Australian Eucalypts Research Articles

Using machine learning to link climate, phylogeny and leaf area in eucalypts through a 50‐fold expansion of leaf trait datasets

Abstract Leaf area varies within and between species, and previous work has linked this variation to environment and evolutionary history. However, many previous studies fail to examine both these factors and often are data‐limited. To address this, our study developed a new workflow using machine learning to automate the extraction of leaf area from herbarium collections of Australian eucalypts (Eucalyptus, Angophora and Corymbia). This dataset included 136,599 measurements, expanding existing data on this taxon's leaf area by roughly 50‐fold. Our methods were validated using field standard metrics of accuracy, and comparisons to manual measurements both from the present study and existing datasets. With this dataset for the eucalypt clade, we observed positive relationships between leaf area and mean annual temperature and precipitation similar to those reported for the global flora. However, these relationships were not consistently observed within species, potentially due to gene flow suppressing local adaptation. When we examined these relationships at different phylogenetic levels, the slope of trait–climate associations within lineages converged towards the overall eucalypt slope at shallow phylogenetic scales (5–12 MY), suggesting that effects of gene flow relax just above the species level. The strengthening of trait–climate correlations at evolutionary scales just beyond the intraspecific level may represent a widespread phenomenon across various traits and taxa. Future studies can unveil these relationships with the larger sample sizes of new trait datasets generated through machine learning. Synthesis. Using machine learning, researchers are able to confirm current positive global relationships between leaf area and mean annual temperature and precipitation. Additionally, they were able to take this a step further and examine how it changes across time. Here they saw that at roughly 5–12 million years ago in the phylogenetic tree, the trait–climate slope begins to show significantly less variation. Overall, the study shows the potential of machine learning in ecology, with exciting new potential findings with its use.

OzCBI: the composite burn index adapted to assess fire severity and key fauna habitat features in Australian ecosystems

ABSTRACT Although fire management is essential to conserve ecosystems and protect communities in Australia, the best way to achieve these goals is controversial. Recent advances that use satellite imagery to map fire severity focus on canopy effects and provide limited ecological information. Fires and prescribed burns can also occur over weeks to months, limiting the relevance of a single post-fire image. We adapted the composite burn index, a field-truthing method commonly used in North America, to include parsimonious metrics that assess resprouting dynamics common among Australian eucalypts and the retention and recovery of key fauna habitat attributes. We used multitemporal satellite imagery to compile the greatest impacts within fire boundaries over several months and derive the maximum differenced normalised burn ratio (dNBR max). We used the dNBR max and a new field method, the OzCBI, to create distinct fire-severity models for three forested biogeographical regions in southwest Western Australia. Ecological outcomes were used to set thresholds between severity classes that were common to the three models. Balanced accuracies averaged above 0.7 across the models. This study demonstrates a practical method to incorporate ecological assessment into fire-severity maps. The approach informs efforts to achieve best-practice fire management that balances risk reduction and the conservation of natural environments.

Aridity drives coordinated trait shifts but not decreased trait variance across the geographic range of eight Australian trees.

Large intraspecific functional trait variation strongly impacts many aspects of communities and ecosystems, and is the medium upon which evolution works. Yet intraspecific trait variation is inconsistent and hard to predict across traits, species and locations. We measured within-species variation in leaf mass per area (LMA), leaf dry matter content (LDMC), branch wood density (WD), and allocation to stem area vs leaf area in branches (branch Huber value (HV)) across the aridity range of seven Australian eucalypts and a co-occurring Acacia species to explore how traits and their variances change with aridity. Within species, we found consistent increases in LMA, LDMC and WD and HV with increasing aridity, resulting in consistent trait coordination across leaves and branches. However, this coordination only emerged across sites with large climate differences. Unlike trait means, patterns of trait variance with aridity were mixed across populations and species. Only LDMC showed constrained trait variation in more xeric species and drier populations that could indicate limits to plasticity or heritable trait variation. Our results highlight that climate can drive consistent within-species trait patterns, but that patterns might often be obscured by the complex nature of morphological traits, sampling incomplete species ranges or sampling confounded stress gradients.

Rarity or decline: Key concepts for the Red List of Australian eucalypts

The 822 eucalypt species (Angophora, Corymbia, Eucalyptus) within Australia were assessed using IUCN Red List Categories and Criteria. Overall, 193 (23%) eucalypts qualified as threatened and 36 were considered Data Deficient. One hundred and thirty-four threatened species qualified under criterion A2, representing a past and irreversible population decline of >30%. The remainder were narrow-range species with ongoing threats (mostly mining or urbanisation), or naturally rare. Habitat conversion to crops and pastures was the cause of decline for most threatened eucalypts. Threatened species were concentrated where deforestation and high eucalypt richness coincide, especially south-western Western Australia. Corymbia or Angophora species, and relatively few tropical eucalypts are threatened. Fire, timber harvesting and disease were rarely sufficient threats to eucalypts to warrant a threatened status. Sheep grazing limits regeneration in temperate woodlands, but requires further quantification for individual species. Prior to this study, 89 eucalypts were listed as threatened under Australian environmental law. This assessment recommends that 32 of these species be downgraded to Near Threatened or Least Concern. A further 11 species were identified as Data Deficient, while an additional 147 species were proposed for listing as threatened. This systematic assessment of Australian eucalypts emphasises the importance of decline rather than rarity when compared with previous listings, with broad implications for listing long-lived plants in deforested landscapes.

An Array of Bioactive Compounds From Australian Eucalypts and Their Relevance in Pancreatic Cancer Therapeutics.

Pancreatic cancer (PC) is one of the most devastating human cancers, and despite the significant advances in the current therapeutic options, the overall survival rate for PC has remained static for the past 50 years. Plant-derived bioactive compounds play a vital role in cancer therapeutics by providing new lead compounds for future drug development. Therefore, the isolation, characterization, and identification of new bioactive compounds for the prevention and treatment of cancer continue to be an important aspect of natural product research. Many in vitro and in vivo studies published in the last few decades have established strong links between the phytochemical profile of eucalypts and anticancer activity. However, only a small number of these reports have attempted to demonstrate a relationship between the biological activity of eucalypt extracts and PC. This review focuses on potential anti-PC effects of an array of bioactive compounds present in various species of eucalypts. It also highlights the necessity for further in vitro and in vivo studies to develop a complete understanding of the potential this group of plants has for the development of potent and specific chemotherapeutic drugs for PC.

Assessing the potential of wood welding for Australian eucalypts and tropical species

The wood welding potential of Australian and tropical species has been investigated. Optimized parameters for Eucalyptus saligna, Eucalyptus pilularis, Corymbia maculata, Ochroma pyramidale, and Tectona grandis were determined using a standard tensile strength test. The results confirmed the importance of density in the optimisation process. The grain direction also proved to have a significant impact on the welded joint strength of species featuring large wood rays or vessels in diagonal and/or radial pattern. Wood welding could therefore be an alternative for such species where gluing is required.

Wood planing properties of Australian plantation-grown Eucalypts

Wood planing properties of Australian plantation-grown Eucalypts

Using biodiversity databases to verify and improve descriptions of tree species climatic requirements

Understanding tree species climatic adaptability, as well as climatic conditions within their natural distributions, is crucial for managing forests for both commercial and conservation objectives under climate change. Multi-million dollar investments in biodiversity databases are providing forestry professionals with freely accessible tools to carry out these kinds of analyses for many tree species. The climatic requirements of hundreds of tree species have been described in the commercially available Forestry Compendium developed by CAB International, but these descriptions have often relied on expert opinion where information is lacking. It is desirable that descriptions of tree species climatic requirements should, as far as possible, be explicit, quantitative and based on specific observations. This paper describes how the Atlas of Living Australia (ALA) and the Global Biodiversity Information Facility (GBIF) can provide specific observations to assist verifying and, where necessary, improving descriptions of tree species climatic requirements. It focuses mainly on Australian species as the ALA is one of the most sophisticated biodiversity databases currently available for a single country. However, the ALA also has international relevance as Australian eucalypts and acacias are important plantation species in many countries. Data in the GBIF complement the ALA data by providing very useful information on where Australian tree species are growing outside Australia. Analyses of a commercially important species (Eucalyptus nitens) and a lesser-known species (E. botryoides) demonstrate how descriptions of climatic requirements can be verified and, if necessary, improved. However, the general methods described have the potential to be applied to many tree species. Some of the advantages and disadvantages of these systems are discussed and possible improvements are suggested.

Macroecology meets invasion ecology: performance of Australian acacias and eucalypts around the world revealed by features of their native ranges

Native geographical range extent has frequently emerged as a correlate of invasiveness, especially for plant species. We tested whether dimensions of the native range (measured by the area-of-occupancy and its scaling patterns) of 720 Australian eucalypts (genera Angophora, Eucalyptus and Corymbia) could explain introduction and invasion success. We also compared our results with a previous study on 979 Australian acacias (previously grouped in Acacia subgenus Phyllodineae) to investigate whether features of their native ranges explained the much higher invasion success in this group compared to eucalypts. From nine databases we found records that 373 eucalypts have been introduced to areas outside their native ranges; 82 of these have become naturalised, and eight are invasive. A similar proportion of Australian acacias have been introduced, but almost three times as many are invasive (384 species introduced, 71 of which are naturalized and 23 invasive). Eucalypts with large native ranges are more likely to have been introduced and subsequently naturalise, as is the case with acacias. Unlike acacias, however, the native range size of invasive eucalypts was not significantly greater than naturalised (but not invasive) species. Intriguingly, the human preference for introducing species with larger ranges was much greater for acacias than for eucalypts as the geometric mean range sizes of introduced, naturalised and invasive acacias are 2.04, 1.88 and 3.59 times those of eucalypts at the same stage. Moreover, the percolation exponent (i.e. the slope of occupancy scaling) becomes more extreme towards the end of the introduction–naturalization–invasion continuum, decreasing for acacias but increasing for eucalypts, with acacias, except for non-introduced species, having a lower exponent than eucalypts. The selection preference of acacias during introduction is thus for species that can rapidly expand their range; in contrast, slow-spreading eucalypts have been selected for dissemination. In other words, humans appear to have selected for highly invasive acacias but against introducing highly invasive eucalypts.

Biogeography constrains acclimation to warming in two Australian eucalypts: a climate shift experiment

Biogeography constrains acclimation to warming in two Australian eucalypts: a climate shift experiment

Interspecific hybridisation in tuart (Eucalyptus gomphocephala, Myrtaceae): a conservation management issue?

The anthropogenic movement of Eucalyptus species beyond their natural distributions is increasing the opportunity for interspecific hybridisation. The conservation implications arising from hybridisation between indigenous and introduced eucalypt species in modified urban landscapes is an increasingly important management issue that requires an assessment of risk. It has been claimed that much of the tuart (Eucalyptus gomphocephala DC., Myrtaceae) seed in Kings Park, a large urban bushland remnant in Perth, Western Australia, is of hybrid origin with introduced eastern Australian eucalypts, and especially with E. cladocalyx. Using molecular markers, we tested this claim and determined whether hybridisation in tuart is a conservation management issue in Kings Park, as well as the adjacent Bold Park. Eight microsatellite markers were used to genotype 220 open-pollinated tuart seedlings from 19 families. Allele frequency estimates for tuart were generated by genotyping 42 mature tuart trees. Forty-four trees of four alternative species thought to be capable of hybridising with tuart in these parks, including two non-indigenous species, E. cladocalyx and E. camaldulensis, and two indigenous species, E. decipiens and E. rudis, were also genotyped. Pairwise FST between tuart and each alternative species for these markers ranged from 0.105 to 0.204. A hybrid-index analysis of seedling genotypes showed no significant evidence for hybridisation, and no alternative species private alleles (n = 35) were found in any tuart offspring genotypes. A likelihood analysis showed that the maximum likelihood of observing no private alleles of the alternative species in the progeny occurred at a hybridisation frequency of zero for all four alternative species. We conclude that hybridisation between tuart and non-indigenous species is not currently a conservation management issue in Kings Park and Bold Park. Rather, the invasion of pure non-indigenous species, and in particular E. cladocalyx, as weeds into bushland is of greater management concern.

Invasion potential and host shifts of Australian and African ectomycorrhizal fungi in mixed eucalypt plantations

• Transportation of forestry materials results in unintended co-introduction of nonnative species that may cause enormous ecological or economic damage. While the invasion ecology of plants and animals is relatively well-known, that of microorganisms, except aboveground pathogens, remains poorly understood. • This work addresses host shifts and invasion potential of root symbiotic ectomycorrhizal fungi that were co-introduced with Australian eucalypts and planted in clear-cut miombo woodlands in Zambia, south-central Africa. • By use of rDNA and plastid intron sequence analysis for identification and phylogenetic techniques for inferring fungal origin, we demonstrated that host shifts were uncommon in the Australian fungi, but frequent in the African fungi, especially in mixed plantations where roots of different trees intermingle. • There was evidence for naturalization, but not for invasion by Australian ectomycorrhizal fungi. Nevertheless, the fungi introduced may pose an invasion risk along with further adaptation to local soil environment and host trees. Inoculation of eucalypts with native edible fungi may ameliorate the potential invasion risks of introduced fungi and provide an alternative source of nutrition.

INVESTIGATING EUCALYPT DISEASES OF UNKNOWN ETIOLOGY: THE MUNDULLA YELLOWS EXPERIENCE

Diseases of eucalypts cause significant losses worldwide. Pathogens include Phytophthora spp., fungi, bacteria and phytoplasmas, but so far no viruses have been isolated or characterised from eucalypts despite observations of mosaic, chlorosis, leaf curl and leaf spot symptoms. A new lethal dieback disease of Australian eucalypts, known as Mundulla Yellows (MY) has emerged as a threat to natural vegetation, ancient iconic trees, natural wildlife habitats and conservation programs. Symptoms are an asymmetric progressive yellowing and slow dieback of the crown. Similar symptoms have been observed in eucalypts growing in Spain, Peru and Syria. No fungi, bacteria or phytoplasmas were found to be associated with MY. Traditional infectivity assays were unsuitable for testing whether MY is a virus-associated disease, so component analysis is being used to seek disease-associated nucleic acids or proteins which may implicate a virus-like agent in the etiology of MY. A number of physically distinct small RNAs were found preferentially in diseased trees, but none had sequences related to those of known viruses. Specific nucleoprotein fractions from MY affected trees contained disease-associated 84 kDa and 116 kDa proteins and quasi-spherical particles 30-40 nm in diameter. Limited sequence analysis of the 84 kDa protein and RNA also associated with the nucleoprotein fraction showed that neither had similarities to known plant viruses. It is concluded that the disease-associated nucleic acids and proteins could either be components of a previously undescribed type of intracellular plant pathogen, or host products resulting from pathogenic changes in affected trees. Targets for future research are the 30-40 nm particles, and the MY associated protein.

A comparison of reflectance characteristics of some Australian eucalyptus species based on high spectral resolution data — discriminating using the visible and NIR regions

Laboratory measurements of the spectral reflectance of leaves from eleven common eastern Australian eucalypts were made over the 400–2400 nm range using an Infra‐Red Intelligent Spectroradiometer (IRIS) spectroradiometer. Spectral differences among the different species were studied in terms of reflectance (550 nm, 630 nm, 800 nm, green peak maximum reflectance and chlorophyll well maximum absorption) and wavelength positions (red edge, green peak maximum reflectance, chlorophyll well maximum absorption and red edge inflection point). This paper discusses the differences between the species in the visible and red‐edge regions only Results indicate that, while spectra from different eucalyptus species appear similar in terms of shape and positions of absorption features, statistically significant differences do exist. These differences are in terms of absolute reflectance, depths of absorption features and the relative position of change in terms of the wavelength.

A hypothesis to explain why the south-western subspecies of the Crested Shrike-tit (Falcunculus frontatus leucogaster) is rare and declining

The south-western subspecies of the Crested Shrike-tit (Falcunculus frontatus leucogaster) is uncommon and declining in abundance. Moreover, populations fail to persist in even large remnants of native vegetation within agricultural areas. Reasons for the scarcity of Shrike-tits in south-western Australia, their decline, and their failure to survive in fragmented habitats are unclear, but are possibly related to the scarcity of persistent decorticating bark on south-western Australian eucalypts relative to eucalypts in habitats where the species is abundant in eastern Australia. At two widely separated areas of eucalypt forest and woodland in eastern Australia, where Shrike-tits have been studied and appear relatively abundant, they take most of their prey from bark, particularly loose and decorticating bark. By contrast, in woodlands of south-western Australia, most prey appears to be obtained by foliage gleaning. I suggest that bark substrates provide a richer food resource for Shrike-tits than foliage, and that Shrike-tits in south-western Australia must forage over much larger areas to obtain adequate food than those that have been studied in the east. Other studies have shown that canopy arthropods are less abundant on eucalypts in south-western than in eastern Australia. Thus, as a result of both differences in foraging substrate availability and lower arthropod abundances, Shrike-tit population densities are lower in south-western Australia than much of eastern Australia. Low population densities and the need for large home-ranges typify organisms sensitive to habitat fragmentation. It is therefore hypothesised that both low numbers and a failure to persist in habitat fragments by Shrike-tits in southwestern Australia are a consequence of the limited abundance of suitable bark substrates for foraging, a reliance on foliage gleaning, and lower arthropod abundances. Conservation of this species in south-western Australia therefore requires protection of large contiguous areas of eucalypt woodlands and forests.

Paropsine beetles (Coleoptera: Chrysomelidae) in south-eastern Queensland hardwood plantations: identifying potential pest species

SummaryParopsine chrysomelid beetles are significant defoliators of Australian eucalypts. In Queensland, the relatively recent expansion of hardwood plantations has resulted in the emergence of new pest species. Here I identify paropsine beetles collected from Eucalyptus cloeziana Muell. and E. dunnii Maiden, two of the major Eucalyptus species grown in plantations in south-eastern Queensland, and estimate the relative abundance of each paropsine species. Although I was unable to identify all taxa to species level, at least 17 paropsine species were collected, about one-third of which have not been previously associated with hardwood plantations. Paropsis atomaria Olivier and P. charybdis Stål were the most abundant species collected in E. cloeziana plantations, while Chrysophtharta cloelia (Sål) and P. atomaria were most commonly collected from E. dunnii. Occasional collections from Corymbia citriodora (Hook.) Hill and Johns, ssp. variegata revealed an additional four species implicated in plantation damage. Abundance and voltinism varied between species and sites. I predict which paropsine species are likely to threaten plantation productivity.

Understanding a flammable planet – climate, fire and global vegetation patterns

Understanding a flammable planet – climate, fire and global vegetation patterns

Post-burn vegetation development of rehabilitated bauxite mines in western Australia

Alcoa World Alumina Australia has been rehabilitating bauxite mines in the jarrah ( Eucalyptus marginata) forest of Western Australia for more than 35 years. Mines rehabilitated in the early 1980s contain some eastern Australian eucalypts and have built up substantial fuel loads (23–35 t/ha) that may be reduced through prescribed burning. The aim of this study was to document vegetation changes in areas rehabilitated in the early 1980s for 6 years following prescribed burning and ascertain the most appropriate fire regime to apply in these areas to achieve identified rehabilitation completion criteria. Following both autumn and spring burning, rehabilitated areas rapidly re-accumulated fuel in the first year after burning, but fuel loads have remained relatively constant since then at a level of 8–9 t/ha. Burning was successful in removing dead aerated fuel that dominated the midstorey of the vegetation and stimulating plant growth in the understorey, making the burnt rehabilitated areas more like the unmined forest. Plant density, live plant cover, Acacia density and Acacia cover were generally higher following autumn than spring burning, although differences were reduced over time. Weed density did not differ significantly between autumn and spring burning, peaking 2 years after burning and then declining back to pre-burn levels. Similarly, species richness peaked in the first few years following burning and then declined, consistent with the predictions of the initial floristic composition model of succession. Tree growth was lower in burnt than unburnt areas for the first 2 years, but 4 and 6 years after burning tree growth was not significantly different between autumn, spring and no burn areas. Alcoa is required to integrate rehabilitated areas into the fire management regime of the surrounding jarrah forest to meet completion criteria. The results suggest that this can be achieved by burning rehabilitated areas containing non-native eucalypt species in spring under low to moderate intensity. This fire regime will lead to reduced fuel accumulation, a less prominent midstorey layer resulting from reduced recruitment of Acacia spp., lower densities of eastern Australian eucalypt species, and greater similarity in the composition and abundance of the understorey to the unmined forest.

Fatty acids in honeybee-collected pollens from six endemic Western Australian eucalypts and the possible significance to the Western Australian beekeeping industry

Western Australian eucalypt pollens in this research have low levels of lipid (0.59–1.9%) when compared with many other plant species that have evolved alongside the European honeybee. Eucalypt-pollen lipid was dominant in linoleic acid (35.7–48%). The six other major fatty acids that were present in the lipid were myristic, palmitic, stearic, oleic, linolenic and arachidic acids. Linoleic acid was dominant in eucalypt pollen at average concentrations of 2.77–5.81 mg/g pollen. These results could be of significance to the Australian beekeeping industry in refining disease-management strategies in the light that other researchers have found that 2 economically damaging bee diseases (EFB and AFB) are inhibited by certain concentrations of the acid. Redgum- or marri (Corymbia calophylla)-pollen lipid was also dominated by 2 other known antibacterial fatty acids: myristic (0.25 mg/g pollen) and linolenic (1.06 mg/g pollen), when compared with the other eucalypts studied.

A comparative study of interspecific variation in fruit size among Australian eucalypts

A comparative study of interspecific variation in fruit size among Australian eucalypts