Invading rainforest pioneers initiate positive fire‐suppression feedbacks that reinforce shifts from open to closed forest in Eastern Australia

Messmate stringybark is common in forests across south-eastern Australia. The bark of these trees is persistent and produces firebrands that contribute to house loss and the difficulty of fire suppression during wildfires. The trees typically survive fire with the amount of bark depleted. We compared two common methods to assess messmate bark fuels: (1) field-based hazard assessment, and (2) desk-based assessment using mapped time since fire. Our measurements included space-for-time field surveys and laboratory flammability tests. Although several physical properties of bark could be approximated from both assessment methods, some bark properties important to flammability were not captured. Ignitability was found to be dependent on the amount of char on bark fragments and could be predicted by the site assessment methods, whereas sustainability was dependent on bark fragment dimensions and could not be predicted by current methods. Bark fragment properties were found to be partially a function of tree size. Overall, these findings indicate that current bark assessment methods do not capture all the key bark properties that contribute to messmate bark’s flammability. Further research is warranted to improve bark assessment methods so they better reflect bark’s contribution to fire behaviour.

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Developmental Pattern and Structural Organisation of Leaf Chloroplasts in Lepidozamia peroffskyana

Australian Journal of Botany ◽

10.1071/bt9900053 ◽

1990 ◽

Vol 38 (1) ◽

pp. 53 ◽

Cited By ~ 6

Author(s):

PM Bonatti ◽

RB Fornasiero

Keyword(s):

Leaf Development ◽

Natural Habitat ◽

High Ratio ◽

Light Conditions ◽

Structural Pattern ◽

Chl A ◽

Eastern Australia ◽

Closed Forest ◽

Weak Light ◽

Characteristic Features

The ontogenesis of chloroplasts during leaf development in Lepidozamia peroffskyana Regel is described; this cycad lives in the ground layer of the evergreen subtropical closed forest of south-eastern Australia. Characteristic features in young plastids are long bands of multilayered thylakoids, resembling photosynthetic structures of some green algae and ferns. 'Optional' structures, namely prothylakoid bodies and crystalline inclusions, are present in the pre-grana stages, in relation to the slow rate of leaf development. Mature chloroplasts are characterised by a great number of randomly oriented high grana stacks, a lack of starch, a high ratio of appressed to exposed thylakoids, and a low ratio of Chl a to Chl b; these shade features appear coherent with the natural habitat of Lepidozamia. However, since similar structures have been reported in mature chloroplasts of other cycads living in exposed sites, the existence of a genetically superimposed structural pattern is hypothesised, reflecting a primitive adaptation to weak light conditions of this group of ancient seed plants.

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The extraordinary 2019/20 Australian bushfire season: contributing processes and environmental impacts

10.5194/egusphere-egu2020-3804 ◽

2020 ◽

Author(s):

Albert van Dijk ◽

Marta Yebra

Keyword(s):

Fire Suppression ◽

Fire Severity ◽

Critical Factor ◽

Fuel Load ◽

Fire Season ◽

Native Forest ◽

Environmental Consequences ◽

Eastern Australia ◽

Ability To Regenerate ◽

History Of

<p>The recent Australian summer witnessed bushfire at a scale that is without historical precedent. We analysed the scale and severity of the fires, the main processes contributing to their scale, and environmental consequences that have already become apparent.&#160; We did this by combining satellite-derived information of vegetation cover, biomass and history, of soil and vegetation moisture content, and of fire extent and severity. More than 80,000 km2 was burnt, much of it native forest. Fire severity varied, but was overall greater than in preceding years. A critical factor contributing to fire conditions was a multi-year drought in Eastern Australia, which culminated in 2019 with the hottest and driest year in more than a century. During the fire season, fire danger conditions were further exacerbated by oceanic modes in the Indian and Southern Oceans, which limited circulation and caused excessive heating of the Australian land mass. Fuel availability in forests was unusually high. Reasons for this were several, including afforestation and regrowth as well as effective fire suppression in preceding years, while a contributing role for CO<sub>2</sub> fertilisation is also plausible. Combined with the drought and associated vegetation mortality, this created a high and flammable fuel load. The fires strongly affected Australia&#8217;s total living carbon pool, which was already depleted by several years of below-average rainfall. Greenhouse gas releases associated with drought and bushfires are not considered in official emission accounts, but are of comparable magnitude. The smoke emissions also caused direct health impacts, affecting cities like Sydney, Melbourne and Canberra for prolonged periods. Most of the burnt forests are resilient to fire and will regenerate, assuming rainfall conditions improve. The severity, scale and connectedness of some of the fire complexes suggest ecological recolonization may be very slow, while a number of threatened species may not recover. Perhaps most concerning, some of the forests affected had burnt only years before, whereas other areas contained vegetation communities not experiencing fire for centuries, raising questions about their ability to regenerate and possibly permanent ecological regime shifts.</p>

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Population Studies on Acacia melanoxylon R. Br. I. Variation in Seed and Vegetative Characteristics

Australian Journal of Botany ◽

10.1071/bt9780365 ◽

1978 ◽

Vol 26 (3) ◽

pp. 365 ◽

Cited By ~ 44

Author(s):

TP Farrell ◽

DH Ashton

Keyword(s):

Environmental Parameters ◽

Morphological Characters ◽

Annual Rainfall ◽

Clinal Variation ◽

Acacia Melanoxylon ◽

Open Forest ◽

Popu Lations ◽

Eastern Australia ◽

Closed Forest ◽

Shape And Size

Considerable variation in phyllode shape and size was found between populations of Acacia melanoxylon sampled over the wide geographical range (27° of latitude) of this species in tropical and temperate eastern Australia. Communities sampled range from closed-forest to open-forest and grassy woodland. Some evidence of relationships between morphological characters of the phyllodes and environ- mental conditions of the collecting site was found, although such relationships are complex and not easily understood. The most important factors determining phyllode shape and size were the distance of the collecting site from the coast, and the seasonal distribution of the annual rainfall. Phyllodes tended to be smaller and more symmetric in the drier inland areas. Differences were found between seed characteristics of selected populations, although there was no evidence of correlation of these with selected environmental parameters. Seedlings of 17 popu- lations of A. melanoxylon grown under uniform glasshouse conditions showed some differences in leaf morphology. The age at which conversion to phyllodes begins is correlated with the mean annual rainfall at the site of origin of the seeds. The occurrence of this species in such a wide variety of habitats in eastern Australia is probably due to its clinal variation.

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Ecological studies of Acmena smithii (Poir.) Merrill & Perry with special reference to Wilson's Promontory

Australian Journal of Botany ◽

10.1071/bt9760453 ◽

1976 ◽

Vol 24 (4) ◽

pp. 453 ◽

Cited By ~ 20

Author(s):

DH Ashton ◽

J Frankenberg

Keyword(s):

Rain Forest ◽

Forest Canopy ◽

First Year ◽

Podzolic Soils ◽

Slow Development ◽

Eastern Australia ◽

Wide Range ◽

Closed Forest ◽

In Fire ◽

Colluvial Soils

The Acmena smithii species complex occurs in a wide range of rain-forests (closed-forests) from 11� to 39� S. in eastern Australia. At its southernmost limit on Wilson's Promontory, it forms a structurally and floristically simple closed-forest of the microphyll fern type, and usually occurs up to altitudes of 300 m on relatively fertile alluvial and colluvial soils. It is replaced by thickets of Melaleuca spp. on very waterlogged soils and by nanophyll mossy forests of Nothofagus cunninghamii and Atherosperma moschatum at higher altitudes. It is often associated with emergent fire-induced strata of Acacia melanoxylon and Eucalyptus obliqua. On Wilson's Promontory, A. smithii rain-forest is a climax in fire-sheltered lowland gullies. In the prolonged absence of fire many adjacent wet sclerophyll (tall-open) forests are replaced by such rain-forest. A. smithii is extremely shade-tolerant and regenerates readily under dense forest canopy and in gaps. The seed is easily killed by desiccation and is frequently decimated by birds and insects. Slow development of seedlings in the first year renders them susceptible to drought and browsing. After the second year they are extremely persistent owing to the development of a lignotuber. The litter fall is heavy and decays rapidly to form a mull humus on relatively fertile loams and poor podzolic soils. The shoots of A. smithii grow during the frost-prone seasons of the year. This characteristic is correlated with its restriction to low altitudes in a mild maritime environment. The problems of the dispersal and past distribution of A. smithii are briefly discussed.

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Short-term impact of a mega-fire on small mammal communities during prolonged drought

Proceedings of the Royal Society of Victoria ◽

10.1071/rs12061 ◽

2012 ◽

Vol 124 (1) ◽

pp. 61 ◽

Cited By ~ 2

Author(s):

Mike Stevens ◽

John White ◽

Raylene Cooke

Keyword(s):

Small Mammal ◽

Prescribed Burning ◽

Fire Suppression ◽

Fire Severity ◽

Mammal Species ◽

Management Actions ◽

Conservation Implications ◽

Eastern Australia ◽

Significant Life ◽

The Impact

Increased size, severity and frequency of wildfire is predicted as a consequence of prolonged droughts associated with climate change. In south-eastern Australia severe landscape-scale wildfires (mega-fires) have elicited a strong anthropocentric response due to the significant life and property impacts. However, the impact of mega-fires on fauna, habitat and subsequent management actions are poorly understood. Small mammals were surveyed to examine mega-fire impact using the post-2006 wildfire landscape of the Grampians National Park, Victoria, Australia. Long-term research sites were established with 9620 trap nights completed in autumn 2008 across thirty-six sampling units. Vegetation structure, floristics, fire severity, patch size and overall fuel hazard were measured to investigate correlations with changes in small mammal abundance.Two years post-wildfire, rapid resurgence of house mouse (Mus musculus) was detected, conversely the abundance of native small mammal species was severely impacted. No sampling category within the burnt perimeter provided superior refuge presenting potential conservation implications. A habitat vacancy model is introduced where small mammal recolonisation post-wildfire depends on a lack of isolation and connectivity of populations. Floristic and structural contributions of vegetation to higher overall fuel hazard areas are essential in maintaining diverse fauna assemblages. As such, prescribed burning or fire suppression tactics such as ‘patching out’ or ‘burning out’ require consideration when contributing to further reduction of complex habitat patches following fires.

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