Australian Journal of Botany
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A review of the genus Tristania R. Br. (Myrtaceae): a heterogeneous assemblage of five genera The genus Tristania is reviewed, with particular emphasis on the Australian species, on the basis of morphological and anatomical evidence and, as a result, divided into five genera. The genus Tristania R.Br. em. Schott is monotypic, the genera Welchiodendron and Ristantia are newly described and Lophostemon Schott and Tristaniopsis Brongn. & Gris are reinstated from synonymy. One new species, Tristaniopsis collina, is described and 33 new combinations made: Welchiodendron longivalve, Ristantia pachysperma, Lophostemon confertus, L. grandijlorus ssp. grandiflorus and ssp. riparius, L. Iactifluus, L. suaveolens, Tristaniopsis anomala, T. beccarii, T. bilocularis, T. burmanica, T. clementis, T. decorticata, T. elliptica, T. exiliflora, T. ferruginea, T.fruticosa, T. grandifolia, T. laurina, T. littoralis, T. macrosperma, T. merguensis, T. micrantha, T. oblongifolia, T. obovata, T. oreophila, T.pentandra, T. polyandra, T.pontianensis, T. razakiana, T. rufescens, T, stellata and T. whiteana. Two further species, Tristania psidioides and Tristania umbrosa, are transferred to Xanthostemon.
Australian Journal of Botany - Tập 30 Số 4 - Trang 413 - 1982
Facultative autogamy in Cyrtopodium polyphyllum (Orchidaceae) through a rain-assisted pollination mechanism
Cyrtopodium includes ~42 species, among which is Cyrtopodium polyphyllum (Vell.) Pabst ex F. Barros that occurs in a rainforest in south-eastern Brazil. Its non-rewarding flowers, which attract Centridini bees by deceit, are rain-assisted self-pollinated, a phenomenon rarely found in orchids and other plant families. In addition, self-pollination has never been reported in Cyrtopodiinae and data on the pollination of South American orchids are scarce. Flowers were observed at different times of the day, on both sunny and rainy days, to record floral morphology, visitors and the effects of rainfall on flowers. On rainy days, water accumulates on the stigma and dissolves the adhesive substance of the stigmatic surface. A viscous drop thus forms, which contacts the pollinarium. When evaporation makes the viscous drop shrink, the drop moves the pollinarium with the anther onto the stigmatic surface and promotes self-pollination. Fruit set in natural habitat was low, with 2.4% at one study site, where a similar value (2.2%) was recorded in flowers self-pollinated by rain. In C. polyphyllum, facultative self-pollination assisted by rain is thus an important strategy that guarantees fruit set when pollinator’s visits are scarce, which is common in species pollinated by deceit.
Australian Journal of Botany - Tập 56 Số 4 - Trang 363 - 2008
Biogeography of Fire-Killed and Resprouting Banksia Species in South-Western Australia Banksia includes 38 fire-killed (seeders) and 20 resprouting species, and two species with contrasting
ecotypes, in south-western Australia. There may be up to 12 seeders per 50 × 50 km grid cell in the
southern sandplains and 12 resprouters in the northern sandplains. The patterns of distribution of
species across soil type and eight climatic attributes is similar for both life forms, except that greater
numbers of resprouting species occur at higher rainfalls and where there is greater seasonal spread of
rainfall. Most seeders occur on white sands and rocky substrates, and resprouters occur on yellow sands
and the more fertile lateritic soils. Nutrient requirements for both life forms appear to be similar.
Resprouters are more widespread than seeders which suggests that resprouters show greater
environmental tolerances. The distribution of grid cells containing each life form across soil types and
eight climatic attributes is similar and any differences in climatic profile for all species in each category
are considered biologically insignificant. Both life forms in section Abietinae are well represented in
the climatically distinct southern and northern sandplains indicating no climatic preferences within the
lineage. There are no consistent trends in environmental attributes from fire-killed to resprouting
ecotypes of B. ashbyi E.G.Baker and B. violacea C.A. Gardner. Multiple-partitioning classification of
the floristic data produced 10 groups varying greatly in geography, species richness, and proportion and
endemism of each life form. The Lesueur (northern) district has four endemic seeders, six endemic
resprouters and a mean of 10 resprouters per cell. The East Eyre (southern) district has five endemic
seeders, no endemic resprouters and one resprouter per cell. Both groups have a mean growing season
of 5 months. The relative aridities and fluctuations of present and past (Quaternary and late Tertiary)
climates are invoked to explain the much higher proportion of resprouters in the northern than southern
sandplains and the absence of seeders in the most marginal cells. The absence of endemic species yet
high proportion of resprouters (73%) in the extreme south-western corner of the region might be
explained by elimination of seeders through frequent burning by Aborigines in the late Quaternary. The
increase in the proportion of fire-killed species along the south coast from 23% to 100% at the edge of
the Nullarbor Plain also requires an explanation.
Australian Journal of Botany - Tập 43 Số 3 - Trang 283 - 1995
Fungi and fire in Australian ecosystems: a review of current knowledge, management implications and future directions Fungi are essential components of all ecosystems in roles including symbiotic partners, decomposers and nutrient cyclers and as a source of food for vertebrates and invertebrates. Fire changes the environment in which fungi live by affecting soil structure, nutrient availability, organic and inorganic substrates and other biotic components with which fungi interact, particularly mycophagous animals. We review the literature on fire and fungi in Australia, collating studies that include sites with different time since fire or different fire regimes. The studies used a variety of methods for survey and identification of fungi and focussed on different groups of fungi, with an emphasis on fruit-bodies of epigeal macrofungi and a lack of studies on microfungi in soil or plant tissues. There was a lack of replication of fire treatment effects in some studies. Nevertheless, most studies reported some consequence of fire on the fungal community. Studies on fire and fungi were concentrated in eucalypt forest in south-west and south-eastern Australia, and were lacking for ecosystems such as grasslands and tropical savannahs. The effects of fire on fungi are highly variable and depend on factors such as soil and vegetation type and variation in fire intensity and history, including the length of time between fires. There is a post-fire flush of fruit-bodies of pyrophilous macrofungi, but there are also fungi that prefer long unburnt vegetation. The few studies that tested the effect of fire regimes in relation to the intervals between burns did not yield consistent results. The functional roles of fungi in ecosystems and the interactions of fire with these functions are explained and discussed. Responses of fungi to fire are reviewed for each fungal trophic group, and also in relation to interactions between fungi and vertebrates and invertebrates. Recommendations are made to include monitoring of fungi in large-scale fire management research programs and to integrate the use of morphological and molecular methods of identification. Preliminary results suggest that fire mosaics promote heterogeneity in the fungal community. Management of substrates could assist in preserving fungal diversity in the absence of specific information on fungi.
Australian Journal of Botany - Tập 59 Số 1 - Trang 70 - 2011
Allometry for estimating aboveground tree biomass in tropical and subtropical eucalypt woodlands: towards general predictive equations A fundamental tool in carbon accounting is tree-based allometry, whereby easily measured variables can be used to estimate aboveground biomass (AGB). To explore the potential of general allometry we combined raw datasets from 14 different woodland species, mainly eucalypts, from 11 sites across the Northern Territory, Queensland and New South Wales. Access to the raw data allowed two predictor variables, tree diameter (at 1.3-m height; D) and tree height (H), to be used singly or in various combinations to produce eight candidate models. Following natural log (ln) transformation, the data, consisting of 220 individual trees, were re-analysed in two steps: first as 20 species–site-specific AGB equations and, second, as a single general AGB equation. For each of the eight models, a comparison of the species–site-specific with the general equations was made with the Akaike information criterion (AIC). Further model evaluation was undertaken by a leave-one-out cross-validation technique. For each of the model forms, the species–site-specific equations performed better than the general equation. However, the best performing general equation, ln(AGB) = –2.0596 + 2.1561 ln(D) + 0.1362 (ln(H))2, was only marginally inferior to the species–site-specific equations. For the best general equation, back-transformed predicted v. observed values (on a linear scale) were highly concordant, with a slope of 0.99. The only major deviation from this relationship was due to seven large, hollow trees (more than 35% loss of cross-sectional stem area at 1.3 m) at a single species–site combination. Our best-performing general model exhibited remarkable stability across species and sites, when compared with the species–site equations. We conclude that there is encouraging evidence that general predictive equations can be developed across sites and species for Australia’s woodlands. This simplifies the conversion of long-term inventory measurements into AGB estimates and allows more resources to be focused on the extension of such inventories.
Australian Journal of Botany - Tập 53 Số 7 - Trang 607 - 2005
Above-Ground Biomass of a Mixed Eucalypt Forest in Eastern Victoria Eleven trees of Eucalyptus muellerana and 10 trees both of E. agglomerata and of E. sieberi growing in an uneven-aged mixed sclerophyll forest on duplex granitoid soils in eastern Victoria were felled, measured. separated into branch and stem components, sampled and weighed. Understorey vegetation and litter were also sampled for dry weight determination. Both linear and allometric regressions were developed for each species to predict branch and stem component dry weights from branch and tree dimensions. The predicted component weights for all branches on each tree were summed to estimate crown component dry weights, and regressions were then fitted for these crown component dry weights as functions of tree dimensions. Land area estimates of above-ground tree biomass were made by measuring tree diameters on sample plots. applying the appropriate regressions relating stem and crown component dry weights to tree diameter, and summing the predicted weights for each plot. The above-ground biomass of the forest ecosystem. which had a tree density of 123 stems per ha, was estimated to be 344.100 kg ha-1 of which 94.6% was in the forest overstorey. The proportions of each tree component in the overstorey were stem wood 60.1%, stem bark 15.8%. branch wood 16.5%, branch bark 3.9%, twigs 2.0%, and leaves 1.7%.
Australian Journal of Botany - Tập 27 Số 6 - Trang 725 - 1979
Composition, leaf area index and standing biomass of eucalypt open forests near Darwin in the Northern Territory, Australia
Savanna communities dominate the wet–dry
tropical regions of the world and are an important community type in monsoonal
northern Australia. As such they have a significant impact on the water and
carbon balance of this region. Above the 1200-mm isohyet, savanna’s are
dominated by Eucalyptus miniata–E. tetrodonta open
forests. We have described in detail the composition and structure as well as
seasonal patterns of leaf area index and above-ground biomass in the
E. miniata–E. tetrodonta open forests of the Gunn
Point region near Darwin in the Northern Territory of Australia. In all, 29
tree species from four phenological guilds were recorded in these forests.
Stand structure suggests that the forests were still recovering from the
impacts of cyclone Tracy and subsequent frequent fires.
Eucalyptus miniata and
E. tetrodonta were significant contributors to
overstorey leaf area index and standing biomass (>70%), and both
leaf area index and biomass were strongly correlated to basal area. Leaf area
index was at a maximum (about 1.0) at the end of the wet season and declined
over the dry season by about 30–40%. There were proportionally
greater changes in the understorey reflecting the greater contribution of
deciduous and semi-deciduous species in this strata. Standing biomass was
about 55 t ha –1 . Detailed descriptions of leaf
area index and biomass are important inputs into the development of a water
and carbon balance for the savanna’s of northern Australia.
Australian Journal of Botany - Tập 48 Số 5 - Trang 629 - 2000
Biomass and Structure of a Subtropical Eucalypt Forest, North Stradbroke Island The plant biomass of a Eucalyptus signata-dominated forest 15 m tall growing on infertile sands off
the Queensland coast is characterized in detail. The forest has a biomass of 180 t/ha, 90% of which
is found in the nine species achieving > 2.5 m height. Of the total biomass, 42.5 % is below ground.
Pteridium esculentum occupies 41 % of the understorey biomass, with 50 shrub and herb species
partitioning the remainder. Dimension analysis of 10-11 individuals of each of three tree species-
Eucalyptus signata, E. umbra subsp. umbra and Banksia aemula-has served to characterize the
above- and below-ground growth forms of each species, and provide regressions of the mass of tree
components on easily measured plant parts. The size distribution of tree and shrub stems on the
site suggests that the major species have evolved quite different reproductive strategies for main-
taining a steady-state population in the face of recurrent fires.
Australian Journal of Botany - Tập 25 Số 2 - Trang 171 - 1977
Internal secretory spaces in thickened underground systems of Asteraceae species
Secretory structures are present in many vascular plants and have an important ecological role as a plant defence mechanism against herbivors and pathogens. Internal secretory spaces of lipid substances are widespread in the Asteraceae. However, information about the occurrence of these structures in thickened underground systems is sparse, compared with what we know about aerial systems. The main objective of the present paper was to investigate the occurrence, formation and chemical nature of the secretory structures in six Asteraceae species belonging to the following tribes: Eupatorieae (Mikania cordifolia and M. sessilifolia), Mutisiae (Trixis nobilis), Plucheeae (Pterocaulon alopecuroides) and Vernonieae (Vernonia elegans and V. megapotamica). The samples were collected in areas of Cerrado (tropical savanna) in the state of São Paulo, Brazil. The secretory structures found were cortical canals in roots (T. nobilis, P. alopecuroides, V. elegans and V. megapotamica), cortical cavities in roots (M. cordifolia, M. sessilifolia and P. alopecuroides), cavities in the secondary phloem of roots (T. nobilis), cortical cavities in the xylopodium (M. cordifolia, M. sessilifolia, P. alopecuroides and V. megapotamica) and in the underground stem (T. nobilis), and canals in the secondary xylem in the xylopodium (M. cordifolia and M. sessilifolia). Histochemical tests showed the presence of lipid substances in all structures.
Australian Journal of Botany - Tập 57 Số 3 - Trang 229 - 2009
The origin and anatomy of rhizophores in Vernonia herbacea and V. platensis (Asteraceae) from the Brazilian Cerrado
The aim of this work is to study the origin and anatomy of rhizophores in two Asteraceae species from the Brazilian Cerrado: Vernonia herbacea (Vell.) Rusby and V. platensis (Spreng.) Less. In both species, axillary buds from the cotyledonary node give rise to the first rhizophores. As rhizophores develop, these organs branch to form new rhizophores from their axillary buds that constitute a sympodial system of underground branches. Nodes, internodes and axillary buds, protected by cataphylls, are evident in these underground organs. The primary root degenerates and all the root system arises adventitiously from the rhizophores. Under natural conditions, the axillary buds give rise to new rhizophores, but when exposed to the light, these buds develop into aerial stems. When rhizophores are fragmented, each of these structures, which accumulate fructans, are important organs for vegetative propagation mainly in areas subjected to environmental disturbances, such as the Cerrado, where fire and drought frequently occur.
Australian Journal of Botany - Tập 53 Số 3 - Trang 273 - 2005
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