Landscape variation in plant leaf flammability is driven by leaf traits responding to environmental gradients:

© 2018 Krix and Murray. Landscape differences in environmental conditions select for divergences among plant species in strategically important leaf traits such as leaf mass per area (LMA) and leaf area (LA). Interspecific variation in some of these same leaf traits has been associated to varying degrees with differences among species in leaf flammability, including the attributes ignitibility, sustainability, and combustibility. Yet, how environmentally selected variation in leaf traits drives variation in leaf flammability at landscape scales remains largely unknown. Here, we compared leaf traits and flammability attributes between species of sheltered forest vegetation (low light, moist habitat) and plant species of exposed woodland vegetation (high light, dry habitat) in a fire-prone landscape of south-eastern Australia. We found that leaves of sheltered forest species were significantly more flammable via both higher ignitibility and combustibility compared with exposed woodland species. These significant differences in leaf ignitibility and combustibility were underpinned by sheltered forest species having leaves with significantly larger LA and lower LMA compared with exposed woodland species. Further, multiple regression analyses revealed that both LA and LMA were significantly and uniquely related to faster time to ignition (TTI; ignitibility) and higher mean mass loss rate (combustibility). Most notably, although significantly higher fuel moisture content (FMC) of leaves of sheltered forest species significantly lengthened TTI, the lower LMA of these species played a more critical role in reducing TTI, with low LMA explaining more unique variation (partial r2 = 0.78) in high leaf ignitibility than low FMC (partial r2 = 0.49). Our findings provide the first evidence that landscape-scale variation in leaf flammability is tightly coordinated with the primary strategic response of the leaf traits LMA and LA to an environmental gradient. Furthermore, projections for increasing wildfire frequency and intensity in the region will likely allow wildfires to overcome the once protective nature provided by topography to sheltered forest vegetation, which means that higher leaf flammability in sheltered forest species has the potential to exacerbate the effects of changing weather conditions to place sheltered forest habitat, their plants, and their animals, at even higher risk of catastrophic wildfire

A Predictive Model of Leaf Flammability Using Leaf Traits and Radiant Heat Flux for Plants of Fire-Prone Dry Sclerophyll Forest

The differential flammability of individual plant species in landscape-scale fire behaviour is an important consideration, but one that is often overlooked. This is in part due to a relative dearth in the availability of plant flammability data. Here, we present a highly accurate predictive model of the likelihood of plant leaves entering flaming combustion as a function of leaf mass per area (LMA), leaf area (LA) and radiant heat flux using species of fire-prone dry sclerophyll forests of south-eastern Australia. We validated the performance of the model on two separate datasets, and on plant species not included in the model building process. Our model gives accurate predictions (75–84%) of leaf flaming with potential application in the next generation of fire behaviour models. Given the global wealth of species’ data for LMA and LA, in stark contrast to leaf flammability data, our model has the potential to improve understanding of forest flammability in the absence of leaf flammability information.</jats:p

Selecting low-flammability plants as green firebreaks within sustainable urban garden design

In response to an increasing risk of property loss from wildfires at the urban–wildland interface, there has been growing interest around the world in the plant characteristics of urban gardens that can be manipulated to minimize the chances of property damage or destruction. To date, considerable discussion of this issue can be found in the ‘grey’ literature, covering garden characteristics such as the spatial arrangement of plants in relation to each other, proximity of plants to houses, plant litter and fuel reduction, and the use of low-flammability plants as green firebreaks [1,2,3,4]. Recently, scientific studies from a geographically wide range of fire-prone regions including Europe [5], the USA [6], Australia [7], South Africa [8], and New Zealand [9] have been explicitly seeking to quantify variation among plant species with respect to different aspects of their flammability and to identify low-flammability horticultural species appropriate for implementation as green firebreaks in urban landscapes. The future prospects of this scientific work will ultimately depend on how successfully the results are integrated into the broader context of garden design in fire-prone regions at the urban–wildland interface. Although modern design of urban gardens must consider more than just the issue of green firebreaks, we and others [10,11] believe that selection of low-flammability plants should be high on the priority list of plant selection criteria in fire-prone regions

Calibrating assessment literacy through benchmarking tasks

© 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group. In calibration tasks students assess exemplar texts using criteria against which their own work will be assessed. Typically, these tasks are used in the context of training for peer assessment. Little research has been conducted on the benefits of calibration tasks, such as benchmarking, as learning opportunities in their own right. This paper examines a dataset from a long-running benchmarking task (∼500 students per semester, for four semesters). We investigate the relationship of benchmarking performance to other student outcomes, including ability to self-assess accurately. We show that students who complete the benchmarking perform better, that there is a relationship between benchmarking performance and self-assessment performance, and that students appreciate the support for learning that benchmarking tasks provide. We discuss implications for teaching and learning flagging the potential of calibration tasks as an under-explored tool

Shoot flammability patterns among plant species of the wildland–urban interface in the fire-prone Greater Blue Mountains World Heritage Area

Background: Mitigation of wildfires at the wildland–urban interface (WUI) will be enhanced by understanding the flammability of plants growing in this zone. Aims: We aimed to: (1) compare shoot flammability among wildland native, and both urban native and urban exotic ornamental plants; (2) quantify relationships between shoot traits and flammability; and (3) establish flammability scores to distinguish low- from high-flammability species. Methods: Flammability and traits of field-collected shoots were measured and relationships quantified in 44 species from the Blue Mountains World Heritage Area, Australia. Key results: In our study area, urban exotic plants were less flammable than wildland and urban native plants. Slow-igniting shoots had high fuel moisture and bulk density; short-burning shoots had low bulk density and volume; shoots recording low maximum temperatures had high fuel moisture, low bulk density and volume; and shoots with low biomass consumed in flames had high fuel moisture and low volume. Our novel flammability scores distinguished low-flammability (e.g. Lophostemon confertus) from high-flammability native species (e.g. Callistemon citrinus). Conclusions and implications: Low-flammability plantings at the WUI should preferably use native species given potential ecological impacts of exotics. We suggest that future work should seek to identify broader suites of low-flammability native species

Relationships among leaf flammability attributes and identifying low-leaf-flammability species at the wildland-urban interface

© 2019 IAWF. Leaf flammability is a multidimensional plant functional trait with emerging importance for wildfire risk management. Understanding relationships among leaf flammability attributes not only provides information about the properties of leaves as fuels in the wildland-urban interface (WUI), it can also offer an effective way to identify low-leaf-flammability species. We examined relationships between leaf ignitibility, sustainability and combustibility among 60 plant species of the WUI of eastern Australia. We found that leaf ignitibility and sustainability worked in opposition to each other as dimensions of flammability. Species with leaves that were slow to ignite were those with leaves that sustained burning for the longest, whereas species with leaves that were fast to ignite had leaves that burned for the shortest periods of time. Low leaf combustibility was related to short leaf burning sustainability but not to ignitibility. We created an overall leaf flammability index (OLFI) to rank species on emergent properties of ignitibility, sustainability and combustibility attributes in combination. We found that low-leaf-flammability species with low OLFI values had small leaf area, high leaf mass per area and high leaf water content. Our findings have implications for species selection for green firebreaks in the WUI

Increasing radiant heat flux affects leaf flammability patterns in plant species of eastern Australian fire-prone woodlands.

Leaf flammability is a functional trait that can vary widely among plant species. At present, however, the effects that increasing radiant heat flux have on variation in leaf flammability among species are not well understood. Yet, such effects could have important implications for wildfire models that take into account species' differences in flammability. We examined how five leaf flammability attributes spanning ignitibility (times to incandescence and flaming), sustainability (incandescence and flame durations) and combustibility (proportion of leaves entering flaming combustion) responded to increasing radiant heat fluxes (29.6 to 96.6 kWm-2 ) in 10 species of fire-prone woodlands. As radiant heat flux increased, times to incandescence and flaming became significantly faster and proportions of leaves entering flaming combustion became significantly higher. In contrast, incandescence duration became significantly shorter at high radiant heat flux. Differences among species in these flammability attributes decreased with increasing radiant heat flux, with species becoming significantly more similar to each other. Differences among species in flame duration, however, were not significantly affected by increasing radiant heat flux, with leaf flaming durations in each species remaining relatively fixed across the radiant heat flux gradient. Our findings show that leaf flammability is significantly affected by increasing radiant heat flux. We suggest that of the flammability attributes assessed in our study, flame duration is the most informative to include in wildfire models which explicitly consider species' flammability, given that differences among species in flame duration are maintained across a radiant heat flux gradient

Ecological impacts of fire trails on plant assemblages in edge habitat adjacent to trails

© 2017 Association for Fire Ecology. All rights reserved. Fire trails provide access into vegetation for controlled burns in fire-prone regions of the world. We examined the ecological impacts of fire trails on plant assemblages in edge habitat adjacent to trails in eucalypt woodlands of World Heritage Blue Mountains National Park, southeastern Australia. We found that understory plant species richness, total plant density, and leaf mass per area (LMA) were significantly higher in fire-trail edge habitat than in the understory of interior woodland habitat without fire trails. Understory plant species composition also differed significantly between fire-trail edge and interior habitats. Higher total plant density, higher LMA, and compositional differences in understory assemblages of fire-trail edge habitat were significantly related to increases in the availability of photosynthetically active radiation. In addition, higher soil clay content in fire-trail edges, which is linked to increased soil water availability for plant growth, was significantly related to higher species richness and compositional differences in the understory, as well as to compositional differences in overstory assemblages. From a conservation and management perspective, we suggest that, although significant ecological effects of fire trails on plant assemblages in edge habitats were detected, our work provides evidence that fire trails are unlikely to lead to serious conservation issues such as local extirpations of native species or the facilitation of exotic plant invasion. Nevertheless, our study has identified those plant species that are unique to, or particularly sparse or common in, fire-trail habitat, which should be prioritized for demographic and distributional monitoring should the need arise to increase the extent of fire trails in the future

Patterns of plant species composition in mesic woodlands are related to a naturally occurring depth-to-groundwater gradient

© Akadémiai Kiadó, Budapest. Groundwater-dependent ecosystems (GDEs) are threatened by over-extraction of groundwater for human needs across the world. A fundamental understanding of relationships between naturally occurring gradients in depth-to-groundwater (DGW) across landscapes and the ecological properties of vegetation assemblages is essential for effective management of the impacts of groundwater extraction. Little is known, however, about relationships between DGW and the ecology of mesic woodlands in GDEs. Here, we investigated relationships between a naturally occurring DGW gradient and plant species composition, richness and abundance in mesic Eucalyptus woodlands of eastern Australia. Across 16 sites varying in DGW from 2.4 m to 43.7 m, we found that plant species composition varied significantly in relation to DGW, independently of a range of 14 physical and chemical attributes of the environment. Nine understorey species, representing only 7% of the pool of 131 plant species, were identified as contributing to up to 50% of variation in species composition among the study sites. We suggest this dominant pattern driver in the understorey is explained by differential abilities among understorey species in their ability either to tolerate extended dry conditions at deeper DGW sites during periods of low rainfall, or to withstand periodically waterlogged conditions at shallow sites. Plant species richness and total plant abundance (a measure of plant productivity) were not significantly and independently related to DGW or any of the other 14 environmental attributes. Our finding for a direct relationship between DGW and plant species composition provides important reference information on the ecological condition of these mesic woodlands in the absence of groundwater extraction. Such information is vital for setting ecological thresholds that ensure sustainable extraction of groundwater

Ecological effects of increasing time since invasion by the exotic African olive (Olea europaea ssp. cuspidata) on leaf-litter invertebrate assemblages

© 2016, Springer International Publishing Switzerland. Invasive African olive, Olea europaea ssp. cuspidata (Wall. ex G.Don) Cif., forms increasingly dense stands between initial and mature stages of invasion, leading to a progressive decline in native plant diversity. Here, we examined the response of leaf-litter invertebrates to increasing time since olive invasion. We compared invertebrate assemblages among early-stage olive (0–7 years since invasion, scattered olive shrubs and seedlings in native woodland), mature olive (>15 years, uniform olive stands dominated by multi-trunked trees) and uninvaded native grassy woodland habitats (both mature stands and edges) in a critically endangered ecological community of south-eastern Australia. Invertebrate species richness was significantly reduced in mature olive compared with early-stage olive and mature native woodland habitats. Species richness did not differ significantly between early-stage olive habitat and mature native woodland, demonstrating resistance in species richness to initial invasion. Invertebrate species composition of native woodlands differed significantly from both mature olive and early-stage olive habitats, demonstrating a lack of resistance in species composition to initial olive invasion. Compositional differences were principally driven by reduced abundances within Coleoptera, Hymenoptera and Polyxenida in mature olive habitat compared with mature native woodland. These changes were significantly correlated with an increase in bare ground, plant canopy cover and litter depth, and higher moisture and lower temperature within leaf litter, in mature olive habitat. Our findings show that negative ecological impacts of invasive African olive extend beyond plants to leaf-litter invertebrate assemblages and that significant impacts on invertebrate species assemblage composition occur early in the invasion process