Dry Sclerophyll Woodland Research Articles

Soil microbial community composition and functions are disrupted by fire and land use in a Mediterranean woodland

The intersection of fire, land use transformations, and climate change is putting Mediterranean climate-type ecosystems at risk of soil degradation and loss of ecosystem services. Ondik et al. (2022b) showed that in a Mediterranean dry sclerophyll woodland of South Australia, high severity fire and clearing and grazing practices impacted both physicochemical and biological soil quality indicators. Building upon the work of Ondik et al. (2022b) this study aims to 1) identify soil physicochemical properties impacted by fire and land management that are indirect drivers of changes to soil microbial community composition and 2) determine whether the observed changes to soil microbial community composition affect soil microbial functions. Via a redundancy analysis, we identified fire and management-induced changes to pH, soil water repellency, nutrient stoichiometry, and total nutrient content as significant drivers of the composition of soil microbial communities. We then measured basal respiration, substrate induced respiration, and the carbon mineralisation quotient, and calculated functional trait distributions among microbial communities by linking 16S and 18S rRNA sequences to respiration modes and functional guilds, respectively. We found that fire reduced soil microbial respiration and the relative abundance (RA) of microbial symbionts, anaerobic bacteria, and microaerophilic bacteria, while increasing the RA of aerobic bacteria. Furthermore, management increased the RA of post-fire ectomycorrhizal fungi and may have reduced pathogenic load, microbial efficiency, and wood saprotrophs, while increasing litter, soil, and other saprotrophic species that are adapted to grasslands. This study shows that, through changes to microbial community composition, high severity wildfire and land management affected soil respiration rates, bacterial modes of respiration, prevalence of symbiotic bacteria and fungi, and microbial substrate preference. Having identified the main physicochemical drivers of changes to microbial community composition, we provide valuable insights into how fire and land management can impact soils in Mediterranean woodland.

Fire and land use impact soil properties in a Mediterranean dry sclerophyll woodland

Fire directly impacts soil properties responsible for soil function and can result in soil degradation. Across the globe, climate change-induced droughts and elevated temperatures are exacerbating fire regime severity, breadth, and frequency, thus posing a threat to soil function and dependent ecosystem services. In Australia, the 2019–2020 fire season consumed nearly 50% of Kangaroo Island, South Australia, burning both dry sclerophyll woodland and adjacent historically cleared and grazed pastureland. Due to exacerbated fire regime elements, e.g., intensity and area affected, and interactions with historical land use, post-fire recovery of soil function was uncertain. This study assessed the impacts of a) the 2019–2020 fire event in Western River, Kangaroo Island on dry sclerophyll woodland and b) the interaction between this fire event and historical clearing and grazing on post-fire function of the soil. To do so, the following physicochemical and biological soil properties were analysed: labile active carbon, total carbon, total nitrogen, carbon to nitrogen ratio (C/N), pH, electrical conductivity, soil water repellency, aggregate stability, microbial community composition, and microbial diversity. Our results showed that the fire was of high severity, causing a reduction in nutrient content, an extreme rise in pH, and significant modifications to fungal communities in burnt compared to unburnt dry sclerophyll woodland. Furthermore, clearing and grazing raised post-fire soil nutrient levels and soil microbial diversity but reduced soil C/N and the abundance of ectomycorrhizal fungi in burnt pastureland compared to burnt woodland soils. This study highlights the role of management and fire severity in post-fire outcomes and emphasizes the need for comprehensive soil function assessments to evaluate the impacts of disturbance on soil. Taking direct measure of soil properties, as done here, will improve future assessments of fire season impacts and post-fire recovery in fire-prone landscapes.

Lack of vulnerability segmentation among woody species in a diverse dry sclerophyll woodland community

Abstract Recent findings suggest that tree mortality and post‐drought recovery of gas exchange can be predicted from loss of function within the water transport system. Understanding the susceptibility of plants to hydraulic damage requires knowledge about the vulnerability of different plant organs to stress‐induced hydraulic dysfunction. This is particularly important in the context of vulnerability segmentation between plant tissues which is believed to protect more energetically ‘costly’ tissues, such as woody stems, by sacrificing ‘cheaper’ leaves early under drought conditions. Differences in vulnerability segmentation between co‐occurring plant species could explain divergent behaviours during drought, yet there are few studies considering how this characteristic may vary within a plant community. Here we investigated community‐wide vulnerability segmentation by comparing leaf/shoot and stem vulnerability in all coexistent dominant canopy and understory woody species in a diverse dry sclerophyll woodland community, including multiple angiosperms and one gymnosperm. Previously published terminal leaf/shoot vulnerability to loss of water transport capacity was compared with stem xylem vulnerability to embolism measured on the same species at the same site. We calculated hydraulic safety margins for stems to determine variation in the risk of hydraulic failure during drought among species. The xylem of all species was found to be highly resistant to hydraulic dysfunction, with only two of the eight species exhibiting significantly different vulnerability to the overall mean. No evidence of vulnerability segmentation between shoots/leaves and stems was found in seven of the eight species. Phylogenetically diverse canopy and understory species in this evergreen sclerophyll woodland appear to have evolved similar strategies of drought resistance, including low xylem vulnerability to embolism and general lack of vulnerability segmentation. This convergence in hydraulic safety indicates a lack of hydraulic niche partitioning in this woodland community. A free plain language summary can be found within the Supporting Information of this article.

Water relations of selected wallum species in dry sclerophyll woodland on the lower north coast of New South Wales, Australia

The present study examined the water relations of wallum dry sclerophyll woodland on the lower north coast of New South Wales (NSW). Wallum is the regionally distinct vegetation of Quaternary dunefields and beach ridge plains along the eastern coast of Australia. Wallum sand masses contain large aquifers, and previous studies have suggested that many of the plant species may be groundwater dependent. However, the extent of this dependency is largely unknown, despite an increasing reliance on the aquifers for groundwater extraction. Fifteen species from five growth-form categories and seven plant families were investigated. The pre-dawn and midday xylem water potential (ψx) of all species was monitored over a 20-month period from December 2007 to July 2009. Pressure–volume curve traits were determined for each species in late autumn 2008, including the osmotic potential at full (π100) and zero (π0) turgor, and bulk modulus of elasticity (ε). Carbon isotope ratios (δ13C) were determined in mid-autumn 2008 to measure water use efficiency (WUE). Comparative differences in water relations could be loosely related to growth forms. A tree (Eucalyptus racemosa subsp. racemosa) and most large shrubs had low midday ψx, π100 and π0, and high ε and WUE; whereas the majority of small and medium shrubs had high midday ψx, π100 and π0, and low ε and WUE. However, some species of similar growth form displayed contrasting behaviour in their water relations (e.g. the herbs Caustis recurvata var. recurvata and Hypolaena fastigiata), and such differences require further investigation. The results suggest that E. racemosa subsp. racemosa is likely to be groundwater dependent, and large shrubs such as Banksia aemula may also utilise groundwater. Both species are widespread in wallum, and therefore have the potential to play a key role in monitoring ecosystem health where aquifers are subject to groundwater extraction.

Revision of the Australian species of the ant genus Anochetus (Hymenoptera: Formicidae)

The Australian species of the ponerine ant genus Anochetus are revised. Fourteen species are known from Australia with eight described here for the first time (alae n. sp, armstrongi McAreavey, avius n. sp., graeffei Mayr, isolatus Mann, paripungens Brown, rectangularis Mayr, renatae n. sp., rufolatus n. sp., rufostenus n. sp., turneri Forel, veronicae n. sp., victoriae n. sp., wiesiae n. sp.). Twelve are endemic to Australia while two are shared with Australia’s northern neighbours. Most species are restricted to tropical regions with only two known from southern Australia. While the majority of species are found in forested habitats, ranging from rainforest to dry sclerophyll woodlands, in southern regions they extend into drier shrub and bush dominated sites.

Evolutionary origins and diversification of dragon lizards in Australia’s tropical savannas

Australia’s monsoonal tropics are dominated by the largest and least modified savanna woodlands in the world, and they are globally significant for their high biodiversity and regional endemism. Despite this, there have been very few molecular studies of the evolutionary origins and diversification of vertebrates in this region. The semi-arboreal dragon lizards of Lophognathus and Amphibolurus are widely distributed in the savanna and dry sclerophyll woodlands of Australasia, including the monsoon tropics. We sequenced a ∼1400bp region of mitochondrial DNA and a ∼1400bp nuclear gene (RAG1) to investigate the phylogenetic relationships and phylogeographic structuring of all seven species of Lophognathus and Amphibolurus. Our analyses show that there is a higher level of species and generic diversity in the monsoon tropics than previously thought, and a full morphological review and taxonomic revision of these genera is required. Relaxed molecular clock analyses indicate that species across both genera originated in the late Miocene and early Pliocene, with significant phylogeographic structure within species. We did not find any evidence that the monsoon tropics species were a monophyletic group that had diversified within the region; instead Amphibolurus and Lophognathus represent at least three independent evolutionary colonizations of the monsoon tropics. It is probable that the origins and phylogeographic patterns of the northern Lophognathus species have evolved under the climatic influence of the Australian monsoon, rather than being either an ancient Gondwanan lineage that pre-dates the monsoon or the result of a more recent dispersal event across Wallace’s Line.

A metacommunity‐scale comparison of species‐abundance distribution models for plant communities of eastern Australia

Various models of the species‐abundance distribution (SAD) have been proposed to fit empirically derived data however there is no general consensus as to which model provides the best fit. Further, the zero‐sum multinomial SAD model (ZSM) was proposed as a metacommunity model, yet it has not previously been fitted at the metacommunity scale. We note that SAD models based on compound lognormal distributions (such as the Poisson‐lognormal, PLN, and the negative binomial‐lognormal models, NBLN) can also be thought of as metacommunity models, and we compare these with the ZSM when fitted as metacommunity models to SADs of related communities.We collected five datasets in the Sydney Basin, eastern Australia, representing five different types of subtropical/temperate plant communities ranging from closed warm‐temperate rainforest to open wet sclerophyll forest to dry sclerophyll woodland. For each type of plant community, five local communities were identified across the Sydney Basin, and SAD data collected in five randomly placed 0.2‐ha quadrats at each local community. Analysis was performed at two levels: all abundance data from each local community were pooled across each metacommunity and analysed as a single pooled community; and a metacommunity model was fitted to all five local communities of a community type, simultaneously. For the pooled data, we considered the negative‐binomial (NB) and the log‐series (LS) models in addition to ZSM, PLN and NBLN. All five models performed similarly, however the LS had a better fit to three pooled communities and the ZSM and PLN to the remaining two communities. By contrast, the ZSM performed statistically better against the PLN and NBLN when considered as a metacommunity model. We conclude that the ZSM generally provides a more reliable null model for metacommunity abundance data than the lognormal model.

Invertebrate prey of the bark-foraging insectivore Phascogale tapoatafa: distribution of biomass amongst alternative foraging substrates within south-western Australian woodlands

The bark of trees is an important foraging substrate for a range of vertebrate insectivores. This study aimed to investigate the distribution of food resources available to the bark-foraging insectivore Phascogale tapoatafa, and to compare prey biomass on bark versus the litter layer. We conducted nocturnal sampling for arthropods on tree trunks and litter in a forest in south-western Australia. The bark fauna biomass was dominated by spiders, with cockroaches, beetles and ants also well represented. In contrast, the litter was dominated by orthopterans. Invertebrate biomass was much greater in the litter layer than on tree trunks. Prey items in bark were more plentiful in Melaleuca swamps than in the surrounding dry sclerophyll woodland. Within swamps, trees with the highest invertebrate densities had thin trunks or loose bark, whilst in woodland it was trees with thick bark. Water availability may increase the prey resource used by bark-foraging insectivores.

A 23,000-yr pollen record from Lake Euramoo, Wet Tropics of NE Queensland, Australia

A new extended pollen and charcoal record is presented from Lake Euramoo, Wet Tropics World Heritage rainforest of northeast Queensland, Australia. The 8.4-m sediment core taken from the center of Lake Euramoo incorporates a complete record of vegetation change and fire history spanning the period from 23,000 cal yr B.P. to present. The pollen record is divided into five significant zones; 23,000–16,800 cal yr B.P., dry sclerophyll woodland; 16,800–8600 cal yr B.P., wet sclerophyll woodland with marginal rainforest in protected pockets; 8600–5000 cal yr B.P., warm temperate rainforest; 5000–70 cal yr B.P., dry subtropical rainforest; 70 cal yr B.P.–AD 1999, degraded dry subtropical rainforest with increasing influence of invasive species and fire. The process of rainforest development appears to be at least partly controlled by orbital forcing (precession), though more local environmental variables and human activity are also significant factors. This new record provides the opportunity to explore the relationship between fire, drought and rainforest dynamics in a significant World Heritage rainforest region.

Latitude, seed predation and seed mass

AbstractAim We set out to test the hypothesis that rates of pre‐ and post‐dispersal seed predation would be higher towards the tropics, across a broad range of species from around the world. We also aimed to quantify the slope and predictive power of the relationship between seed mass and latitude both within and across species.Methods Seed mass, pre‐dispersal seed predation and post‐dispersal seed removal data were compiled from the literature. Wherever possible, these data were combined with information regarding the latitude at which the data were collected. Analyses were performed using both cross‐species and phylogenetic regressions.Results Contrary to expectations, we found no significant relationship between seed predation and latitude (log10 proportion of seeds surviving predispersal seed predation vs. latitude, P = 0.63; R2 = 0.02; n = 122 species: log10 proportion of seeds remaining after postdispersal seed removal vs. latitude, P = 0.54; R2 = 0.02; n = 205 species). These relationships remained non‐significant after variation because of seed mass was accounted for. We also found a very substantial (R2 = 0.21) relationship between seed mass and latitude across 2706 species, with seed mass being significantly higher towards the tropics. Within‐species seed mass decline with latitude was significant, but only about two‐sevenths, as rapid as the cross‐species decline with latitude. Results of phylogenetic analyses were very similar to cross‐species analyses. We also demonstrated a positive relationship between seed mass and development time across ten species from dry sclerophyll woodland in Sydney (P < 0.001; R2 = 0.77; Standardized Major Axis slope = 0.14). These data lend support to the hypothesis that growing period might affect the maximum attainable seed mass in a given environment.Main conclusions There was no evidence that seed predation is higher towards the tropics. The strong relationship between seed mass and latitude shown here had been observed in previous studies, but had not previously been quantified at a global scale. There was a tenfold reduction in mean seed mass for every c. 23° moved towards the poles, despite a wide range of seed mass within each latitude.

The structure and dynamics of an assemblage of small birds in a semi-arid eucalypt woodland in south-western Australia

The small birds present in 25 ha of dry sclerophyll woodland near Kalgoorlie, Western Australia, were monitored twice weekly over 18 months. The birds that fed solely upon invertebrates were largely resident and their abundances fluctuated little. The numbers of species and the abundances of honeyeaters varied much more, but with no clear relationship to the nectar present in the erratically flowering eucalypts present. Some resident meliphagid honeyeaters were either predominantly gleaners or only opportunistic flower-feeders. Only larger-scale studies are likely to resolve patterns among the more mobile birds in such assemblages.

Digging by vertebrates as an activity promoting the development of water-repellent patches in sub-surface soil

Dry sclerophyll woodlands in south-western Australia are refugia for remnant populations of woyliesBettongia penicillata . These marsupials create holes as they forage for the fruiting bodies of hypogeous fungi. The effect of these holes on the water-repellent woodland soils was evaluated using simulated diggings. Water repellency was significantly higher in surface than in sub-surface soils, although patches of moderately water-repellent sub-soils did occur. In situ assessments of simulated diggings that were allowed to decay showed a five-fold increase in water repellency in sub-surface soil once they had become filled-in. Buried organic material was found in many decayed diggings that were severely water-repellent, and very severe water repellency occurred where masses of fungal hyphae were present. This suggests that vertebrate diggings in which surface litter and organic debris become trapped can provide a site for the development of sub-surface water repellency.

SPECIES IN THE TAIL OF RANK–ABUNDANCE CURVES

At focal sites within dry sclerophyll woodland and temperate rain forest, species were identified that were of low local abundance and hence in the tail of the rank–abundance curve. We then asked the question: What proportion of tail species within a given community are constitutive members of the tail everywhere throughout their geographical range, versus what proportion are found as substantially more abundant somewhere within their range? Out of 55 tail species identified from dry sclerophyll woodland and 116 tail species identified from temperate rain forest, 91% and 95%, respectively, were significantly more abundant at other locations (“somewhere-abundant” species), versus 9% and 5% “everywhere-sparse” species. Among eight attributes in dry sclerophyll woodland and nine attributes in temperate rain forest compared between somewhere-abundant and everywhere-sparse species, none discriminated consistently between the two groups of species. The size and dispersal morphology of seeds, flowering and fruiting durations and seasons, regeneration strategy after fire, size of geographical ranges, maximum plant height, and size class revealed no consistent distinctions. For the small minority of species that are everywhere-sparse, some general explanation may exist as to why they are in the tail of rank–abundance curves, though none was located among the attributes compared in this paper. For the majority of tail species that are somewhere-abundant, any explanation as to why they are in the tail will need to account for different outcomes in different places.

The relocation of ant nest entrances: Potential consequences for ant‐dispersed seeds

AbstractThe rate at which ant nests relocate may affect the fate of ant‐dispersed seeds by influencing nutrient and seed accumulation in localized areas. In this study, the movement of ant nest entrances was monitored in fixed quadrats in dry sclerophyll woodland in Kuringai Chase National Park, NSW. Changes in entrance location were rapid for most species, with few entrances remaining in use for more than 6 months. Approximately 30% of entrances that closed were subsequently re‐opened. There was no obvious seasonal pattern in entrance relocation. After 1 year, between 5 and 40% of the ground surface of the quadrats had been within 10 cm of a nest entrance. New nest entrances did not cluster near old entrances, indicating that nest entrance relocation may be accompanied by changes in underlying nest structure. Nutrient levels in soil samples from active nests of Rhytidoponera metallica, Aphaenogaster longiceps, Pheidole sp. 1 and Iridomyrmex sp. 8 did not differ significantly from random locations.The rapid changes in entrance location and the lack of nutrient enrichment may be the result of continual and progressive underground shifts in nest location. Such shifts have three potential consequences for seeds that remain buried within the nests. First, seeds will not benefit following germination by being in a nutrient‐rich microsite. Second, a proportion of seeds collected by harvester ant species may escape predation if left in an abandoned section of the nest. Third, concentrations of seeds in localized areas may be reduced, leading to a reduction in competition between establishing seedlings.

A new species of Thyrostroma from Australia

Thyrostroma eucalypti sp. nov. has been found associated with stem cankers and dieback of several dry sclerophyll woodland eucalypt species in pastoral areas of south east Australia. The fungus is characterized by acervular or pulvinate sporodochial conidiomata, branched, septate, percurrently, proliferating conidiophores and holoblastic, pigmented, euseptate, muriform conidia.

Ecology of Co-Existing White-Cheeked and New Holland Honeyeaters

The ecology and breeding biology of White-cheeked Phylidonyris nigra and New Holland P. novaehollandiae Honeyeaters has been studied since 1967 in the Brisbane Waters National Park north of Sydney, NSW. This is an area where the ranges of the two birds overlap and in one study plot, a heath, both nest close to each other. Only the White-cheeked occurs in a second plot, a dry sclerophyll woodland, near the heath. Breeding bird censuses have revealed that during most years similar numbers of honeyeaters nest during the autumn and spring but there can be considerable variation in numbers between years. The number of nesting pairs may be related to weather and to long-term changes in vegetation but there is no consistent pattern and numbers may be determined by environmental factors outside the study area. Both species forage in similar ways and take insects and nectar from the same places. It is suggested that the presence of both on the heath for part of the year is related to the abundance of nectar. In other places where the species overlap they are separated by habitat. Data on clutch size, nest sites and breeding success are presented and discussed.