bluuebunny/crossref_metadata_2025 huggingface dataset:
A Radio and Optical Study of the Active Young F Star HR 1817 (=HD 35850)
Authors: Budding E. , Carter B. D. , Mengel M. W. , Slee O. B. , Donati J.-F.
Published: March 2003

This paper presents the results of a multiwavelength observational study of the active young F-type star HR 1817. The star was monitored at 4.80 and 8.64 GHz over 2 × 12 h allocations with the Australia Telescope Compact Array on 8 and 9 December, 2000. The Anglo-Australian Telescope was used for simultaneous optical spectropolarimetry during a 2 h period on 9 December.

The low levels of observed radio emission have characteristics that are similar to those seen in other active stars, and a gyrosynchrotron mechanism is proposed to explain them; this is supported by the relatively low fractions of circular polarisation measured in HR 1817.

Comparison of the emissions from 4.80 and 8.64 GHz shows a very strong cross-correlation peak, indicative of a common origin, although the shift of this peak indicates that 8.64 GHz variations tend to precede those at 4.80 GHz by, typically, ˜20 min.

The optical spectropolarimetry reveals polarisation signals characteristic of surface magnetic fields, with profile changes indicating a complex dynamo-type magnetic topology is present on the star. This result makes HR 1817 the star with the earliest spectral type on which dynamo magnetic fields have been detected directly up to now.
The Use of Online Discussion Forums as a Learning and Teaching Tool in Astronomy
Authors: Mazzolini Margaret
Published: March 2003

Swinburne Astronomy Online (SAO) is an online graduate program in astronomy intended particularly for amateur astronomers, science communicators and educators. SAO emphasises the development of conceptual understanding and good communication skills in astronomy. The use of asynchronous discussion forums is a central feature of SAO. These 'online tutorials' were introduced partly with the intention of breaking down the isolation of distance education, but mainly to provide a venue where students could deepen their conceptual understanding of astronomy and hone their science communication skills while discussing course material with other students and instructors.

In this project aspects of the use of discussion forums in SAO were investigated, with comparisons made between average marks awarded for discussion forum contributions and those awarded for other assessment tasks, plus analysis of the rate at which students post to the forums, and an investigation of whether gender makes a significant difference to participation rate and assessment results. Responses by students to surveys that probe their ability to express themselves and communicate with classmates in this online form of distance education are discussed. Finally, possible implications for the use of discussion forums as a supplement to face-to-face teaching in astronomy are explored.
Asexual propagation of Stackhousia tryonii: a step towards restoration of a rare metallophyte
Authors: Bhatia Naveen P. , Bhatia Poonam , Ashwath Nanjappa
Published: March 2003

Stackhousia tryonii Bailey is a rare, serpentine-endemic herb, with potential for use in phytoremediation and/or phytomining. This study evaluates the use of herbaceous heel cuttings to propagate S. tryonii on three rooting media [sand, Medium I; a commercial nursery mix, Medium II; and sand : peat moss : perlite (2 : 2 : 1; v/v), Medium III] following the application of plant growth hormones, viz. indole-3-butyric acid and naphthalene acetic acid (both as pure and commercial formulations, viz. Clonex Gel-green, Gel-purple and Gel-red), and honey. Cutting survival, rooting percentage, the number of primary and secondary roots produced, the length of the longest root and the total root length were evaluated after 10 weeks. Results show that there was a positive (P < 0.001) influence of plant growth regulator treatments on cuttings' survival. Medium III failed to support survival of cuttings. Percentage rooting (as a proportion of original number of cuttings) was 10–30% higher in Medium I than in Medium II. Cuttings treated with Clonex Gel-red, IBA at 1000 ppm and NAA at 250 ppm had 60–70% higher percentage rooting in Medium�I than in Medium II. Total number of primary roots per rooted cuttings was significantly (P�<�0.05) higher in Medium I with Clonex Gel-red and NAA at 1000 ppm. Treatments did not have significant effects on the number of secondary roots, the length of the longest root and the total root length. However, values for these parameters were significantly (P < 0.05) higher in Medium I than in Medium II. We conclude that cuttings from mature plants of S. tryonii could be used effectively to multiply S. tryonii, particularly with sand as rooting medium and prior to treatment of cuttings with Clonex Gel-red.
The wound pathogen Chondrostereum purpureum, its history and incidence on trees in North America
Authors: Setliff E. C.
Published: March 2003

Since Percival's inoculation studies in 1902 with the wound pathogen Chondrostereum purpureum (Pers.�:�Fr.) Pouz. on plum trees in England, this fungus has become well known as the cause of silver-leaf disease of rosaceous fruit trees. However, its pathological impact on forest trees has been little studied and appreciated. Therefore, the question is raised about the pathogenic role and incidence of C. purpureum on other trees in damaged forests. A survey of 561 collections of this fungus in herbaria of Canada and the United States found that the highest incidence occurred in the Betulaceae (45%), especially Betula (27%) and Alnus (15%). The second-most favoured host family was the Salicaceae (20%) with a 15 and 5% occurrence on Populus and Salix, respectively. The third-most favoured substrate was apparently the Rosaceae at 11%, but this reflected a bias of agricultural research in orchards. A 6% incidence was found in the Fagaceae, 4% in the Aceraceae and 3% in the Ulmaceae. From 1 to 3% of the collections occurred for each of the Cornaceae, Juglandaceae, Magnoliaceae and Pinaceae. Incidences <1% were indicated for each of the Aquifoliaceae, Caprifoliaceae, Cupressaceae, Grossulariaceae, Hamamelidaceae, Hippocastanaceae, Myrtaceae, Oleaceae, Rhamnaceae and Tiliaceae. The host survey data indicate that C.�purpureum is an important pathogen with epidemic potential in forest trees, especially species in the Betulaceae and Salicaceae. The silvering symptom is inconspicuous in birch and other non-rosaceous trees. Forests with greatest vulnerability are those subjected (1) to physical forces that cause stem injuries to susceptible trees, (2) to environmental conditions conducive for infection and (3) to high levels of basidiospore inoculum from fruiting bodies on hardwood slash that result from timber harvesting and storm damage. Silver-leaf is an important fungal disease of many tree species in North America and is largely responsible for the birch dieback in North American forests. Control data from several mycoherbicide experiments support this conclusion.
Mixed mating in Banksia media
Authors: Wooller S. J. , Wooller R. D.
Published: March 2003

Differential exclusion of vertebrates and invertebrates from the inflorescences of Banksia media R.Br. on the south coast of Western Australia showed the species to be partially self-compatible. Access by invertebrates increased fruit set and additional access by vertebrates resulted in even greater fruit set. Honeyeater birds and marsupial nectarivores were abundant and widespread in the study area and most carried the pollen of Banksia media while it flowered. However, although B. media had the floral characteristics attributed to vertebrate pollination, self-pollination and pollination by insects clearly also play major roles in seed production. Banksia media regenerates solely from seed released after fire and we suggest that its mixed mating strategy is a compromise between inbreeding depression and risk of elimination from areas prone to occasional fires.
Cytogenetics and reproductive biology of mangroves in Rhizophoraceae
Authors: Tyagi Anand Prakash
Published: March 2003

Three mangrove species, Bruguiera gymnorrhiza (L.) Lam., Rhizophora samoensis (Hochr.) Salvoza, Rhizophora stylosa Griff. and a putative hybrid Rhizophora ×selala (Salvoza) between the latter two species were studied for their cytogenetics and reproductive biology. Although chromosome numbers in all four taxa were confirmed as 2n = 36, the size of the chromosomes was slightly larger in genus Bruguiera. Regular chromosome pairing was observed in the three species; however, in the hybrid meiosis was very irregular. Pollen viability in all three species was very high (>80%); however, in the hybrid pollen viability was <10%. This could be due to non-homology in the chromosomes of the two parental species and irregular meiosis in the hybrid. Due to highly irregular meiosis in the hybrid and uneven distribution of chromosomes to the two poles, most of the pollen was non-viable. All three species were fully self-compatible. Between B. gymnorrhiza and the two Rhizophora species, pollen in crosses and reciprocal crosses failed to germinate, indicating cross-incompatibility between these two genera. Partial cross-compatibility was recorded between R. samoensis and R. stylosa. In many crosses, pollen tubes were observed growing freely up to the base of the style. This also accords with occasional crossing of these species in nature. However, due to only partial homology in the chromosomes of these two species, the hybrids produced are always sterile. Similarly, cross-compatibility between the hybrid and its two parental species was also partial. This could be attributed to allelic differences between the two species and their hybrid and also to physiological and/or chemical hindrance of the pollen-tube growth through the stylar tissue.
A rapid and accurate visual assessment of nectar production can reveal patterns of temporal variation in Banksia ericifolia (Proteaceae)
Authors: Lloyd Samantha , Ayre David J. , Whelan Rob. J.
Published: March 2003

Banksia species are conspicuous in Australian heathlands and woodlands and provide a major source of nectar for a range of vertebrate and invertebrate pollinators. However, nectar production by Banksia is difficult to measure because inflorescences comprise large numbers (hundreds to thousands) of tiny flowers. Our aim was to quantify variation in nectar volume among B. ericifolia L.f. plants, but existing techniques were too time consuming or required destructive sampling of inflorescences. We estimated nectar volume by counting the number and estimating the size of nectar drops on a sample of flowers on each inflorescence. Our technique was fast (10 min per inflorescence) and a highly significant positive relationship was found between visual estimations and direct measures (capillary tubes and micropipettes) of nectar volume (r = 0.92; P ≤ 0.0001). This technique thus provides an alternative to current techniques for measuring nectar volume in plants that have large numbers of small flowers arranged in dense inflorescences. By using this technique, we found significant variation among days in nectar volume produced by each of five B. ericifolia plants (P ≤ 0.02). Furthermore, days of high and low nectar production were synchronised among plants. We concluded that the temporal variation found may be the result of fluctuations in environmental variables, rather than the age of an inflorescence. Indeed, nectar volume was found to be significantly correlated with a range of weather variables including daily maximum temperature (°C), precipitation (mm), wind speed (km h–1) and relative humidity (%). However, larger-scale and longer-term studies are needed to adequately examine any relationship between environmental variables and nectar production.
Comparison of green leaf eucalypt spectra using spectral decomposition
Authors: Coops Nicholas , Dury Stephen , Smith Marie-Louise , Martin Mary , Ollinger Scott
Published: March 2003

Vegetation function and dynamics are key parameters in terrestrial carbon-cycle models. The strong linkages between biochemical constituents in foliage with photosynthetic capacity and ecosystem productivity makes the development of methods to characterise patterns of foliage biochemistry a potentially powerful approach for estimating leaf function and carbon fluxes at a variety of scales. Eucalypt foliage spectra were obtained over a range of species and locations in southern New South Wales, covering a significant productivity and climatic gradient. We applied a spectral decomposition technique, based on multivariate factor analysis, which allows inter-correlations of underlying factors affecting a set of variables to be assessed. A small number of factors capture virtually all of the variation observed in the foliage spectra and each factor contains significant information relating to species and plot variation over the region. Factor analysis indicated that key chlorophyll, nitrogen, protein and water absorption features could be accurately identified across the spectra. In addition, significant correlations existed between factor loadings and environmental data of the region, including mean annual rainfall and a soil fertility index.
Foliar mineral content of Nothofagus species on ultramafic soils in New Caledonia and non-ultramafic soils in Papua New Guinea
Authors: Read Jennifer , Ferris John M. , Jaffré Tanguy
Published: March 2003

Nothofagus species dominate the upper canopy of some New Caledonian rainforests on ultramafic soils. The characteristics of Nothofagus that facilitate its dominance of these forests are uncertain, but may include a superior capacity to resist the severe soil conditions. In this study, we compared foliar concentrations of macronutrients and heavy metals of Nothofagus species from ultramafic soils in New Caledonia with those from non-ultramafic soils in New Guinea.
The concentrations of N and P were significantly lower (4–5-fold difference) and Fe, Cr and Ni significantly higher (140–600-fold difference) in the New Caledonian soils than in the New Guinean soils. The magnitude of difference between the two regions in mean foliar mineral concentrations was considerably less. Analysis of the full leaf data set indicated significant differences between the five New Caledonian and five New Guinea species only in P (c. 2.5-fold higher in New Guinean species) and Cr (c. 6-fold higher in New Caledonian species). The absence of significant differences between regions for most foliar elements is associated with leaf : soil ratios (foliar concentration : soil concentration) that show negative correlations with soil mineral-element concentrations. The highest leaf : soil ratios were recorded in New Caledonian species in K and Ca : Mg. The lowest ratios were recorded in the New Caledonian species in Cr, Ni and Fe. There is no evidence of accumulation of heavy metals in the New Caledonian species, with foliar concentrations similar to those of other New Caledonian species growing on non-ultramafic soils. Instead, the limited evidence suggests they are 'excluders'. In general, the New Caledonian Nothofagus species appear to have relatively low foliar concentrations of macronutrients compared with other New Caledonian rainforest species, suggesting that canopy dominance may be in part due to high nutrient efficiency in terms of growth rate per unit nutrient uptake.
Occurrence and distribution of native and introduced C4 grasses in Tasmania
Authors: Hovenden Mark J. , Morris Dennis I.
Published: March 2003

Of the 137 species of grass considered native to Tasmania, only eight use the C4 photosynthetic pathway. There are also approximately 137 grass species considered as introduced to Tasmania and 21% of these are C4. In total, there are 41 species from 20 genera of C4 grass recorded from Tasmania. Many of the introduced C4 species have a very limited distribution, however, and are generally confined to urban areas and along roadsides. Overall, Tasmania has fewer C4 grasses than would be expected from climate alone and few of the C4 grass species are widely distributed or abundant. However, the proportion of grasses recorded from Tasmania that use the C4 pathway has been increasing for the past century and is still increasing. General distribution and habitat notes are provided for all C4 grasses known to be native or naturalised in Tasmania.
Comparative morphology of Cladopus (including Torrenticola, Podostemaceae) from East Asia to north-eastern Australia
Authors: Rutishauser Rolf , Pfeifer Evelin
Published: March 2003

Cladopus (with 12 or less species) is an Asian and Australian genus of Podostemaceae–Podostemoideae. They are haptophytes that grow in rivers. The developmental morphology and anatomy of Cladopus austro-osumiensis Y.Kadono & N.Usui, C. austrosatsumensis Koidzumi, C. chinensis Chao, C. japonicus Imamura and C. queenslandicus [Domin] C.D.K. Cook & Rutish. (syn. Torrenticola queenslandica [Domin] Domin ex Steenis) are studied by scanning electron microscope and microtome. The architecture of the examined species fits with the bauplan known from other Asian Podostemoideae. Rosulate shoots arise in zigzag patterns or as opposite pairs from narrow or broad green ribbons which may be interpreted as adhesive creeping roots. Cladopus is the only podostemaceous genus known with both endogenous and exogenous lateral roots along the mother root. Exogenous lobes (which may develop into daughter roots) are next to the sites of root-borne shoots which, finally, give rise to terminal flowers. Cladopus species have the following features (synapomorphies) in common: (1) leaves on older and reproductive shoots with one or two median, long filaments (caducous) and 1–4 lateral short lobes (persistent) on either side of the leaf, which are called stipules; (2) spathella (i.e. mantle-like flower cover) with an apical two-tipped papilla; (3) spathella splitting more or less circumscissilely; (4) capsules globose or nearly so, smooth or with three faint ribs per valve.
Effect of biotic factors on the isolation of Lupinus albus protoplasts
Authors: Sinha Anupam , Wetten Andrew C. , Caligari P. D. S.
Published: March 2003

Several tissue types of Lupinus albus L. were investigated as sources for the isolation of protoplasts. Cotyledons from in vitro seedlings were found to yield the highest number of protoplasts compared with leaves, hypocotyls and roots. A combination of the protoplast isolation enzymes, cellulase and Pectolyase Y23, was capable of releasing the highest number of protoplasts compared with a combination of cellulase and Macerase. Protoplast yield increased with increasing cotyledon age but was accompanied by a progressive decline in protoplast viability. The optimal combination of protoplast yield and viability occurred when the protoplasts were isolated from 14- to 18-day-old cotyledons. The ratio between the volume of enzyme solution and the tissue biomass did not affect the protoplast production significantly. This is the first report of the isolation of protoplasts from a lupin cotyledon and, following the procedure described in this paper, an average yield of 1.2 × 106 protoplasts per gram of fresh tissue was obtainable.
A reassessment of tribal affinities of the enigmatic genera Printzia and Isoetopsis (Asteraceae), based on three chloroplast sequences
Authors: Bayer Randall J. , Cross Edward W.
Published: March 2003

The tribal affinities of two dubiously placed genera of the Asteraceae, Printzia and Isoetopsis, were assessed by using three chloroplast DNA sequences, the trnL/F spacer, the trnL intron and the matK coding region. The outgroup was represented by two species of the tribe Barnadesieae, whereas one to six genera (43 species including Printzia and Isoetopsis) of the tribes of the Asteroideae [Anthemideae (six genera), Astereae (five) Calenduleae (two), Gnaphalieae (six), Heliantheae s.l. (five), Inuleae s.str. (three), Plucheeae (two), Senecioneae (four)] and Cichorioideae [Arctotideae (one), Cardueae (two), Lactuceae (two), Liabeae (one), Mutisieae (one), Vernonieae (one)] were chosen as the ingroup. Phylogenetic analysis indicates that both Printzia and Isoetopsis have a strong affinity with members of the tribe Astereae. At some point in their taxonomic history, both genera had been placed in this tribe and there are good morphological and chemical characters that justify this placement.
Reproductive ecology of the Australian herb Trachymene incisa subsp.incisa (Apiaceae)
Authors: Davila Yvonne C. , Wardle Glenda M.
Published: March 2003

Within the Apiaceae, subtle variation in reproductive characters such as dichogamy, pollinator specificity and umbel density may cause cryptic specialisation and be responsible for the diversity of life histories and gender expression in the family. To address the paucity of information for Australian species we investigated the reproductive ecology of the native perennial herb, Trachymene incisa Rudge subsp. incisa. T. incisa exhibits protandry within flowers and umbels; however, an overlap of 3 days in male and female phases among umbels of consecutive orders permits geitonogamous pollination. There are 72 ± 2.0 (n = 74) white flowers per umbel and nectar is presented during the male and female phases. Apis mellifera appears to be the main diurnal pollinator. The pollen : ovule ratio is 1902 : 1, indicating that T. incisa is a facultatively xenogamous species. The long phase of pollen presentation and the low natural seed set of about 45% implies that many flowers are functioning as pollen donors only. Controlled pollination experiments showed that self-pollen led to lower seed set than cross, open and supplemental applications. Early and late-produced cohorts differed in days to emergence but not in seed mass or final percentage emergence.
Sexual and apomictic seed development in the vulnerable grass Bothriochloa biloba
Authors: Yu Ping , Prakash N. , Whalley R. D. B.
Published: March 2003

Embryological investigations on three populations of the vulnerable grass species Bothriochloa biloba point to a complex reproductive system involving both sexual and apomictic mechanisms. The apomictic mode in this species is far more complicated than has been reported earlier in the genus. It includes non-recurrent parthenogenesis and pseudogamy in the sexual embryo sac, as well as recurrent apospory and adventive embryony from somatic cells. Furthermore, multiple aposporous embryo sacs occur that are not limited to the typical Hieracium and Panicum types. Evidence from bagging individual inflorescences and pollination of dissected gynoecia indicated that sexually reproducing florets were self-compatible. Both diploid and tetraploid plants were found in three populations, and one population had triploid and hexaploid plants as well.
Chromosome numbers in Byblidaceae
Authors: Conran John G. , Houben Andreas , Lowrie Allen
Published: March 2003

Cytological studies carried out on the six species of Byblis (Byblidaceae) support the recent separation of taxa from within the Byblis liniflora Salisb. complex, as well as confirming the previously reported numbers of 2n = 18 for B. gigantea s.str. and 2n = 32 for B. liniflora s.str. Byblis sp. nov. aff. gigantea also has a chromosome number of 2n = 18, whereas B. filifolia Planch., B. rorida Lowrie & Conran and B. aquatica Lowrie & Conran have counts of 2n = 16. This gives base counts of x = 8 for the B. liniflora complex and x = 9 for the B. gigantea complex, with B. liniflora as a tetraploid.
Changes in photosynthesis during leaf expansion in Corymbia gummifera
Authors: Choinski Jr J. S. , Ralph P. , Eamus D.
Published: March 2003

Growth, pigment levels and various photosynthesis parameters were measured in expanding leaves of Corymbia gummifera (Solander ex Gaertner) Hochreutiner. C. gummifera trees were studied growing in sandstone plateau woodland communities in Royal National Park, New South Wales, in a recently burned open habitat. Young leaves (horizontally oriented to maximise light exposure) were found to be conspicuously red until they reached approximately 75% of their full size. As the leaves expanded, anthocyanin content declined and chlorophyll levels proportionately increased. Young red leaves showed net negative carbon assimilation rates, although CO2 assimilation rate, transpiration rate, stomatal conductance, actual quantum yield of PSII (ΦPSII) and apparent electron transport rate (ETR) all increased in a similar pattern as the leaves expanded. Measurements of maximum quantum yield of dark-adapted leaves (Fv/Fm) were also correlated with leaf area. Younger leaves had lower Fv/Fm ratios than did mature leaves, whether measured at midday or 2 h after sunset, indicating that young leaves exhibited some degree of chronic photoinhibition. It is concluded that C. gummifera exhibits a transient red pattern of anthocyanin expression and that photosynthesis is limited in young leaves because of low stomatal conductance, low chlorophyll content, immature chloroplasts and an attenuation of light caused by anthocyanins.
Flowering, seed dispersal, seed predation and seedling recruitment in two pyrogenic flowering resprouters
Authors: Denham Andrew J. , Auld Tony D.
Published: March 2003

A few resprouting plants in fire-prone environments have no local seed bank (soil or canopy) when a fire occurs. These species rely on post-fire flowering and the production of non-dormant seeds to exploit favourable post-fire establishment and growth conditions. For two such pyrogenic flowering species (Doryanthes excelsa Correa and Telopea speciosissima (Smith) R.Br.), we examined the timing of seed release, patterns of fruit production, seed dispersal, seed predation and seedling establishment following a fire in the Sydney region of south-eastern Australia. Both species took some 19 months after the fire to flower and the first seeds were released 2 years after the fire. D. excelsa flowered and fruited only once after the fire. For T. speciosissima, plants also flowered at least once more in the subsequent 5 years, but produced seed in only the first three post-fire flowering years. Fruit production differed between species, with fruiting individuals of D. excelsa producing fewer infructescences, similar numbers of follicles, but many more seeds per follicle than fruiting individuals of T. speciosissima. Ultimately, D. excelsa produced approximately six times as many seeds per m2 and four times as many seeds per adult in one flowering season than T. speciosissima did after four flowering (three successful fruiting) seasons. Seeds were passively dispersed from fruits borne 3–4 m (D. excelsa) or 1–2 m (T. speciosissima) above the ground. Most seeds were found within 5 m (D. excelsa) or 3 m (T. speciosissima) of parent plants. The primary seed shadow of both species was a poor predictor of the distribution of seedlings, with more seedlings occurring further from the adults than expected from the distribution of seeds. Seed loss to predators was high in both species in exclusion experiments where mammals had access to clumps of seeds (77–88%). It was variable and generally lower (8–65%) in experiments where seeds were not locally clumped. However, for T. speciosissima, at one site, some 65% of seeds were lost to mammals and invertebrates in these latter experiments. At this site, these losses appeared to influence subsequent recruitment levels, as very low seedling densities were observed.
For both species, germination of seedlings first occurred some 2.5–3 years after the passage of the fire. The percentage of seeds produced to seedlings successfully established was low in D. excelsa (2–3%) and more variable across sites and years in T. speciosissima (0–18%). Resultant post-fire seedling densities of D. excelsa (two sites) and T. speciosissima at one site were similar, but they were much lower at the T. speciosissima site that had high levels of seed predation. Both D. excelsa and T. speciosissima are amongst the slowest woody resprouting species to recruit seedlings after fire in south-eastern Australia and lag years behind species with soil or canopy seed banks.
Decomposition rates of coarse woody debris—A review with particular emphasis on Australian tree species
Authors: Mackensen J. , Bauhus J. , Webber E.
Published: March 2003

We reviewed the decay patterns and lifetimes (time to reach 95% mass loss) of coarse woody debris (CWD) on the forest floor. The objectives were to identify the factors influencing the decomposition process of CWD and to provide estimates of lifetimes for CWD from Australian tree species. This information is required for greenhouse accounting of forestry activities and land use change as well as the sustainable management of CWD in forest ecosystems. The analysis of a global data set on decay rates of CWD showed that, in particular, the mean annual temperature was a main driver of decomposition, accounting for 34% of the variation in decay rates. The Q10, the factor by which biological processes accelerate when temperature increases by 10�C, was 2.53. Additional determinants of CWD decay rates were the initial density of wood and the diameter of logs. Median and average lifetimes derived from 184 decay rates were 49 and 92 years, respectively, which is considerably higher than the 10-year default for all litter proposed by the Intergovernmental Panel on Climate Change. The pattern of decay in most cases followed a negative exponential curve. To overcome the paucity of information on decomposition of CWD in Australian forests and woodlands, decay rates for a large number of species were derived from wood durability and decay resistance studies. For native Australian species, lifetimes ranged from 7 years in Eucalyptus regnans to 375 years in E. camaldulensis. The lifetimes for timber durability Classes 1–4 were 54, 39, 26 and 11 years, respectively, below 30� latitude and without the influence of termites. However, the experimental conditions under which durability and decay resistance are commonly determined are substantially different from the situation under which CWD decomposes in the field. These estimates must therefore be regarded as minimum lifetimes for CWD of most species. To determine decay rates of CWD with greater certainty, long-term field experiments in a wide range of ecosystems are required.
Ontogeny of floral organs and morphology of floral apex in Phellodendron amurense (Rutaceae)
Authors: Zhou Qingyuan , Wang Yinzheng , Jin Xiaobai
Published: March 2003

The ontogeny of floral organs and the morphology of floral apex in the dioecious Phellodendron amurense Rupr. were investigated by light microscopy (LM), scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM). Investigations indicated that P. amurense is hermaphroditic in its organisation and a common set of floral organs (sepals, petals, stamens and carpels) arise in all flowers during the early stages of development. Later, selective abortion of gynoecium and androecium occurs resulting in dimorphic unisexual flowers. The carpels in male flower buds become different from those in female flower buds soon after their initiation. The stamens of female flowers are not differentiated into anthers and filaments before abortion. The poorly differentiated carpel of male flowers never develops normal structures. Floral morphological evidence supports that Zanthoxylum, Tetradium and Phellodendron are related to one another in a linear sequence. LSCM revealed some interesting features on the apical meristem surface such as zonal differentiation, a triangular or sectorial cell, radiating cell files and linear rows of anticlinal cell walls fluorescing relatively brightly. The concept of carpel-enhancing meristem in the floral apex is tentatively proposed to account for the different fates of carpel development in male and female flowers in P. amurense.
Effectiveness of three seed-trap designs
Authors: Page M. J. , Newlands L. , Eales J.
Published: March 2003

Vegetation monitoring is essential to evaluate management and assess condition. However, methods that have been used cannot assess the viability of the community or provide indicators of future condition. Seed traps can be used to measure reproductive potential of a vegetation community via seed rain. This study evaluates three different seed-trap designs and compares their effectiveness in terms of the diversity and abundance of seed captured, the presence of seed-predating insects, cost, manufacturing ease and serviceability. Field trials were conducted in open, grassy woodlands in south-western and south-eastern Queensland. The results showed that the tall funnel-trap design was the least effective, while the wet wind trap and pitfall funnel trap proved more effective. On the basis of the results of this study, further investigations are recommended for testing trap performance in different vegetation communities, seed predation in relation to seed production and variation in seed production over time. Seed traps that monitor seed rain are potentially useful in assessing the health and viability of a vegetation community. Used in conjunction with other monitoring methods, they may offer valuable insights about the dynamics of entire communities and/or individual species, and therefore appropriate management strategies.
In vitro uptake of minerals by Gypsophila paniculata and hybrid eucalypts, and relevance to media mineral formulation
Authors: Gribble Karleen , Conroy Jann P. , Holford Paul , Milham Paul J.
Published: March 2003

Despite the importance of mineral nutrition for plantlet growth in vitro, there have been few studies on mineral uptake from growth media or on optimising the media used in tissue culture. As plants in vitro experience abnormal growth conditions and may not possess roots, they may use different mechanisms of mineral uptake than plants growing ex vitro. To examine this possibility, plantlets of Gypsophila paniculata were grown on media in which the K or Ca concentration was varied. Mineral analysis showed a linear relationship between concentrations of K or Ca in the growth medium and plantlet tissues, suggesting uptake is by passive diffusion. However, interactions occurred between K, Ca and Mg uptake; therefore, other mechanisms are also likely to be involved in regulating mineral concentrations in tissue. The study also demonstrated that critical mineral concentrations could be estimated by using tissue-culture systems, as the concentration ranges of K and Ca in vitro correlated well with data for a related species ex vitro. This knowledge of critical concentrations, in conjunction with tissue analysis and ion speciation modelling, can be used to optimise in vitro mineral formulations through cycles of culture, tissue analysis and medium reformulation. To test this proposal, plantlets of Eucalyptus europhylla × grandis were grown on a proprietary medium formulation (SEM) and one modified as a result of tissue analysis (MEM). Plantlets cultured on SEM had chlorotic leaves and serious mineral imbalances. In contrast, plantlets cultured on MEM were not chlorotic, had more uniform growth and a more balanced mineral content. However, modification of mineral concentrations in the culture medium did not always result in similar changes in plant tissues. These differences in the proportions of minerals in the medium and those in the plant indicate that there are interactions between minerals in the medium and/or between minerals and the agar matrix that influence mineral availability and uptake.
Demographic characteristics of mallee pine (Callitris verrucosa) in fire-prone mallee communities of central New South Wales
Authors: Bradstock R. A. , Cohn J. S.
Published: March 2003

Aspects of the demography of Callitris preissii subsp. verrucosa (Cunn. ex. Endl.) J.Garden populations were studied in semi-arid mallee communities situated on sandy soils in central New South Wales. Rates of survival and fecundity were estimated in a range of populations of differing age (year of origin or last fire: 1920, 1957, 1972, 1974 and 1985) that were monitored between 1987 and 1997. Rates of survival of juveniles and adults were high (>0.99 p.a.), although juveniles less than 5 years of age survived at lower rates. Estimated seedbank at the time of first tagging (no. of closed cones per plant) followed an increasing trend with plant age. Density, overstorey, topography and within-age-class site factors had significant effects on stored seedbanks in particular age-classes. There was high interannual variation (1989 v. 1990) in the size of crops of new cones. Trends in seedbank with plant age and seed release rates from tagged cones indicated that the species exhibits strong serotiny. Measurements of litter weight and depth beneath plants from 1920 and 1957 age-classes, indicated relatively low fuel loadings (about 0.2�kg m–2). Bark was sufficiently thick in c. 60-year-old plants to render stems resistant to low-intensity fires. Thus, it is predicted that the probability of propagation of fire in populations >50 years old may decline and that survival of fire in this age range may increase. Given patterns of survivorship, fecundity and seedbank accumulation, populations may decline when fires are relatively frequent (<15-year interval). At longer intervals there is potential for population densities to remain stable or increase, although the nature of variability in sizes of individual seed crops may have a predominant influence on dynamics. The combination of strong serotiny and negative feedback effects of plant populations on their flammability is a paradox, given the likelihood that seedling establishment is tightly keyed to fire.
Spatial distribution of fungal endophyte genotypes in a Woollsia pungens (Ericaceae) root system
Authors: Midgley David J. , Chambers Susan M. , Cairney John W. G.
Published: March 2003

Fungal endophytes were isolated from hair roots of Woollsia pungens Cav. (Muell.) and mapped according to the root portions from which they were isolated. A total of 119 isolates was obtained and restriction fragment length polymorphism (RFLP) analysis of the internal transcribed spacer (ITS) region indicated that the isolate assemblage comprised five RFLP types. ITS sequence comparison revealed that RFLP Types I and II had 99.6–99.8% sequence identity with known ericoid mycorrhizal endophytes from Australian epacrids. The remaining three RFLP types were most similar to non-mycorrhizal ascomycetes. Eighty-five per cent of isolates obtained were of RFLP Type I and these were widespread within the root system. Inter-simple sequence repeat PCR suggested that 94% of RFLP Type I isolates were of a single genotype that was widely distributed within the root system, with the remaining five isolates each representing a different genotype. Apparent spatial dominance of the root system by a single fungal genotype may indicate limited functional diversity in the mycorrhizal endophyte assemblage.
Spectrometric prediction of secondary metabolites and nitrogen in fresh Eucalyptus foliage: towards remote sensing of the nutritional quality of foliage for leaf-eating marsupials
Authors: Ebbers M. J. H. , Wallis I. R. , Dury S. , Floyd R. , Foley W. J.
Published: March 2003

Near-infrared reflectance spectroscopy provides an excellent means of assessing the chemical composition of Eucalyptus foliage but the standard methods of drying and grinding the samples limit the speed at which spectra can be collected and thus are unsuitable for measurements in the field. We investigated whether reliable spectra could be collected from whole fresh and dry leaves of E. melliodora and E. globulus and whether we could predict the concentration of total nitrogen, the volatile terpene, 1,8 cineole and the phenolic antifeedant compound, sideroxylonal A, from these spectra. Water absorbance peaks did not obscure the absorption spectrum of 1,8 cineole and so cineole concentration was readily predicted from spectra of whole, fresh E. melliodora leaves. Similarly, both total nitrogen and sideroxylonal A could be predicted from spectra of fresh leaf in E. melliodora even though water absorption obscured some spectral features. The predictions of cineole and total nitrogen concentration in E. globulus were not as good as those in E. melliodora, possibly due to interference from waxes on the leaf surface of E. globulus juvenile foliage. Overall, these results suggest that certain important ecological attributes of Eucalyptus foliage can be predicted from spectra of whole fresh leaves. Thus, it is feasible to investigate the collection of spectra by portable or airborne spectrophotometry.
Assessing the role of light availability in the regeneration of Araucaria angustifolia (Araucariaceae)
Authors: Duarte L. S. , Dillenburg L. R. , Rosa L. M. G.
Published: March 2003

The role of Brazilian pine (Araucaria angustifolia) in the process of forest succession is a topic of increasing controversy. While some authors consider the species to be pioneer, others consider it to be a climax species in relict temperate forests. We designed a field experiment to assess the role of light availability on the regeneration of A. angustifolia. The following three forests, with contrasting patterns of the species regeneration, were selected at a National Forest in southern Brazil: a Pinus plantation, an Araucaria plantation and a native araucarian forest. We analysed the population structure of Brazilian pine, the vegetation architecture, the light regime experienced by seedlings and the height growth of seedlings and sprouts. Brazilian pine colonisation and regeneration were observed in the Pinus and Araucaria plantations, respectively. No seedlings were found in the native forest. The greatest foliage area index and canopy cover were found in the native forest and the smallest in the Pinus plantation. In spite of the architectural differences, the native forest and the Araucaria plantation had similar light conditions and they both had lower levels of irradiances than the Pinus plantation. Seedlings and sprouts of Brazilian pine were found to occupy spots in the Araucaria plantation with canopy cover greater than the average forest conditions. Considering the similarity of understorey light conditions between the Araucaria plantation and the native forest (where no regeneration was taking place), we concluded that light availability was not limiting the regeneration of the species. Tolerance to shading and other aspects of the species indicate that Brazilian pine is not strictly heliophyllous and pioneer and is able to be established in the forest understorey.
Genetic pollution of native eucalypt gene pools—identifying the risks
Authors: Potts B. M. , Barbour R. C. , Hingston A. B. , Vaillancourt R. E.
Published: March 2003

The contamination of native-eucalypt gene pools via exotic pollen is of concern as (i) pollen dispersal is believed to be much more widespread than seed dispersal, (ii) reproductive barriers are often weak between closely related species, (iii) European settlement has already had a major impact on Australia's eucalypt woodlands and mallee, (iv) there has been a rapid expansion of eucalypt plantations and restoration plantings in Australia and (v) Australia is the custodian of an internationally important genetic resource. Pollen flow between plantation and native eucalypt species has already been reported and implementation of strategies to minimise the risk and consequences of genetic pollution is important if Australian forestry is to be considered sustainable. The risks associated with the introduction of non-native species, provenances and hybrids include direct effects on the gene pool through genetic pollution as well as indirect effects on dependent biodiversity. In many cases, the risk of genetic pollution will be small due to strong barriers to hybridisation between distantly related species, differences in flowering time or poor fitness of hybrids. There is no risk of hybridisation between species from the different major eucalypt genera and/or subgenera (e.g. symphyomyrts, monocalypts, eudesmids, bloodwoods and angophora). The main plantation species are symphyomyrts and within this subgenus, the probability of successful hybridisation generally decreases with increasing taxonomic distance between species. The planting of non-local provenances or improved material within the range of native populations has the potential to have an impact on local gene pools to varying degrees, indicating the requirement for the adoption of management strategies to reduce this risk. Naturally small or remnant populations are at particular risk. A framework for assessment of the risk of genetic pollution is developed herein.
Changes in alpine vegetation related to geomorphological processes and climatic change on Hill One, Southern Range, Tasmania, 1989 - 2000
Authors: Kirkpatrick J. B. , Bridle K. L. , Lynch A. J. J.
Published: March 2003

Photographs of 84 plots in alpine vegetation, largely consisting of fjaeldmark and bolster heath, on Hill One, Southern Range, Tasmania, were taken in both 1989 and 2000 to compare cover characteristics. Between these two observations, vegetation cover declined in the fjaeldmark, largely as a result of erosion. Declines also occurred on the active depositional lobes, through burial of bolster heath. Within the parts of Hill One where vegetation cover was not lost, graminoids decreased and Pterygopappus lawrencei increased in the bolster heath and tall shrubs displaced bolster heath. Thirty-six per cent of the rocks visible in the 1989 photographs had moved by 2000, the mean area of the individual rocks that moved being 95 cm2. Larger rocks were moved on the exposed western slope than on the leeward eastern slope. Analyses of climatic data from nearby stations for 1979–2000 indicated a decline in both precipitation and temperatures and an increase in the frequency of the highest wind speeds, all of which are consistent with the nature of vegetation and geomorphological changes that occurred on the mountain, although a climatic cause is far from proven. Localised cooling and drying, in the two hottest and wettest decades recorded for the globe, emphasises the importance of local data in determining the possible impacts of climatic change on biota.
Water sorption characteristics of seeds of four Western Australian species
Authors: Merritt D. J. , Touchell D. H. , Senaratna T. , Dixon K. W. , Sivasithamparam K.
Published: March 2003

The relationship between storage temperature, relative humidity and seed water content was investigated for four species native to Western Australia: Acacia bivenosa DC., Anigozanthos manglesii D.Don., Banksia ashbyi E.G.Baker and Mesomelaena tetragona (R.Br.) Benth. Water sorption isotherms were constructed at 5, 23 and 50�C and the enthalpy of water sorption was calculated by van�t Hoff analysis. Seeds of three species, A. manglesii, B.�ashbyi and M. tetragona, showed a sigmoidal relationship between seed water content and relative humidity. Intact seeds of Acacia bivenosa maintained a constant water content at temperatures of 23�C or less due to the impermeable seed coat; however, isotherms of scarified seeds were similar in shape to those of the other species at all temperatures. The enthalpy of water sorption ranged from –19 kJ mol–1 for M. tetragona seeds to –29 kJ mol–1 for B. ashbyi seeds and was dependent on water content. However, all species had a maximum sorption strength at 2–6% water content and three regions of water-binding strength were evident. Each of these species has water sorption characteristics consistent with orthodox storage behaviour and the results of this study provide a framework for improving seed storage methods for the highly diverse Western Australian flora.