Inability of fire to control vegetation dynamics in low-productivity mulga (Acacia aneura)-dominated communities of eastern Australia

2017 ◽  
Vol 26 (10) ◽  
pp. 896 ◽  
Author(s):  
J. L. Silcock ◽  
J. Drimer ◽  
J. Fraser ◽  
R. J. Fensham
Keyword(s):  
Vegetation Structure ◽  
Seedling Recruitment ◽  
Fire Severity ◽  
Basal Area ◽  
Fire Frequency ◽  
Historical Record ◽  
Livestock Grazing ◽  
Eastern Australia ◽  
Australian Continent ◽  
Acacia Aneura

Reduced fire frequency and severity associated with livestock grazing are cited as a cause of woody plant encroachment and thickening in rangelands, but such paradigms are difficult to test experimentally owing to limited opportunities to burn. Mulga (Acacia aneura) dominates 25% of the Australian continent and epitomises this quandary. We measured the effect of rare wildfires on tree and shrub mortality and subsequent regeneration in mulga-dominated communities to critically examine prevailing but unsubstantiated paradigms of vegetation structural change. Mortality of mature mulga trees was positively correlated with fire severity, which was negatively correlated with tree basal area per hectare. High-severity fires killed the majority of mulga, but only occurred in more open areas, whereas low-severity fires typical of many mulga communities did not kill substantial proportions of mature mulga. The majority of mulga saplings were killed across all sites regardless of fire severity. Seedling germination was stimulated by fire, but not dependent on it. Green turkey bush (Eremophila gilesii) was the only shrub species with >50% mortality across all sites. Combined with the rarity of fire events in the historical record, our results, particularly limited fire mortality and enhanced post-fire seedling recruitment, suggest that the role of fire in shaping vegetation structure in mulga-dominated communities has been overstated. The decoupling of fire and vegetation structure is consistent with emerging regional studies in low-productivity semiarid environments.

scholarly journals Fixed or mixed? Variation in tree functional types and vegetation structure in a forest-savanna ecotone in West Africa

2020 ◽  
Vol 36 (4) ◽  
pp. 133-149
Author(s):  
George K.D Ametsitsi ◽  
Frank Van Langevelde ◽  
Vincent Logah ◽  
Thomas Janssen ◽  
Jose A Medina-Vega ◽  
...  
Keyword(s):  
West Africa ◽  
Vegetation Structure ◽  
Basal Area ◽  
Fire Frequency ◽  
Soil Water Storage ◽  
Vegetation Types ◽  
Above Ground Biomass ◽  
Area Index ◽  
Tropical Vegetation ◽  
Species Grouping

AbstractWe analysed thirty-five 400-m2 plots encompassing forest, savanna and intermediate vegetation types in an ecotonal area in Ghana, West Africa. Across all plots, fire frequency was over a period of 15 years relatively uniform (once in 2–4 years). Although woodlands were dominated by species typically associated with savanna-type formations, and with forest formations dominated by species usually associated with closed canopies, these associations were non-obligatory and with a discrete non-specialized species grouping also identified. Across all plots, crown area index, stem basal area and above-ground biomass were positively associated with higher soil exchangeable potassium and silt contents: this supporting recent suggestions of interplays between potassium and soil water storage potential as a significant influence on tropical vegetation structure. We also found an average NDVI cover increase of ~0.15% year−1 (1984–2011) with plots dominated by non-specialized species increasing more than those dominated by either forest- or savanna-affiliated species. Our results challenge the traditional view of a simple forest vs. savanna dichotomy controlled by fire, and with our newly identified third non-specialized species grouping also potentially important in understanding ecotonal responses to climate change.

Post-fire recruitment and resprouting of a threatened montane eucalypt

2021 ◽  
Vol 69 (1) ◽  
pp. 21
Author(s):  
Heidi Zimmer ◽  
Jan Allen ◽  
Rob Smith ◽  
Rebecca Gibson ◽  
Tony Auld
Keyword(s):  
Seedling Recruitment ◽  
Fire Regime ◽  
New South ◽  
Fire Severity ◽  
Short Interval ◽  
Fire Event ◽  
High Severity ◽  
South Wales ◽  
Eastern Australia ◽  
One Year

Changing climate is predicted to result in increased frequency and size of wildfires in south-eastern Australia. With increasing area burnt there is increased potential for entire species distributions to be burnt in a single fire event. This is particularly the case for range-restricted threatened species. Eucalyptus canobolensis (L.A.S.Johnson & K.D.Hill) J.T.Hunter is restricted to Mount Canobolas, New South Wales, Australia. In 2018, the majority of the E. canobolensis population was burnt by wildfire. One-year post-fire, we measured recruitment, resprouting and mortality of E. canobolensis. At higher fire severities, smaller trees were more likely to resprout from their bases only, as their stems were killed (i.e. ‘top kill’). Seedling regeneration only occurred in burnt plots. Our study demonstrates that E. canobolensis has a fire response typical of many eucalypts, characterised by seedling recruitment and larger trees resprouting epicormically, even after high-severity fire. Nevertheless, E. canobolensis response to repeat and short-interval fire remains unknown, and smaller trees appear to be vulnerable to top kill. Although much of Australia’s flora can respond to fire, this response is likely to be challenged as fire extents increase, especially if this is combined with increasing fire severity and/or frequency. These changes to the fire regime are a particular threat to species with restricted distributions.

scholarly journals The Effect of Antecedent Fire Severity on Reburn Severity and Fuel Structure in a Resprouting Eucalypt Forest in Victoria, Australia

Forests ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 450
Author(s):  
Luke Collins ◽  
Adele Hunter ◽  
Sarah McColl-Gausden ◽  
Trent D. Penman ◽  
Philip Zylstra
Keyword(s):  
Seedling Recruitment ◽  
Fire Severity ◽  
Fire Weather ◽  
Canopy Layer ◽  
Eucalypt Forest ◽  
Crown Scorch ◽  
Eastern Australia ◽  
Eucalypt Forests ◽  
High Level

Research highlights—Feedbacks between fire severity, vegetation structure and ecosystem flammability are understudied in highly fire-tolerant forests that are dominated by epicormic resprouters. We examined the relationships between the severity of two overlapping fires in a resprouting eucalypt forest and the subsequent effect of fire severity on fuel structure. We found that the likelihood of a canopy fire was the highest in areas that had previously been exposed to a high level of canopy scorch or consumption. Fuel structure was sensitive to the time since the previous canopy fire, but not the number of canopy fires. Background and Objectives—Feedbacks between fire and vegetation may constrain or amplify the effect of climate change on future wildfire behaviour. Such feedbacks have been poorly studied in forests dominated by highly fire-tolerant epicormic resprouters. Here, we conducted a case study based on two overlapping fires within a eucalypt forest that was dominated by epicormic resprouters to examine (1) whether past wildfire severity affects future wildfire severity, and (2) how combinations of understorey fire and canopy fire within reburnt areas affect fuel properties. Materials and Methods—The study focused on ≈77,000 ha of forest in south-eastern Australia that was burnt by a wildfire in 2007 and reburnt in 2013. The study system was dominated by eucalyptus trees that can resprout epicormically following fires that substantially scorch or consume foliage in the canopy layer. We used satellite-derived mapping to assess whether the severity of the 2013 fire was affected by the severity of the 2007 fire. Five levels of fire severity were considered (lowest to highest): unburnt, low canopy scorch, moderate canopy scorch, high canopy scorch and canopy consumption. Field surveys were then used to assess whether combinations of understorey fire (<80% canopy scorch) and canopy fire (>90% canopy consumption) recorded over the 2007 and 2013 fires caused differences in fuel structure. Results—Reburn severity was influenced by antecedent fire severity under severe fire weather, with the likelihood of canopy-consuming fire increasing with increasing antecedent fire severity up to those classes causing a high degree of canopy disturbance (i.e., high canopy scorch or canopy consumption). The increased occurrence of canopy-consuming fire largely came at the expense of the moderate and high canopy scorch classes, suggesting that there was a shift from crown scorch to crown consumption. Antecedent fire severity had little effect on the severity patterns of the 2013 fire under nonsevere fire weather. Areas affected by canopy fire in 2007 and/or 2013 had greater vertical connectivity of fuels than sites that were reburnt by understorey fires, though we found no evidence that repeated canopy fires were having compounding effects on fuel structure. Conclusions—Our case study suggests that exposure to canopy-defoliating fires has the potential to increase the severity of subsequent fires in resprouting eucalypt forests in the short term. We propose that the increased vertical connectivity of fuels caused by resprouting and seedling recruitment were responsible for the elevated fire severity. The effect of antecedent fire severity on reburn severity will likely be constrained by a range of factors, such as fire weather.

scholarly journals Evolutionary history and genetic connectivity across highly fragmented populations of an endangered daisy

Heredity ◽  
2021 ◽  
Author(s):  
Yael S. Rodger ◽  
Alexandra Pavlova ◽  
Steve Sinclair ◽  
Melinda Pickup ◽  
Paul Sunnucks
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Genetic Differentiation ◽  
Evolutionary History ◽  
Livestock Grazing ◽  
Genetic Connectivity ◽  
Evolutionary Divergence ◽  
Common Component ◽  
A Genome ◽  
Eastern Australia

AbstractConservation management can be aided by knowledge of genetic diversity and evolutionary history, so that ecological and evolutionary processes can be preserved. The Button Wrinklewort daisy (Rutidosis leptorrhynchoides) was a common component of grassy ecosystems in south-eastern Australia. It is now endangered due to extensive habitat loss and the impacts of livestock grazing, and is currently restricted to a few small populations in two regions >500 km apart, one in Victoria, the other in the Australian Capital Territory and nearby New South Wales (ACT/NSW). Using a genome-wide SNP dataset, we assessed patterns of genetic structure and genetic differentiation of 12 natural diploid populations. We estimated intrapopulation genetic diversity to scope sources for genetic management. Bayesian clustering and principal coordinate analyses showed strong population genetic differentiation between the two regions, and substantial substructure within ACT/NSW. A coalescent tree-building approach implemented in SNAPP indicated evolutionary divergence between the two distant regions. Among the populations screened, the last two known remaining Victorian populations had the highest genetic diversity, despite having among the lowest recent census sizes. A maximum likelihood population tree method implemented in TreeMix suggested little or no recent gene flow except potentially between very close neighbours. Populations that were more genetically distinctive had lower genetic diversity, suggesting that drift in isolation is likely driving population differentiation though loss of diversity, hence re-establishing gene flow among them is desirable. These results provide background knowledge for evidence-based conservation and support genetic rescue within and between regions to elevate genetic diversity and alleviate inbreeding.

scholarly journals The possibility of reclamation criteria success in Indonesia: soil condition, vegetation structure and species composition

2021 ◽  
Vol 9 (1) ◽  
pp. 3201-3210
Author(s):  
Tedi Yunanto ◽  
Farisatul Amanah ◽  
Nabila Putri Wisnu
Keyword(s):  
Species Composition ◽  
Vegetation Structure ◽  
Diversity Index ◽  
Basal Area ◽  
Mineral Resources ◽  
Soil Condition ◽  
Mine Reclamation ◽  
Soil Conditions ◽  
Standard Interval ◽  
Chemical Conditions

There are two regulations for mine reclamation success in the forestry area in Indonesia, namely Minister of Forestry Regulation No. P.60/Menhut-II/2009 and Minister of Energy and Mineral Resources Decree No. 1827.K/30/MEM/2018. Both regulations rule vegetation and soil success. This study aims to analyse criteria parameters from both regulations in the mine reclamation and compare them to the surrounding secondary natural forest (SNF). This study was conducted in 6 six types of mine reclamation stand structures: 1, 4, 6, 9, 11-year-old plantation and SNF using 1 hectare of the circular plot each (total 6 ha). Soil samples were collected from 40 cm depth to analyse physical, biological and chemical conditions. Mine reclamation areas had almost similar physical, biological and chemical soil conditions with SNF. Nevertheless, due to the potential acid-forming (PAF) material from overburden, the 1-year-old plantation had pH = 3.23-3.27. The highest diversity index and the number of species and families in all reclamation areas were H’ = 1.82 (11-year-old); 14 species (9-year-old); and 11 families (9-year-old), comparing with SNF were H’ = 3.48; 67 species, and 31 families. Conversely, vegetation structure parameters in mine reclamation areas were higher than SNF (diameter at height breast (DBH; 1.3 m) = 28.42 cm; tree density = 469/ha; basal area = 35.04 m2/ha; and total height = 16.85 m). Compared to the SNF, vegetation structure and soil conditions are mostly possible for mine reclamation success. Still, species composition needs to be considered further as a standard interval to meet the criteria.

scholarly journals Improving statistical forecasts of seasonal streamflows using hydrological model output

2012 ◽  
Vol 9 (7) ◽  
pp. 8701-8736 ◽  
Author(s):  
D. E. Robertson ◽  
P. Pokhrel ◽  
Q. J. Wang
Keyword(s):  
Hydrological Model ◽  
Historical Record ◽  
Base Flow ◽  
Seasonal Forecasting ◽  
Streamflow Forecasting ◽  
Eastern Australia ◽  
True Source ◽  
Hybrid Forecasting ◽  
Forecasting System ◽  
Seasonal Streamflow

Abstract. Statistical methods traditionally applied for seasonal streamflow forecasting use predictors that represent the initial catchment condition and future climate influences on future streamflows. Observations of antecedent streamflows or rainfall commonly used to represent the initial catchment conditions are surrogates for the true source of predictability and can potentially have limitations. This study investigates a hybrid seasonal forecasting system that uses the simulations from a dynamic hydrological model as a predictor to represent the initial catchment condition in a statistical seasonal forecasting method. We compare the skill and reliability of forecasts made using the hybrid forecasting approach to those made using the existing operational practice of the Australian Bureau of Meteorology for 21 catchments in eastern Australia. We investigate the reasons for differences. In general, the hybrid forecasting system produces forecasts that are more skilful than the existing operational practice and as reliable. The greatest increases in forecast skill tend to be (1) when the catchment is wetting up but antecedent streamflows have not responded to antecedent rainfall, (2) when the catchment is drying and the dominant source of antecedent streamflow is in transition between surface runoff and base flow, and (3) when the initial catchment condition is near saturation intermittently throughout the historical record.

scholarly journals Reproductive trajectories over decadal time-spans after fire for eight obligate-seeder shrub species in south-eastern Australia

2014 ◽  
Vol 62 (5) ◽  
pp. 369 ◽  
Author(s):  
Annette M. Muir ◽  
Peter A. Vesk ◽  
Graham Hepworth
Keyword(s):  
Seed Storage ◽  
Fire Frequency ◽  
Reproductive Maturity ◽  
South Eastern ◽  
Reproductive Response ◽  
Eastern Australia ◽  
Maturity Period ◽  
Fire Planning ◽  
In Fire ◽  
South Eastern Australia

Intervals between fires are critical for the persistence of obligate-seeding shrubs, and are often used in planning fires for fuel reduction and biodiversity conservation in fire-prone ecosystems worldwide. Yet information about the trajectories of reproductive performance for such species is limited and information is often qualitative. To test existing assumptions about reproductive maturity periods for eight obligate-seeding shrubs (with both canopy and soil seedbanks) in foothill forests of south-eastern Australia, we used a chronosequence approach, with sites from 2 years to >40 years post-fire. Quantitative measurements of flowering and fruiting were used to fit models of reproductive response in relation to time-since-fire for each species. Inferred reproductive maturity for each species, based on modelled times to reach 80% of maximum flower production, varied from 5 to 18 years post-fire. For a subset of three species, models predicted 80% maximum seed production occurring 1–7 years later than flowering. Our results confirmed or extended assumptions about post-fire reproductive maturity for these species, and provided a basis for improved incorporation of plant life-history in ecological fire planning. We infer that increased fire frequency makes one of our study taxa, Banksia spinulosa var. cunninghamii (Sieber ex Rchb.) A.S.George, vulnerable to decline because of its long reproductive maturity period and serotinous seed storage.

scholarly journals Predictive Ecosystem Mapping of South-Eastern Australian Temperate Forests Using Lidar-Derived Structural Profiles and Species Distribution Models

2019 ◽  
Vol 11 (1) ◽  
pp. 93 ◽  
Author(s):  
Melissa Fedrigo ◽  
Stephen B. Stewart ◽  
Stephen H. Roxburgh ◽  
Sabine Kasel ◽  
Lauren T. Bennett ◽  
...  
Keyword(s):  
Species Distribution ◽  
Vegetation Structure ◽  
Species Distribution Models ◽  
Sustainable Forest Management ◽  
Continuous Distribution ◽  
Forest Monitoring ◽  
Distribution Models ◽  
Study Region ◽  
South Eastern ◽  
Eastern Australia

Modern approaches to predictive ecosystem mapping (PEM) have not thoroughly explored the use of ‘characteristic’ gradients, which describe vegetation structure (e.g., light detection and ranging (lidar)-derived structural profiles). In this study, we apply a PEM approach by classifying the dominant stand types within the Central Highlands region of south-eastern Australia using both lidar and species distribution models (SDMs). Similarity percentages analysis (SIMPER) was applied to comprehensive floristic surveys to identify five species which best separated stand types. The predicted distributions of these species, modelled using random forests with environmental (i.e., climate, topography) and optical characteristic gradients (Landsat-derived seasonal fractional cover), provided an ecological basis for refining stand type classifications based only on lidar-derived structural profiles. The resulting PEM model represents the first continuous distribution map of stand types across the study region that delineates ecotone stands, which are seral communities comprised of species typical of both rainforest and eucalypt forests. The spatial variability of vegetation structure incorporated into the PEM model suggests that many stand types are not as continuous in cover as represented by current ecological vegetation class distributions that describe the region. Improved PEM models can facilitate sustainable forest management, enhanced forest monitoring, and informed decision making at landscape scales.

Heterogeneity in fire severity within early season and late season prescribed burns in a mixed-conifer forest

2006 ◽  
Vol 15 (1) ◽  
pp. 37 ◽  
Author(s):  
Eric E. Knapp ◽  
Jon E. Keeley
Keyword(s):  
Sierra Nevada ◽  
Prescribed Burning ◽  
Fire Severity ◽  
Basal Area ◽  
Conifer Forest ◽  
Fuel Loading ◽  
Early Season ◽  
Late Season ◽  
Fuel Loads ◽  
In Fire

Structural heterogeneity in forests of the Sierra Nevada was historically produced through variation in fire regimes and local environmental factors. The amount of heterogeneity that prescription burning can achieve might now be more limited owing to high fuel loads and increased fuel continuity. Topography, woody fuel loading, and vegetative composition were quantified in plots within replicated early and late season burn units. Two indices of fire severity were evaluated in the same plots after the burns. Scorch height ranged from 2.8 to 25.4 m in early season plots and 3.1 to 38.5 m in late season plots, whereas percentage of ground surface burned ranged from 24 to 96% in early season plots and from 47 to 100% in late season plots. Scorch height was greatest in areas with steeper slopes, higher basal area of live trees, high percentage of basal area composed of pine, and more small woody fuel. Percentage of area burned was greatest in areas with less bare ground and rock cover (more fuel continuity), steeper slopes, and units burned in the fall (lower fuel moisture). Thus topographic and biotic factors still contribute to the abundant heterogeneity in fire severity with prescribed burning, even under the current high fuel loading conditions. Burning areas with high fuel loads in early season when fuels are moister may lead to patterns of heterogeneity in fire effects that more closely approximate the expected patchiness of historical fires.

The Southern Oscillation Index as a predictor of seasonal rainfall in the arable areas of the inland Australian subtropics

1993 ◽  
Vol 44 (6) ◽  
pp. 1337 ◽  
Author(s):  
JS Russell ◽  
IM McLeod ◽  
MB Dale ◽  
TR Valentine
Keyword(s):  
Southern Oscillation Index ◽  
Southern Oscillation ◽  
Linear Trend ◽  
Summer Rainfall ◽  
Seasonal Rainfall ◽  
Four Seasons ◽  
Eastern Australia ◽  
Australian Continent ◽  
Ace Algorithm ◽  
Linear Trends

A detailed study has been carried out in four regions in the subtropics of Eastern Australia to determine the relationship between the Southern Oscillation Index (SOI) and subsequent seasonal rainfall. The period studied was from 1915 to 1991 for 3-monthly periods of spring (SON), summer (DJF), autumn (MAM) and winter (JJA). The 3-monthly prior SOI values were plotted against seasonal rainfall of the four regions and four seasons. These data were widely scattered but with a linear trend showing increased seasonal rainfall as the SOI increased. Linear trends were plotted for each season and region. Comparisons were made between the use of the ACE algorithm, which transforms the SOI and rainfall data, and the use of linear trends. Polynomials were used to calculate equations for each region and season, but only spring and summer produced satisfactory ACE functions. Estimates were made of spring and summer rainfall relative to prior SOI values for each region. While the SOI as a predictor of rainfall broadly estimates spring and summer rainfall, this variable has limited usefulness on its own. One of the options available with the ACE program is that additional independent variables can be added as required. Current research suggests that sea surface temperature data from specific ocean areas surrounding the Australian continent is the most useful additional variable at present. However the complexity of such an analysis is greatly increased.

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