Australian Journal of Botany最新文献

Phytoliths constitute an important source of silicon in terrestrial and aquatic ecosystems. Schoenoplectus californicus (C.A.Mey.) Soják (Cyperaceae) is an important phytolith producer.

We investigated the spatio-temporal variation in phytolith content of S. californicus in shallow lakes of the Pampean region, considering biomass and its relation to soil silicon content and lignin content.

Calcination techniques were applied to quantify phytoliths. The biomass was estimated by destructive methods. Soil silicon concentration was determined through ultraviolet–visible spectrophotometry by means of the silicomolybdate method. For lignin determination, a fibre analyser and sulfuric acid were used.

No significant differences were observed in the spatio-temporal analysis. There were no differences in the biomass estimation and in the phytolith per m² contribution. Regarding soil silicon content, when the concentration was low, the phytolith production was low. Lignin content remained constant between sites. No correlation was observed between phytolith and lignin content.

S. californicus is an accumulator of amorphous silica, generating a constant quantity of phytoliths over the years and between sites. The variation in some environmental conditions does not seem to be enough to be reflected in plant silica production. No relation between lignin and silica was found, perhaps due to their different roles in plant structure.

The inclusion of other wetlands with more contrasting conditions may reveal the environmental constraints for the amorphous silica production. This study shows the importance of this community as a silicon source, and the implications of its displacement by other communities or urban development.

Here we present ‘APCalign’, an R package and accompanying browser-sourced application to align and update scientific names for Australian vascular plants to the most likely currently accepted name in the Australian Plant Census (APC) or a name in the Australian Plant Names Index (APNI). Scientific names are the label assigned to unique taxon concepts by the scientific community, but this common terminology is most useful if a taxon concept is consistently referred to by the same name. These links can be broken because of either spelling mistakes or taxonomic changes. Automated tools are required to resolve taxon lists, aligning and updating long lists of possibly erroneous scientific names to the most likely currently accepted names. It is essential that tools specific to the APC/APNI be developed, because these lists specify an endorsed national-level nomenclature used in government legislation and include the uniquely Australian concept of phrase names, absent in global taxonomic datasets. To align input names to names within the APC or APNI, ‘APCalign’ works progressively through a sequence of checks that combine different permutations of the input name, exact versus fuzzy matches, matches that consider the entire name input versus a subset of words, and character strings that indicate a name can be resolved only to a genus or family. The aligned names are then, when possible, updated to a currently accepted taxon concept within the APC. This package should facilitate all research outputs that require diverse scientific name lists to be merged or outdated lists to be updated.

Tabular records of plant-trait data are essential for diverse research purposes. Here we present scorings for a trio of core plant traits, plant growth form, woodiness and life history, for nearly all (>99%) accepted taxon concepts included in the Australian Plant Census (APC). This dataset is predominantly derived from Australia’s state and national floras, supplemented by the taxonomic literature and diverse web resources. In total, 29,993 species and infraspecific taxa were scored for plant growth form, 30,279 for woodiness and 30,056 for life history, with taxa scored as displaying a single or multiple trait values, as appropriate. We provide sample R code that shows how to access and interrogate the dataset. This resource will enable rapid assessment of plant responses to disturbance events and new biogeographic analyses of trait distributions, better understandings of evolutionary trajectories, and ecological strategies.

The response of most native plant species in New South Wales (NSW) to infection by the oomycete pathogen Phytophthora cinnamomi Rands is unknown, which makes decisions about disease management difficult.

We aim to improve knowledge about the potential threat from P. cinnamomi by testing a further 32 threatened species for their response to the pathogen and developing a method for prioritising management and susceptibility testing.

Susceptibility to infection and host response were evaluated in glasshouse experiments where the pathogen was introduced to pots containing the threatened species, and the results were compared with control uninoculated pots. Our prioritisation used modelled habitat suitability for P. cinnamomi, proximity to known P. cinnamomi occurrences, and numbers of plant species populations at least 1 km apart to rank 928 rare and threatened plant species native to NSW for either management or susceptibility testing.

Phytophthora cinnamomi was re-isolated from the roots of 10 of the 32 species assessed, most of which also showed significant mortality or disease symptoms. Darwinia peduncularis B.G.Briggs, Hibbertia circinata K.L.McDougall & G.T.Wright, Isopogon fletcheri F.Muell., Phebalium speciosum I.Telford, Pultenaea baeuerlenii F.Muell. and Pultenaea parrisiae J.D.Briggs & Crisp were the most severely affected species. The effect of P. cinnamomi is known for only 63 rare and threatened species in NSW. The Greater Sydney region is a hotspot for rare and threatened plant species with a high priority for susceptibility testing.

The prognosis in the wild for rare and threatened plant species affected by P. cinnamomi depends on (1) habitat suitability for the pathogen, with subalpine and arid-zone species unlikely to be affected, (2) the number of unaffected populations, with two severely affected species that occur only on infested sites (Hibbertia circinata and Prostanthera marifolia R.Br.) facing extinction in the near future and (3) climate, with some species (e.g. Pomaderris delicata N.G.Walsh & Coates) apparently affected only in unusually wet years. Further susceptibility testing of rare and threatened species is required. This should be supported by taxonomic studies of genera (e.g. Hibbertia, Pultenaea) commonly affected by the pathogen.

Many more plant species in NSW are likely to be severely affected by P. cinnamomi than currently known, and may require active management of the disease for their long-term survival.

Semiarid environments, such as the Patagonian shrublands, are characterised by having shrubby patches surrounded by grasses with different ecophysiological strategies to tolerate long dry periods.

We hypothesised that coexisting grasses of the Patagonian rangeland, already classified as drought-escaping or drought-tolerant, have different traits according to the season and the annual rainfall events.

Two dominant native grasses were selected: Pappostipa speciosa (evergreen) and Poa ligularis (deciduous). Samples were collected in the four seasons for the term of 1 year. Rainfall events and soil water content of each season were determined. Spring was the wettest season and autumn the driest. Physiological (relative water content, pigments, hormones), biochemical (polyphenols, antioxidant activity) and morphological traits were measured in the four seasons.

P. speciosa was characterised by keeping evergreen leaves with high production of polyphenols as secondary metabolites with high antioxidant capacity during the dry autumn and winter seasons. P. ligularis was characterised by high contents of gibberellin (GA₁), auxin (IAA), total phenols, total flavonoids and tartaric acid esters, and high antioxidant capacity in roots during the autumn dry season. In addition, P. ligularis leaves had higher content of carotenoids and polyphenols than P. speciosa during the summer dry season.

The major adaptive strategy to tolerate dry periods is the high activity of the secondary metabolism, mainly in leaves in P. speciosa (a drought-tolerant grass) and in roots in P. ligularis (a drought-escaping grass).

Rainfall variations during a year can affect the phenological growth stages and the metabolism of two native grasses from Argentina characterised by different drought resistance mechanisms.

Alpine ecosystems are threatened by warming and an associated increase in fire frequency. There is a gap in our knowledge of succession in Tasmanian alpine heath more than 50 years after fire. The literature suggests that the alpine successional progression usually involves decreasing rates of change, decreasing differences among fire ages, ongoing transitions among shrub species, ongoing transitions from some lifeforms/species to others, and that warming results in increases in species richness.

We test for these tendencies up to 75 years from fire in alpine vegetation on kunanyi/Mount Wellington, Tasmania, Australia.

We documented the changes in vegetation structure and composition between 1998 and 2022 in plots on either side of an alpine fire boundary in the alpine heathland and used earlier data and observations to extend the record of change after fire to 75 years. We put these changes in the context of the only area of alpine vegetation that was not burnt in 1947 or later.

The area last burnt in 1947 exhibited declines in all lifeform covers between 1998 and 2022. All lifeforms except tall shrubs and mat shrubs declined in cover in the area last burnt in 1962. By 2022, shrub cover in the 1962-burnt area had not attained equivalence with the area last burnt in 1947. Herbs had the most dramatic decline in both fire-age classes. There were few shrub seedlings in 2022. All but six taxa, three being exotic, were observed in both the plots and previous broader surveys. Increases in species richness caused by the upward migration of lower-elevation species were not observed. The long-unburnt patch lacked the major dominant of the 1947-burnt plots, namely Orites acicularis, and was dominated by a gymnosperm absent from most of the mountain.

Succession follows the initial floristic composition model. The differences in trajectories from the 1947 and 1962 fires could possibly be due to desiccation or abrasion damage from increasing wind speeds and temperatures. There are strong indications of further potential change in the absence of fire.

The slow rate of recovery and its on-going nature emphasise the importance of keeping fire out of this vegetation type.

For plant species that have evolved in fire-prone environments, declines after wildfires are often driven by the combination of fire and other threatening processes. Mitigating the impacts of these threatening processes can sometimes effectively support post-fire population recovery.

We test the effectiveness of: (1) phosphite application to mitigate Phytophthora dieback; (2) fencing to exclude browsing by mammalian herbivores; and (3) translocation to sites where threats can be practically managed, for conservation of threatened flora affected by wildfires in 2018 and 2019 in the Stirling Range (Koi Kyeunu-ruff), south-western Australia.

Survival of Phytophthora-susceptible flora was compared in repeatedly sampled plots from prior to and after wildfire and ± recurrent phosphite application. Survival and growth of browsing-susceptible flora was compared post-fire in fenced and control plots. Survival, growth and flowering was compared between wild populations recruiting after wildfire and translocated populations.

Phosphite application increased survival of most Phytophthora-susceptible flora. Fencing led to greater growth and often increased survival. Translocated populations, with supplemental water, had greater growth rates and earlier flowering than wild populations, and a non-significant trend for higher survival.

These findings provide strong evidence supporting continuation of phosphite application, herbivore exclusion and translocation for post-fire recovery of the threatened flora of the Stirling Range.

With increasing wildfire extent, frequency and impact across the globe, successful management of non-fire threats will be crucial for post-fire conservation of threatened flora, with the approaches proving effective in this study likely to have conservation value elsewhere.

It is important to understand the way in which wild herbivore grazing affects decadal vegetation dynamics after cessation of unnatural disturbances, especially in a context of climate change.

We investigated the decadal effects of different grazing regimes on treeless subalpine vegetation recovery from stock grazing and burning, on sites of different environmental character and initial state.

At each of four sites, two fenced areas that excluded mammalian herbivores, two that allowed in only rabbits and two grazed control plots were monitored every 5 years between 1991 and 2021. General linear models were developed to explain variation in change over the 30 years in different cover types. The years in which peak and trough values occurred were also determined, as were the incidence and direction of differences between treatments in sites and years.

There was marked variation in change over 30 years between the sites and lifeforms. Exclusion of mammalian herbivores increased the slow rate of revegetation. There was little effect from rabbits by themselves. Unexpectedly, the cover of both short and tall herbs was not promoted by grazing exclusion. Short term climatic variation affected some cover types, with many peaks and troughs in the dry year of 2001, but it was not possible to disentangle decades scale climate change effects from the process of recovery after disturbance.

The slight increase in revegetation rates in the absence of native herbivores and rabbits does not justify culling. Restoration interventions appear to be unnecessary. The prospect of increasing fire incidence and deer numbers suggests that it is desirable to continue monitoring the plots.