@article {bnh-5094, title = {Can a growth model be used to describe forest carbon and water balance after fuel reduction burning in temperate forests?}, journal = {Science of the Total Environment}, volume = {615}, year = {2018}, month = {02/2018}, pages = {1000-1009}, chapter = {1000}, abstract = {

Empirical evidence from Australia shows that fuel reduction\ burningsignificantly reduces the incidence and extent of unplanned fires. However, the integration of environmental values into\ fire management\ operations is not yet well-defined and requires further research and development.

WAVES, a plant growth model that incorporates Soil-Vegetation-Atmosphere Transfer, was used to simulate the hydrological and\ ecological effects\ of three fuel management scenarios on a\ forest ecosystem. WAVES was applied using inputs from a set of forest plots for one year after three potential scenarios: (1) all litter removed, (2) all litter and 50\% of the\ understorey\ removed, (3) all litter and understorey removed. Modelled outputs were compared with sites modelled with no-fuel reduction treatment (Unburnt).

The key change between unburnt and fuel reduced forests was a significant increase in soil moisture after fire. Predictions of the recovery of aboveground carbon as plant biomass were driven by model structure and thus variability in available light and soil moisture at a local scale. Similarly, effects of fuel reduction burning on\ water processes\ were mainly due to changes in vegetation interception capacity (i.e. regrowth) and soil evaporation. Predicted effects of fuel reduction burning on total\ evapotranspiration\ (ET) {\textendash} the major component of\ water balance\ {\textendash} were marginal and not significant, even though a considerable proportion of ET had effectively been transferred from understorey to overstorey. In common with many plant growth models, outputs from WAVES are dictated by the assumption that overstorey trees continue to grow irrespective of their age or stage of maturity. Large areas of eucalypt forests and woodlands in SE Australia are well beyond their aggrading phase and are instead over-mature. The ability of these forests to rapidly respond to greater availability of water remains uncertain.

}, doi = {https://doi.org/10.1016/j.scitotenv.2017.09.315}, url = {https://www.sciencedirect.com/science/article/pii/S0048969717326669?via\%3Dihub}, author = {Gharun, Mana and Malcolm Possell and R. Willem Vervoort and Adams, Mark A. and Bell, Tina} } @article {bnh-3325, title = {Calibration of water balance using digital photography}, number = {241}, year = {2017}, month = {01/2017}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

Prescribed fires impact the hydrological cycle in forested catchments because they remove vegetation and modify the amount of evapotranspiration (ET) that occurs. Evapotranspiration is the most important component of the hydrological cycle and perturbations to it can substantially affect the water balance of an ecosystem. However, our understanding of ET responses to disturbance is very limited and this makes post-fire assessment of water balance difficult.


In this study we used relationships between tree size and tree water use, and leaf area index (LAI) and forest water use to investigate the impact of fuel-reduction burning (FRB) on water availability. Leaf area index is an important input for estimating ET and measurement techniques such as digital photography can potentially be used by land managers as a means of rapidly quantifying the impact of FRB on water balance at both the plot- and catchment-scale. Our results will enable land managers to identify hydrologically sensitive areas in accordance with their management objectives.

}, issn = {241}, author = {Gharun, Mana and Malcolm Possell and Bell, Tina} } @article {bnh-4118, title = {Improving forest sampling strategies for assessment of fuel reduction burning}, journal = {Forest Ecology and Management}, volume = {392}, year = {2017}, month = {05/2017}, pages = {78-89}, chapter = {78}, abstract = {

Land managers\ typically make\ post hoc\ assessments of the effectiveness of fuel reduction burning (FRB), but often lack a rigorous sampling framework. A general, but untested, assumption is that variability in soil and fuel properties increases from small (\~{}1\ m) to large spatial scales (\~{}10{\textendash}100\ km). Based on a recently published field-based sampling scheme, we addressed the following questions: (i) How much variability is captured in measurements collected at different spatial scales? (ii) What is the optimal number of sampling plots required for statistically robust characterisation of burnt areas? (iii) How can land managers improve their assessment of the effectiveness of FRB? We found that measurement variability does not increase with scale for all fuel components. Results showed that\ coarse woody debris\ is as variable at the small scale (plot, m) as it is at the landscape scale (km). For certain fuel components, such as litter biomass (in unburnt areas),\ overstorey\ biomass and leaf area, and\ soil properties\ such as total carbon and total nitrogen, samples taken at the small (plot) scale were indicative of variation at the larger scale of an individual FRB and more broadly across the landscape.

We then tested the hypothesis that site stratification can reduce variability between sampling plots and as a consequence will reduce the required number of sampling plots. To test this hypothesis we used Landsat Normalized Difference Vegetation Index (NDVI) across areas treated with FRB and compared the number of sampling plots required to estimate mean fuel biomass with and without stratification. Stratification of burnt areas using remotely sensed vegetation indices reduced the number of sampling plots required. We provide a model of green biomass from Landsat NDVI and make recommendations on how sampling schemes can be improved for assessment of fuel reduction burning.

}, doi = {https://doi.org/10.1016/j.foreco.2017.03.001}, url = {http://www.sciencedirect.com/science/article/pii/S0378112716310751?via\%3Dihub}, author = {Gharun, Mana and Malcolm Possell and Jenkins, Meaghan E. and Lai Fan Poon and Bell, Tina and Adams, Mark A.} } @conference {bnh-3875, title = {Modelling feedback between fuel reduction burning and forest carbon and water balance in eucalypt forests}, booktitle = {AFAC17}, year = {2017}, month = {09/2017}, publisher = {Bushfire and Natural Hazards CRC}, organization = {Bushfire and Natural Hazards CRC}, address = {Sydney}, abstract = {

Empirical evidence from Australia shows that fuel-reduction burning significantly reduces the incidence and extent of unplanned fires. However, the integration of environmental values into fire management operations is not yet well-defined and requires further research and development.

While in reality carbon and water processes in forested ecosystems are coupled, effects of fire on these processes are often studied in isolation. Models that simulate the dynamic interaction and feedbacks between these processes are essential for investigations of the effects of fuel management in an environmental setting.\ 

WAVES, a soil-vegetation-atmosphere transfer (SVAT) model, was used to simulate the hydrological and ecological effects of four fuel management scenarios on a forest ecosystem. WAVES was applied using inputs from a set of forest plots across south-east Australia for a period of 1 year after four potential scenarios: (1) no fuel- reduction treatment (unburnt), (2) all litter removed, (3) all litter and 50\% of the understorey vegetation removed, 4) all litter and all of understorey vegetation removed.

The impacts of fuel-reduction burning on water processes were mainly due to changes in vegetation interception capacity and soil evaporation. The effect of fuel-reduction burning on evapotranspiration is discussed considering the balance of vegetation biomass in the overstorey and the understorey. Recovery of aboveground carbon as plant biomass was strongly linked to variability in available light and soil moisture. We describe how these modelling efforts can be used for impact assessment in terms of water, vegetation and carbon outcomes for planning of fuel reduction burning.

}, author = {Gharun, Mana and Malcolm Possell and Bell, Tina} } @article {bnh-4117, title = {Optimisation of fuel reduction burning regimes for carbon, water and vegetation outcomes}, journal = {Journal of Environmental Management}, volume = {203}, year = {2017}, month = {12/2017}, pages = {157-170}, chapter = {157}, abstract = {

Fire plays a critical role in biodiversity, carbon balance, soil erosion, and nutrient and hydrological cycles. While empirical evidence shows that fuel reduction burning can reduce the incidence, severity and extent of unplanned fires in Australia and elsewhere, the integration of environmental values into fire management operations is not well-defined and requires further research and development. In practice, the priority for fuel reduction burning is effective mitigation of risk to life and property. Environmental management objectives, including maintenance of high quality water, reduction of CO2\ emissions and conservation of biodiversity can be constrained by this priority. We explore trade-offs between fuel reduction burning and environmental management objectives and propose a framework for optimising fuel reduction burning for environmental outcomes.

}, doi = {https://doi.org/10.1016/j.jenvman.2017.07.056}, url = {http://www.sciencedirect.com/science/article/pii/S0301479717307387?via\%3Dihub}, author = {Gharun, Mana and Malcolm Possell and Bell, Tina and Adams, Mark A.} } @article {bnh-3093, title = {Application of statistical techniques to pyrolysis-GC-MS data from soil to identify the impact of fire}, number = {226}, year = {2016}, month = {09/2016}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

Soil organic matter has strong effects on many soil properties such as water holding capacity, soil structure and stability, nutrient availability and cation exchange capacity.\  Therefore, characterising soil organic matter is necessary to improve soil management.\  Pyrolysis coupled to gas chromatography-mass spectrometry (pyr-GC-MS) is one of many techniques that have been successfully used in this characterisation.\  However, a major limitation of pyr-GC-MS is that generates large amounts of mass-spectrometry data preventing fast, high throughput data analysis.\  This hinders our ability to identify compounds in complex matrices such as SOM that could be useful for predicting their characteristics.\  In this study, we aimed to investigate whether it was possible to rapidly identify significant differences among pyr-GC-MS data from soil from burnt and unburnt areas using an unsupervised statistical approach and identify the specific features that cause them.\  Of nearly 400 useful compounds extracted from the pyr-GC-MS data, only 15 were found to be necessary to classify between burnt and unburnt soil.\  We discuss how these features could be useful in the classification of soil disturbance such as fire or, potentially, as a quantitative measure of fire impact (intensity or severity).

}, author = {Malcolm Possell and Gharun, Mana and Bell, Tina} } @article {bnh-3413, title = {Mapping spatial and temporal variation in tree water use with an elevation model and gridded temperature data}, journal = {Agricultural and Forest Meteorology}, volume = {200}, year = {2015}, month = {01/2015}, pages = {249-257}, chapter = {249}, abstract = {

Tree water use is a major component of the water balance in forested catchments of semi-arid areas, as more than 80\% of the incoming rainfall may be used by overstory trees. Managers are unable to easily predict water use and thus water yield, for the majority of eucalypt-dominated catchments in south-east Australia, owing to the variety of dominant and co-dominant species, their distributions with respect to landform, and the lack of species- and landform-specific knowledge of the regulation of water use. Moreover, the costs incurred to quantify input variables for available complex, process-based models, generally encourage finding alternative approaches. This study tested the adequacy of using just two easily measured variables for estimating rates of tree water use, using a model derived from data-learning techniques. The inputs are (1) measured daily atmospheric demand for water and (2) potential incoming radiation derived from surface topography and solar declination. Artificial neural networks (ANNs) and genetic programming (GP) models were trained and validated using in situ observations of vapour pressure deficit (VPD) and estimates of potential solar radiation (Qpot), for a period of two years, at each of 10 forest stands across the high country of the states of New South Wales and Victoria. The models were tested using a random 50\% of the collected data that was independent, i.e. not used in model development.

Atmospheric demand was selected because it strongly affects tree water use irrespective of site and species. Potential solar radiation was selected as a proxy for radiation, because it is relatively easy to estimate for any location for which elevation data are available in digital format, and since radiation strongly controls photosynthesis (through stomatal behaviour) and thermal balance.

Genetic programming resulted in models better able to predict rates of sap flux. A selected GP model was able to describe the relationship between tree sap flux, VPD, and potential radiation with good accuracy, and was used to map tree water use across the catchment.

}, doi = {10.1016/j.agrformet.2014.09.027}, url = {http://www.sciencedirect.com/science/article/pii/S0168192314002512}, author = {Gharun, Mana and Turnbull, Tarryn L. and Joseph Henry and Adams, Mark A.} } @article {bnh-3412, title = {Short-term forecasting of water yield from forested catchments after bushfire: a case study from south-east Australia}, journal = {Water}, volume = {7}, year = {2015}, month = {02/2015}, pages = {599-614}, chapter = {599}, abstract = {

Forested catchments in southeast Australia play an important role in supplying water to major cities. Over the past decades, vegetation cover in this area has been affected by major bushfires that in return influence water yield. This study tests methods for forecasting water yield after bushfire, in a forested catchment in southeast Australia. Precipitation and remotely sensed Normalized Difference Vegetation Index (NDVI) were selected as the main predictor variables. Cross-correlation results show that water yield with time lag equal to 1 can be used as an additional predictor variable. Input variables and water yield observations were set based on 16-day time series, from 20 January 2003 to 20 January 2012. Four data-driven models namely Non-Linear Multivariate Regression (NLMR), K-Nearest Neighbor (KNN), non-linear Autoregressive with External Input based Artificial Neural Networks (NARX-ANN), and Symbolic Regression (SR) were employed for this study. Results showed that NARX-ANN outperforms other models across all goodness-of-fit criteria. The Nash-Sutcliffe efficiency (NSE) of 0.90 and correlation coefficient of 0.96 at the training-validation stage, as well as NSE of 0.89 and correlation coefficient of 0.95 at the testing stage, are indicative of potentials of this model for capturing ecological dynamics in predicting catchment hydrology, at an operational level.

}, doi = {10.3390/w7020599}, url = {http://www.mdpi.com/2073-4441/7/2/599}, author = {Gharun, Mana and Mohammad Amzi and Adams, Mark A.} } @article {bnh-3414, title = {Stomatal structure and physiology do not explain differences in water use among montane eucalypts}, journal = {Oecologia}, volume = {177}, year = {2015}, month = {04/2015}, pages = {1171-1181}, chapter = {1171}, abstract = {

Understanding the regulation of water use at the whole-tree scale is critical to advancing the utility of physiological ecology, for example in its role in predictive hydrology of forested catchments. For three eucalypt species that dominate high-elevation catchments in south-eastern Australia, we examined if whole-tree water use could be related to three widely discussed regulators of water use: stomatal anatomy, sensitivity of stomata [i.e. stomatal conductance (gs)] to environmental influences, and sapwood area. While daily tree water use varied sixfold among species, sap velocity and sapwood area varied in parallel. Combined, stomatal structure and physiology could not explain differences in species-specific water use. Species which exhibited the fastest (Eucalyptus delegatensis) and slowest (Eucalyptus pauciflora) rates of water use both exhibited greater capacity for physiological control of\ gs[indicated by sensitivity to vapour pressure deficit (VPD)] and a reduced capacity to limit\ gsanatomically [indicated by greater potential\ gs\ (gmax)]. Conversely,\ gs\ was insensitive to VPD and\ gmax\ was lowest for\ Eucalyptus radiata, the species showing intermediate rates of water use. Improved knowledge of stomatal anatomy will help us to understand the capacity of species to regulate leaf-level water loss, but seems likely to remain of limited use for explaining rates of whole-tree water use in montane eucalypts at the catchment scale.

}, doi = {10.1007/s00442-015-3252-3}, url = {https://link.springer.com/article/10.1007/s00442-015-3252-3}, author = {Gharun, Mana and Turnbull, Tarryn L. and Sebastian Pfautsch and Adams, Mark A.} } @article {BF-3122, title = {Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker}, journal = {Forest Ecology and Management}, volume = {270}, year = {2012}, month = {4/2012}, pages = {1 - 10}, abstract = {We estimated plot level water use from sap flux measurements over a 9-month period, in post-fire regrowth and mature plots of Eucalyptus delegatensis R. Baker (Alpine ash) in high elevation catchments near Falls Creek, Victoria, Australia, seven years after a major stand-replacing bushfire. Water use was more than double (460 {\textpm} 100 mm year-1 more) in regrowth as compared to mature plots, whereas sap flux was similar between age classes. This difference in water use reflected 72\% greater sapwood area index and 35\% greater leaf area index in regrowth than in mature plots. A small part of the difference in water use can be attributed to nocturnal transpiration, which was greater in regrowth than in mature plots (10.3 {\textpm} 0.8\% vs 7.3 {\textpm} 0.8\% of diel totals). As evaporative demand was 41\% greater in mature than in regrowth plots, these data suggest mean transpiration rate and stomatal conductance per unit leaf area were approximately 1.6 and 2.3 times greater, respectively, in the regrowth. However, mid-day leaf water potential and photosynthetic capacity were similar in both age classes. Evaporative demand was the primary environmental driver of water use in all cases, whereas soil moisture was not a strong driver of either water use or canopy conductance (estimated as sap flux/evaporative demand). Together, our results suggest (a) stand water use rapidly recovers after fire in these high elevation forests and quickly surpasses rates in mature stands, confirming projections by Kuczera (1987) for lower-elevation Mountain Ash (E. regnans) forests and highlighting the potential impact of tree water use on water yield in the first decade of forest regeneration after fires, and (b) stomatal conductance and sapwood area/leaf area ratio are both less in tall, older Alpine ash trees, whereas leaf water status and photosynthetic capacity appear to be sustained {\textendash} consistent with predictions from optimisation theory but not Pipe-Model Theory.}, issn = {03781127}, doi = {10.1016/j.foreco.2012.01.008}, author = {Buckley, TN and Turnbull, Tarryn L. and Sebastian Pfautsch and Gharun, Mana and Adams, Mark A.} }