Sclerophyllous Research Articles

The leaf economic and plant size spectra of European forest understory vegetation

Forest understories play a vital role in ecosystem functioning and the provision of ecosystem services. However, the extent to which environmental conditions drive dominant ecological strategies in forest understories at the continental scale remains understudied. Here, we used ~29 500 forest vegetation plots sampled across Europe and classified into 25 forest types to explore the relative role of macroclimate, soil pH and tree canopy cover in driving abundance‐weighted patterns in the leaf economic spectrum (LES) and plant size spectrum (PSS) of forest understories (shrub and herb layers). We calculated LES using specific leaf area (SLA) and leaf dry matter content (LDMC) and PSS using plant height and seed mass of vascular plant species found in the understories. We found that forest understories had more conservative leaf economics in areas with more extreme mean annual temperatures (mainly Fennoscandia and the Mediterranean Basin), more extreme soil pH and under more open canopies. Warm and summer‐dry regions around the Mediterranean Basin and areas of Atlantic Europe also had taller understories with heavier seeds than continental temperate or boreal areas. Understories of broadleaved deciduous forests, such asFagusforests on non‐acid soils, or ravine forests, more commonly hosted species with acquisitive leaf economics. In contrast, some coniferous forests, such asPinus,LarixandPiceamire forests, orPinus sylvestrislight taiga and sclerophyllous forests, more commonly hosted species with conservative leaf economics. Our findings highlight the importance of macroclimate and soil factors in driving trait variation of understory communities at the continental scale and the mediator effect of canopy cover on these relationships. We also provide the first maps and analyses of LES and PSS of forest understories across Europe and give evidence that the understories of European forest types are differently positioned along major axes of trait variation.

Seeing the forest for the trees-and the grasses: revisiting the evidence for grazer-maintained grasslands in Madagascar's Central Highlands.

Seeing the forest for the trees-and the grasses: revisiting the evidence for grazer-maintained grasslands in Madagascar's Central Highlands.

Assessing the Australian Termite Diversity Anomaly: How Habitat and Rainfall Affect Termite Assemblages

Termites are important ecosystem engineers in tropical habitats, with different feeding groups able to decompose wood, grass, litter, and soil organic matter. In most tropical regions, termite abundance and species diversity are assumed to increase with rainfall, with highest levels found in rainforests. However, in the Australian tropics, this pattern is thought to be reversed, with lower species richness and termite abundance found in rainforest than drier habitats. The potential mechanisms underlying this pattern remain unclear. We compared termite assemblages (abundance, activity, diversity, and feeding group composition) across five sites along a precipitation gradient (ranging from ∼800 to 4,000 mm annual rainfall), spanning dry and wet savanna habitats, wet sclerophyll, and lowland and upland rainforests in tropical North Queensland. Moving from dry to wet habitats, we observed dramatic decreases in termite abundance in both mounds and dead wood occupancy, with greater abundance and activity at savanna sites (low precipitation) compared with rainforest or sclerophyll sites (high precipitation). We also observed a turnover in termite species and feeding group diversity across sites that were close together, but in different habitats. Termite species and feeding group richness were highest in savanna sites, with 13 termite species from wood-, litter-, grass-, dung-, and soil-feeding groups, while only five termite species were encountered in rainforest and wet sclerophyll sites—all wood feeders. These results suggest that the Australian termite diversity anomaly may be partly driven by how specific feeding groups colonized habitats across Australia. Consequently, termites in Australian rainforests may be less important in ecosystem processes, such as carbon and nutrient cycling during decomposition, compared with termites in other tropical rainforests.

Combining cameras and citizen science to define the distribution and behaviour of dingoes and foxes in New South Wales

We used two survey methods - citizen science for private land and cameras for protected areas - to map the distribution of dingoes/wild dogs and foxes in NSW. Dingo/wild dog records were mostly confined to the east coast and ranges, with scattered locations in western NSW. This contrasts to the distribution of foxes, in which occupancy was high across most of the state. Data from 200 WildCount camera sites within protected areas also showed marked differences in the distribution of the two canid species. At the scale of the state, dingoes/wild dogs are uncommon, with the greatest concentration being in the north-east of the state, as well as a marked presence in the south-east. Foxes are common and widespread within protected areas, but less common in the north-east of the state. The camera data also indicated that feral cats are widespread within protected areas. The second aim of our study was to examine the WildCount data for behavioural patterns of the canid species. Foxes and dingoes/wild dogs significantly separated within two sub-formations of dry sclerophyll forest based on the Keith (2004) classification of NSW vegetation. From species pairwise interactions at sites, we found only limited evidence for significant interactions, and then only for the co-occurrence of fox-rabbit and fox-swamp wallaby, but no avoidance for any of the predators with each other. Camera records of the time of day of being active showed little effect of the presence of dingoes/wild dogs on the times of activity of foxes, but foxes curtailed the activity times of dingoes/wild dogs. From the analysis of inter-animal times at sites where both canids were recorded, there was little difference between the time since the other species was present. Thus, there was no evidence that dingoes/wild dogs or foxes inhibit the other from being at a site. We concluded that at the landscape level, both vegetation type and land tenure play a role in the interactions between dingoes/wild dogs and foxes. We also concluded that citizen science and cameras are complementary, not alternative techniques, especially as they sample different land tenures, and that cameras in protected areas and occupancy from citizen science have produced higher resolution maps and behaviour patterns than have been previously available. We can confirm that foxes are a ubiquitous threat throughout NSW, whereas dingoes/wild dogs are concentrated into a much smaller area of eastern, particularly north-eastern, NSW.

Classification of forest and shrubland vegetation in Mediterranean Turkey

AbstractQuestionsWhat are the main vegetation types of forest and shrubland vegetation at the alliance level in Mediterranean Turkey? What is their syntaxonomical position? Can we integrate them into the European vegetation classification system? Which environmental factors are the main drivers of the floristic differentiation of vegetation types?LocationSouthern and western Turkey.MethodsWe collected 4,717 vegetation plots of forest and shrubland vegetation in Mediterranean Turkey and performed an unsupervised classification of this data set. We described vegetation types based on the classification results, expert knowledge and information from the literature. We defined diagnostic species and prepared distribution maps for each vegetation type. To support the interpretation of the vegetation types, we determined the most important environmental variables using canonical correspondence analysis.ResultsThe studied vegetation was divided into 21 types related to three vegetation belts: (a) thermo‐ and meso‐mediterranean, comprising coniferous (Pinus brutia, Pinus pinea) and sclerophyllous forests, as well as macchia, garrigue and phrygana; (b) supra‐mediterranean, comprising Pinus nigra subsp. pallasiana forests, thermophilous deciduous forests dominated by various oak species and Ostrya carpinifolia, and forests dominated by temperate species such as Fagus orientalis; and (c) oro‐mediterranean, comprising forests and shrublands dominated by Abies cilicica, Cedrus libani, Juniperus excelsa and Juniperus communis subsp. nana. Elevation was identified as the main environmental driver of the vegetation pattern. Among climatic variables, the most important are the mean temperatures (annual and of driest, coldest, and warmest quarters), minimum temperature of winter, precipitation of warmest and driest quarters and precipitation seasonality. These factors indicate the decreasing effect of the Mediterranean climate with increasing elevation.ConclusionsThe vegetation of Mediterranean Turkey is arranged along climatic gradients depending on elevation and the distance from the Mediterranean Sea. Most vegetation types in this area correspond to the syntaxa accepted in EuroVegChecklist, while others were described as new.

Leaf litter hides post-dispersed seeds from invasive alien removers in a sclerophyll forest in central Chile

Aim of the study: Seed removal may be a determining filter for regeneration. Factors such as leaf litter, tree cover and seed density affect seed removal. This aims to assess three aspects involving on post dispersal seed removal of four woody species (Lithraea caustica, Maytenus boaria, Quillaja saponaria and Retanilla ephedra) of a sclerophyll forest. Study area: Andean Mediterranean sclerophyll forest of Quillaja saponaria and Lithraea caustica located in the Río de Los Cipreses National Reserve, Chile. Materials and methods: Seven experimental plots were set up, in which seeds were offered in an experiment with variations in leaf litter, tree cover and seed density. Generalized Linear Mixed Models (GLMM) were used for the statistical analysis. Camera traps were installed to identify the seed removers. Main results: Q. saponaria seeds were more removed than the seeds of the other species (0.84, observed mean). Whereas that M. boaria and R. ephedra did not show significant differences on the removal of their seeds (0.77 and 0.67 respectively), both were more removed than L. caustica (0.59). The removal of M. boaria, Q. saponaria and R. ephedra seeds was lower in the presence of leaf litter. No factor influenced the removal of L. caustica seeds. Seed removers were identified as invasive alien species such as Rattus sp. and Oryctolagus cuniculus and native species such as Lycalopex culpaeus. Research highlights: Three woody species of this forest suffer severe seed removal by invasive alien fauna with major implications for the resilience of these forests. The coverage of leaf litter is key to hide away the seeds, increasing survival and could promote germination. Keywords: invasive alien fauna; Mediterranean forest; sclerophyll forest; seed removal factors.

Field studies of a high elevation population of northern Greater glider Petauroides volans minor in the Bluff State Forest, Far North Queensland

ABSTRACT We present the results of field surveys and a radio-tracking study of the Greater glider Petauroides volans minor in the Bluff State Forest, North Queensland. Twenty-three spotlighting transects were surveyed twice in July 2018, mean abundance of P. v. minor was 0.24 ha-1 in wet sclerophyll and 0.38 ha-1 in dry sclerophyll forest. Field observations (n= 330) were collected from nine radio-collared animals across three field sites from July to October 2019. 95% kernel home range estimates varied, ranging from 1.03 – 11.45 ha. Observations of denning (n=66) across 22 den trees identified that the gliders utilised between 1 and 4 dens during the study. Den trees were predominantly large Blue gum Eucalyptus tereticornis, with Gum-topped box Eucalyptus moluccana, Narrow-leafed ironbark Eucalyptus drepanophylla, Tindale’s stringybark Eucalyptus tindaliae and unidentifiable tree stags were used to lesser extent in one field site. Mean availability of suitable den trees was 2.07±1.12 per ha in Site 1 and 2, and 1.57±1.24 in Site 3. Foraging observations (n=148) were collected, Pink Bloodwood Corymbia intermedia and E. moluccana were the most commonly observed feed trees utilised by the study animals during the tracking period. This study provides baseline data for P. v. minor within high elevation habitat (950 to 1000 m) at its most northern extent. Given the widespread decline of P. volans across much of its range, these data may be used for developing local conservation strategies for the species in North Queensland.

How much survey effort is required to assess bird assemblages in fire-prone eucalypt forests using acoustic recorders?

Abstract Context Forest fire activity is expected to increase in many parts of the globe over the course of the 21st century, with corresponding potential for heightened levels of proximate and ultimate threats to avian diversity. Landscape-scale investigations of the responses of birds in locations where current extreme fire regimes represent those expected in the future provide opportunities to identify potentially vulnerable species in advance. Autonomous acoustic recorders are well suited to survey birds in the typically large and remote natural areas with low accessibility required for these types of studies, because they offer cost-effective and relatively safe options for obtaining reliable data. Aims The present study aimed to optimise survey using acoustic recorders to achieve a satisfactory assessment of montane dry sclerophyll forest bird assemblages using these devices. Survey completeness, or the number of species detected as a percentage of total species, was used as a metric to gauge survey suitability. Methods Acoustic recorders were deployed in 10 ridge-top forest sites in the Blue Mountains, south-eastern Australia. Extensive field recordings were processed by an analyst, with species detected by their calls recorded in a series of 20-min samples. A results-based approach, incorporating a stopping rule that established when to conclude sampling at a site, was applied to the data. The results guided the target survey completeness and sampling effort levels assigned to a set of fixed-effort survey methods, which were subsequently evaluated. Key results The optimal survey method involved using recordings from five 20-min sampling periods immediately following dawn for 2 days, achieving an average survey completeness level of 69%. Conclusions The optimal survey method can obtain results that are suitable for many types of studies involving assessments of bird assemblages, because the method can detect all common and moderately common species in assemblages, plus a fair proportion of rare species. Implications The present study has systematically developed an effective method of using autonomous acoustic recorders to research and monitor montane bird assemblages in fire-prone dry sclerophyll forests. This methodological approach may also be applied in systems subject to altered patterns of flood, storm or other extreme weather under climate change.

Foliage Senescence as a Key Parameter for Modeling Gross Primary Productivity in a Mediterranean Shrubland

AbstractAlthough drylands cover >40% of the land surface, models of ecosystem gross primary productivity (GPP) generally have been designed for mesic temperate ecosystems. Arguably, GPP models often lack a good representation of vegetation phenology, particularly not estimating the ecosystem effects of the prolonged foliage senescence which may be common in drylands. To estimate daily GPP for a water‐limited Mediterranean shrubland, we propose a simple framework (GPPmod) using light use efficiency, a spectral vegetation index derived from digital cameras, and five meteorological variables, including an index of functional senescence of foliage (i.e., heat degree‐days). We tested the model with different combinations of meteorological variables but without senescence, using 1 year's data. The best formulation showed good agreement with GPP derived from eddy covariance (GPPEC; r2 = 0.53, RMSE = 0.77). However, including the foliage senescence parameter significantly improved model performance (r2 = 0.74, RMSE = 0.49), especially during the fall season. In the following year, we validated the parameters: The overall GPPmod and GPPEC comparison yielded an r2 = 0.78. We postulate that models that mainly rely on meteorological variables or greenness indices could yield an overestimation of annual GPP between 24% and 90%, while models including the foliage senescence parameter reduced that bias by 10% to 34%. Our results highlight the importance of incorporating the phenology of foliage senescence in models regarding productivity in drylands or dry sclerophyll ecosystems.

The concept of vegetation class and order in phytosociological syntaxonomy

In order to stabilize the defining concepts of the higher rank syntaxonomic units such as class or order, the criteria of floristic content and unity of origin are enunciated. This is done with the aim of preventing the fragmentation of the large classes and the subsequent typological inflation. For orders, the criterion of specific floristic content is discussed, with orders that have been described to encompass seral secondary forests or the separation of forest vegetation from that which is dominated by shrubs rejected, due to their weak floristic characterization. These criteria have been applied to two forest vegetation classes: the European temperate (Querco-Fagetea) and the Mediterranean (Quercetea ilicis). For the first, it is argued in favor of maintaining a single class for all temperate deciduous forests in Europe instead of dividing them into four. Within this single class five orders are distinguished: Fagetalia, Quercetalia roboris, Quercetalia pubescenti-petraeae, Alno-Fraxinetalia and Populetalia albae, rejecting the orders that have been proposed for secondary forests because they have few characteristic taxa. For the sclerophyllous and macchia forests of Mediterranean Europe, the Quercetea ilicis class can be split into two or three geographical orders, rejecting the Pistacio-Rhamnetalia alaterni as a shrubby physiognomic unit. Taxonomic reference: Castroviejo S (coord. gen.) (1986–2012) Flora iberica 1–8, 10–15, 17–18, 21. Real Jardín Botánico, CSIC, Madrid, ES. Syntaxonomic reference: Mucina et al. (2016).

Divergent lineages in a semi-arid mallee species, Eucalyptus behriana, correspond to a major geographic break in southeastern Australia.

AimTo infer relationships between populations of the semi‐arid, mallee eucalypt, Eucalyptus behriana, to build hypotheses regarding evolution of major disjunctions in the species' distribution and to expand understanding of the biogeographical history of southeastern Australia.LocationSoutheastern Australia.Taxon Eucalyptus behriana (Myrtaceae, Angiospermae).MethodsWe developed a large dataset of anonymous genomic loci for 97 samples from 11 populations of E. behriana using double digest restriction site‐associated DNA sequencing (ddRAD‐seq), to determine genetic relationships between the populations. These relationships, along with species distribution models, were used to construct hypotheses regarding environmental processes that have driven fragmentation of the species’ distribution.ResultsGreatest genetic divergence was between populations on either side of the Lower Murray Basin. Populations west of the Basin showed greater genetic divergence between one another than the eastern populations. The most genetically distinct population in the east (Long Forest) was separated from others by the Great Dividing Range. A close relationship was found between the outlying northernmost population (near West Wyalong) and those in the Victorian Goldfields despite a large disjunction between them.ConclusionsPatterns of genetic variation are consistent with a history of vicariant differentiation of disjunct populations. We infer that an early disjunction to develop in the species distribution was that across the Lower Murray Basin, an important biogeographical barrier separating many dry sclerophyll plant taxa in southeastern Australia. Additionally, our results suggest that the western populations fragmented earlier than the eastern ones. Fragmentation, both west and east of the Murray Basin, is likely tied to climatic changes associated with glacial‐interglacial cycles although it remains possible that major geological events including uplift of the Mount Lofty Ranges and basalt flows in the Newer Volcanics Province also played a role.

A comparison of terrestrial and UAS sensors for measuring fuel hazard in a dry sclerophyll forest

In recent years, Unoccupied Aircraft Systems (UAS) have been used to capture information on forest structure in unprecedented detail. Pioneering studies in this field have shown that high spatial resolution images and Light Detecting And Ranging (LiDAR) data captured from these platforms provide detailed information describing the dominant tree elements of canopy cover and biomass. However, to date, few studies have investigated the arrangement of vegetation elements that contribute directly to fire propagation in UAS LiDAR point clouds; that is the surface, near-surface, elevated and intermediate-canopy vegetation. This paper begins to address this gap in the literature by exploring the use of image-based and LiDAR 3D representations collected using UAS platforms, for describing forest structure properties. Airborne and terrestrial 3D datasets were captured in a dry sclerophyll forest in south-eastern Australia. Results indicate that UAS LiDAR point clouds contain information that can describe fuel properties in all strata. Similar estimates of canopy cover (TLS: 68.27% and UAS LiDAR: 64.20%) and sub-canopy cover (Elevated cover TLS: 44.94%, UAS LiDAR: 32.27%, combined surface and near-surface cover TLS: 96.10% UAS LiDAR: 93.56%) to TLS were achieved using this technology. It was also shown that the UAS SfM photogrammetric technique significantly under performed in the representation of the canopy and below canopy structure (canopy cover - 20.31%, elevated cover 10.09%). This caused errors to be propagated in the estimate of heights in the elevated fuel layer (TLS: 0.51 m, UAS LiDAR: 0.34 m, UAS SfM: 0.15 m). A method for classifying fuel hazard layers is also presented which identifies vegetation connectivity. These results indicate that information describing the below canopy vertical structure is present within the UAS LiDAR point clouds and can be exploited through this novel classification approach for fire hazard assessment. For fire prone countries, this type of information can provide important insight into forest fuels and the potential fire behaviour and impact of fire under different scenarios.

Assessment of the cycle and availability of major and trace alkali and alkaline earth metals in the coastal Carmel Ridge, eastern Mediterranean

Major alkali and alkaline earth metals (Na, K, Mg, Ca) have been investigated extensively due to their role in soil, natural waters, living organisms, and agriculture, whilst their trace congeners (Li, Rb, Sr, Ba) are less well studied. Such information is of special interest for semi-arid Mediterranean ecosystems, in which these elements are believed to accumulate during prolonged dry seasons. However, data on the speciation, (bio)availability, and cycling of these metals are limited. We studied the fluxes of these metals in truly dissolved/reactive and ʻoperationally dissolvedʼ (microfiltrate, < 0.20 µm) forms in the sequence of ʻrainwater–throughfall water–litter leachateʼ in a restored mixed sclerophyll forest on the eastern Mediterranean coast. Truly dissolved metals were separated using an ion-exchange chromatography technique. The results suggest that decomposing plant litter followed by throughfall water are the main sources of the metals to underlying soils, whilst the contribution from rainwater is small, except for Na. Thereafter, the main flux of the water-mobile metals occurs within a semi-closed and rather self-sustaining soil–plant system. Only a portion of the water-mobile (< 0.20 µm) Na, K, Ca, and Mg was in truly dissolved/reactive form. The high-molecular-weight organic matter produced by leaf excretions in throughfall water and decomposing litter seems to play a major role in the speciation and transport of the metals, as well as in the mechanism of excretion of excess Na and Ca.

The effectiveness of fuel reduction burning for wildfire mitigation in sclerophyll forests

ABSTRACT The wildfires in south-eastern Australia in the 2019–20 fire season were some of the worst in recent memory. The effectiveness of fuel-reduction burning as a risk mitigation strategy is, once again, being scrutinised. Some argue that more fuel-reduction burning is needed, while others suggest that it is of limited use in such extreme fires. In this study, we tested the effectiveness of fuel-reduction burning at a landscape scale in terms of its ability to reduce the severity of subsequent wildfire. To achieve this, we selected all the recent (2015–2019) fuel-reduction burns undertaken in New South Wales and Victoria that intersected with the extent of the 2019–20 wildfires and evaluated whether the fire severity was significantly different in the recently treated areas to that of similar untreated areas in the vicinity. To determine fire severity, Sentinel 2 satellite imagery and the change in normalised burn ratio (a common metric used for rapid and broadscale fire severity mapping) was used. Our results showed that 48% of the 307 recent fuel-reduction burns resulted in statistically significant decreased fire severity. Our results also indicated that more recent fuel-reduction burns had a greater impact, with 66% of burns undertaken in 2019 significantly reducing severity, compared with 42% from 2015. We also analysed each fuel-reduction burn in the context of a range of metrics, including location, elevation, slope, aspect and forest heterogeneity, to assess whether these factors influenced the likelihood that a burn would be effective. Location and, to a lesser degree, forest heterogeneity were found to be significant factors. Our results support the view that recent fuel-reduction burns reduce fire severity. It is unclear, however, whether the differences would be operationally significant under extreme conditions, when wildfires are driven largely by weather, irrespective of fuel loads.

Effects of 38 years of wildfires on tree density in the Blue Mountains, Australia

AbstractForests are vital for biodiversity, carbon storage and ecosystem services, but can be potentially threatened by fires. Given the significance of forests and fire in a changing climate, research into the long‐term effects of fire on forests plays an important role in understanding the global carbon cycle by the forests functioning as a large terrestrial carbon sink or source. In this study, we used aerial photography from 1975 and 2013 to count the change in the number of trees in 560 dry sclerophyll plots (40 × 40m) in the Blue Mountains of Australia. We analysed the relationship between the number of fires and severe fires in that period on the change in numbers of trees. We found that the average response was an increase of 1 tree per plot over 38 years. The number of fires had a small positive effect on tree numbers; plots with 2 or 3 severe fires had 1 and 2 extra trees, respectively, than those without fire. One exception was a severe fire in 2001 that did not show this positive effect, probably because it corresponded with extensive drought. Our findings suggest that number of forest canopy trees is resilient to the number of fires and number of severe fires.

A recent review of fire behavior and fire effects on native vegetation in Central Chile

Central Chile experienced a very extended and devastating fire season during 2016–17. After 3 years, here we present the results of an analysis of behavior of the wildfires occurred in that season. We used a modeling approach to estimate the physical parameters of fire behavior: speed of linear spread, front-line intensity and flame length; as well as qualified fire severity, and the potential danger of recurrent fires. We selected eight study areas in four regions of Central Chile, under sclerophyllous forest and shrublands with variable composition. To run the model, we gathered data on vegetation structure and composition, and physical information. The values of the physical parameters were in a comparable range in the eight studied areas, with two of these areas showing maximum values. This could result from differences in vegetation. We detected rapid regrowth post-fire, despite the high levels of fire intensity and damage, ascribed to a high availability of very dry fine biomass. Given the predictions of increased drought, we should expect recurrence of wildfires. Based on our results, we anticipate fires of high severity and damage, with emphasis in areas with very high increase of dry biomass. We suggest restoration programs, with frequent monitoring of passive restoration practices, resorting to more active physical support in areas more severely affected.

No room to move: bat response to rainforest expansion into long-unburnt eucalypt forest

The expansion of rainforest trees into long-unburnt open forests is widespread globally, including in high-rainfall regions of eastern Australia. Increased tree density can reduce insectivorous bat activity and species richness by constraining echolocation and foraging success. Yet it is unknown whether sclerophyll and rainforest trees differ in their effects on open forest bat communities. We sampled insectivorous bats and nocturnal flying insects at two heights (understorey, canopy) in dry sclerophyll forest of eastern Australia with contrasting fire histories and levels of rainforest pioneer invasion. We found that both time since fire and functional identity of midstorey trees influenced the local bat community, whereas insect biomass had little effect. Long-unburnt forests with a rainforest pioneer midstorey had lower bat activity (63% lower) and species richness (35% lower) than recently burnt forests with a more open midstorey. Bat species richness also declined beneath the dense sclerophyll midstorey in long-unburnt forests, although was unaffected in the canopy above. Strong negative correlations between rainforest tree density and bat community activity and richness indicate that rainforest trees, in contrast with sclerophyll trees, exert additional negative control over open forest bat communities. Our results show that habitat suitability for clutter-intolerant bats declined well before the often-recommended maximum fire-intervals for dry open forest, providing evidence of an upper threshold for fauna conservation in rainforest-invaded open forests. To conserve bat communities in dry open forests vulnerable to rainforest invasion, fire should occur with sufficient frequency to prevent rainforest pioneers developing a dense midstorey that displaces clutter-intolerant bats.

Bark attributes determine variation in fire resistance in resprouting tree species

Predicting the impact of wildfires on ecosystem services and habitat values requires quantifying rates of post-fire tree mortality and topkill. For those species that resprout epicormically (i.e. from above-ground buds), rates of post-fire topkill (death of aboveground biomass) can vary considerably. Laboratory studies indicate that bark attributes are key determinants of post-fire topkill in these resprouting species. Specifically, bark thickness and bark density influence the capacity of bark to insulate the cambium from the lethal temperatures generated during wildfires. Field studies are generally consistent with these laboratory studies and demonstrate that smaller trees, with thinner bark, are more vulnerable to post-fire topkill. However, comparatively few studies model topkill explicitly as a function of bark thickness, and fewer still model topkill as a function of bark density. In this study we measured post-fire mortality and topkill across eight tree species with varying bark types. We also estimated pre-fire bark thickness (from relationships between stem diameter and bark thickness derived from unburnt forest) and measured bark density. We undertook our study at two dry sclerophyll eucalypt forests located in eastern Australia. The two study areas were subject to wildfire 18 months prior to measurements, with one site characterised by a semi-arid climate, and the second site (located 400 km south-east) characterised by a humid climate. We found that species with thick bark and a low bark density were most resistant to topkill. We defined vulnerability to topkill as the stem diameter associated with a 50% probability of topkill, estimated from logistic regressions. Multiple linear regression indicated that bark thickness and density accounted for 65% of the variation in vulnerability to topkill among species. This regression excluded one species; Eucalyptus crebra, which was identified as an outlier. This species was the most vulnerable to topkill and was located at the semi-arid study site. This study site had been subject to a more severe pre-fire drought than the mesic site, suggesting that drought may also have influenced post-fire topkill. However, it is not possible to exclude other species-specific factors or site factors such as climate or fire intensity, which may also have impacted the probability of topkill. Our results demonstrate that bark thickness and density are critically important in developing predictive models of post-fire topkill in resprouting forests.

Changes in bat activity over 10 years in silviculturally treated wet sclerophyll forest

A range of silvicultural treatments are applied to timber production forests, resulting in varied vegetation structural complexity. We compared the bat assemblage across three silvicultural treatments (unlogged forest, unthinned regrowth and thinned regrowth), two locations (on and off track) and three time periods (pre-thin, plus one and six years post-thinning) in wet sclerophyll forests, with treatments implemented at a small catchment scale. Linear edges provided important habitat for bats as total bat activity was substantially greater on tracks than off tracks, especially in unlogged and unthinned regrowth forest. Bat activity off track was greater in unlogged areas than in thinned and unthinned regrowth. Activity and species richness off track were greater in thinned than unthinned regrowth, but the time by treatment interaction was not significant for activity, indicating this difference cannot be ascribed to thinning alone. Thinning also led to a species composition that more closely resembled unlogged forest than unthinned regrowth. These patterns in bat activity across silvicultural treatments in wet sclerophyll forests were broadly consistent with other forest types, but subtleties, such as a subdued response to thinning, requires more replication to resolve. Nevertheless, differences between forest types need to be considered when developing management strategies.

Extinction of eastern Sahul megafauna coincides with sustained environmental deterioration

Explanations for the Upper Pleistocene extinction of megafauna from Sahul (Australia and New Guinea) remain unresolved. Extinction hypotheses have advanced climate or human-driven scenarios, in spite of over three quarters of Sahul lacking reliable biogeographic or chronologic data. Here we present new megafauna from north-eastern Australia that suffered extinction sometime after 40,100 (±1700) years ago. Megafauna fossils preserved alongside leaves, seeds, pollen and insects, indicate a sclerophyllous forest with heathy understorey that was home to aquatic and terrestrial carnivorous reptiles and megaherbivores, including the world’s largest kangaroo. Megafauna species diversity is greater compared to southern sites of similar age, which is contrary to expectations if extinctions followed proposed migration routes for people across Sahul. Our results do not support rapid or synchronous human-mediated continental-wide extinction, or the proposed timing of peak extinction events. Instead, megafauna extinctions coincide with regionally staggered spatio-temporal deterioration in hydroclimate coupled with sustained environmental change.