@article {bnh-8081, title = {Understanding post-fire fuel dynamics using burnt permanent forest plots}, number = {674}, year = {2021}, month = {06/2021}, institution = {Bushfire and Natural Hazards CRC}, address = {MELBOURNE}, abstract = {

The main goal of this study is to obtain empirical measurements of fuel load, structure and hazard within the first two years after a fire to complement the measurements of fuel loads taken directly before the fires.\  This will not only allow us to precisely quantify the fuel loads consumed by a range of fires, but it will also give us a baseline measurement of fuel loads.\  We can use this baseline to anchor measurements of fuel accumulation in wet eucalypt forests that are part of related TERN and BNHCRC studies attempting to measure both the effects of climate and stand age on fuel accumulation in wet forests.

Current state of knowledge

The flammability of tall wet eucalypt forests is poorly understood. A globally unique forest type, these forests consist of a highly-flammable Eucalyptus overstorey and a moist, non-flammable understorey consisting of rainforest and broadleadf trees and shrubs. As a result, these forests are rarely available to burn, and almost no data exists on flammability and fire behaviour. While current fire behaviour models assume that fuel load and hence flammability increase asymptotically as a function of time since previous fire,\ there is much debate over whether this is the true trajectory of flammability in these forests. Understanding how fire severity is influenced by fuels and time since fire is a critical question in these forests.

As the rate of spread and intensity of a fire is a function of fuels, fire weather and topography, and as only the latter can be physically manipulated, the effect of fuel load and structure on fire behaviour, and the subsequent reduction in fuels, is extremely important to understand.\  Planned burning, the intentional use of low-severity fire, is the most commonly employed fuel reduction technique in Australia.\  The underlying concept is that burning off fuel loads across a landscape leads to an increased encounter rate with low fuel load areas.7 While reducing fuel ages has been shown to reduce both the extent and incidence of unplanned fires, the effect of low severity fires on actual fuel loads has not been explicitly quantified, especially in wet forests where planned burning is less commonly practiced than in dry forest.\  Further, low-severity fires have historically been overlooked in wet forests, as high-severity fires are though to be the important disturbance type due to the serotinous nature of many eucalypts. But recent research indicates that low-severity fires could play a more important role that previously realised.

Related projects

This study is building a large dataset of pre- and post-fire permanent plot measurements to complement existing studies on the fire regime of wet eucalypt forests. As mentioned above it utilised infrastructure set up as part of the TERN forests Ausplots network, and the Warra Chronosequence plots. Such a dataset will allow for analyses such as\  the validation of fire behaviour models, analysis of the resilience wet forests to wildfire, and help understand how fire severity affects subsequent fire hazard. Data from this study has already added a valuable validation section to a study providing the first-ever explicit description of the fire regime of mature wet Eucalyptus forests across Australia.26\ 

This project has also contributed a valuable high-resolution field-based validation for the BNHCRC project Using pre and post fire LiDAR to assess the severity of the 2019 Tasmanian Bushfires. This project will create, among other things, a high-resolution fire-severity map of the Riveaux Road Fire. With these data, we will be able to perform geospatial analyses to untangle the drivers of fire severity during this bushfire. Importantly the area burned in the fire includes the WARRA silvicultural experiment, in which a number of silvicultural treatments were trialled in a small area. This will allow an investigation into the effects of different silvicultural practices on flammability and fire severity in tall wet Eucalyptus forests.

Research questions

This study plans to focus on three major research questions:

}, keywords = {burnt, dynamics, forest, fuel, permanent, plots, post-fire}, issn = {674}, author = {Furlaud, James M. and David Bowman} } @article {bnh-7484, title = {Plasticity of leaf respiratory and photosynthetic traits in Eucalyptus grandis and E. regnans grown under variable light and nitrogen availability}, journal = {Frontiers in Forests and Global Change}, year = {2020}, month = {02/2020}, abstract = {

Plant growth strategies are adapted to resource availability in native habitat(s), and thus reflected in traits such as photosynthetic and respiratory capacities of leaves. We explored acclimation of such traits to contrasting light and nitrogen supply for Flooded Gum (Eucalyptus grandis) and Mountain Ash (E. regnans) saplings growing under warm-temperate conditions. We focused on respiration parameters that are not routinely measured, but could expand our mechanistic understanding of trait correlation networks [interdependencies between leaf mass per area (LMA), foliar nitrogen concentration (Nmass), photosynthetic capacity (mass- based Amax) and respiration (R)]. We measured temperature responses of leaf R via calorimetric methods, in order to derive three respiration parameters that are useful to characterize capacity and flux mode of respiratory oxygen reduction in mature source leaves and young sink leaves. Subtropical\ E. grandis\ saplings produced 3-fold more biomass than\ E. regnans, and responded more strongly to enhanced supplies of nitrogen, in particular under semi-shade conditions. Acclimation of LMA to growth irradiance was more plastic in\ E. grandis, but light treatment had no effect on Nmass\ and mass-based Amax\ in this species. In\ E. regnans, growth under abundant nitrogen and full sunlight caused significant increases in foliar Nmass{\textendash}albeit not matched by relatively modest increases in mass-based Amax. Cool-temperate\ E. regnans\ saplings appeared to allocate a substantial share of leaf-N to protective functions upon exposure to full sunlight. Foliar nitrogen was used more effectively for the production of new foliage in\ E. grandis, owing to better coordination with foliar capacity and flux mode of mitochondrial oxygen reduction. Most of the variation in three respiration parameters can be explained by a few physiological/anatomical variables, responding to variation in absolute and relative demand for ATP, reducing power and anabolic intermediates. These demands strongly depended on leaf developmental stage and also varied between species and treatments. Our approach opens a path to improved process- based understanding of respiratory flux control, which could facilitate predictions of plant respiration in a changing environment.

}, keywords = {Eucalyptus forest, forest}, doi = { https://doi.org/10.3389/ffgc.2020.00005}, url = {https://www.frontiersin.org/articles/10.3389/ffgc.2020.00005/full}, author = {Jorg Kruse and Turnbull, Tarryn L. and Heinz Rennenberg and Adams, Mark A.} } @article {bnh-4697, title = {The Unquantified Risk of Post-Fire Metal Concentration in Soil: a Review}, journal = {Water, Air, \& Soil Pollution}, volume = {228}, year = {2017}, month = {04/2017}, abstract = {

Forest fire is a natural disturbance that occurs in many terrestrial ecosystems specifically in the semi-arid environments and is considered to be an important cause of environmental change. Though many causes of fire are identified, including lightning, volcanic eruption, power line sparks, etc., human involvement is the most significant factor. Fire events are able to alter the physical, chemical and biogeochemical properties of the soil and surface materials and are able to release major and trace metals into the environment. This may be more significant in mining-affected and industrial landscapes, where elevated concentrations of metals present in the soil. After the fire event, metals become more mobile due to the increase in soil surface exposure and the mobility associated with ash dispersal. This mobility may increase the bioavailability of the metals, which may generate water quality issues and may contribute to human and environmental health concerns. Even though, the influences of fire on many soil properties are well established, the behaviour of metals with respect to fire is not well investigated. However, a few studies report that major and trace metals include Cd, Cr, Co, Cu, Hg, Mn, Ni, Pb, Zn and As are mobilized after fire with increased concentrations in soil and water resources and this might pose a risk to human health and ecosystems. Climate change may increase the intensity, frequency and areal extend of fire events and hence increase the metal concentrations and their potential health impacts. This paper reviews post-fire (wild fire) mobility of metals in soil common in contaminated forest ecosystems. The human and ecological health risks of these metals are also considered.

}, keywords = {Climate change, environment, fire., forest, soil}, doi = {10.1007}, url = {https://link.springer.com/article/10.1007/s11270-017-3338-0$\#$citeas}, author = {Joji Abraham and Kim Dowling and Singarayer Florentine} }