherche du Sud‐Piémont près Watkinsville, GA pendant 1989 et 1990 pour évaluer la période critique d'interférence interspécifique entre différentes densités de Cynodon dactylon et de coton (Gossypium hirsutum) dans un système de labour. Le coton a été exposé au cynodon pendant 0, 4, 7, 19 et 25 semaines. La hauteur du coton, le rendement et la teneur en haut du sol ont été examinés. Le volume d'eau du sol a été déterminée par reflectométrie. La hauteur du coton, et les rendements ont été réduits significativement par l'exposition au cynodon et la réduction de productivité du coton a augmenté avec l'augmentation de la densité du cynodon. Le volume d'eau du sol dans les 30 premiers centimètres a diminué avec l'augmentation de la densité du cynodon. La période critique du cynodon pour le coton a été déterminée comme se situant 4 à 7 semaines après la plantation.

Konkurrenz von Cynodon dactylon (L.) Pers. mit Baumwolle (Gossypium hirsutum L.) bei konservierender Bodenbearbeitung — Kritische Periode und Bezug zur Bodenfeuchte

Zur Ermittlung der kritischen Periode der Konkurrenz von Cynodon dactylon (L.) Pers. mit Baumwolle (Gossypium hirsutum L.) bei konservierender Bodenbearbeitung wurde die Kultur in Feldversuchen 1989 und 1990 auf der Piedmont‐Versuchsstation für 0, 4, 7, 10 und 25 Wochen mit dem Unkraut in unterschiedlicher Dichte wachsen gelassen. Höhe und Ertrag der Baumwoll‐Pflanzen wurden durch die Verunkrautung signifikant reduziert, und mit steigender Unkrautdichte nahm die Produktivität genauso wie die Bodenfeuchte in den obersten 30 cm ab. Die kritische Periode der Konkurrenz zwischen dem Unkraut und der Kulturpflanze lag zwischen der 4. und der 7. Woche.
Rapid seed extraction from soils by a flotation method
Authors: TSUYUZAKI S.
Published: July 2006

Summary: Résumé: Zusammenfassung

In this study a flotation method is described which enables the rapid extraction of seeds from soil. Essentially, soil is mixed with 11.0 M K2CO3 and thoroughly dispersed by mechanical stirring for 3–6 min. The dispersed soil samples were delivered to plastic tubes, then centrifuged at more than 4000 g for about 5 min. Buried seeds and lighter organic materials floated in the supernatant and could be removed by filtration, washed and subsequently identified. This method performed reliably using soil samples artificially loaded with white clover and a range of cultivated grass species. In addition, a wide range of weed seeds which differed in size and density were also effectively recovered from a range of soil types from loam to gravel.

Extraction rapide de graines à partir du sol par une méthode de flotation

Cet article décrit une méthode de flotation qui permet l'extraction rapide de graines à partir du sol. Pour l'essentiel, le sol est mélangé avec du K2CO3 11,0 M et complètement dispersé par agitation mécanique pendant 3 à 6 min. Les échantillons de sol dispersé sont placés dans des tubes en matière plastique et contrifugés à plus d 4000Xg pendant environ 5 min. Les graines enfouies et le matériel organique plus léger flottent dans le surnageant, sont récupérées par filtration, lavées et identifiées. Cette méthode s'est révélée fiable avec des échantillons de sol portant artificiellement de fortes densités de trèfle blanc et une série de graminées cultivées. De plus, de nombreuses graines de mauvaises herbes qui différaient par leur taille et leur densité ont été efficacement récupérées de plusieurs types de sol (limons à graviers).

Schnellmethode zur Bestimmung des Samengehalts im Boden durch Abschwemmen

Es wird eine Methode beschrieben, mit der Samen aus Boden schnell ausgelesen werden konnen. Bazu wird dem Boden 11,0 M K2CO3 zugesetzt und der Boden 3 bis 6 Min. lang grundlich gemischt. Danach wird das Bodenmaterial in Plastikzylindern bei mehr als 4.000 g 5 Min. lang zentrifugiert. Die im Boden enthaltenen Samen und organisches Material sammeln sich im Uberstand und konnen durch Filtration abgetrennt und nach dem Waschen identifiziert werden. In einem Modellversuch, bei dem Samen von Weiß‐Klee und einer Reihe Graser dem Boden beigemischt worden waren, erwieß sich diese Methode als zuverlassig. Auch andere Samen unterschiedlicher Große und Dichte wurden in verschiedenen Bodenarten von Lehm bis grobem Sand vollstandig wieder aufgefunden.
Using phenology prediction in weed management: a review
Authors: GHERSA C. M. , HOLT J. S.
Published: July 2006

The success of weed management based on ecological principles and weed biology will depend on a better understanding of the effect of environment on lift history strategies, growth, and competition of weeds; and crops, and particularly upon the ability to predict weed and crop phenology, This paper reviews the importance of phenotypic plasticity to weed and crop competition and other biological interactions. We also discuss the utility of phenological predictions in weed management and review current weed phenology models that are based on thermal time. By understanding the variables that drive plant phenotypic responses, new approaches and more long‐term solutions for weed problems can be developed.
Seed dynamics in populations of A vena sterilis ssp. ludoviciana
Authors: DEL ARCO M. J. SANCHEZ , TORNER C. , QUINTANILLA C. FERNANDEZ
Published: July 2006

Seed populations of Avena sterilis ssp. ludoviciana (Durieu) Nyman were monitored in a naturally occurring infestation throughout its life cycle. Considering the large weed population present (298panicles m−2), total seed production was relatively low: 3838 seeds m−2. Only 68% of these seeds were recovered from the soil surface and a further 3% were removed with wheat grain and straw during harvest operations. The numbers of seeds from the stubble between mid‐July and mid‐September were relatively low (10%). Ploughing the stubble in October buried most of the recently produced seed rain and resulted in a relatively uniform vertical distribution of the seedbank. Maximum seed persistence in the soil ranged from 27 to 43 months (depending on the experimental technique used to do the study). Seed decline followed an exponential pattern on a yearly basis, with the greatest decline taking place between October and April (57–90% in year 1 and 10–40% in year 2), Between May and September the buried seed populations remained practically constant. Seedbank depletion was primarily due to seedling production (25%) and ‘lethal’ germination (24%). Although the depth of burial had very little effect on seed survival, the mode of seed disappearance was closely related to their depth in the soil. Seed depletion through ‘lethal’ germination increased with increasing depth in the soil, whereas depletion through seedling emergence decreased with increasing depth.
The effect of pre‐germination chilling on subsequent growth and flowering in three arable weeds
Authors: FENNER M.
Published: July 2006

This experiment investigated the effect of pre‐germination moist chilling of seeds (for 3 weeks at 2^C) of 10 common arable weeds on the subsequent growth and flowering of the plants. In only three of the species (Alopecurus myosuroides Huds., Veronica persica Poir. and Trifolium dubium Sibth.) was flowering markedly increased by the seed chilling treatments. At 3 months, the mean number of flowers and seed heads per plant on the treated plants was greater than that on the controls by factors of 13.9, 2.02 and 1.74 respectively. Shoot lengths of the seed‐chilled plants were also significantly greater in all three species, though dry weights did not differ significantly from those of the controls. Thus, the plants showed morphological changes associated with reproduction but no significant alteration in total dry weight. The ecological implications of the data are discussed in relation to possible effects of climatic change on species which require seed vernalization.
The allelopathic effect of three Amaranthus spp. (pigweeds) on wheat (Triticum durum)
Authors: QASEM J. R.
Published: July 2006

The allelopathic effect of Amaranthus retroflexus L., Amaranthus blitoides S. Wats, and Amaranthus gracilis Desf. on wheat Triticum durum L. was investigated under laboratory, glasshouse and field conditions. Laboratory experiments showed that fresh shoot or root extract of the three weed species reduced germination, coleoptile length, root length and root dry weight of wheat seedlings. The inhibitory effects were rate dependent, with low concentrations of shoot extract promoting shoot growth of wheat. Fresh plant extracts were more phytotoxic than dried plant extracts and shoot extracts had higher detrimental effects than root extracts. In pot experiments, dried shoot extract of A. gracilis increased shoot and root dry weights of wheat seedlings. For A retroflexus and A. blitoides the extracts of these and dried shoots (8 g kg−1), which had been added to soil mixtures significantly reduced ger‐mination and growth of wheat seedlings. Addition of up to 16 g kg−1 of A. gracilis residues promoted shoot growth of wheat and had no significant harmful effect on root growth. Roots appeared more sensitive to allelopathic effect than shoots. Under field conditions, incorporation of A. retroflexus or A. blitoides residues in the soil reduced height, grain and straw yield of wheat, whereas A. gracilis residues stimulated plant height and increased yield.
Interaction between timings and doses of quindorac in rice
Authors: STREET J. E. , TERESIAK HOLGER , BOYKIN D. L. , ALLEN R. L.
Published: July 2006

Quinclorac (3,7‐dichloro‐8‐quinolinecarboxylic acid) is a new herbicide in United States rice production. Field studies were conducted in 1990 and 1991 in Mississippi to determine the influence of application timings and rates on weed control efficacy and rice yield. Control of Echinochloa crus‐galli (L.) Beauv. (barnyard‐grass), Sesbania exaltata (Raf.) Rydb. ex A. W. Hill (hemp sesbania) and Ipomoea wrightii Gray (palmleaf morning glory) were greatest with early post‐emergence application. Efficacy of pre‐emergence application depends strongly on soil moisture, with significantly reduced weed control resulting when applied to dry soil. Weed control with pre‐emergence application to moist soil was comparable with early post‐emergence application at higher rates of quinclorac. Pre‐plant and incorporated quinclorac controlled weeds effectively. Control of E. crus‐galli, S. exaltata and I. wrightii ranged from 73 to 99%, 75 to 99%, and 92 to 99% at 28 days after treatment, respectively. Rice yield generally reflected weed control. No rice injury was observed for any treatment. Results indicate that early post‐emergence application of quinclorac is the best time for using reduced rates and field conditions at application should be considered with these rates pre‐emergence.
Degradation of primisulfuron‐methyl and metsulfuron‐methyl in soil
Authors: JAMES T.K. , KLAFFENBACH P. , HOLLAND P.T. , RAHMAN A.
Published: July 2006

A newly developed chemical assay was used to determine the degradation in soil of two sulfonylurea herbicides, primisulfuron‐methyl and metsulfuron‐methyl, under both controlled and field conditions. The results from the chemical assay were compared with those from traditional bio‐assays for determination of persistence in the field. Phytotoxic effects of these herbicides were not observed after 6 weeks following application to an acidic (pH 5.7) soil with high organic matter content (7.3% o.c). Half‐lives of 13 to 29 days were measured for primisulfuron‐methyl at different soil‐water contents and temperatures while those for metsulfuron‐methyl ranged from 8 to 36 days. The rate of degradation of metsulfuron‐methyl was more sensitive to temperature than that of primisulfuron‐methyl. Persistence in the field was shorter than expected considering the results from the controlled environment studies. However, determination of the persistence by both chemical assay and bioassay methods produced very similar results.
Physiological mechanisms for the rapid growth of Pennisetum clandestinum in Mediterranean climates
Authors: WILEN C. A. , HOLT* J. S.
Published: July 2006

Pennisetum clandestinum Hochst ex Chiov. (kikuyugrass) is a C4 grass that has become an invasive weed in temperate climates. We examined ecophysiological mechanisms that have allowed it to become a successful weed in these locations by comparing P. clandestinum and two other common turigrass species, Festuca arundinacea Schreb. (tall fescue cv. Mojave), a C3 cool‐season grass, and Stenotaphrum secundatum (Walt.) Kuntze (St. Augustinegrass), a C4 warm‐season grass, grown in a warm or cool growth regime. We measured rates of photosynthesis over a range of leaf temperatures and also measured growth rate parameters of these species. At leaf temperatures between 25^C and 40^C P. clandestinum maintained the highest rates of photosynthesis in both temperature regimes. Under warm temperatures, this species rapidly increased biomass and leaf area to a greater extent than either of the other two grasses. Theoretical whole plant photosynthesis (mean leaf area × mean photosynthetic rate) was higher for P. clandestinum than for the other two species in both growth regimes and over most leaf temperatures. Our results suggest that P. clandestinum is a successful weed in Mediterranean climates as a result of its capacity to photosynthesize over the full range of temperatures found in those climates, its rapid growth during warm weather and its apparent tolerance to moderately cool temperatures.
Surfactant and salt affect glyphosate retention and absorption
Authors: NALEWAJA J. D. , DEVILLIERS B. , MATYSIAK R.
Published: July 2006

The influence of nonylphenoxy surfactants and glyphosate salt formulation on spray retention, phytotoxicity and [14C]glyphosate uptake was investigated in wheat (Triticum aestivum L). and Kochia scoparia L. The amount of spray retained, and uptake of [14C]glyphosate increased with increasing hydrophilic‐lipophilic balance (HLB) value of surfactants. The volume of spray delivered to the plant treatment area and retained by wheat and K. scoparia plants increased with increasing surfactant HLB values, but this only partly accounted for the higher spray retention. Spray retention by leaves of plants was not affected by calcium chloride, either alone or with ammonium sulphate in the glyphosate spray solution. [14C]Glyphosate absorption by wheat and K. scoparia was reduced by calcium chloride alone, but not in mixtures with ammonium sulphate, regardless of surfactant. Phytotoxicity and uptake of glyphosate salt formulations for wheat was: isopropylamine > ammonium > sodium > calcium; these results indicate that the surfactant selected is important to maintain glyphosate efficacy and that sodium and calcium cations antagonize glyphosate by forming salts that are absorbed less than commercial isopropylamine formulations.
Resistance to paraquat in Hordeum glaucum is temperature dependent and not associated with enhanced apoplasmic binding
Authors: LASAT M. M. , DITOMASO J. M. , HART J. J. , KOCHIAN L. V.
Published: July 2006

Response to paraquat was investigated in two Hordeum glaucum Steud. (wall barley) biotypes grown at warm (30^C) and cool (15^C) temperatures. Paraquat‐resistant (R) plants were nearly seven‐fold more tolerant when grown at 15^C than when grown at 3CPC. In contrast, there was a tendency for susceptible (S) plants to be more tolerant when grown at the higher temperature. The difference in response between the two biotypes grown at 30^ and 15^C increased from 3‐ to >40‐fold. Forty‐eight hours after foliar application, 62% less radiolabelled paraquat had translocated basipetally in the R compared with the S biotype. In addition, 26% more herbicide was retained within the treated zone of R compared with S plants. Thus, paraquat movement was restricted in the R biotype. It has been postulated that reduced mobility of the herbicide in the R plants is due to enhanced apoplasmic binding. In this study, paraquat binding to the cell walls and its release into the external solution was investigated in roots of R and S biotypes of H. glaucum grown under warm or cool conditions. No significant differences between the two biotypes were measured at either growth temperature. We propose that the mechanism of resistance to paraquat may involve a temperature‐dependent alteration in symplasmic transport of the herbicide.
Weeds in the traditional slash/mulch practice of frijol tapado: indigenous characterization and ecological implications
Authors: KETTLER J. S.
Published: July 2006

Weeds in the secondary vegetation of the fallow in slash/mulch or shifting cultivation systems have been identified as important components of the system. Weeds found in the traditional slash/mulch or frijol tapado bean (Phaseolus vulgaris L.) production system in southern Costa Rica were identified and given preliminary rankings based on fanner surveys. The variance of these rankings was used as a measure of farmer uncertainty. Weed rankings were further characterized by key informant interviews. This study also investigated the ecological implications of the vegetative dynamics in the system. Biomass estimates of individual weed species, nutrient dynamics and crop yield response are considered in conjunction with the farmers' rankings of weeds. A negative correlation was found between weed rankings and bean yield, and between weed rankings and C:N ratios.
An emerging system management approach for biological weed control in crops: Senecio vulgaris as a research model
Authors: And H. MÜLLER‐SCHÄRER , FRANTZEN J.
Published: July 2006

A ‘system management’ approach of biological weed control in crops is proposed and compared with other method's of biological weed control. It is based on the management of a weed pathosystem in order to maximize the natural spread and disease severity of a native or naturalized pathogen. This approach may be well‐suited to situations where it is necessary to control single weed species in crops, and where no immediate and complete control is required, the production of large amounts of the agent is rather limiting (e.g. when using biotrophic fungi), and/or the importation of an exotic agent is not possible. This strategy provides fundamental knowledge of underlying mechanisms of crop production systems and is aligned with the view of modern agro‐ecology, in which complete eradication of weeds is not desirable. The fundamental research required for a successful application of the ‘system management’ approach will be illustrated with the biological control project of Senecio vulgaris L. using the naturalized rust fungus Puccinia lagenophorae Cooke. A five‐step procedure, together with selected results, will be presented. Main emphasis is given to the infection window, the study of the genetic structure of the plant and pathogen population, and the management of the infection conditions (a) to maximize the spread of the disease and the impact on the plants, and (b) to minimize the development of resistant plant populations. Joint application of herbicides at low doses, additional necrotrophic pathogens, and of biochemicals interfering with the weed's defence also will be envisaged, as well as their integration into general pest control practices. In this regard, biological weed control agents have to be seen as stress factors, not as weedkillers, and biological weed control as an integral part of a well‐designed pest management strategy, not as a sole cure.
Movement and persistence of imazaquin, oxyfluorfen, flurochloridone and terbacil in soil
Authors: MILANOVA S. , GRIGOROV P.
Published: July 2006

The movement and persistence of imazaquin, oxyfluorfen, flurochloridone and terbacil residues were studied using a bioassay based on the shoot growth of Raphanus sativus L. var, radicula DC (radish) in a sandy loam soil under field conditions in 1992 and 1993. Imazaquin (0.3 kg a.i. ha‐1) was more mobile in the soil than the other three compounds. In 1992, under heavy rainfall conditions, the herbicide was distributed down to 60 cm in amounts of about 0.01 mg kg‐1. Conversely, in the dry year of 1993, the maximum depth of penetration was 20 cm and persistence in the surface soil layer (0‐5 cm) was greater. After the first month in 1992, residues of terbacil were distributed in the 0‐20 cm layer, and after 2, 3 and 5 months the herbicide had penetrated to a depth of 40 cm. In 1993, terbacil residues were distributed in the 0‐10 cm layer only. In both years, residues of flurochloridone (1.0 kg a.i. ha‐1) were located mainly in the 0‐5 cm layer, but there was some penetration to 10 cm. Oxy‐fluorfen (1.2 kg a.i, ha‐1) showed least mobility in the soil profile. It was retained in the 0‐5 cm layer throughout the experimental period in both. years.
Evaluation of three pesticide leaching models with experimental data for alachlor, atrazine and metribuzin
Authors: WALKER A. , WELCH S. J. , MELACINI A. , MOON Y.‐H.
Published: July 2006

The persistence and movement of residues of alachlor, alrazine and metribuzin were measured in a mini‐lysimeter system in the field. This comprised a number of soil columns (11 cm diametert; 30 cm long), and permitted the vertical distribution of residues to be determined at. intervals alter application and the collection and analysis of leaehale water. Laboratory experiments were also performed to determine the degradation rates of the three herbicides and their strengths of adsorption by the test soil. The results showed an order of degradation rate of metribuzin> alachlor>atrazine and an order of adsorption of alacblor>atrazine>melribuzin. Movement of residues in the soil columns and concentrations in the leachate were inversely related to the strength of adsorption. Parameters derived from the laboratory data were used in conjunction with weather data for the period of the field experiment in three mathematical models of pesticide leaching: VARLEACH, LEACHP and PRZM2. In most instances, the models gave acceptable predictions of the distribution of residues in soil. This was particularly so for the less mobile compound alachlor. With the most mobile compound, metribuzin, residues were not well predicted at the later sampling dates. All three models gave accurate predictions of the volumes of drainage water, but none of them predicted the concentrations of herbicide in the leachate, presumably because they do not take account of preferential flow pathways of water and solute in the soil.
Influence of water stress on absorption, translocation and phytotoxicity of fenoxaprop‐ethyl and imazamethabenz‐methyl in Avena fatua
Authors: XIE H. S. , HSIAO A. I. , QUlCK W. A. , HUME J. A.
Published: July 2006

The influence of water stress on the absorption and translocation of 14C‐labelled fenoxapropethyl and imazamthabenz‐methyl in Avena fatua L. (wild oat) was studied. The phytoioxicity to A. fatua of both herbicides with a droplet application was also examined under water stress conditions. The absorption of both fenoxaproethyl and imazamethabenz‐methyl was reduced by waler stress when the plants were harvested within 24 h after herbicide application. Up to 48 h after the application, the translocation out of the treated lamina of both herbicides, based on percentage of applied 14C. was reduced under water stress conditions. When havested 96 h after herbicide application, however, water stress no longer significantly affeaed the absorption and translocation of either herbicide. When the herbicides were applied as individual droplets, water stress reduced the phytotoxicity of fenoxaprop‐ethyl but not that of imazamethabenz‐methyl. It is concluded that the changes in herbieide absorption and translocation may not be the major physiological processes associated with differential whole‐plant response oi A faiua to fenoxaprop‐ethyl and imazamefhabenz‐methyl under water stress.
Effects of depth of seed burial and soil aggregate size on seedling emergence of Alopecurus myosuroides, Galium aparine, Stellaria media and wheat
Authors: CUSSANS G.W. , RAUDONIUS S. , BRAIN P. , CUMBERWORTH S.
Published: July 2006

Seedling emergence of Alopecurus myosuroides Huds., Stellaria media L. (Vill.), Galium aparine L. and wheat (Triticum aestivum L.) was compared at a range of depths of soil cover from 2 to 11 cm. The covering soil was a fertile agricultural soil with 60% clay content which had been sieved into four aggregate sizes. The aggregate sizes used were 26‐50 mm. 14‐25 mm. 6‐13 mm and below 6 mm. Total emergence of all species was reduced with increased depth of sou cover. With A. myosuroides and S. media, total emergence was lowest in fine soil conditions. Alopecurus myosuroides showed a marked interaction whereby response to depth of sowing was least with fine tilth. The time to 50% emergence showed a similar response. With all four species, seedling emergence was slowest at greater depths of sowing and with the finest tilth, the differences tending to increase with increasing depth of sowing. A vert high proportion of the time to 50% emergence was accounted for by the lag time between sowing and the first recorded emergence.
Competition between winter wheat and Veronica hederifolia: influence of weed density and the amount and timing of nitrogen application
Authors: ANGONIN C. , CAUSSANEL J.‐P. , MEYNARD J.‐M.
Published: July 2006

The effects at Veronica hederifolia. densities on the yield of winter wheat (Triticum aestivum L.) were studied in field trials conducted at the same location in 1992 and 1993. In 1992, nitrogen at 60 kg ha‐1 was applied at tillening followed by a further 80 kg ha‐1 at the first node of stem elongation. In 1993. four regimes of nitrogen applications were compared: a total of 140 kg ha‐1 supplied at three dales. 60 kg ha‐1 supplied at tillering, 60 kg ha‐1 Supplied al the first node of stem elongation and no nitrogen as the control. Competitive effects from V. hederifolia (ranging from 17 to 192 plants m‐22), were greatest in 1993, the year with the best early growth development of this weed. In 1993, yield losses, as described with a non‐linear model changed for each regime of fertilization. In both years, V. hederifolia decreased wheat ear number per unit area for each nitrogen treatment. This is explained hy an increase in tiller mortality and a nitrogen deficiency in wheat at the stem elongation and flowering stages. Nevertheless, with late application of nitrogen, individual grain weight increased and the effect of V. hederifolia on wheat yield loss was lowest. The results are discussed in relation to the effects on all yield components, and show the importance of choosing the rieht nitrogen fertilization for specific yield targets of wheat production when infested by weeds.
Variation in total phenols and condensed tannins in Eucalyptus: leaf phenology and insect grazing
Authors: MACAULEY BARRY J. , FOX LAUREL R.
Published: July 2006

Total phenols and condensed tannins in leaves of seven species of Eucalyptus ranged from 4–40% and 0–27% respectively of the leaf dry weight. The concentrations of these compounds were variable but usually high in young and older leaves throughout the growing season, and typically increased during winter, but no other trends with season or leafage were apparent. This pattern of seasonal variation in concentrations of total phenols and condensed tannins is different to that studied for other plant species. This difference may be related to repeated production of new leaves by Eucalyptus during the growing season, and the probability that these leaves will be attacked by herbivorous insects.
The effects of temperature and moisture on the inception of diapause in eggs of the Australian plague locust, Chortoicetes terminifera Walker (Orthoptera: Acrididae)
Authors: WARDHAUGH K. G.
Published: July 2006

Chortoicetes terminifera lays a mixture of diapause and non‐diapause eggs during the autumn months of March and April. Diapause eggs cease development in late anatrepsis when kept in moist soil at 32.5°C. These conditions favour rapid embryogenesis and hatching in non‐diapause eggs.

Significant reductions in the incidence of diapause were obtained when newly‐laid eggs were kept for 40 days at either 15.5°C or 32.5°C in conditions that prevented the uptake of water. In eggs held for a similar period in moist soil at 15.5°C, diapause was virtually eliminated. These eggs did not develop to the stage at which water uptake occurs. It is suggested that the inception of diapause is dependent upon the occurrence of warm, moist conditions at the time of laying and that these requirements are an integral part of the overall inductive process, which also involves the temperature and photoperiod at which the parent insects are reared.

A flow‐diagram illustrating the development of diapause eggs in relation to temperature and moisture is discussed in relation to the survival of the species.
The distribution and abundance of species of Danthonia DC on the New England Tablelands (Australia)
Authors: SCOTT A. W. , WHALLEY R. D. B.
Published: July 2006

The distribution and percent frequency of the 13 species and one variety of Danthonia recorded on the New England Tablelands were examined in a survey of 110 predominantly pastoral sites. The relationships between site factors and the presence and percent frequency of the different Danthonia species were subjected to canonical correlation analysis. Individual species were found to have particular sets of environmental factors associated with their distribution and percent frequency; a fact not well recognized in the past.

The most common factor associated with the abundance of Danthonia was either a long time since the last cultivation or no cultivation at all. Other factors such as altitude, drainage, soil parent material, soil texture and total soil phosphorus status were also of some importance.

The six species most commonly recorded throughout the New England Tablelands were D. racemosa RBr, D. pilosa RBr, D. laevis J. Vickery, D. linkii Kunth., D. richardsonii Cashmore and D. tenuior (Steud.) Conert. Of these the first three are ecologically wide species. The first two can coexist with other naturalized species under grazing while D. laevis tends to disappear with disturbance. D. linkii and D. richardsonii require fairly narrow habitat conditions but these conditions and consequently these species are common. Both species respond positively to disturbance. Danthonia linkii increases with cultivation and D. richardsonii colonizes eroded soil surfaces. Danthonia tenuior has more restricted requirements and is not so frequent

The other seven species and one variety did not occur often enough for detailed study and the occurrence of two of these species, D. carphoides and D. caespitosa must be considered as rare.
Above‐ and below‐ground litter decomposition in an Australian salt marsh
Authors: VAN DER VALK A. G. , ATTIWILL P. M.
Published: July 2006

Decomposition of litter and the release of nutrients during decomposition were studied both above‐ and below‐ground in a salt marsh in southern Australia. Above‐ground litter of two species, Sclerostegia arbuscula and Sarcocomia quinqueflora, placed in a salt marsh bordering Westernport Bay, Victoria lost significantly different amounts of weight (61% and 50%, respectively) after 272 days in the field. Below‐ground litter buried at depths of 10, 20 and 30 cm lost only 35‐43% of its initial weight during the same period. Above‐ground litter lost more N than below‐ground litter (ca. 50% versus 30%, respectively), more P (ca. 80% versus 45%), more K (ca. 90% versus 65%), more Ca (ca. 50% versus 10%), and more Mg (ca. 40% versus 25%). Significant differences in the rate at which elements (N, P, Ca, and Mg) were lost occurred at different depths in below‐ground litter. Above‐ground litter of the two species examined also differed in the rates and amount of most elements (N, P, Ca, and Mg) lost.
Mean annual population density of Collembola and Acari in the soil and litter of three indigenous South Australian forests
Authors: HUTSON BARRY R. , VEITCH L. G.
Published: July 2006

A quantitative study of the soil and litter fauna of three South Australian low open forests was made for two years. The soil and vegetation of the sites were similar but the mean annual rainfall of the areas differed; 635, 690 and 1050 mm/y, respectively for the ‘dry’, ‘medium’ and ‘wet’ sites. Monthly samples were taken of litter, and the upper 0–4 cm and lower 4–8 cm soil layers, and the method used to estimate the numbers of active animals is also described.

Mean annual population densities of Collembola and Acari were greatest at the medium site (9.5 and 48.6 × 103/m2, respectively) and least at the dry site (4.9 and 35.1 × 103/m2, respectively) and values are discussed in relation to site organic carbon content. Over all the sites, between 11–21, 67–75 and 10–15% of the collembolan populations, and 10–13, 66–72 and 16–21% of the acarine populations inhabited the litter layer and upper and lower soil layers respectively. Isotomidae were the most abundant collembolan family in each level at each site, but the overall proportion of Entomobryidae increased from the dry to wet site. Prostigmata were the most abundant acarine order in each level at two sites. Cryptostigmata were dominant in the litter layer of the wet site, and their overall proportion increased from the dry to wet site. Seasonal density changes were similar on all sites with minima in the summer and maxima in the winter months.

The results obtained here combined with those from other published investigations indicate a trend of faunal population change over various ecosystems in Australia. Prostigmatid mites and iso‐tomid Collembola dominate at arid sites. As sites become less arid and the amount of soil organic matter increases, the proportion of cryptostigmatid and mesostigmatid mites increases, and other groups of Collembola, particularly Entomobryidae, become more frequent.
Comparison of distance based density estimates for some arid rangeland vegetation
Authors: LAMACRAFT ROBIN R. , FRIEDEL MARGARET H. , CHEWINGS VANESSA H.
Published: July 2006

A method was required for determining the effect of management on extensive populations of trees and shrubs in central Australian rangelands. One useful indicator of change in these populations is the density of individuals, and there are several methods available based on distance measurement for density estimation. This study compared those procedures.

Samples were drawn by computer from ground maps of actual plant distributions for Acacia aneura, Cassia nemophila and Atalaya hemiglauca and from a map generated at random. These samples were drawn to examine the properties of the nearest neighbour, point centred quarter, conditioned distance and compound T‐square estimates of density. Samples were drawn by two methods: simple random sampling and semisystematic sampling.

In general, there was a tendency for all estimators of density to underestimate the true density of naturally occurring populations with the compound T‐square method (Byth 1982) being most robust. The compound T‐square method was least biased but its variance increased for more aggregated spatial distributions. Estimates of density were not altered by the use of semisystematic sampling, when compared to simple random sampling.

The spatial distributions examined in this study have not previously been studied as theoretical models. Acacia aneura and Cassia nemophila showed some aggregation of clusters, while the Atalaya hemiglauca showed a more extreme form of clustering due to its root suckering propagation.
A floristic framework of Australian rainforests
Authors: WEBB L. J. , TRACEY J. G. , WILLIAMS W. T.
Published: July 2006

In the first comprehensive floristic classification of Australian rainforests and monsoon forests, fresh insights made possible by the use of floristic as distinct from structural data are outlined. A set of 561 individual communities, on sites ranging from North Queensland westwards to the Kimberley region and southwards to Tasmania, is defined by the presence or absence of 1316 tree species, or 406 genera. The data have been subjected to numerical classification, first with respect to species, then to genera.

The species classification first divides into three ‘ecofloristic regions’: A, temperate (microtherm) and subtropical (mesotherm) humid evergreen rainforests; B, tropical (megatherm) humid evergreen grading into highly seasonal raingreen (monsoon) forests; and C, subtropical (mesotherm) moderately seasonal humid/subhumid raingreen forests. The sites are further divided into eight ‘ecofloristic provinces’, for each of which a core area is identified and the ten most common diagnostic tree species listed for selected floristic elements, whose ecological relationships are briefly described.

Gradients of quantitative thermal‐moisture indices are added to standard climatic typology to provide a more flexible identification of local climates that characterize community‐types of each province across a wide latitudinal/altitudinal range. Community disjuncts and outliers of a particular province are interpreted as the results of past environmental sifting (in which ecological factors are not entirely determinate), of previously more continuous rainforest vegetation.

The genera classification first divides into humid eastern coastal and subhumid western and subcoastal sites, then four thermal types, and finally nine groups of floristic ‘paleo‐provinces’. Where the species and genera classifications are not in substantial agreement, a wide‐ranging generic element across the provinces in northern and northeastern Australia is interpreted in paleogeographic terms.

The relict distribution of existing community types, as the result of climatic sifting of ancient floral stocks, is discussed in support of emerging ideas about the autochthony of Australian rainforests, especially those tropical types that are not intrusive.

It is argued that the unique ecological relationships of Australian rainforests justify the most conservative uses of the relatively small remaining areas.
Distribution of invertebrates on foliage in forests of south‐eastern Australia
Authors: WOINARSKI J. C. Z. , CULLEN J. M.
Published: July 2006

Nearly 1500 foliage samples were collected from a total of 156 plant species, distributed at 16 study sites representing a wide range of forests and woodlands in south‐eastern Australia. Samples were collected in all months. Invertebrates present in samples were counted, sorted into 13 categories, and the number present (> 3 mm in length) converted into density estimates. Densities of all invertebrates combined and invertebrate diversity were also calculated.

Despite high variability there were some obvious distributional patterns for most categories. Three major dichotomies affected abundance and distribution of invertebrates: these were presence or absence of flowers, whether the plant species was Eucalyptus or other, and if Eucalyptus, whether the plant species was Symphyomyrtus or Monocalyptus. The presence of flowers in foliage samples increased the abundance of most invertebrate taxa. Compared to foliage of non‐Eucalyptus species, Eucalyptus foliage had more lerp‐forming psyllids and miscellaneous larvae, but fewer Arachnida, Coleoptera, Psocoptera, Hemiptera (other), Thysanoptera, Diptera, and total arthropods. Foliage of Symphyomyrtus species had higher densities of most categories (and particularly lerp‐forming psyllids) than that of Monocalyptus.

There were seasonal variations in abundance in most invertebrate taxa, but these patterns were different for Eucalyptus and non‐Eucalyptus species. For most sites abundance of all arthropods combined was lowest in winter, but this decline was not especially pronounced, and was reversed at more xeric sites.

For most categories there were significant differences between study sites in abundance and for some this was related to position of sites on a moisture gradient. In general total arthropod densities were highest at intermediate and xeric sites. There were some significant differences in arthropod communities for the same plant species at different study sites.

Sample height, plant height, and the ratio of these were relatively unimportant variables. Likewise, the ratio of leaf width: leaf length was not significantly correlated with abundance for any invertebrate category across 128 plant species, but mean leaf size was negatively correlated with densities of Arachnida and total invertebrates. The distributions of some invertebrate categories were inter‐correlated.
The impact of water buffalo on the monsoon forest ecosystem in Kakadu National Park
Authors: BRAITHWAITE R. W. , DUDZINSKI M. L. , RIDPATH M. G. , PARKER B. S.
Published: July 2006

The intensity of use of forested country in the Kakadu National Park area by feral Asiatic water buffalo can be largely predicted from the area of river floodplain in the vicinity of the site, and tree canopy cover on the site. Thus some areas of monsoon forest appear to have sustained intensive use by buffalo for over a century whereas other areas have probably been little used.

With sites exhibiting little buffalo use, mean DBH of trees increased with foliage height diversity (FHD). However, the sites more intensively used by buffalo had a lower canopy and did not exhibit any increase in mean DBH with a pronounced increase in FHD. Other vegetational relationships displayed by the two groups of sites are discussed. Comparison of the monsoon forest sites suggests that compaction of soil by buffalo has caused the death of large trees due to poor recharge of groundwater.

The two groups of monsoon forest sites exhibited a wide variety of faunal relationships with FHD. Some species appear to be favoured while others are disadvantaged to various degrees by the habitat changes caused by the buffalo. The most intensively used site appears to have exceeded a threshold in that a number of faunal trends were reversed on that site.

The impact of buffalo on some monsoon forest sites is much more fundamental than anticipated. But other sites which appear to be naturally protected by their location have experienced much less change due to buffalo.
Is insect defoliation in eucalypt forests greater than that in other temperate forests?
Authors: OHMART C. P.
Published: July 2006

Claims have been made in the past that insect defoliation in eucalypt forests of Australia is both chronically high and greater than defoliation levels in northern temperate forests. Recent published data, however, indicate that some eucalypt forests may sustain low level defoliation. Careful reexamination of the literature on defoliation in eucalypt forests indicates that there are not enough data available to quantify defoliation on an Australian‐wide basis. Therefore it cannot be claimed that insect defoliation in eucalypt forests is greater than that in other temperate forests. There are also insufficient data to claim that insects are a major factor responsible for the growth differential between indigenous and overseas plantation‐grown eucalypts. The ecological impact of herbivorous insects in eucalypt and northern temperate forests is also discussed.
Mortality of lignotuberous seedlings of Eucalyptus species after an intense fire in montane forest
Authors: NOBLE I. R.
Published: July 2006

The survival of lignotuberous seedlings of Eucalyptus pauciflora, E. dalrympleana and E. dives following an intense experimental fire was monitored in montane forest in the Brindabella Ranges, Australian Capital Territory. Percentage survival was the same for each species (60%), but it was shown that an individual was more likely to survive if it was large and growing vigorously before the fire. Survival was also enhanced if the individual was growing in a patch of low litter load and if it experienced a locally low fire intensity. Lignotuberous seedlings of E. dalrympleana, a species of the subgenus Symphyomyrtus, recovered more quickly than the other two species which are of the subgenus Monocalyptus. This result parallels conclusions concerning different initial growth rates between seedlings of the subgenera.
Temporal and spatial variability in insect grazing of the canopies of five Australian rainforest tree species
Authors: LOWMAN M. D.
Published: July 2006

Herbivory was measured monthly for 2 years on leaves of permanently marked replicate branches in the canopies of five Australian rainforest tree species. Variability in insect grazing activities was evident with respect to several factors:

leafage — young leaves were preferred over older leaf tissue:

height — leaves closer to ground level were more heavily grazed:

light — shade leaves were preferred to sun leaves:

time — grazing was intense during spring and summer months, and almost negligible during autumn and winter, but was cumulatively similar between the 2 years:

space — grazing was extremely variable on small spatial scales such as between individual leaves and branches, but similar where hundreds of leaves were pooled on larger scales between individual canopies and among geographically different sites:

tree abundance — grazing was heavier at sites where a tree species was common than where it was rare:

host tree species.

Long term observations resulted in higher but more accurate estimates of herbivory since it was possible to quantify losses of leaves totally eaten, an event not accounted for infield methods of discrete sampling whereby leaves are merely harvested and measured for area missing. Variability in herbivory is discussed in terms of plant‐insect phenologies, plant defences, successional status of tree species, and insect behaviour.
Seasonal variation and the effects of drought on the abundance of arthropods in savanna woodland on the Northern Tablelands of New South Wales
Authors: BELL H. L.
Published: July 2006

Monthly samples of arthropods were collected for 3 years in savanna woodland at Wollomombi, New South Wales, from the foliage of eucalypts, bipinnate acacias, Olearia viscidula Jacksonia scoparia, Exocarpos cupressiformis and Cassinia spp., and from the ground‐layer. The second and third years of the study coincided with the worst drought recorded for the area. Biomass of arthropods matched primary productivity and decreased greatly during the drought. In the first year there was a pronounced summer peak and winter low. Some species of plants showed peaks that did not conform to the overall pattern. Most arthropod groups were greatly reduced in number during the drought and some groups virtually disappeared, although coleopterans were not significantly affected. Arthropods were less severely reduced in shrubs than they were in the tree‐layer of eucalypts. Arthropods were on average smaller during winter.