Eucalypt Forest Research Articles

The Fuel Moisture Index Based on Understorey Hygrochron iButton Humidity and Temperature Measurements Reliably Predicts Fine Fuel Moisture Content in Tasmanian Eucalyptus Forests

Fine fuel moisture content (FFMC) is a key determinant of wildfire occurrence, behaviour, and pyrogeographic patterns. Accurate determination of FFMC is laborious, hence managers and ecologists have devised a range of empirical and mechanistic measures for FFMC. These FFMC measures, however, have received limited field validation against field-based gravimetric fuel moisture measurements. Using statistical modelling, we evaluate the use of the relationship between gravimetric FFMC and the Fuel Moisture Index (FMI), based on Hygrochron iButton humidity and temperature dataloggers. We do this in Tasmanian wet and dry Eucalyptus forests subjected to strongly contrasting disturbance histories and, hence, percentage of canopy cover. We show that 24 h average FMI based on data from Hygrochron iButtons 0.75 m above the forest floor provides reliable estimates of gravimetric litter fuel moisture (c. 1 h fuels) that are strongly correlated with near surface gravimetric fuel moisture sticks (c. 10 h fuels). We conclude FMI based on Hygrochron iButton data provides ecologists with an economic and effective method to retrospectively measure landscape patterns in fuel moisture in Tasmanian forests.

Detection of Eucalyptus Leaf Disease with UAV Multispectral Imagery

Forest disease is one of the most important factors affecting tree growth and product quality, reducing economic values of forest ecosystem goods and services. In order to prevent and control forest diseases, accurate detection in a timely manner is essential. Unmanned aerial vehicles (UAVs) are becoming an important tool for acquiring multispectral imagery, but have not been extensively used for detection of forest diseases. This research project selected a eucalyptus forest as a case study to explore the performance of leaf disease detection using high spatial resolution multispectral imagery that had been acquired by UAVs. The key variables sensitive to eucalyptus leaf diseases, including spectral bands and vegetation indices, were identified by using a mutual information–based feature selection method, then distinguishing disease levels using random forest and spectral angle mapper approaches. The results show that green, red edge, and near-infrared wavelengths, nitrogen reflectance index, and greenness index are sensitive to forest diseases. The random forest classifier, based on a combination of sensitive spectral bands (green, red edge, and near-infrared wavelengths) and a nitrogen reflectance index, provided the best differentiation results for healthy and three disease severity levels (mild, moderate, and severe) with overall accuracy of 90.1% and kappa coefficient of 0.87. This research provides a new way to detect eucalyptus leaf diseases, and the proposed method may be suitable for other forest types.

What drives forest carbon storage? The ramifications of source-sink decoupling.

This article is a Commentary on Martínez‐Sancho et al. (2022), 236: 58–70.

Fire severity has lasting effects on the distribution of arboreal mammals in a resprouting forest

AbstractWildfire severity is assumed to be an important driver of habitat availability and species' distributions in forest ecosystems. Many studies have focused on the immediate or short‐term effects of fire severity in fire‐prone ecosystems, with much less focus on how long the effect of fire severity may persist. We examined the effect of fire severity on the distribution of arboreal mammals at 3 and 10 years post‐fire, in a temperate forest ecosystem dominated by eucalypts that have strong resistance and resilience to low and high severity fire, respectively. The study took place within areas affected by the 2009 Kilmore East‐Murrindindi wildfires in south‐eastern Australia. Sites were established across a gradient of fire severity (unburnt through to canopy consumption) and surveyed at 3 and 10 years following fire. Owing to low detection rates for many species, analyses were limited to greater glider (Petauroides volans) occurrence and arboreal species richness. At both 3 and 10 years post‐fire, the greater glider was restricted to unburnt forest or sites affected only by understorey fire, which acted as fire refugia. Greater gliders were absent from sites affected by high severity, canopy‐consuming fires at both points in time. Greater glider occurrence was associated with high levels of canopy cover (>50%), which were typically those areas that were unburnt or burnt at low severity. The richness of arboreal mammals increased over time and was greater in unburnt or minimally affected forest. Our findings emphasize: (i) that fire severity is an important driver of the distribution of arboreal mammals; and (ii) the importance of recognizing longer‐term effects of fire severity in assessing species distributions, even in highly resilient forest communities. Recent advances in mapping fire severity provide new opportunities to assess the effects of fire severity on the distributional patterns of fauna in eucalypt forests.

Effects of different amendments on the quality of burnt eucalypt forest soils – A strategy for ecosystem rehabilitation

The magnitude of forest fires’ impacts on the environment is directly related to the changes induced on soil physical, chemical and biological properties. Using available organic resources to rehabilitate burnt forest soils can help reduce post-fire soil fertility loss, accelerating ecosystem recovery. In the present study, the potential of four soil amendments: a mycotechnosol, a eucalypt residue mulch, dredged sediments from a freshwater lagoon and an organic-mineral biofertilizer, to improve the quality of burnt forest soils in terms of organic matter, carbon, nitrogen and phosphorus contents, was evaluated. Two experiments were set-up, one in a recently burnt eucalypt plantation and another in the laboratory using soils from the same area, to assess the effects of the amendments on soil quality, with both experiments lasting for 7 months. The effects of the amendments on nutrient leaching along the soil profile were also evaluated in the laboratory, to investigate possible negative impacts on groundwater and surface water quality. All amendments increased the organic matter and nutrient contents of burnt soils, confirming their potential for ecosystem rehabilitation. The biofertilizer, however, was found to promote nutrient losses by leaching, largely owing to its high solubility, increasing the risk of contamination of ground and surface waters. Using available organic resources to rehabilitate burnt forests as was done in the present work complies with the idea of a circular economy, being key for the sustainability of forest ecosystems.

Rapid bird species recovery following high‐severity wildfire but in the absence of early successional specialists

AbstractAimThe distribution and abundance of forest biodiversity can be shaped by multiple drivers, including disturbances like wildfires. We quantified the influence of wildfire severity and bird life history attributes on temporal patterns of bird site occupancy.LocationWet eucalypt forests of Victoria, Australia.MethodsWe employed a Before, After, Control, Impact experimental design, gathering occupancy data on birds 5 years before, and for 10 years after, a wildfire in 2009. We quantified post‐fire decline and then recovery on sites subject to high‐severity fire, comparing these temporal patterns with those for birds at sites that were unburnt or burnt at moderate severity. We also tested the influence of life history attributes on bird responses to wildfire. Data were analysed using joint species distribution modelling, accounting for imperfect detection.ResultsWe found a two‐way interaction between fire severity and time period for overall bird site occupancy. The largest change between time periods was on sites burnt at high severity where bird occupancy declined immediately after fire followed by a strong recovery. Occupancy patterns remained largely unchanged on unburnt sites. For many individual species, interactions between fire severity and time period were similar to overall species occupancy. On sites subject to high‐severity fire, most species recovered to pre‐fire levels within 6 years. We found no evidence of a three‐way interaction between fire severity, time period, and life history attributes, with all trait groups of birds examined largely recovered to pre‐fire site occupancy levels 10 years post‐fire.Main conclusionsThe Victorian 2009 wildfires were severe, but their impacts on common bird species were relatively short‐lived, with immediate post‐fire declines mostly reversed within ~10 years. Rapid post‐fire stand regeneration appears a likely driver of these responses and may account for the relatively limited influence of life history attributes on bird species recovery. However, diet influenced bird species occupancy after fire, with nectivores recovering slower than insectivores on sites subject to high severity fire. Our findings may be relevant to other forests types globally where there can be rapid post‐fire vegetation growth and stand regeneration.

Fuel in Tasmanian Dry Eucalypt Forests: Prediction of Fuel Load and Fuel Hazard Rating from Fuel Age

This paper presents equations for fuel load and fuel hazard rating (FHR) models based on the time since last fire for dry eucalypt forests in eastern Tasmania. The fuel load equations predict the load of the surface/near-surface and elevated fine fuel. The FHR equations predict the surface, near-surface, combined surface and near-surface, bark, and overall FHR. The utility of the “Overall fuel hazard assessment guide” from Victoria, Australia, is assessed for Tasmanian dry eucalypt forests: we conclude that, when fuel strata components are weighted according to their influence on fire behaviour, the Victorian guide provides a rapid, robust, and effective methodology for estimating FHR. The equations in this paper will be used for operational planning and on-the-ground performing of hazard reduction burning, prediction of fire behaviour for fire risk assessments and bushfire control, and providing inputs into the new Australian Fire Danger Rating System.

Fences foil foragers from fueling forest fires: Can large herbivores alter fire behaviour in coastal eucalypt forests?

Fences foil foragers from fueling forest fires: Can large herbivores alter fire behaviour in coastal eucalypt forests?

Incorporating management flexibility: a Real Options Approach to harvesting Eucalyptus plantations

ABSTRACT The decision to harvest planted forests transcends the adopted silvicultural schedule, given that external market factors such as fluctuations in demand for timber products intensify managerial responses regarding the supply of raw materials. Therefore, forest managers need prior planning to correctly model market uncertainties and risks and thus remain nimble in decision-making. We identify the best probability distribution for modelling the price of Eucalyptus wood to assist managerial decision-making when advanced- or postponed-harvesting options are available for planted forests. Our study was based on a planted forest of Eucalyptus in an area of 11 677 ha belonging to a forest-based company in the Midwest region of the state of São Paulo, Brazil. We tested harvesting in the sixth, seventh and eighth year under the single-rotation silvicultural management system of forest reform. Our decisions are based on econometric tests and incorporate flexibility through the Real Options Approach with the Monte Carlo simulation method. The modelling of the recommended wood price was performed using fractional Brownian motion, which resulted in an expanded present value of USD 40 747 966 – that is, an increase of 161% over the static present value, with a 62.7% probability of the harvest occurring in the seventh year. Thus, we conclude that the incorporation of managerial flexibility in decisions on the timing of planted-forest harvesting adds value to forest investment projects considered economically unfeasible by traditional methodologies.

Laying low: Rugged lowland rainforest preferred by feral cats in the Australian Wet Tropics.

Invasive mesopredators are responsible for the decline of many species of native mammals worldwide. Feral cats have been causally linked to multiple extinctions of Australian mammals since European colonization. While feral cats are found throughout Australia, most research has been undertaken in arid habitats, thus there is a limited understanding of feral cat distribution, abundance, and ecology in Australian tropical rainforests. We carried out camera‐trapping surveys at 108 locations across seven study sites, spanning 200 km in the Australian Wet Tropics. Single‐species occupancy analysis was implemented to investigate how environmental factors influence feral cat distribution. Feral cats were detected at a rate of 5.09 photographs/100 days, 11 times higher than previously recorded in the Australian Wet Tropics. The main environmental factors influencing feral cat occupancy were a positive association with terrain ruggedness, a negative association with elevation, and a higher affinity for rainforest than eucalypt forest. These findings were consistent with other studies on feral cat ecology but differed from similar surveys in Australia. Increasingly harsh and consistently wet weather conditions at higher elevations, and improved shelter in topographically complex habitats may drive cat preference for lowland rainforest. Feral cats were positively associated with roads, supporting the theory that roads facilitate access and colonization of feral cats within more remote parts of the rainforest. Higher elevation rainforests with no roads could act as refugia for native prey species within the critical weight range. Regular monitoring of existing roads should be implemented to monitor feral cats, and new linear infrastructure should be limited to prevent encroachment into these areas. This is pertinent as climate change modeling suggests that habitats at higher elevations will become similar to lower elevations, potentially making the environment more suitable for feral cat populations.

A cool spot in a biodiversity hotspot: why do tall Eucalyptus forests in Southwest Australia exhibit low diversity?

Background and aimsSouthwest Australia is a biodiversity hotspot, with greatest plant species diversity on the most severely phosphorus (P)-impoverished soils. Here, non-mycorrhizal species with highly-effective carboxylate-releasing P-acquisition strategies coexist with mycorrhizal species that are less effective at accessing P on these soils. Non-mycorrhizal carboxylate-releasing species facilitate P acquisition of mycorrhizal neighbours that are better defended against pathogens. In the Southwest Australian Biodiversity Hotspot, there are also ‘cool spots’ of low-diversity tall mycorrhizal Eucalyptus communities on P-impoverished soils. These Eucalyptus trees obviously do not require facilitation of their P acquisition by carboxylate-releasing neighbours, because these are only a minor component of the low-diversity communities. We hypothesised that in low-diversity tall Eucalyptus forests, mycorrhizal species release carboxylates to acquire P. Thus, they would not depend on facilitation, and must be strong competitors. However, because they would not depend on external mycorrhizal hyphae to acquire P, they would also not be able to access soil organic nitrogen (N), for which they would need external hyphae.MethodsSince carboxylates not only mobilise P, but also manganese (Mn), we used leaf Mn concentrations ([Mn]) in the natural habitat to proxy rhizosphere carboxylates. To verify this proxy, we also measured carboxylate exudation of targeted species with high leaf [Mn] using seedlings grown in low-P nutrient solutions.ResultsUsing these complementary approaches, we confirmed our hypothesis that dominant Eucalyptus species in ‘cool spots’ release carboxylates. Since mineralisation of organic N is associated with fractionation of N, enriching organic N with 15N while nitrate is depleted in 15N, we measured the stable N isotope composition of leaf material. The results show that dominant Eucalyptus species did not access organic N, despite being ectomycorrhizal.ConclusionsThe low diversity of tall Eucalyptus forests in southwest Australia can be explained by dominant mycorrhizal species exhibiting a carboxylate-releasing strategy. The tall eucalypts are therefore strong competitors that do not require facilitation, but also do not access organic N.

A modelling approach to evaluate land management options for recently burnt catchments

AbstractScars left by wildfires are easily visible in the Mediterranean landscape and, like any wound, even those left by fires must be treated to regenerate properly. If not managed, spontaneous vegetation regeneration will eventually cover the affected area, restoring the hydrological cycle. The reforestation of burned stands, involving ploughing the land and building terraces on steep slopes, together with fertilisation of the area, is also common. The Soil and Water Assessment Tool (SWAT) was used to simulate three post‐fire land management options for a small catchment in central Portugal. The choice of this basin relates to the implementation of terraces to create a eucalyptus forest production area 7 months after a fire completely burned the catchment. Two alternative post‐fire scenarios were designed, one simulating the spontaneous recovery of the ecosystem and the second reproducing a catchment‐scale implementation of a highly effective erosion mitigation measure (mulching). Then, the mulch scenario and the actual eucalyptus cycle were compared with the spontaneous recovery scenario to appraise the best management choice. The post‐fire and post‐terracing periods showed a satisfactory agreement between simulated and observed daily parameters. Concerning the management alternatives evaluated, mulching and terracing reduced soil loss and sediment transported in streams compared to spontaneous recovery. However, higher flow volumes and phosphorus exports were predicted under terraced conditions, likely due to increased infiltration capacity and accelerated leaching processes, raising concerns about stream water quality. These findings can be applied to other Mediterranean catchments affected by wildfires and in which post‐fire management actions are planned, making stakeholders aware of the impacts and uncertainties of post‐fire scenarios, thus improving the management of burnt areas.Highlights Calibration of SWAT model for three different post‐fire management practices. Satisfactory model performance in simulating water quantity and quality for both periods. Spontaneous recovery evidenced high soil losses during all the simulated period. The implementation of terraces and the application of mulch reduced sediment transport.

Fine fuel changes due to timber harvesting and frequent prescribed burning in eucalypt forests of southeastern Australia

Forests are managed for a range of ecological and economic values. Prescribed burning and timber harvesting are two widely used and often co-occurring forest management activities. Both may alter wildfire risk by changing fuel characteristics. Prescribed burning alters the amount and arrangement of fuel, which changes the probability of ignition and rate of fire spread. Timber harvesting may influence future fuel composition, amount and structure directly via the addition of harvesting residue and indirectly by changing stand structure and fine fuel accumulation. Whilst there is reasonable understanding of how fuel changes immediately after a single prescribed burn or harvest in temperate eucalypt forests, the long-term effects of frequent prescribed burning combined with timber harvesting are poorly understood. We used a long-term (∼25 year) prescribed burning experiment conducted in ∼1000 ha of temperate eucalypt forest in southeastern New South Wales, Australia to determine the effects of a single selective timber harvest and 0–6 subsequent prescribed burns on the accumulation and composition of fine fuel (<25 mm thickness). It was found that fine fuel loads differed between harvested and unharvested stands, with 30 % less leaves and fine twigs (<6 mm) in the litter bed but 24 % more green understorey fuel up to 10 years post-burn in harvested stands. Frequent prescribed burning did not change total fine fuel load in harvested stands but did change fine fuel composition, with 4 times more leaves in the litter bed and 6 times less green understorey fuel in plots burnt at high frequencies (>4 fires in 25 years) versus low frequencies (0 fires in 25 years). Similar trends were observed in unharvested stands following frequent burning, however, there was 45% more leaves in the litter bed of frequently burnt, unharvested stands compared to frequently burnt, harvested stands. Our results suggest that irrespective of harvesting, frequent burning (>4 fires over 25 years) in temperate eucalypt forest may be a suitable strategy for lowering wildfire risk as it can reduce the amount of green understorey fuel, which may reduce flame heights and the likelihood of canopy fire. However, the decrease in green understorey fuel may be offset by the increase in leaves in the litter bed, which support fire ignition and spread. Our results highlight how the presence of timber harvesting changes the accumulation and composition of fine fuel post-fire, yet timber harvesting is currently not well integrated into many landscape fuel models, which often focus solely on time since last fire. Overlooking key attributes of disturbance history (timber harvesting, number of past fires), may jeopardise the accuracy of fuel models, and therefore the reliability of fire behaviour predictions.

Influence of the climate on productivity and the eucalyptus drought response and a proposal for maximizing wood productivity in function of soil attributes in Brazil

The genetic gains from eucalyptus breeding programs have decreased, compared to the previous decades, while the productivity has declined in recent years. This drop is mainly attributed to climate change, which, according to studies, has limited the productivity and altered the adaptation of forest species. In addition to this, it is considered that the soil is one of the components of the forest production that acts directly on the dynamics of water and nutrients for trees, and it is intended to evaluate the attributes of soils that maximize the productivity of wood to assist forestry companies in the indication of soils with better productive capacity to produce wood. Thus, the aim of the present study was to evaluate the influence of climate and soil attributes on the productivity of the eucalyptus forest and on the response to drought in Brazil (tropical and subtropical) in places with three types of climate: sub-humid, humid and super-humid. In addition, we sought to calculate a proposal for optimal values of stable soil attributes over a forest cycle/rotation to maximize Eucalyptus productivity. To do so, 24 experiments were installed in Brazil with 4 common clones in all the experiments to obtain strong edaphoclimatic contrasts, and, thus, to measure the productivity and the response to drought and to describe its relationship with the attributes of the soils. Three climatic groups were evaluated: Sub-humid (precipitation rate: evapotranspiration between 0.5 to 1.0, Wet (precipitation rate: evapotranspiration between 1.0 to 2.5), Super-humid (precipitation rate: evapotranspiration between 2.5 to 5.0). Wood productivity varied among Eucalyptus clones, with an average of 1.86 being the variation range. The genotype versus environment interaction (G X E) was strongly noted, and it was observed that some clones are more affected by the climate in relation to others. The optimal values of Sand, Clay, Silt, CEC, O.M to maximize the wood productivity were: 54.68 %, 18.94 %, 7.02 %, 31.49 mmolc/dm³, 27.17 g/cm³.

Legacy of harvesting methods on coppice-rotation Eucalyptus at experimental and operational scales

Coppice-rotation stands comprise 20 to 30% of the Eucalyptus forests in Brazil and understanding the factors influencing the production ecology of the coppice-rotation is fundamental to improving silvicultural prescriptions. We investigated the effect of harvesting method, stump height and stump cleaning on survival, uniformity, growth, above-ground biomass and light use efficiency in a short rotation of a highly productive E. grandis x E. urophylla clone at two scales in Brazil. At the field experiment scale, treatments were composed of harvesting techniques (Chainsaw and Feller Buncher), stump height (High and Low) and stump cleaning (No harvesting residues over the stump or with residues). The treatments strongly affected growth in height and volume, with less effect on diameter. The largest response came from harvesting method, with mechanized harvesting with a 33% lower mean annual increment (MAI, 33 m³ ha−1 y−1) than harvesting with the chainsaw (50 m³ ha−1 y−1). Stump height did not influence growth in chainsaw clear-cut, but low stumps after Feller Buncher harvesting reduced growth by 23% (30 m³ ha−1 y−1) compared with high stumps (36 m³ ha−1 y−1). Stumps cleaning increased survival only in the semi-mechanized harvest but did not result in a difference in yield. Leaf area index and light use efficiency at the end of rotation were impacted by the clear-cut method, with an average of 3.3 and 2.1 m² m−2, and 0.7 and 0.57 g MJ−1 for chainsaw and Feller Buncher clear cut, respectively. The percentage of stumps that remained intact, the uniformity among individuals, the light capture and the light use efficiency, presented a r² of 67%, 55%, 60% and 86% (p-value < 0.001), respectively. At the operational scale of 12 plantations, we measured MAI, uniformity and survival of the two harvesting methods, all with high stump height and no stump cleaning (current operational prescription). The reduction in coppice-rotation MAI from Feller Buncher harvesting was consistent with the experimental scale, but the difference in MAI (age 4 years) was not as large: 37 m³ ha−1 y−1 for the Feller Buncher harvest and 44 m³ ha−1 y−1 for chainsaw harvest. Harvesting with the Feller Buncher, lowered survival (88%, compared with to 96% with chainsaw harvest) and stand uniformity. Overall, the impacts of harvesting treatment were large enough to those silvicultural systems that include a coppice rotation need to carefully account for the costs and efficiencies of operations for harvesting the planted rotation with subsequent impacts on coppice survival and production.

The fuel-climate-fire conundrum: How will fire regimes change in temperate eucalypt forests under climate change?

Fire regimes are changing across the globe in response to complex interactions between climate, fuel, and fire across space and time. Despite these complex interactions, research into predicting fire regime change is often unidimensional, typically focusing on direct relationships between fire activity and climate, increasing the chances of erroneous fire predictions that have ignored feedbacks with, for example, fuel loads and availability. Here, we quantify the direct and indirect role of climate on fire regime change in eucalypt dominated landscapes using a novel simulation approach that uses a landscape fire modelling framework to simulate fire regimes over decades to centuries. We estimated the relative roles of climate‐mediated changes as both direct effects on fire weather and indirect effects on fuel load and structure in a full factorial simulation experiment (present and future weather, present and future fuel) that included six climate ensemble members. We applied this simulation framework to predict changes in fire regimes across six temperate forested landscapes in south‐eastern Australia that encompass a broad continuum from climate‐limited to fuel‐limited. Climate‐mediated change in weather and fuel was predicted to intensify fire regimes in all six landscapes by increasing wildfire extent and intensity and decreasing fire interval, potentially led by an earlier start to the fire season. Future weather was the dominant factor influencing changes in all the tested fire regime attributes: area burnt, area burnt at high intensity, fire interval, high‐intensity fire interval, and season midpoint. However, effects of future fuel acted synergistically or antagonistically with future weather depending on the landscape and the fire regime attribute. Our results suggest that fire regimes are likely to shift across temperate ecosystems in south‐eastern Australia in coming decades, particularly in climate‐limited systems where there is the potential for a greater availability of fuels to burn through increased aridity.

Performance of native succulents, forbs, and grasses on an extensive green roof over four years in subtropical Australia

To achieve enduring low-maintenance green roofs that provide maximum benefit in the subtropics, plants need to be well adapted to the local climate with extensive green coverage. The use of native plants contributes to ecological restoration, yet there is very limited information available on their performance in the subtropics. This study aimed to determine the performance of nine species of Australian native forbs, succulents, and grasses in monofunctional and functionally-mixed plant communities on an extensive green roof in Brisbane over four years. Green coverage and survival were monitored via image analysis and observational visits. Forbs established slowly, but successfully (82 % green coverage, 67 % survival after four years) with species Hibbertia scandens (100 % survival) and Dianella brevipedunculata (58 % survival and extensive recruitment) performing the best. Grasses, including Themeda triandra, Poa labillardieri and Cymbopogon refractus, achieved a fast initial green coverage (47 % after 10 months), but showed high seasonal variability and declined to 2 %. Contrary to expectations, succulents performed poorly (<5 % green coverage, 14 % survival). Green coverage had an inverse trend to plant survival in successful plots (forbs, functionally-mixed) indicating a gap-filling effect by high performing species. Survival was more strongly linked to individual species than to functional type or plant community arrangement. Based on the results of this study, we recommend consideration of functionally-mixed green roof plantings with a variety of indigenous plants including forbs for low maintenance and resilient green coverage in the subtropics. Habitats that provided suitable plant species for this study were coastal headlands, dunes, montane areas, and open eucalypt forests. Analogous habitats in other regions can be explored to find new native plant species to increase the plant palette of potentially suitable species. It would be beneficial to trial more plants from these habitats over multiple years to increase the knowledge of suitable species available to green roof designers.

Predicting ignitability from firebrands in mature wet eucalypt forests

Forest ignitability varies spatially and temporally across landscapes as a function of fuel moisture. Wetter forests are often more difficult to ignite and therefore act as a barrier to the spread of wildfire. However, when these forests dry out and transition to an ignitable-state, the landscape is primed for large wildfires. Fire managers require information about forest ignitability to predict the timing of this switch. Yet, an understanding of the drivers and thresholds for ignitability in wetter forests remains incomplete. Our study sought to address this knowledge gap by evaluating a range of in-forest and landscape variables as predictors of ignitability in wet eucalypt forests. We conducted ignition experiments over two fire seasons at six sites in mature wet and damp eucalypt forest in south-eastern Australia. Each experiment involved 30 ignition attempts within each site on a single day using two types of flaming firebrands with different heats of combustion. The success and sustainability of each ignition attempt was recorded and this process repeated 8–9 times per site culminating in 1590 ignition attempts across a range of fuel moisture conditions. Ignition results were evaluated against 21 different in-forest and landscape variables. In-forest variables were generally stronger predictors of ignition and sustained ignition than landscape variables. The more energetic firebrand yielded more successful ignitions and sustained ignitions, but rankings for the predictor variables were similar for both types of firebrand. The strongest predictor of ignition and sustained ignition was in-forest vapour pressure deficit (VPD) (R2 = 0.65 for ignition and R2 = 0.55 sustained ignition), which is a measure of atmospheric dryness that is strongly associated with dead fuel moisture content. Past studies have identified strong links between VPD, burned area and fire severity at broader spatial and temporal scales. Our results show that VPD is also important at the time of ignition and could be used to predict wildfire risk in wet eucalypt forests.

Differential effects of ecosystem engineering by the superb lyrebird Menura novaehollandiae and herbivory by large mammals on floristic regeneration and structure in wet eucalypt forests.

Ecosystem engineers that modify the soil and ground‐layer properties exert a strong influence on vegetation communities in ecosystems worldwide. Understanding the interactions between animal engineers and vegetation is challenging when in the presence of large herbivores, as many vegetation communities are simultaneously affected by both engineering and herbivory. The superb lyrebird Menura novaehollandiae, an ecosystem engineer in wet forests of south‐eastern Australia, extensively modifies litter and soil on the forest floor. The aim of this study was to disentangle the impacts of engineering by lyrebirds and herbivory by large mammals on the composition and structure of ground‐layer vegetation. We carried out a 2‐year, manipulative exclusion experiment in the Central Highlands of Victoria, Australia. We compared three treatments: fenced plots with simulated lyrebird foraging; fenced plots excluding herbivores and lyrebirds; and open controls. This design allowed assessment of the relative impacts of engineering and herbivory on germination rates, seedling density, vegetation cover and structure, and community composition. Engineering by lyrebirds enhanced the germination of seeds in the litter layer. After 2 years, more than double the number of germinants were present in “engineered” than “non‐engineered” plots. Engineering did not affect the density of seedlings, but herbivory had strong detrimental effects. Herbivory also reduced the floristic richness and structural complexity (<0.5 m) of forest vegetation, including the cover of herbs. Neither process altered the floristic composition of the vegetation within the 2‐year study period. Ecosystem engineering by lyrebirds and herbivory by large mammals both influence the structure of forest‐floor vegetation. The twofold increase in seeds stimulated to germinate by engineering may contribute to the evolutionary adaptation of plants by allowing greater phenotypic expression and selection than would otherwise occur. Over long timescales, engineering and herbivory likely combine to maintain a more‐open forest floor conducive to ongoing ecosystem engineering by lyrebirds.

Carbon dioxide and particulate emissions from the 2013 Tasmanian firestorm: implications for Australian carbon accounting

BackgroundUncontrolled wildfires in Australian temperate Eucalyptus forests produce significant smoke emissions, particularly carbon dioxide (CO2) and particulates. Emissions from fires in these ecosystems, however, have received less research attention than the fires in North American conifer forests or frequently burned Australian tropical savannas. Here, we use the 2013 Forcett–Dunalley fire that caused the first recorded pyrocumulonimbus event in Tasmania, to understand CO2 and particulate matter (PM2.5) emissions from a severe Eucalyptus forest fire. We investigate the spatial patterns of the two emissions using a fine scale mapping of vegetation and fire severity (50 m resolution), and utilising available emission factors suitable for Australian vegetation types. We compare the results with coarse-scale (28 km resolution) emissions estimates from Global Fire Emissions Database (GFED) to determine the reliability of the global model in emissions estimation.ResultsThe fine scale inventory yielded total CO2 emission of 1.125 ± 0.232 Tg and PM2.5 emission of 0.022 ± 0.006 Tg, representing a loss of 56 t CO2 ha−1 and 1 t PM2.5 ha−1. The CO2 emissions were comparable to GFED estimates, but GFED PM2.5 estimates were lower by a factor of three. This study highlights the reliability of GFED for CO2 but not PM2.5 for estimating emissions from Eucalyptus forest fires. Our fine scale and GFED estimates showed that the Forcett–Dunalley fire produced 30% of 2013 fire carbon emissions in Tasmania, and 26–36% of mean annual fire emissions for the State, representing a significant single source of emissions.ConclusionsOur analyses highlight the need for improved PM2.5 emission factors specific to Australian vegetation, and better characterisation of fuel loads, particularly coarse fuel loads, to quantify wildfire particulate and greenhouse gas emissions more accurately. Current Australian carbon accountancy approach of excluding large wildfires from final GHG accounts likely exaggerates Tasmania’s claim to carbon neutrality; we therefore recommend that planned and unplanned emissions are included in the final national and state greenhouse gas accounting to international conventions. Advancing these issues is important given the trajectory of more frequent large fires driven by anthropogenic climate change.