bluuebunny/crossref_metadata_2025 huggingface dataset:
Ecology of herbaceous perennial legumes: a review of characteristics that may provide management options for the control of salinity and waterlogging in dryland cropping systems
Authors: Cocks P. S .
Published: September 2002

Salinity is a widespread problem caused by an imbalance between rainfall and
transpiration in the dryland cropping systems of southern Australia. The need
to use more perennials has been identified and this paper examines the
possibility of replacing annual with perennial pasture legumes and the
germplasm available to do so. While lucerne is already used widely in eastern
Australia it has only recently been adopted in the wheat belt of Western
Australia. There are doubts about its adaptation to acid soils and to climates
where summer rainfall is low and ambient temperatures are high. There is also
a need to diversify the species available to reduce the likelihood of invasion
by exotic diseases and insects.
Several genera are likely to be of value in this respect, although few will be
as widely adapted as lucerne. Perennial legumes are found in environments
ranging from alpine to desert. Targeted collections of genera from the dry
areas, especially where soils are acid, are likely to yield species of value.
These may include perennial species of Astragalus,
Hedysarum, Lotus,
Onobrychis, Psoralea, and
Trifolium. Some Australian genera, for example
Swainsona, Glycine, and
Cullen may also be of value. Most of these genera are
from alkaline soils, and the need to cope with acid soils that are often high
in free aluminium is seen to limit their use in southern Australia. However,
since virtually nothing is known of the ecology and ecophysiology of species
from the dry areas, it is possible that through selection and the use of
adapted rhizobia, some at least may be of value in Australian conditions.
Cropping in rotation with perennial legumes is likely to involve several
changes in farming systems. It is impossible to predict their nature but it is
essential that we understand what these changes are before the species are
widely introduced. Account must also be taken of their ability to use water.
It is entirely possible that perennials from dry areas are dormant in summer
despite the fact that there is no evidence in the literature to this effect.
It was concluded that although lucerne is suitable for phase farming,
alternatives to lucerne are needed. They will have to match the water-using
and nitrogen-fixing capacities of lucerne, and farming systems will be
required that make full use of the new germplasm. Collaboration with
institutions in the Mediterranean basin and elsewhere is needed and a
beginning has been made in this direction.
Potential deep drainage under wheat crops in a Mediterranean climate. II. Management opportunities to control drainage
Authors: Asseng S. , Dunin F. X. , Fillery I. R. P. , Tennant D. , Keating B. A.
Published: September 2002

High rates of deep drainage in Western Australia are contributing to
groundwater recharge and secondary salinity. Strategies are being sought to
increase water use in cropping systems and to reduce deep drainage.
Quantifying potential drainage through measurements is hampered by the high
degree of complexity of these systems as a result of diverse soil types, a
range of crops, and in particular the inherent seasonal variability.
Simulation models can provide the appropriate means to extrapolate across time
and space. The Agricultural Production Systems Simulator (APSIM) was used to
explore the effect of alternative agronomic practices on wheat production and
deep drainage for representative soils and rainfall regions of the central
wheatbelt of Western Australia. Soil water profiles were reset each year to
the lower limit of plant-available water, assuming maximum water use in the
previous crop. The long-term simulation studies showed that management
practices with N fertiliser directed at yield increase were most effective in
achieving these aims in the medium to high rainfall regions. The corresponding
effect for drainage reduction was marginal. The small effect on drainage
control associated with production increase can be traced to the effect of
rainfall distribution with major occurrences of both rainfall and drainage
during winter (June–August) coinciding with the lowest potential
atmospheric demand for evapotranspiration, in combination with low
water-holding capacity soils. Nitrogen-induced increases in crop transpiration
were in conjunction with reduced soil evaporation, which increased water use
efficiency and occurred mostly after the main drainage period, but had little
effect on deep drainage within the season. Similar outcomes of enhanced
productivity with minor impact on deep drainage were noted with crops sown at
different times and with a hypothetical wheat crop having a deeper rooting
system.
Simulations without resetting soil water each year enabled the quantification
of potential carryover effects on long-term average deep drainage. The
carry-over of soil water left behind at crop harvest reduced the water storage
capacity of the soil in a subsequent year and could increase long-term deep
drainage substantially, depending on soil type. Improved management increased
late water use in the high rainfall region, in particular on better
water-holding soils, and could largely reduce this carry-over effect.
The current wheat-based cropping systems, even with alternative management
practices, continue to be a major threat to sustainability on the low
water-holding soils in the wheatbelt of Western Australia, as a main cause of
secondary salinity.
Using Demonstrations during Lectures
Authors: Fierro Julieta
Published: September 2002

I shall present a series of easy demonstrations that can be carried out during formal astronomy lectures. Since astronomy is physics we have developed on Earth applied to celestial objects, there are many useful experiments that can be carried out with relative ease by physics teachers in order to help pupils grasp the workings of the universe and to relate them with every day experiences. One of the difficulties in teaching science is that we use two-dimensional pictures to explain a three-dimensional reality. Using models helps students understand some of the properties of celestial objects. Although it is important to have pupils experiment on their own, some demonstrations are so simple that it is enough to have the teacher carry them out during the lecture to have pupils grasp their importance or at least keep their attention focused on the topic at hand. The demonstrations can be used in elementary education as well as in introductory astronomy courses and teacher workshops.
On the Gas Surrounding High-Redshift Galaxy Clusters
Authors: Francis Paul J. , Wilson Greg M. , Woodgate Bruce E.
Published: September 2002

Francis & Hewett (1993) identified two 10 Mpc-scale regions of the high-redshift universe that were seemingly very overdense in neutral hydrogen. Subsequent observations showed that at least one of these gas-rich regions enveloped a cluster of galaxies at redshift 2 ·38. We present improved observations of the three background QSOs with sightlines passing within a few Mpc of this cluster of galaxies. All three QSOs show strong neutral hydrogen absorption at the cluster redshift, suggesting that this cluster (and perhaps all high-redshift clusters) may be surrounded by a ~5 Mpc-scale region containing ~10 12 Mʘ of neutral gas. We show that if most high-redshift clusters are surrounded by such regions, the gas must be in the form of many small (<1 kpc), dense (> 0·03 cm ˗3 ) clouds, each of mass <10 6 Mʘ . These clouds are themselves probably gathered into >20 kpc-sized clumps, which may be galaxy halos or protogalaxies. If this gas exists, it will be partially photoionised by the UV background. We predict the diffuse Lyα flux from this photoionisation, and place observational limits on its intensity.
The Secret Inner Life of the Orion Nebula
Authors: Schultz A. S. B.
Published: September 2002

Beneath the familiar surface of the Orion Nebula is a spectacular molecular hydrogen outflow from a young stellar object, of very unusual morphology. In this paper I briefly discuss this outflow, its possible origins, and its interaction with the Nebula.
QSO-Galaxy Correlations: Lensing or Dust?
Authors: Croom Scott M.
Published: September 2002

We present evidence for an anti-correlation between faint QSOs and B < 23 galaxies.A sample of 192 QSOs in a 2.5 deg2 area has been imaged using the Isaac Newton Telescope Wide-Field Camera. The cross-correlation signal is of a similar amplitude to the galaxy auto-correlation function at the limit of B < 23, but is negative in sign. As fainter galaxies are selected the negative correlation signal becomes less significant, until the signal is effectively zero at B < 26. We propose two alternate explanations for the observed effect. The first is gravitational lensing of the faint background QSOs, which have a flat number count slope. However, the lensing signal is significantly higher than expected in conventional models. The second possibility is that inter-galactic dust absorption is responsible. A reddening of only E(B - V) ≃ 0.02 is required to produce the observed correlation. The large 2dF and SDSS QSO surveys should allow a definitive solution to the question of QSO–galaxy correlations.
Microlensing of Quasars
Authors: Wambsganss Joachim
Published: September 2002

Microlens-induced variability in multiple quasars can be used to study two cosmological issues of great interest, the size and brightness profile of quasars on one hand, and the distribution of compact (dark) matter along the line of sight on the other. Here a summary is given of recent theoretical progress as well as observational evidence for quasar microlensing, plus a discussion of desired observations and required theoretical studies.
X-Ray Microlensing of Bright Quasars
Authors: Mineshige Shin , Yonehara Atsunori , Takahashi Rohta
Published: September 2002

We calculate the expected microlens light curves to see what aspects of flow structures can be extracted by microlensing.We specifically pick up a disk-corona model as a model for bright quasars.We then expect distinct behaviour in the soft and hard X-ray microlens variations. Since soft X-ray emission is produced by Compton up-scattering of soft (optical-UV) photons from the innermost part of the disk, while hard X-ray radiation is via bremsstrahlung within the corona of a large volume, the model calculations predict more rapid soft X-ray changes than hard X-ray ones. Further, bright spots (or blobs) on the disk will produce humps in the microlens light curves. Future microlens observations will constrain such emission processes, thereby probing accretion flow structure.
The 2dF Gravitational Lens Survey
Authors: Mortlock Daniel J. , Madgwick Darren S. , Lahav Ofer
Published: September 2002

The 2 degree Field (2dF) galaxy redshift survey will involve obtaining spectra of approximately 2.5 105 objects which have previously been identified as galaxy candidates on morphological grounds. Included in these spectra should be about ten gravitationally-lensed quasars, all with low-redshift galaxies as deflectors (as the more common lenses with high-redshift deflectors will be rejected from the survey as multiple point-sources). The lenses will appear as superpositions of galaxy and quasar spectra, and either cross-correlation techniques or principal components analysis should be able to identify candidates systematically. With the 2dF survey approximately half-completed it is now viable to begin a methodical search for these spectroscopic lenses, and the first steps of this project are described here.
Using the 6dF Galaxy Redshift Survey to Detect Gravitationally-lensed Quasars
Authors: Mortlock Daniel J. , Drinkwater Michael J.
Published: September 2002

It is possible to detect gravitationally-lensed quasars spectroscopically if the spectra obtained during galaxy surveys are searched for the presence of quasar emission lines. The up-coming 6 degree Field (6dF) redshift survey on the United Kingdom Schmidt Telescope will involve obtaining ~105 spectra of near-infrared selected galaxies to a magnitude limit of K = 13. Applying previously developed techniques implies that at least one lens should be discovered in the 6dF survey, but that as many as ten could be found if quasars typically have BJ – K ~ 8. In this model there could be up to fifty lensed quasars in the sample, but most of them could only be detected by infrared spectroscopy.
UBV Photometry of the Massive Eclipsing Binary TT Aur
Authors: Özdemir S. , Ak H. , Tanriver M. , Gülseçen H. , Gülseçen S. , Saygaç A. T. , Budding E. , Demircan O.
Published: September 2002

UBV observations of the massive binary system TT Aur were carried out mainly at theTurkish National Observatory (TUG). These observations, together with IUE spectra and times of eclipse minima collected from the literature, were used to study the system parameters.

Simultaneous solution of the light curves by the Wilson-Devinney code allows a semi-detached configuration with a slightly larger Roche-lobe filling secondary. This picture is supported by other evidence. The shoulders of the primary minimum suggest some excess absorption, in keeping with circumstellar material in the form of a disk-like structure around the primary component. The deeper primary minimum in the U filter may indicate a hotter region on the secondary-facing hemisphere of the primary.

The period variation of the system can also be related to the possible existence of a third component in a circular orbit around the system.

An alternative detached representation is also considered using optimal curve-fitting techniques. We appeal for further observations to help resolve some outstanding issues in this interesting massive binary.
Total Magnitudes of Virgo Galaxies. II. An Investigation into the mp Scale of Volume I of Zwicky et al.'s Catalogue of Galaxies and of Clusters of Galaxies
Authors: Ke-shih Young Christopher , Shao Zheng-yi
Published: September 2002

We investigate the photographic-magnitude (mp) scale of Volume I of the Catalogue of Galaxies and of Clusters of Galaxies for galaxies in the Virgo direction. It is found that for 11.5 ≤ Bt < 14.5, the mp values listed correspond very closely (with a scatter of only 0.16 magnitude) to blue magnitudes measured to the B = 24.4 isophote. If mp values need to be used as estimates of total blue magnitude the scatter is 0.27 magnitude over the same range in Bt and the mean offset is mp – Bt = 0.28 magnitude. However, a serious scale error at the bright end causes both the isophotal and total luminosities of galaxies brighter than Bt ~ 11.5 to be severely underestimated. At the faint end there also appears to be a significant scale error. This causes galaxy luminosities to be seriously overestimated faintward of Bt ~ 14.5.We demonstrate that this is a real effect based on a detailed galaxy-by-galaxy study of the catalogue’s completeness down to Bt = 17.0. The catalogue is found only to be complete to Bt ~ 14.7 whilst its degree of incompleteness is found to be relatively constant at the 30% level over the range 14.75 ≤ Bt < 15.75. Most of the missing objects are found to be elliptical galaxies and so late-type objects are over-represented at the faint end.
Galactic Structure and the Cosmic Ray Anisotropy at 1018eV
Authors: Clay R. W.
Published: September 2002

Cosmic ray arrival directions at energies a little over 1018 eV have been reported to show an excess from directions close to that of the Galactic centre. That result was originally presented by the AGASA group and was later strengthened by an analysis of SUGAR cosmic ray data. We discuss here a second feature of the AGASA data, a deficit in roughly the Galactic anticentre direction.We interpret this as a result of cosmic ray diffusion past us. We find that the most straightforward interpretation of the data then requires that a strong magnetic field exists out of the plane of our Galaxy to distances of at least several kiloparsecs.
Relativistic Jet Flow from a One Dimensional Magnetic Nozzle—Analytic Solutions
Authors: Liffman Kurt
Published: September 2002

Magnetohydrodynamic devices that can accelerate plasmas to speeds of the order of hundreds of kilometres per second have been designed and built for nearly forty years. Up to the time of writing, however, the theory for such devices has been exclusively non-relativistic. In this paper we derive the special relativistic magnetohydrodynamic (SRMHD) equations and use them to obtain the relativistic, magnetic nozzle equation which describes the production of jet flows with speeds approaching the speed of light.We obtain analytic solutions to this equation and show that, in principle, magnetic field gradients can accelerate a plasma to highly relativistic speeds. We also show that the exit kinetic energy, EK, of a particle is given by the equation EK = m0C2FR, where m0 is the rest mass of the particle and CFR is the fast magnetosonic speed at the start of the flow.

The relativistic nozzle differs in a number of ways from the non-relativistic case.A non-relativistic nozzle has a relatively symmetric converging/diverging shape, while a highly relativistic nozzle converges in the usual manner, but diverges, in an abrupt fashion, at the very end of the nozzle. The gentle divergence of non-relativistic nozzles causes the exit plasma densities and magnetic fields of the flow to have values that are small relative to their values at the start of the nozzle. The abrupt divergence of a highly relativistic nozzle implies that, for a less than perfect nozzle, the exit values of the mass density and the magnetic field strength are comparable to their initial values. This unexpected dichotomy in behaviour may have future application in understanding the ‘radio-loud’ and ‘radio-quiet’ relativistic jets that are produced from astrophysical sources.
On Eagle's Wings: The Parkes Observatory's Support of the Apollo 11 Mission
Authors: Sarkissian John M.
Published: September 2002

At 12:56 p.m., on Monday 21 July 1969 (AEST), six hundred million people witnessed Neil Armstrong's historic first steps on the Moon through television pictures transmitted to Earth from the lunar module, Eagle. Three tracking stations were receiving the signals simultaneously. They were the CSIRO's Parkes Radio Telescope, the Honeysuckle Creek tracking station near Canberra, and NASA's Goldstone station in California. During the first nine minutes of the broadcast, NASA alternated between the signals being received by the three stations. When they switched to the Parkes pictures, they were of such superior quality that NASA remained with them for the rest of the 2-hour moonwalk. The television pictures from Parkes were received under extremely trying and dangerous conditions. A violent squall struck the telescope on the day of the historic moonwalk. The telescope was buffeted by strong winds that swayed the support tower and threatened the integrity of the telescope structure. Fortunately, cool heads prevailed and as Aldrin activated the TV camera, the Moon rose into the field-of-view of the Parkes telescope. This report endeavours to explain the circumstances of the Parkes Observatory's support of the Apollo 11 mission, and how it came to be involved in the historic enterprise.
Equatorial Pulsar Winds
Authors: Kuijpers Jan
Published: September 2002

Atraditional problem in pulsar wind physics has been the nature of the pulsar wind.Ontheoretical grounds, the wind is expected to be dominated by Poynting flux associated with the outgoing magnetic field lines anchored on the polar caps of the rotating neutron star, while observations of the Crab Nebula demonstrate that the wind must be dominated by kinetic energy before the termination shock. Here we suggest a new approach to this old problem by studying the distributed currents rather than the singular sheet currents which have been the object of study in most work.We find that, at a distance well in between the light cylinder and the termination shock, current starvation sets in, and electric fields develop along the magnetic field lines which cause the current to dissipate and convert at least half of the Poynting flux into kinetic energy flux in a relatively thin shell. In the shell, at least half of the current closes across the magnetic field lines, the pitch of the spiralling magnetic field lines jumps downward strongly, and the outer pattern of magnetic field lines slips over the inner pattern.
Propagation Effects on Pulsar Radio Emission
Authors: Luo Qinghuan
Published: September 2002

Propagation effects on radio emission within the pulsar magnetosphere are discussed. Widely accepted pulsar models assume that a pulsar magnetosphere is populated with relativistic pair plasmas produced through electron–positron cascades by accelerated primary particles above the polar cap. Any radio emission produced well inside the light cylinder (the radius at which the rotation speed equals c) must propagate through the magnetospheric plasma and be subject to plasma dispersion effects such as refraction and absorption. The observed pulse profiles should contain some features that reflect the influence of the intervening plasma. I discuss particularly the absorption effect due to cyclotron resonance and its possible observational consequences.
Mode Conversion and Reflection of Langmuir Waves in an Inhomogeneous Solar Wind
Authors: Willes A. J. , Cairns Iver H.
Published: September 2002

Beam-driven Langmuir waves in the solar wind are generated just above the electron plasma frequency, which fluctuates in the inhomogeneous solar wind plasma. Consequently, propagating Langmuir waves encounter regions in which the wave frequency is less than the local plasma frequency, where they can be reflected, mode converted to transverse electromagnetic waves, and trapped in density wells. The aim here is to investigate Langmuir wave reflection and mode conversion at a linear density gradient for typical solar wind parameters. It is shown that higher mode conversion efficiencies are possible than previously calculated, but that mode conversion occurs in a smaller region of parameter space. In addition, the possibility of detecting mode conversion with in situ spacecraft Langmuir wave observations is discussed.
The Relativistic Force-free Equation
Authors: Mestel Leon
Published: September 2002

This paper is a preliminary report on ongoing work, in collaboration with Drs S. P. Goodwyn, A. J. Mestel, and G. A. E. Wright. The non-dissipative force-free condition should be a good approximation to describe the electromagnetic field in much of the pulsar magnetosphere, but we may plausibly expect it to break down in singular domains. The detailed properties of the solutions will be affected critically by the choice of equatorial boundary condition beyond the light-cylinder.
Populations of X-ray Binaries and the Dynamical History of their Host Galaxies
Authors: Wu Kinwah
Published: September 2002

The observed luminosity distributions of X-ray sources indicate the presence of several populations of X-ray binaries in the nearby galaxies. Each population has its formation and evolutionary history, depending on the host environment. The features seen in the log N(>S)–log S curves for different types of galaxies and for different galactic components can be reproduced by a birth–death model, in which the lifespans of the binaries are inversely proportional to their X-ray brightness. Conversely, the dynamical history of a galaxy can be inferred from the luminosity distributions of its X-ray binary populations.
Hydromagnetic Structure of a Neutron Star Accreting at Its Polar Caps
Authors: Melatos A. , Phinney E. S.
Published: September 2002

The hydromagnetic structure of a neutron star accreting symmetrically at both magnetic poles is calculated as a function of accreted mass, Ma, starting from a polytropic sphere plus central magnetic dipole (Ma =0) and evolving the configuration through a quasistatic sequence of twodimensional, Grad–Shafranov equilibria as Ma increases. It is found that the accreted material spreads equatorward under its own weight, compressing the magnetic field into a thin boundary layer and burying it everywhere except in a narrow, equatorial belt. The magnetic dipole moment of the star is given by µ=5.2×1024(B0/1012.5G)1.3(Ma/10−8Mʘ yr−1)0.18(Ma/Mʘ)−1.3Gcm3, and the fractional difference between its principal moments of inertia is given by Є=2.1×10−5(B0/1012.5G)0.27(Ma/10−8Myr−1)0.18(Ma/Mʘ)1.7, for Ma in the range 10−5Ma/Mʘ10−1,where B0 is the pre-accretion magnetic field strength, and Ma is the accretion rate.
Binary Star Observations in Selected Instants of Good Seeing
Authors: Davis John , North Julian R.
Published: September 2002

Video recordings of images of binary stars at the focus of a 0.36m telescope have been used to select images recorded in instants of good seeing. The selected images have been analysed to give separations and position angles for the binary systems which are in good agreement with values predicted from previous observations. In these exploratory observations it has been shown that separations of 0.9 arcseconds can be measured with an accuracy of ~2% and position angles to ~1–2 degrees when the average seeing was ~1.3 arcseconds. These observations demonstrated that the diffraction limit of the telescope could be reached when the seeing was a factor of 2–3 greater than it. A binary with three magnitudes difference in the brightness of its components has been measured with comparable accuracy although difficulties are anticipated for binaries with components closer than ~2 arcseconds with this magnitude difference. The limiting magnitude is determined by the need to limit exposure times of individual frames to be comparable with or less than the atmospheric coherence time.
Filamentary Shell Structures from the AAO/UKST Hα Survey
Authors: Walker A. J. , Zealey W. J. , Parker Q. A.
Published: September 2002

Here we present the first results of a search for new optical supernova remnant candidates and other filamentary objects on films produced by the Anglo-Australian Observatory/UK Schmidt Telescope Há Survey. Sixty-one fields, or 26% of the Galactic plane survey fields, have been visually examined. This has resulted in the detection of four newlarge diameter filamentary structures, and the discovery of extensive new optical emission in two previously known optical supernova remnant candidates.
Arbuscular mycorrhizal associations in the southern Simpson Desert
Authors: O'Connor Patrick J. , Smith Sally E. , Smith F. Andrew
Published: September 2002

The plants of the Simpson Desert are adapted to one of the driest regions on
the Australian continent and grow in generally nutrient-poor soils. Surveys
were conducted at three sites in the southern Simpson Desert to determine the
arbuscular mycorrhizal (AM) status of 52 species from 28 families of annual
and perennial plants. Roots from all plants were examined for the presence of
internal and external hyphae, vesicles, arbuscules and coils to determine
presence and extent of mycorrhizal colonisation. Of the plant species
surveyed, 38 (73%) had formed mycorrhizal associations. The AM status
of 47 species is reported for the first time, including of members of the
Frankeniaceae and Myoporaceae families. No correlations were found between
site (dune or interdune) or life form and the number of species forming AM
associations. Two species in the normally non-mycorrhizal Chenopodiaceae,
Salsola kali L. and
Sclerolaena diacantha (Nees.) Benth. had mycorrhiza.
Arbuscules and/or vesicles were observed in the roots of all mycorrhizal
plants except three species, Solanum ellipticum R.Br.,
Gnephosis eriocarpa (F.Muell.) Benth. and
Eremophila longifolia (R.Br.) F.Muell., in which only
coils of hyphae were observed.
The impact of soil disturbance on root development in woodland communities in Western Australia
Authors: Rokich Deanna P. , Meney Kathy A. , Dixon Kingsley W. , Sivasithamparam K.
Published: September 2002

The impact of soil disturbance of the Banksia woodland
soil profile and particularly the effect of different reconstructed soil
profiles (overburden profile, white profile and yellow profile) and soil
ripping within rehabilitation sites, was investigated in terms of root
development and architecture for eight species that are key structural
elements in Banksia woodland. The aim was to determine
the soil environment best suited for root development and architecture likely
to contribute to high seedling survival in post-mined sites.
Root development and architecture differed significantly between native
woodland, and rehabilitation sites. In general, roots were longer in native
woodland with low lateral root production (for all species studied) compared
to rehabilitation sites where the roots were shorter, tended to divide or lose
geotrophy and consisted of numerous laterals. When comparing the different
soil profiles in the rehabilitation sites, the commonly reconstructed profile
of ‘topsoil over overburden’ (overburden profile) was the least
favourable for root development and architecture. Ripping of the soil to 80 cm
depth had a positive effect on root growth.
There were differences between native woodland and rehabilitation sites, in
soil impedance, soil bulk density, soil moisture percentage and organic carbon
content. In general, reconstructed soils in rehabilitation sites have (1) soil
impedance and soil bulk density values likely to seriously impede root
development and architecture, (2) soil moisture percentages higher than those
in undisturbed woodland during all months of monitoring and at most depths
down to 40 cm and (3) lower organic carbon content than native woodland. When
comparing the different soil profiles in rehabilitation sites, the overburden
profile (a) had the highest impedance values, (b) was one of the profiles with
the highest bulk density values and (c) had the highest soil moisture
percentages during most months and at most depths examined. Ripping the soil
decreased soil impedance and soil moisture contents.
The major conclusion from this study is that soil impedance, which influences
water movement, is a key characteristic of soil conditions that are not
conducive to the development of deep penetrating root systems. These deep root
systems may be directly linked to survival.
Soil and rainforest composition in Tasmania: correlations of soil characteristics with canopy composition and growth rates in Nothofagus cunninghamii associations
Authors: Read Jennifer
Published: September 2002

The relationships between soil chemistry and canopy composition and growth
rate were examined in several Nothofagus cunninghamii
rainforest associations. There was considerable variation in the
concentrations of some of the soil nutrients, with c.
40-fold differences in total phosphorus among surface samples (5–15 cm
depth) and 170-fold differences among deep samples (50–60 cm depth).
Principal components analysis with rotated axes indicated that surface
extractable K, total N and loss of ignition (LOI) contributed most to
Component 1. The factors contributing most to Component 2 were total
exchangeable bases, extractable Mg and LOI of the deep samples and surface
extractable Ca. Total phosphorus (surface and deep), pH and surface C: N
contributed most to Component 3. The soils of
N. cunninghamii-dominated forests had significantly
higher pH and total phosphorus than mixed rainforests (rainforest without a
clear dominant species) and a lower C: N ratio than soils of both mixed
rainforests and P. aspleniifolius-dominated rainforests
(P < 0.05). However, no significant differences were
recorded in any soil parameter between the latter two forest types. Factor 3
of the PCA was positively correlated with the abundance of
N. cunninghamii and negatively correlated with abundance
of P. aspleniifolius and E. lucida
(P < 0.05). In addition, the growth rate of
N. cunninghamii was positively correlated with total
phosphorus after removal of high-altitude sites (≥700 m a.s.l.). These
results, together with previous data on comparative growth rates, suggest that
phosphorus has a significant influence on the canopy composition of these
rainforests via its effect on the growth rate of
N. cunninghamii. Concentrations of both total and
available phosphorus were very low on some sites, overlapping the range of
values recorded in button grass plains, heaths and eucalypt forests from other
studies in Tasmania. More comprehensive data are required to allow detailed
comparisons among these vegetation formations. However, the results are
consistent with Jackson’s (1968, 1983) hypothesis that the absence of
rainforest from some low-nutrient soils may be influenced more by fire
frequency (via the interactions among soil nutrients, vegetation and fire)
than directly by soil nutrients.
Can long-distance dispersal be inferred from the New Zealand plant fossil record?
Authors: Pole Mike S.
Published: September 2002

New Zealand is generally thought to have been physically isolated from the
rest of the world for over 60 million years. But physical isolation may not
mean biotic isolation, at least on the time scale of millions of years. Are
New Zealand’s present complement of plants the direct descendants of
what originally rafted from Gondwana? Or has there been total extinction of
this initial flora with replacement through long-distance dispersal (a
complete biotic turnover)? These are two possible extremes which have come
under recent discussion. Can the fossil record be used to decide the relative
importance of the two endpoints, or is it simply too incomplete and too
dependent on factors of chance? This paper suggests two approaches to the
problem—the use of statistics to apply levels of confidence to first
appearances in the fossil record and the analysis of trends based on the
entire palynorecord.
Statistics can suggest that the first appearance of a taxon was after New
Zealand broke away from Gondwana—as long as the first appearance in
the record was not due to an increase in biomass from an initially rare state.
Two observations can be drawn from the overall palynorecord that are
independent of changes in biomass:
(1) The first appearance of palynotaxa common to both Australia and New
Zealand is decidedly non-random. Most taxa occur first in Australia. This
suggests a bias in air or water transport from west to east.
(2) The percentage of endemic palynospecies in New Zealand shows no simple
correlation with the time New Zealand drifted into isolation.
The conifer macrorecord also hints at complete turnover since the Cretaceous.
Gondwana, vicariance biogeography and the New York School revisited
Authors: Nelson G. , Ladiges P. Y.
Published: September 2002

The many methods of biogeographic analysis proposed in recent years generate
artefactual results that impede understanding, discovery and progress.
Eliminating geographic paralogy from data reduces or eliminates artefactual
interpretation. Recent cladistic studies of extant
Nothofagus agree in showing only three informative nodes
relevant to intercontinental relationships. In cladistic representations of
global distributions, Gondwana is at or near the base of the geographically
informative nodes, which force Gondwana to appear as a centre of origin of
modern life in general. Centres of origin are artefacts of comparison based on
geographically uninformative and paralogous nodes. Postmodern revivals of
dispersalism fail to acknowledge, explain, avoid, learn from and improve on
the artefactual centres of origin of the 20th century dispersalism, as
represented particularly by the New York School: W. D. Matthew
(1871–1930), K. P. Schmidt (1890–1957), G. G. Simpson
(1902–1984), P. J. Darlington, Jr (1904–1983) and G. S.
Myers (1905–1985).
Altitudinal trends in photosynthetic rate and leaf characteristics of Miscanthus populations from central Taiwan
Authors: Kao Wen-Yuan , Chang Kuo-Wei
Published: September 2002

Leaf photosynthetic rate and leaf characteristics including chlorophyll
content, leaf width, leaf mass per area (LMA), stomatal density and the
dimensions of guard cells were measured in C 4
Miscanthus spp. growing along an altitudinal gradient
from 390 to 2700 m in central Taiwan. The main objective of this study was to
understand if morphological and physiological variation occur in leaves of the
C 4 plants growing along the altitudinal gradient.
Measurements were taken during the growing season, May, July and September, of
1997. Photosynthetic rate, leaf width and guard cell dimensions decreased
while LMA and stomatal density increased with altitude. The pattern of
continuous variation in the analysed parameters suggests that it is related to
some underlying environmental factors (mainly air temperature and CO
2 concentration) associated with changing altitude.
Rate and timing of vegetative growth, flowering and fruit development of Persoonia virgata (Proteaceae)
Authors: Bauer L. M. , Johnston M. E. , Williams R. R.
Published: September 2002

Persoonia virgata R.Br. is harvested from the wild in
both its vegetative and flowering stages. There has been no systematic study
published on the annual growth cycle and anecdotal reports are conflicting.
The growth pattern, flowering and fruit development of
P. virgata in its natural habitat was recorded monthly
for two consecutive years. The main growth period occurred in late
spring–mid-autumn (November–May) when the shrubs were producing
little or no fruit. Very few open flowers were observed at the site over the 2
years, with only 6.7 and 12.7% of stems bearing open flowers in January
and February 1996, respectively. A second study of flowering on
container-grown shrubs showed that individual flowers were open for only
2–5 days, with individual stems taking 3–8.5 weeks to complete
flowering. The main fruit growth period occurred from May to September, and in
June and July 1996 the total fruit set per stem was 41.6 and 36.1%,
respectively. The fruit took at least 6 months to develop during which
vegetative growth was minimal. The harvesting of plants in the flowering or
fruiting stages removes the annual seed crop, which may reduce regeneration of
this obligate seed regenerator and threaten its survival after fire.
Reproductive and ecophysiological attributes of the rare Gardenia actinocarpa (Rubiaceae) compared with its common co-occurring congener, G. ovularis
Authors: Osunkoya Olusegun O. , Swanborough Perry W.
Published: September 2002

Gardenia actinocarpa Puttock (rare) and
G. ovularis F.M.Bailey (widespread) are closely related
co-occurring shrub–small trees of rainforests of far north Queensland,
Australia.Gardenia actinocarpa is endemic to alluvial
lowlands along Noah–Oliver Creeks of Cape Tribulation,
whereasG. ovularis spans a wider habitat and occurs on a
range of substrates and altitudes. The rare
G. actinocarpa is cryptically and strictly dioecious,
with a longer reproductive period (9 months) and a low fecundity (1.77 fruits
per female tree). In contrast, G. ovularis, although
also dioecious, has a shorter reproductive phase (4 months) and produces more
fruits (35.76 fruits per female tree), some of which may occur in the absence
of fertilisation (apomixis). Under different regimes of photosynthetically
active radiation (PAR), seed germination percentages and patterns were similar
(70–90%) in the two species, although at 37% PAR G.
actinocarpa has lower germination (55–68%).
The rare G. actinocarpa loses seed viability very
rapidly (G. ovularis (37%).
Gardenia actinocarpa grows and survives in both closed
forest understorey and in small gaps, while G. ovularis
prefers light gaps (both small and large). Net photosynthetic measurements of
seedlings grown at 2.5 and 37% PAR suggest that the physiological
performance of G. actinocarpa is not inferior to that of
G. ovularis, although the latter exhibits greater
plasticity. In a density-dependent seedling growth experiment,
G. actinocarpa, surprisingly, has a superior competitive
ability. Thus, the rarity ofG. actinocarpa may be a
result of limited fecundity, reduced seed dispersal ability and lack of soil
seed-banks rather than inferior vegetative and ecophysiological traits.
Production and consumption of nectar in flowers of Tasmanian leatherwood, Eucryphia lucida (Eucryphiaceae)
Authors: Mallick Stephen A.
Published: September 2002

The production and consumption of nectar by
Eucryphia lucida (Labill.) flowers were studied at two
locations in Tasmania. Flowers secreted a relatively dilute nectar
(concentration 20% wt/wt). Nectar was produced continuously,
although secretion rates were substantially lower at night. At dawn, flowers
contained a standing crop of liquid nectar, which was rapidly dehydrated on
warm days. Due to continuous daytime production, small amounts of concentrated
nectar were always present in flowers; this nectar was highly attractive to
insects and flowers received multiple insect visitors. Nectar production was
independent of temperature and humidity and was not affected by local shading.
Flowers protected from insect visitors and in which nectar was allowed to
accumulate showed no evidence of reabsorption of sugar. Patterns of nectar
production in E. lucida are interpreted in terms of
maximising the frequency of insect visits to flowers in a cool temperate
environment in which weather conditions during anthesis can be highly
variable.
Are plants growing close to the floors of tropical forests exposed to markedly elevated concentrations of carbon dioxide?
Authors: Holtum J. A. M. , Winter K.
Published: September 2002

The study tested the frequently expressed perception that the concentration of
CO2 in the vicinity of establishing seedlings growing
close to tropical forest floors is generally high. CO2
concentration was monitored 10 cm from the forest floor over several days
during wet and dry seasons at three Panamanian lowland and montane tropical
forest sites. Air was sampled at a low flow rate with a peristaltic pump to
minimise contamination by air from other strata. The average
CO2 concentrations observed during the dry and wet
seasons were 387 and 423 L CO2
L–1 air, respectively, a relatively small
enrichment compared with the above-canopy CO2
concentrations. The highest CO2 concentration recorded
at 10 cm was 494 L L–1. The generally modest
levels of enrichment—far below concentrations required to saturate
photosynthesis—were nonetheless sufficient to significantly increase the
rates of CO2 uptake relative to above-canopy
CO2 concentrations by shade-grown seedlings of
Piper cordulatum C. DC., an understorey shrub and
Virola surinamensis(Rol.) Warb., a late successional
tree species.
The long-term ability of phosphite to control Phytophthora cinnamomi in two native plant communities of Western Australia
Authors: Tynan K. M. , Wilkinson C. J. , Holmes J. M. , Dell B. , Colquhoun I. J. , McComb J. A. , Hardy G. E. St J.
Published: September 2002

This study examined the ability of foliar applications of the fungicide
phosphite to contain colonisation of
Phytophthora cinnamomi in a range of plant species
growing in natural plant communities in the northern sandplain and jarrah
(Eucalyptus marginata) forest of south-western
Australia. Wound inoculation of plant stems with
P. cinnamomi was used to determine the efficacy of
phosphite over time after application. Colonisation by
P. cinnamomi was reduced for 5–24 months after
phosphite was applied, depending on the concentration of phosphite used, plant
species treated and the time of phosphite application. Plant species within
and between plant communities varied considerably in their ability to take up
and retain phosphite in inoculated stems and in the in planta concentrations
of phosphite required to contain P. cinnamomi. As spray
application rates of phosphite increased from 5 to 20 g
L–1, stem tissue concentrations increased, as did
the ability of a plant species to contain P. cinnamomi.
However, at application rates of phosphite above 5 g
L–1 phytotoxicity symptoms were obvious in most
species, with some plants being killed. So, despite 10 and 20 g
L–1 of phosphite being more effective and
persistent in controlling P. cinnamomi, these rates are
not recommended for application to the plant species studied. The results of
this study indicate that foliar application of phosphite has considerable
potential in reducing the impact of P. cinnamomi in
native plant communities in the short-term. However, in order to maintain
adequate control, phosphite should be sprayed every 6–12 months,
depending on the species and/or plant community.
Effects of cytokinin-auxin combinations on cell arrangement in the basal stems and tropane alkaloid production in cultured non-rooted shoots of Duboisia myoporoides
Authors: Khanam Nurussaba , Khoo Cheang , Khan Abdul G.
Published: September 2002

In non-rooted shoots regenerated from calluses induced with nine different
cyokinin–auxin combinations, basal stem elongation and the cell
arrangement in the basal stem sections depended on the cytokinin–auxin
combinations used at the callus-induction stage. Elongated basal stems like
seedling and large cells in the secondary xylem were found in the non-rooted
shoots regenerated from calluses induced with benzyladenine (BA) 10 µM
+ naphthaleneacetic acid (NAA) 1 µM and BA 10 µM
+ indole-3-butyric acid (IBA) 0.1 µM. Tropane alkaloids were
detected in these shoots. The peak hyoscyamine and scopolamine contents were
38.5 × 10 –4 and 6.5 × 10
–4 % dry weight, respectively. Various
patterns of vascular regions without large cells in the secondary xylem were
found in the basal stem sections of the non-rooted shoots regenerated from
calluses induced with the other cytokinin–auxin combinations. No tropane
alkaloids were detected in these shoots.
Development of disease caused by Phytophthora cinnamomi in mature Xanthorrhoea australis
Authors: Aberton M. J. , Wilson B. A. , Hill J. , Cahill D. M.
Published: September 2002

Over the past 30 years, heathland and open forest communities in south-eastern
Australia dominated by Xanthorrhoea australis R.Br. have
been severely affected by disease caused by
Phytophthora cinnamomi Rands. The disease has caused a
sharp decline in numbers of individuals within populations of
X. australis; however, the etiology of the disease is
unclear. The characteristics and disease symptoms induced by
P. cinnamomi were analysed within nine mature
X. australis plants that had been removed from the
field. Seven plants showed typical disease symptoms that ranged from chlorotic
leaves through to plant death. Plants showing disease symptoms had different
numbers of infected roots, ranging from 0% in one dead plant,
40% infected roots in a plant showing yellowing of leaf tips and 67 and
86%, respectively, in two plants with severe chlorosis. There was
variation within the roots, with some infected close to the stem while others
were infected at more distal regions. Within stems of all plants,
P. cinnamomi was difficult to isolate but was found in
the desmium and stem apex and was associated with massive lesions within the
central area of the stem. The symptoms of disease in
X. australis are caused by a combination of damage to
tissues of the roots and stem that may lead to a reduction in water and
mineral transport throughout the plant.
A method of estimating stomatal density in Paspalum notatum (Poaceae)
Authors: Santos Marisa , de Oliveira Paulo Luiz , Miguens Flávio Costa
Published: September 2002

Stomatal density was recorded on adaxial and abaxial leaf surfaces of
Paspalum notatum var.
notatum FlÜgge. As in other Poaceae, stomata
observation and counting were very difficult from a frontal view because of
the morphology of the P. notatum (bahiagrass) leaves:
the leaf blade is extremely sinuous on its adaxial surface and trichomes or
papillae can hide the stomata. The stomatal number per unit area was
determined on both adaxial and abaxial leaf surfaces by using two methods:
frontal view and leaf blade cross-section. From these results, we concluded
that the use of a cross-section to determine the stomatal density in these
plants is the most suitable. Such a method can be used for any plants with
stomata organised in longitudinal rows and having a morphological character
that makes observation of the stomata difficult.