Article

Silvicultural recovery in ash forests following three recent large bushfires in Victoria

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

The contrasting regeneration outcomes of alpine ash (Eucalyptus delegatensis) and mountain ash (E. regnans) forests (collectively called ash) after the extensive and severe 2003, 2006/07 and 2009 bushfires in Victoria demonstrate the complexity of factors that influence the establishment of ash regeneration after bushfire. About 189 000 ha of ash forest was killed or severely damaged by the three bushfires, which burnt a land area totalling over 2.6 million ha. Silvicultural recovery work included aerial sowing of about 7100 ha of fire-killed regrowth in state forests with about 6400 kg of seed. This regrowth was less than 15–20 years of age and thus too immature to bear effective quantities of seed to achieve natural self-regeneration.This article includes a brief description of ash regeneration silviculture, a summary of relevant statistics for each of the three fires under consideration and the silvicultural recovery programs. Aspects of the recovery programs for the fires, including strategic seed-crop assessments, seedbed assessments, seed collection and management and aerial sowing operations are described, and their results are provided and discussed. The concept of ‘ecological stocking’, where regeneration levels are less than those required for commercial timber production, is also discussed.The natural seedling stocking levels resulting from the 2003 bushfires, which affected mostly alpine ash forests, were generally very satisfactory in stands of seed-bearing age. In contrast, after the bushfires of 2006/07, both natural and artificially sown eucalypt regeneration levels were often below commercial forestry standards. Natural stocking levels after the 2009 fires were again very satisfactory.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... It incorporates the Kosciuszko National Park in New South Wales and the Alpine National Park in Victoria. The region experienced major bushfires in 2003 and 2006/ 2007 which together, burnt an area of about 25,000 km 2 (Fagg et al., 2013). Whilst the alpine regions have been recovering towards their pre-burnt ecosystem states (Camac et al., 2013), less than a third of studied sites in the Kosciuszko National Park had fully recovered after 10 years (McDougall et al., 2015). ...
... The first of these is in the Australian Alpine Region (Fig. 1b Region B) which was used to assess the accuracy of the timing of breakpoint events. In 2003 the Kosciuszko National Park and the northeastern part of the Victorian Alpine National Park experienced one of largest bushfires in Australian history (Fagg et al., 2013;McDougall et al., 2015). This was followed by another large bushfire in 2006/2007 which burnt a large portion of the southeast part of the Victorian Alpine National Park (Fagg et al., 2013). ...
... In 2003 the Kosciuszko National Park and the northeastern part of the Victorian Alpine National Park experienced one of largest bushfires in Australian history (Fagg et al., 2013;McDougall et al., 2015). This was followed by another large bushfire in 2006/2007 which burnt a large portion of the southeast part of the Victorian Alpine National Park (Fagg et al., 2013). The changes to the ecosystem structure caused by these fires persist in many parts of this region (Coates et al., 2012;McDougall et al., 2015). ...
Article
Dryland degradation is an issue of international significance as dryland regions play a substantial role in global food production. Remotely sensed data provide the only long term, large scale record of changes within dryland ecosystems. The Residual Trend, or RESTREND, method is applied to satellite observations to detect dryland degradation. Whilst effective in most cases, it has been shown that the RESTREND method can fail to identify degraded pixels if the relationship between vegetation and precipitation has broken-down as a result of severe or rapid degradation. This paper presents an extended version of the RESTREND methodology that incorporates the Breaks For Additive Seasonal and Trend method to identify step changes in the time series that are related to significant structural changes in the ecosystem, e.g. land use changes. When applied to Australia, this new methodology, termed Time Series Segmentation and Residual Trend analysis (TSS-RESTREND), was able to detect degradation in 5.25% of pixels compared to only 2.0% for RESTREND alone. This modified methodology was then assessed in two regions with known histories of degradation where it was found to accurately capture both the timing and directionality of ecosystem change.
... Although the primary juvenile period of alpine ash is stated as being in the order of 20 years (Cremer et al. 1984;Ellis and Lockett 1991;Sebire and Fagg 2009;Fagg et al. 2013), this is essentially a management 'rule-of-thumb' rather than a definitive measure of actual time to maturity. It has been reported previously that individuals in some stands can flower and fruit at less than 10 years after a stand-replacing fire (Fielding 1956;Cremer et al. 1984;House 1997) although the actual viability figures of these individuals are not documented in the literature. ...
... There is therefore a potential for this response trait to provide a buffering mechanism against the loss of some alpine ash populations to multiple short-interval fire events in some parts of the species range. Although the amount of regeneration under these circumstances may not be adequate from a silvicultural point of view (Fagg et al. 2013), it may be just adequate to allow the persistence of the species in less dense stands, satisfying a stocking standard suitable in a National Park context (Bassett et al. 2015). We are not suggesting that management of alpine ash stands needs to be relaxed in light of early viability; rather, that early viability may both explain the persistence of alpine ash in multiply burnt stands and also enable some management flexibility as regarding where and when to reseed stands. ...
... Much younger stands with much smaller seed crops may not reach this threshold and hence adequate germination may not occur from early maturing alpine ash, particularly as alpine ash seeds need some months of cold temperatures in situ before they germinate, exposing them to potential ant predation. Other major factors that may affect demographic dynamics include competitive effects from understorey vegetation (Cunningham and Cremer 1965;Florentine and Westbrooke 2004) and post fire climatic conditions including drought (Kitajima and Fenner 2000;Fagg et al. 2013). ...
Article
Full-text available
Eucalyptus delegatensis R.T. Baker subsp. delegatensis is an interval-sensitive, fire-killed eucalypt that dominates large tracts of montane forest in the Australian Alps. Although it has been widely accepted in forest management that E. delegatensis takes 20 years to flower and fruit after stand-replacing fire events, recent observations after high intensity fires in the Australian Alps have shown that early flowering and fruiting is occurring from what can be termed ‘precocious’ individuals in some areas. In some instances, early flowering and fruit set is occurring within 6 years after stand-replacing fire. One historical study in the ACT had noted that such seed was viable, but we found no reported experiments documenting this or detailing the degree of viability. Here we discuss the results of a germination experiment undertaken on seed collected from Namadgi National Park from early-maturing alpine ash trees. Although at the low end of known viability estimates for E. delegatensis, seed from these individuals was nonetheless found to be viable, with a mean of 455 (SD = 139) germinants per 10 g of chaff and seed mix. We discuss this result in relation to fire management in the Australian Alps and suggest further research that needs to be undertaken to better document and understand the phenomenon.
... As all seed is stored in the canopy of mature mountain ash trees, the occurrence of tree-killing fires before the production of viable canopy seedbanks could cause the widespread collapse of mountain ash forest ecosystems ( Fig. 1) Gilbert, 1959;Lindenmayer, 2009b). Indeed, we have already begun to see large areas of forest dominated by obligate seeding species require artificial reseeding to maintain ecosystem persistence (Bassett et al., 2015;Fagg et al., 2013). In the context of reduced fire return intervals, the objectives of this study were to determine the extent to which relevant environmental variables influence the growth of tree height and stem diameter, and investigate how these size components interact with the environment to influence the age to seed production in mountain ash. ...
... As true reproductive capacity is reached only at the end of this developmental period (when fruit capsules have fully matured and seeds become viable), nearly 3.5 years after inflorescence buds become visible, it is the timing of this final stage that determines the ability of an individual to produce offspring. It is also of note that fruit capsules mature during the austral summer, with seeds becoming ready for dispersal around the same time (late January or early February) that wildfires frequently occur, and that shifts in either the timing of wildfires or the maturation of fruit capsules can influence the level of seedfall and resultant germination (Fagg et al., 2013). ...
... Most authors appear to use a basic extrapolation of these statements or other aspects of Ashton's research, and either implicitly or explicitly suggested that the overriding determinant of reproductive maturity in mountain ash is time. Various publications over the past few decades have suggested that individuals or stands either begin reproducing or are reproductively viable at 15-20 years (Gill, 1975;Fagg et al., 2013;Smith et al., 2014referencing Gill, 1981Fairman et al., 2015referencing Ashton, 1976, 20 years Table 1 Response and predictor variables considered in analyses of mountain ash (Eucalyptus regnans) height growth, stem diameter growth and fruit capsule production models. Interactions between AGE and all environmental and climatic variables were included in global models. ...
Article
Anthropogenic modifications to climate and natural fire regimes are occurring globally, leading to the production of environments that may be unsuitable for some species. Fire-intolerant plant species that rely on specific fire regimes for reproduction are at risk of population decline when successive fires occur in less than the time taken to produce seed. Quantifying key fire-related life history traits in such species is therefore critical for developing models of population viability, species distributions and ecosystem persistence. We studied the Australian mountain ash (Eucalyptus regnans), the world’s tallest angiosperm and an ecologically and economically important keystone species. We tested whether mountain ash populations exhibit variation in susceptibility to increasing fire frequency by characterising the response of key vital rates to stand age (time since fire) under different environmental conditions. We found that the time taken to produce seed varied geographically. Mean growth rates were greater in areas receiving higher levels of solar radiation, a trend that became stronger with tree age. Tree size and age had the strongest influence on the production of fruit capsules. Mature fruit capsules were found in trees as young as 11 years old, but stands may not contain reproductively viable seed crops until they are more than 21 years old. Our results show that environmental factors influence the primary juvenile period of a keystone obligate seeder, in turn affecting the time taken for a population to develop a reproductively viable seed amount of seed. Reduced fire return intervals may therefore constrain the species’ realised niche (and geographic distribution) to areas where it can tolerate shorter fire return intervals due to faster growth and maturation. We suggest that populations of obligate seeders that reach reproductive viability faster are thus more likely to persist when exposed to multiple fires in short succession. Intra-stand variation in seed crops suggests that selection could also act on rapidly-maturing individuals, resulting in some populations exhibiting high levels of precocious reproductive activity.
... These two species are among the tallest flowering plants on Earth, and the forests they form are important for biodiversity as well as their extremely high carbon density (Jackson, 1968;Keith et al., 2009;Lindenmayer et al., 2011;Tng et al., 2012;Bowman et al., 2014;Enright et al., 2015) (Fig. 1). In brief, fire disturbance drives the stand dynamics of ash eucalypt forests because fire stimulates pulses of regeneration by creating a receptive seedbed (competition-free, nutrientenriched mineral soil), stimulating the release of canopystored seeds and removing aboveground competition from established trees (Fagg et al., 2013). If fire intervals are shorter than the time required for regenerating seedlings to reach reproductive maturity (c. ...
... Interval squeeze is also affected by the interactions between climate, fire and demographic processes. For example, in low-elevation lodgepole pine (Pinus contorta) forests, serotiny increases markedly with stand age (Schoennagel et al., 2003), and in E. delegatensis, there is very little seed produced by surviving trees for 3-5 years following fire because floral buds are aborted at the time of the fire (Fagg et al., 2013). Furthermore, under climate change, fire seasons are starting earlier at a time when the aerial seed crop of E. delegatensis is immature, increasing the risk of regeneration failure (Fagg et al., 2013). ...
... For example, in low-elevation lodgepole pine (Pinus contorta) forests, serotiny increases markedly with stand age (Schoennagel et al., 2003), and in E. delegatensis, there is very little seed produced by surviving trees for 3-5 years following fire because floral buds are aborted at the time of the fire (Fagg et al., 2013). Furthermore, under climate change, fire seasons are starting earlier at a time when the aerial seed crop of E. delegatensis is immature, increasing the risk of regeneration failure (Fagg et al., 2013). However, some of these effects could be offset by possible increases in fecundity as a result of elevated CO 2 , as has been demonstrated for loblolly pine (Pinus taeda) (Way et al., 2010). ...
Article
Full-text available
Forests that regenerate exclusively from seed following high-severity fire are particularly vulnerable to local extinction if fire frequency leaves insufficient time for regenerating plants to reach sexual maturity. We evaluate the relative importance of extrinsic (such as fire weather and climate cycles) and intrinsic (such as proneness to fire due to stand age and structural development) factors in driving the decline of obligate seeder forests. We illustrate this using obligate seeding alpine ash (Eucalyptus delegatensis) forests in the montane regions of Victoria, Australia, that were burnt by megafires in 2003 (142,256 ha) or 2007 (79,902 ha), including some twice-burnt areas (11,599 ha). Geospatial analyses showed only a small effect of stand age on the remote sensing estimates of crown defoliation, but a substantial effect of forest fire weather, as measured by forest fire danger index (FFDI). Analysis of meteorological data over the last century showed that 5-year increases in FFDI precede cycle major fires in the E. delegatensis forests. Such strong extrinsic climate/weather driving of high-severity fires is consistent with the 'interval squeeze model' that postulates the vulnerability of obligate seeder forests to landscape-scale demographic collapse in response to worsening fire weather under climate change.
... Previous fire research in alpine ash forests has focussed on empirical investigations of seed dispersal after fire (Morgan et al., 2017), effects of fire severity and wildfire interval on regeneration and fuel characteristics (Bowman et al., 2014;Rodriguez-Cubillo et al., 2020;Gale & Cary, 2021), vegetation structure and fauna (O'Loughlin et al., 2020) and post-fire management (Bassett et al., 2015;Bowman & Kirkpatrick, 1986;Fagg et al., 2013;Grose, 1960). Although some work has considered the direct effects of climate change on the survival of alpine ash (Morgan et al., 2017), no studies have used a multidecadal landscape fire simulation framework to examine effects of changing fire regimes with changing climates on the persistence of alpine ash, despite the acknowledged threat posed by more frequent and severe wildfires (Morgan et al., 2017). ...
... While some individual alpine ash trees have been noted to exhibit early flowering as young as 6 years (Doherty et al., 2017), <5% of individuals exhibited early maturation in Kosciusko National Park ten years after stand-replacing fire (Doherty et al., 2017). The threshold value of 20 years to bear effective quantities of seed to achieve standlevel regeneration is widely supported (Bassett et al., 2015;Fagg et al., 2013); however, there is probably more of a continuum (Gale & Cary, 2021). Here, we are modelling stand-level reproductive maturity, not the primary juvenile period of an individual (von Takach Dukai et al., 2018). ...
Article
Full-text available
Aim Many species are adapted to a particular fire regime and major deviations from that regime may lead to localized extinction. Here, we quantify immaturity risks to an obligate‐seeder forest tree using an objectively designed climate model ensemble and a probabilistic fire regime simulator to predict future fire regimes. Location Alpine ash (Eucalyptus delegatensis) distribution, Victoria, south‐eastern Australia. Methods We used a fire regime model (FROST) with six climate projections from a climate model ensemble across 3.7 million hectares of native forest and non‐native vegetation to examine immaturity risks to obligate‐seeder forests dominated by alpine ash (Eucalyptus delegatensis), which has a primary juvenile period of approximately 20 years. Our models incorporated current and future projected climate including fuel feedbacks to simulate fire regimes over 100 years. We then used Random Forest modelling to evaluate which spatial characteristics of the landscape were associated with high immaturity risks to alpine ash forest patches. Results Significant shifts to the fire regime were predicted under all six future climate projections. Increases in both wildfire extent (total area burnt, area burnt at high intensity) and frequency were predicted with an average increase of up to 110 hectares burnt annually by short‐interval fires (i.e., within the expected minimum time to reproductive maturity). The immaturity risk posed by short‐interval fires to alpine ash forest patches was well explained by Random Forest models and varied with both location and environmental variables. Main conclusions Alpine ash forests are predicted to be burned at greater intensities and shorter intervals under future fire regimes. About 67% of the current alpine ash distribution was predicted to be at some level of immaturity risk over the 100‐year modelling period, with the greatest risks to those patches located on the periphery of the current distribution, closer to roads or surrounded by a drier landscape at lower elevations.
... Nonetheless, for fire-killed sections of forest, there will be a period of increased vulnerability to recurrent fire in the early years of re-establishment and reproductive immaturity -and this can vary between obligate seeder tree species, from 15 to 20 years for E. regnans (Ashton 1976) and E. delegatensis (Fagg et al. 2013), to 11-13 years for Callitris verrucosa (Keith 1996), 4 years for Pinus attenuata (Keeley et al. 1999) and 30 years for Pinus contorta var. latifolia and Picea mariana (Johnstone et al. 2010). ...
... The premise of increasing 'fire proneness' after timber harvesting has been contested (Ferguson and Cheney 2011;Attiwill et al. 2014). Nonetheless, over 7000 ha of recently logged ash forest needed artificial sowing after the 2003-09 period of large wildfires in Victoria, because harvested stands had not recovered to seed-bearing age (Fagg et al. 2013). This supports the general understanding that recurrent stand-level disturbance within short intervals, irrespective of the type of disturbance, presents significant challenges to the persistence of obligate seeder forests in south-eastern Australia. ...
Article
Full-text available
In temperate Australia, wildfires are predicted to be more frequent and severe under climate change. This could lead to marked changes in tree mortality and regeneration in the region's predominant eucalypt forests, which have been burned repeatedly by extensive wildfires in the period 2003–14. Recent studies have applied alternative stable state models to select 'fire sensitive' forest types, but comparable models have not been rigorously examined in relation to the more extensive 'fire tolerant' forests in the region. We review the effects of increasing wildfire frequency on tree mortality and regeneration in temperate forests of Victoria, southeastern Australia, based on the functional traits of the dominant eucalypts: those that are typically killed by wildfire to regenerate from seed ('obligate seeders') and those that mostly survive to resprout ('resprouters'). In Victoria, over 4.3 million ha of eucalypt forest has been burned by wildfire in the last decade (2003–14), roughly equivalent to the cumulative area burned in the previous 50 years (1952–2002; 4.4 million ha). This increased wildfire activity has occurred regardless of several advancements in fire management, and has resulted in over 350 000 ha of eucalypt forest being burned twice or more by wildfire at short (#11 year) intervals. Historical and recent evidence indicates that recurrent wildfires threaten the persistence of the 'fire sensitive' obligate seeder eucalypt forests, which can facilitate a shift to non-forest states if successive fires occur within the trees' primary juvenile period (1–20 years). Our review also highlights potential for structural and state changes in the 'fire tolerant' resprouter forests, particularly if recurrent severe wildfires kill seedlings and increase tree mortality. We present conceptual models of state changes in temperate eucalypt forests with increasing wildfire frequency, and highlight knowledge gaps relating to the development and persistence of alternative states driven by changes in fire regimes.
... About 50% of the 8.6 million ha of forest area burned between 1962 and 2014 across Victoria has occurred since 2003 (Fairman et al. 2015). Over 2.6 million ha of forest (including 189 000 ha of ash forest) was killed or severely damaged by three major bushfires in 2003-07 and 2009(Fagg et al. 2013. Following the 2013 wildfires in the Australian Alps bioregion an estimated 45 000 ha of forest dominated by obligate seeders and over 300 000 ha of resprouter-dominated forests were burned twice within a 10-year period (Fairman et al. 2015). ...
... Following the 2013 wildfires in the Australian Alps bioregion an estimated 45 000 ha of forest dominated by obligate seeders and over 300 000 ha of resprouter-dominated forests were burned twice within a 10-year period (Fairman et al. 2015). Though there was a high level of natural regeneration of eucalypts following the 2003 and 2009 fires, supplementary seeding across all tenures ensured eucalypt regeneration following the 2006-07 'Great Divide' fires and again following the 2013 'Harrietville' fires (Fagg et al. 2013;Bassett et al. 2015). Taylor et al. (2014) found that fire severity was higher in 7-36 year old stands than in stands younger or older than this in an E. regnans forest burnt in the February 2009 fires. ...
Article
Australia has a highly diverse and variable climate and its forests are well-adapted to climatic variation. However, human-induced changes in climate could exceed historical ranges of variability and have effects on forests well beyond the experience of forest managers. These conditions will require implementation of management practices appropriate to a changing climate but there has been little analysis of potential management options for Australian native forests. The paper analyses potential management options for the tall, wet eucalypt forests in Victoria’s Central Highlands. This region has already experienced a strong drying and warming trend and a high incidence of severe bushfires over the last 15 years. Future changes are likely to include rising CO2, increasing temperatures and an overall decrease and changing seasonal patterns in rainfall. This is likely to result in higher fire danger weather conditions, changes in phenology of flowering, seeding and germination and shifts in forest composition and productivity. A range of different management options were considered and analysed in terms of current practice, costs and implementation feasibility. Many management actions identified to support adaptation to climate change were assessed as currently being implemented as part of sustainable forest management arrangements. Options that are not generally currently implemented include developing gene management programs and off-site gene banks, ex-situ conservation and increasing cooperation in species management, increasing stand and regional species diversity, identification and deployment of more drought- or disturbance-tolerant species or genotypes, planning to reduce disease losses through monitoring and sanitation harvests, managing stand structure to reduce impacts on water availability and implementing silvicultural techniques to promote stand vigour, as practised elsewhere in Australia. The likelihood of more intense rainfall events will require changes to infrastructure, such as forest road design and construction specifications. Implementing adaptation will require new approaches to forest management, potentially involving significant human intervention, new ecological, environmental and social research, new modes of communication with the public, new policies and revised regulations and management prescriptions.
... Timing of the various stand development stages and recovery phases post-disturbance ( Figure 1) is variable and depends on many factors, including disturbance type and site characteristics. The point in time at which forest recovery is achieved relates to its definition and often depends on whether the information need is related to reclamation (Audet et al. 2014), silviculture (Fagg et al. 2013), carbon (Urbano and Keeton 2017), or ecosystem goods and services (Thompson et al. 2013), among others. Indicators of forest recovery can therefore be compositional, functional, structural, or combinations thereof (Gatica-Saavedra et al. 2017;Chazdon et al. 2016). ...
Thesis
Full-text available
Information needs associated with forest monitoring have become increasingly complex. Data to support these information needs are required to be systematically generated, spatially exhaustive, spatially explicit, and to capture changes at a spatial and temporal resolution that is commensurate with both natural and anthropogenic impacts. Moreover, reporting obligations impose additional expectations of transparency, repeatability, and data provenance. The overall objective of this dissertation was to address these needs and improve capacity for large-area monitoring of forest disturbance and subsequent recovery. Landsat time series (LTS) enhance opportunities for forest monitoring, particularly for post-disturbance recovery assessments, while best-available pixel (BAP) compositing approaches allow LTS approaches to be applied over large forest extents. In substudies I and IV, forest monitoring information needs were identified and linked to image compositing criteria and data availability in Canada and Finland. In substudy II, methods were developed and demonstrated for generating large-area, gap-filled Landsat BAP image composites that preserve detected changes, generate continuous change metrics, and provide foundational, annual data to support forest monitoring. In substudy III a national monitoring framework was prototyped at scale over the 650 Mha of Canada’s forest ecosystems, providing a detailed analysis of areas disturbed by wildfire and harvest for a 25-year period (1985–2010), as well as characterizing short- and long-term recovery. New insights on spectral recovery metrics were provided by substudies V and VI. In substudies V, the utility of spectral measures of recovery were evaluated and confirmed against benchmarks of forest cover and height derived from airborne laser scanning data. In substudy VI the influence of field-measured structure and composition on spectral recovery were examined and quantified. By focusing on four key aspects of forest monitoring systems: information needs, data availability, methods development, and information outcomes, the component studies demonstrated that combining BAP compositing and LTS analysis approaches provides data with the requisite characteristics to support large-area forest monitoring, while also enabling a more comprehensive assessment of forest disturbance and recovery.
... But an additional pressure on recruitment is relevant to the persistence of natural ash stands and re-seeding attempts: recruitment of alpine ash requires vernalisation of seed in its seedbed; 6 weeks near-freezing to break dormancy (Bassett et al. 2015). If soil moisture is limited during the austral spring germination period, or the soil surface exceeds 30-32°C, seeds may not germinate (Fagg et al. 2013). Frosts are projected to decline in south-eastern Australia (Timbal et al. 2015). ...
Article
Full-text available
In regions prone to wildfire, a major driver of ecosystem change is increased frequency and intensity of fire events caused by a warming, drying climate. Uncertainty over the nature and extent of change creates challenges for how to manage ecosystems subject to altered structure and function under climate change. Using montane forests in south-eastern Australia as a case study, we addressed this issue by developing an ecosystem state-and-transition model based on a synthesis of expert knowledge and published data, with fire frequency and intensity as drivers. We then used four steps to determine future adaptation options: (1) estimation of changes in ecosystem services under each ecosystem state to identify adaptation services: the ecosystem processes and services that help people adapt to environmental change; (2) identification and sequencing of decision points to maintain each ecosystem state or allow transition to an alternative state; (3) analysis of interactions between societal values, scientific and management knowledge and institutional rules (vrk) required to reframe the decision context for future management, and (4) determining options for an adaptation pathway for management of montane forests under climate change. Our approach is transferable to other ecosystems for which alternative states can be predicted under climate change.
... As with E. regnans, HEMS species did not recruit well when winters had high precipitation. High winter precipitation has been observed to negatively affect regeneration in this forest type (Fagg et al., 2013). Heavy winter rainfalls have been linked with a higher incidence of pathogen attacks on germinants that emerged in autumn and can also lead to seed loss and germinant mortality due to splash out and erosion (Ashton and Chinner, 1999;Fagg, 1981). ...
Article
In the forested landscapes of southeastern Australia, bushfires and timber harvesting are the primary catalysts for regeneration in Eucalyptus regnans, E. delegatensis, and high elevation mixed species (HEMS) forests. Quantifying the role of climate, topography and edaphic conditions on plant regeneration is important for understanding current and future risks of climate change. In this study, we investigated the post—disturbance regeneration dynamics in these forests. We sought to determine the direct impact of climate variability on regeneration and the interactive effects of climate, topography, and edaphic factors on the regeneration success of Eucalyptus. Data was collated from regeneration surveys conducted in 881 coupes, totaling ~55,000 ha of forest harvested and regenerated between 2004–2012. The time—period analysed included the Millennium Drought, an intense and prolonged drought that lasted from 1996 to 2010. To test the influence of climatic, topographic, and edaphic variables on the occurrence and abundance of Eucalyptus regeneration, we used machine learning models. We found that regeneration success was closely tied to the timing of the Millennium Drought. Between 2004 and 2005 Eucalyptus seedlings occurred in less than 50% of survey plots across all three forest types. Declines in regeneration during the period of drought were greater in E. regnans and E. delegatensis than HEMS forests, suggesting that regeneration in the HEMS forests is more resistant to drought. We found that seasonal precipitation and temperature had the greatest influence on regeneration success of Eucalyptus. Responses varied by species, however autumn precipitation had the strongest influence on abundance of regeneration of E. regnans and E. delegatensis, while summer temperature was more important for HEMS species. Our findings highlight the importance of seasonal and annual climate variability on Eucalyptus regeneration and portend potential declines in regeneration success in a warmer and drier future for E. regnans and E. delegatensis.
... The EVC dataset represents the state of vegetation communities from mid-way through the study period and there is no compelling evidence of permanent community change that would have greatly altered results. There were some instances of the failed regeneration after fire of some areas of Damp forest (Bowman et al. 2014b), however much of this was ameliorated by remediation activities (Fagg et al. 2013). The high level vegetation community class was used to define vegetation communities; however the community 'Wet or Damp Forest' was split into 'Wet forests' and 'Damp forests' using sub-community definitions as the differing flammability of the wet forests of the study area have been a focus of past speculation about landscape processes [e.g. ...
Article
Full-text available
Context Wildfires are common in localities where there is sufficient productivity to allow the accumulation of biomass combined with seasonality that allows this to dry and transition to a flammable state. An understanding of the conditions under which vegetated landscapes become flammable is valuable for assessing fire risk and determining how fire regimes may alter with climate change. Objectives Weather based metrics of dryness are a standard approach for estimating the potential for fires to occur in the near term. However, such approaches do not consider the contribution of vegetation communities. We aim to evaluate differences in weather-based dryness thresholds for fire occurrence between vegetation communities and test whether these are a function of landscape aridity. Methods We analysed dryness thresholds (using Drought Factor) for fire occurrence in six vegetation communities using historic fires events that occurred in South-eastern Australia using logistic regression. These thresholds were compared to the landscape aridity for where the communities persist. Results We found that dryness thresholds differed between vegetation communities, and this effect could in part be explained by landscape aridity. Dryness thresholds for fire occurrence were lower in vegetation communities that occur in arid environments. These communities were also exposed to dry conditions for a greater proportion of the year. Conclusions Our findings suggest that vegetation driven feedbacks may be an important driver of landscape flammability. Increased consideration of vegetation properties in fire danger indices may provide for better estimates of landscape fire risk and allow changes to fire regimes to be anticipated.
... Eucalyptus delegatensis subsp. delegatensis from the Australian mainland is an obligate-seeder that was assumed to require 20 years to produce 'replacement' quantities of viable seed (Fagg et al., 2013). In a few areas across its range, successive fires have occurred at intervals < 20 years (Doherty et al., 2017) and under these circumstances a reduced rate of regeneration relative to the response after a single fire has been observed (Bowman et al., 2014). ...
Article
The 822 eucalypt species (Angophora, Corymbia, Eucalyptus) within Australia were assessed using IUCN Red List Categories and Criteria. Overall, 193 (23%) eucalypts qualified as threatened and 36 were considered Data Deficient. One hundred and thirty-four threatened species qualified under criterion A2, representing a past and irreversible population decline of>30%. The remainder were narrow-range species with ongoing threats (mostly mining or urbanisation), or naturally rare. Habitat conversion to crops and pastures was the cause of decline for most threatened eucalypts. Threatened species were concentrated where deforestation and high eucalypt richness coincide, especially south-western Western Australia. Corymbia or Angophora species, and relatively few tropical eucalypts are threatened. Fire, timber harvesting and disease were rarely sufficient threats to eucalypts to warrant a threatened status. Sheep grazing limits regeneration in temperate woodlands, but requires further quantification for individual species. Prior to this study, 89 eucalypts were listed as threatened under Australian environmental law. This assessment recommends that 32 of these species be downgraded to Near Threatened or Least Concern. A further 11 species were identified as Data Deficient, while an additional 147 species were proposed for listing as threatened. This systematic assessment of Australian eucalypts emphasises the importance of decline rather than rarity when compared with previous listings, with broad implications for listing long-lived plants in deforested landscapes.
... It may take decades of growth for a population of plants to produce a viable seed crop (e.g. Fagg et al. 2013;von Takach Dukai et al. 2018; although see Doherty et al. 2017). Hence, fire intervalthe time between firesis particularly important for obligateseeding species: if fire occurs before seed is produced, and there is no soil seedbank, then the species may be extirpated from the site (Keith 1996). ...
Article
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.
... Forests dominated by mountain ash are also considered critically endangered ecosystems, with wildfire and logging causing substantial changes to the age structure and structural characteristics of the forest (Burns et al., 2015;Lindenmayer et al., 2015;von Takach Dukai et al., 2018). With forest stands frequently requiring artificial reseeding to ensure adequate regeneration (Fagg et al., 2013), it is critical that we develop an understanding of the patterns and processes involved in local adaptation in mountain ash, to contribute to the development of ecologically and economically appropriate seed-sourcing strategies for landscape management. ...
Article
Understanding local adaptation is critical for conservation management under rapidly changing environmental conditions. Local adaptation inferred from genotype-environment associations may show different genomic patterns depending on the spatial scale of sampling, due to differences in the slope of environmental gradients and the level of gene flow. We compared signatures of local adaptation across the genome of mountain ash (Eucalyptus regnans) at two spatial scales: a species-wide dataset and a topographically-complex sub-regional dataset. We genotyped 367 individual trees at over 3700 single-nucleotide polymorphisms (SNPs), quantified patterns of spatial genetic structure among populations, and used two analytical methods to identify loci associated with at least one of three environmental variables at each spatial scale. Together, the analyses identified 549 potentially adaptive SNPs at the sub-region scale, and 435 SNPs at the range-wide scale. Thirty-nine genic or near-genic SNPs, associated with 28 genes, were identified at both spatial scales, although no SNP was identified by both methods at both scales. We observed that non-genic regions had significantly higher homozygote excess than genic regions, possibly due to selective elimination of inbred genotypes during stand development. Our results suggest that strong environmental selection occurs in mountain ash, and that the identification of putatively adaptive loci can differ substantially depending on the spatial scale of analyses. We also highlight the importance of multiple adaptive genetic architectures for understanding patterns of local adaptation across large heterogenous landscapes, with comparison of putatively adaptive loci among spatial scales providing crucial insights into the process of adaptation.
... By comparison, in Tasmania, nonstand-replacing fires predominate [12][13][14]. Characteristics of intense, stand-replacing wildfires in eucalypt forests of south-eastern Australia are well documented [9,15,16], but there are few reports documenting the characteristics of non-stand-replacing fires, although their fire histories and post-fire regeneration have been documented [12,17]. ...
Article
Full-text available
Non-stand-replacing wildfires are the most common natural disturbance in the tall eucalypt forests of Tasmania, yet little is known about the conditions under which these fires burn and the effects they have on the forest. A dry lightning storm in January 2019 initiated the Riveaux Road fire. This fire burnt nearly 64,000 ha of land, including tall eucalypt forests at the Warra Supersite. At the Supersite, the passage of the fire was recorded by a suite of instruments measuring weather conditions and fluxes (carbon, water and energy), while a network of permanent plots measured vegetation change. Weather conditions in the lead-up and during the passage of the fire through the Supersite were mild—a moderate forest fire danger index. The passage of the fire through the Supersite caused a short peak in air temperature coinciding with a sharp rise in CO2 emissions. Fine fuels and ground vegetation were consumed but the low intensity fire only scorched the understorey trees, which subsequently died and left the Eucalyptus obliqua canopy largely intact. In the aftermath of the fire, there was prolific seedling regeneration, a sustained reduction in leaf area index, and the forest switched from being a carbon sink before the fire to becoming a carbon source during the first post-fire growing season.
... For the TOF dominated by E. regnans, high-intensity fires are typically stand replacing. If the burnt trees are of reproductive age (older than ∼ 21 years, Fagg et al. 2013, von Takach Dukai et al. 2018), a new, single cohort of E. regnans will establish. If not, the species will become locally extinct and be replaced by communities dominated by non-eucalypts (Fairman et al. 2016). ...
Article
Full-text available
Infrequent, high‐intensity disturbances can have profound impacts on forested landscapes, changing forest structure and altering relative species abundance. However, due to their rarity and the logistical challenges of directly observing such extreme events, both the spatial variability of disturbance intensity and the species‐specific responses to this variability are poorly understood. We used observed patterns of mortality across a fire severity gradient following the 2009 Black Saturday fires in southeastern Australia to simultaneously estimate 1) species‐ and size‐specific susceptibility to fire‐induced mortality and 2) fire intensity. We found broad variation in patterns of fire susceptibility among the 10 tree species (five eucalypts and five non‐eucalypts) sufficiently abundant for analysis. Among the eucalypts, Eucalyptus obliqua was the most resistant to fire‐induced mortality, with trees of ~25 cm DBH having a 50% probability of surviving even the most intense fires. In contrast, E. regnans had 100% mortality across all size classes when subjected to high intensity fire. Basal resprouting occurred in six of the study species and, when accounted for, fundamentally changed the mortality profile of these species, highlighting the importance of resprouting as an adaptation to fire in these landscapes. In particular, the two iconic cool temperate rainforest species (Nothofagus cunninghami and Atherosperma moschatum) were strong resprouters (~45% of individuals were able to resprout after being top‐killed by fire). We also found evidence for compositional shifts in regeneration above threshold values of fire intensity in cool temperate rainforest and mixed forest sites, both of which have important conservation values within these landscapes. The observed patterns of species‐ and size‐specific susceptibility to fire‐induced mortality may be used to anticipate changes in forest structure and composition in the future. In addition, they may also help guide forest management strategies that reduce the length of time individual trees are exposed to potentially lethal fires, thereby increasing the resilience of these forests to future fires.
Article
The devastation wrought by the 2009 fires in southeastern Australia is a powerful demonstration of the need to fully integrate fire risk considerations into land-use planning and management. © 2015, Food and Agriculture Organization of the United Nations. All rights reserved.
Book
For the last three centuries forests have been recognised as providing the best water catchments and valued for their sustained output of high quality water. In Australia, work which was commenced fifty years ago has come to fruition and is providing new information on forest hydrology issues. The book focusses on the issues of small streams, including catchment definition, slope, hydrograph formation, water quality measurement, and annual water yield. The world-wide management issues of sustaining riparian forests are examined, using the River Murray forests as an example. Finally a large amount of information is drawn together to examine the management of forested catchments for water supplies. This book presents an incisive, disciplined, quantitative approach to dealing with forest hydrology matters. Although world-wide in application, the book particularly draws on Australian studies. It is written with the needs of students and forest practitioners in mind.
Article
The vulnerability to repeated high severity fires of tall wet eucalypt forests (TWEF) dominated by obligate seeder species is widely understood. However, 80% of Tasmania’s TWEF are dominated by resprouter species, and while these forests are more resilient to wildfire than those dominated by obligate seeders, the degree of their resilience is not well documented. Recently, two wildfires affected five 1-ha forest plots that had been previously measured, providing the opportunity to assess fire effects on these forest stands. We characterised these wildfires using remote sensing and field measurements of char height (a proxy for fire intensity) and canopy scorch (fire severity). We assessed the influence of tree diameter, fire intensity and seedling densities on the survival and resprouting responses of eucalypt overstorey trees and mixed species understorey trees. Our results showed that these fires were predominantly of low to moderate intensity and severity. Our results showed that mature TWEF were resilient to these wildfires, with overall eucalypt survival of 75%. The major eucalypt species were either mostly not defoliated (E. regnans), or could recover rapidly by epicormic resprouting (E. delegatensis and E. obliqua). Results from this and other studies show recovery from topkill caused by high severity fires occurs but is slower, by basal resprouting (E. obliqua) or from seed (all species). By contrast, understorey species suffered high mortality (85% overall), with few species showing substantial resprouting. Fire resistance in both groups increased markedly with tree diameter. Our results have implications for forest management. The high survival of overstorey eucalypts leads to a multi-aged stand structure in most unlogged old growth TWEF in Tasmania. On the other hand, clearfell logging, originally designed to mimic stand replacing wildfire in obligate seeder systems, creates a vulnerable, even aged stand of young regrowth, and at a landscape scale, it also reduces average tree size, reducing overall resistance to fire. Adopting alternatives to clearfelling, such as partial logging systems, will increase landscape resilience to fire, as well as providing other previously shown benefits.
Chapter
The role of fire in Australian forest hydrology is becoming appreciated. Fire affects forest hydrology in many ways. Firstly it modifies the existing forests. For some species including mountain ash it may completely kill off mature forests, leading to massive regeneration. This has a characteristic forest water use as a function of age. Other species may suffer crown degrade, which in turn leads to the development of epicormic crowns in which transpiration is less regulated. Fire leads to increased water repellency and sediment supply on catchment slopes. This appears to be associated with short-lived but unusually high flows of massive erosion capacity. As such, fire is likely to be an important force in the formation of stream networks.
Article
Forest mega-fires have become a global phenomenon in recent decades including in south-eastern Australia where large areas of forest have been fire-killed with loss of human lives and property and impacting carbon sequestration and greenhouse gas emissions. The vast extent and impact of mega-fires has induced a re-evaluation of fuel reduction methods as a key management strategy in wildfire risk mitigation in many countries. This study investigated the impact of a commercial thinning in Eucalyptus delegatensis forest on fuel hazard, fuel loads and wildfire behaviour, eight years after completion of a bay and outrow thinning operation. At the stand level, thinning reduced overstorey tree stocking by more than 50%, increased canopy openness and stimulated the growth of retained trees. Thinning also encouraged the profuse regeneration of over 1000 saplings ha⁻¹ of E. delegatensis, mostly in the outrows, compared with no sapling regeneration in unthinned forest. A system of additive biomass equations was developed to estimate total biomass and component biomass (stem wood, bark, branches and foliage) of individual trees. The aboveground tree carbon was 433 ± 49 Mg C ha⁻¹ in unthinned forest and 322 ± 47 Mg C ha⁻¹ in thinned forest. Thinning decreased surface fuel hazard ratings and fuel loads but had no significant effect on the mass of coarse woody fuels. Fire simulation under severe to extreme weather conditions, as occurred in the 2006/7 Great Divide Fires, indicated an almost 30% reduction in fireline intensity and about 20% reduction in the rate of spread and spotting distance in thinned forest compared with unthinned forest. This study indicates the potential of thinning to reduce wildfire severity and to increase the fire-survival of E. delegatensis.
Article
Aspects of the scientific discipline of forestry have endured decades of environmental activism aimed at discrediting it. Much of this activism has entailed strategic avoidance of inconvenient truths while promoting myths, half-truths and pseudo-science as though they are absolute fact. However, arguably of greater concern are more recent instances of false or unsupported claims about native forest management contained in some conservation-focussed research published in peer-reviewed scientific journals. This paper examines recent scientific literature which addresses Leadbeater’s possum and broader conservation issues in the forests of Victoria’s Central Highlands. In assessing its contribution to the public and political discourse on forest management we identified the following six areas where much of this research is contentious: • Leadbeater’s possum population estimates • The proportions of forests respectively catering for conservation or wood production • Value of active forest management strategies for conserving Leadbeater’s possum • Forest carbon stocks • The concept of ecosystem collapse • Value of environmental services derived from native forests. This contentious research is characterised by the omission of critically important context, reliance on flawed or wrong assumptions and errant citation practices. In the past, there would have been an expectation of such problems being identified and excluded during effective peer review by appropriate scientists. That this is no longer guaranteed is indicative of broken academic protocols. We conclude that there is evidence of a disturbing synergy between some peer-reviewed science and environmental activism in fashioning and promoting a questionable case for forest management change—in this instance, through advocacy of a proposed new national park that would restrict or end a range of public activities and decimate a significant and sustainable local timber industry.
Article
Eucalyptus delegatensis is native to the Australian Alps (subsp. delegatensis) and montane Tasmania (subsp. tasmaniensis). Post-fire regeneration mechanisms of the obligate-seeder subspecies on the Australian mainland are well-known, but less is known about the resprouter Tasmanian subspecies. In January 2016, large tracts of Eucalyptus delegatensis forests in central Tasmania, logged at different intensities, were burnt by low- and high-severity fire. We used statistical modelling to understand how tree survival, vegetative regeneration and seedling recruitment differed according to understorey type, fire severity, logging intensity and tree size (DBH). Fire severity, defined as unburnt, low-severity (fire scarring on the stem and/or lower canopy burnt) and high-severity (full canopy burnt), affected tree survival: 84% of trees were alive in unburnt transects, compared with 43% in low-severity transects and 36% in high-severity transects. Epicormic resprouting was the dominant mode of vegetative recovery, with < 1% of total trees recovering solely by basal resprouting. Fire severity significantly affected epicormic resprouting, with 70% of live stems resprouting post-fire in low-severity transects and 99% in high-severity transects, compared with 4% in unburnt transects. Tree survival was strongly influenced by tree size: in high-severity transects, 24% of trees with DBH < 20 cm were alive, compared with 88% of trees with DBH ≥ 20 cm. These differences in survival were primarily because large trees were more likely to resprout epicormically, with epicormic shoots present on 24% of live trees with DBH < 20 cm, compared with 79% of live trees with DBH ≥ 80 cm. The strong effect of tree size renders clear-felled forests especially vulnerable to fire during the several decades when all the regenerating trees are small (DBH < 20 cm). Seedling recruitment was uncommon, independent of understorey type and logging intensity, but with higher occurrence on high-severity (54%) than low-severity (19%) or unburnt (15%) transects. When present, seedling densities were typically low: median = 400 and maximum = 4·10⁴ seedlings ha⁻¹. This study highlights that mature forests of Eucalyptus delegatensis in Tasmania are more resilient (able to return to pre-disturbance conditions) to single high-severity fires than their mainland counterparts, because they can recover more quickly through epicormic resprouting. However, clear-felling reduces this resilience for several decades because it decreases median tree size and, hence, leads to higher post-fire mortality. It is difficult to predict how the Tasmanian subspecies will respond to an increased frequency of high-severity fires associated with a projected warmer and drier climate.
Article
Disturbance plays an important role in determining whether forests are carbon sinks or sources. Logging and wildfire are common widespread disturbances known to significantly reduce carbon stocks in carbon rich forests, such as, the tall forests of south-eastern Australia. Most tall forests in south-eastern Australia are dominated by globally unique resprouting Eucalypts that experience limited mortality after high severity wildfire. However, the most carbon dense forests in the region are dominated by non-resprouting Eucalypts that, like many other species associated with carbon dense forests around the world, experience stand replacement after high severity wildfire. We used space-for-time surveys to measure how above ground carbon stocks change with time since logging and time since wildfire in resprouting and non-resprouting Eucalypt forests in south-eastern Australia. Logging reduced above ground carbon stocks much more than wildfire in both forest types. Carbon stock losses caused by wildfire were more substantial in non-resprouting forests than resprouting forests, which experience only minor losses after wildfire. The recovery of carbon stocks after wildfire began to asymptote after approximately 40 years but increased almost continuously with time since logging in both forest types. Carbon stock losses associated with logging represent a much greater departure from natural disturbance in resprouting forests, because wildfire causes relatively little carbon loss in resprouting forests compared to non-resprouting forests. This analysis highlights the need to consider specific biological responses when assessing forest carbon stock losses associated with disturbance. Consideration of these dynamics is essential in addressing carbon stock risk mitigation.
Article
Increased fire frequency can result in a decline of obligate seeding plants, which rely on re‐seeding for population persistence following canopy scorching fire. The resilience of obligate seeding plants to fire at any point in time depends on plant maturity and the size of plants in relation to potential fire scorch height. We investigated variation in the resilience of post‐fire regenerating Eucalyptus delegatensis subsp. delegatensis (alpine ash) to a short inter‐fire interval at its boundaries with E. fastigata (brown barrel) stands. The resilience of post‐fire E. delegatensis regeneration was modelled across these stand boundaries as a function of the height of the plants, their reproductive maturity and predicted fire behaviour derived from local fuel characteristics. We measured these attributes 14 years following the Canberra 2003 wildfires and stratified study sites by fire severity. The height and reproductive maturity of post‐fire E. delegatensis saplings decreased at stand boundaries with E. fastigata, while fuel was uniformly abundant and capable of supporting canopy scorching fire under mild fire weather conditions. This suggests that E. delegatensis is less resilient to frequent fire in the presence of interspecific competition and other environmental conditions that occur at stand boundaries, which represent the edge of the species’ realised niche. With forecasts for increased fire frequency in south eastern Australia, persistence of E. delegatensis may be greatest in pure stands corresponding to the core of the species’ realised niche, and in moist and sheltered topographic areas that are less prone to frequent canopy scorching fire. Our findings suggest the importance of considering fine‐scale spatial variation in important obligate seeding plant traits when predicting and managing the response of obligate seeding species to frequent fire.
Article
Multiple fires in quick succession can cause an abrupt switch from forest to non-forest vegetation in some biomes. A prime example of such type conversion concerns alpine ash forests (Eucalyptus delegatensis subsp. delegatensis), which are endemic to the Australian Alps bioregion. These forests are long lived and can only regenerate following fire disturbance through the release of seed from the tree canopy, but complete regeneration failure of the eucalypt overstorey can occur if immature stands are subsequently reburnt. Wildfires in 2003, 2007 and 2009 burnt over 87% of the Alpine ash forest in Victoria, with some areas being burnt a second or third time within a decade by the 2013 Harrietville-Alpine Bushfire. Using aerial and field surveys we demonstrated that an area burnt two or three times in the Alpine National Park in Victoria would have resulted in loss of alpine ash forest were it not for an aerial sowing program. This sowing program used reduced sowing rates compared to those typically used in forestry silviculture operations in Victoria. Seedling establishment during the first year was lower on sown than natural seedfall areas but fell within the range of acceptable silvicultural stocking rates. Analysis of cohorts of seedlings over their first summer showed mortality was highest in the 2–3 months following emergence, especially during hot dry periods, but there was no difference in mortality rates between artificially and naturally sown areas. While the aerial sowing intervention established a cohort of alpine ash seedlings, the challenge for land managers is to protect these seedlings from wildfires for the next two decades to avoid loss of these forests.
Article
Full-text available
This study investigated the economics of maintaining strategic seedbanks for key eucalypt species to facilitate forest recovery following major fires in fire-sensitive forests of mountain ash (Eucalyptus regnans) and alpine ash (E. delegatensis) in Victoria. The analysis was confined to state forests and used Monte Carlo processes to model the occurrence of good seed-production years, the extent of natural regeneration occurring after major fires, the occurrence of minor and major fires, and the areal extent of those fires. The occurrence of major fires was predicted from estimates of the mean intervals between fires and long-term trends were also superimposed on these values to take account of future climate change. Three alternative scenarios for the extent of seed collection in good seed production years were investigated, together with three alternative strategies for future seed collection and storage facilities. The choice between these strategies and scenarios was evaluated using a discounted net cost criterion, together with consideration of the tradeoffs with risks associated with (1) backlogs of regeneration, (2) biological viability and (3) timber production of each forest type. The results provided clear guidance as to seed collection and storage facilities and to the initial targets for seed collection in good seed-production years. The results for risks raise a number of concerns about the future of these forest types, especially for alpine ash, given the distribution of age classes following major fires in 2003, 2006–2007 and 2009. Beyond 2050, even the high levels of seed collection and storage recommended may not be sufficient to maintain these ash forest types within state forests, which are extremely important for water production, water quality, biodiversity and timber production, and consideration needs to be given to additional measures and research.
Article
Full-text available
The aim of the study was to develop models which predict habitat availability for a rare and endangered marsupial, Leadbeater's possum (Gymnobelideus leadbeateri), in space and time. Measures of forest age, structure and floristics were correlated with the density of Leadbeater's possum at 32 sites in montane ash forests of the Victorian Highlands of south-east Australia. The density of leadbeater's possum was significantly correlated with the number of trees with hollows (PNTs), the number and biomass of Acacia spp., canopy and understory closure, and forest age. Peak densities occurred in regrowth forests (15–50 years), with abundant tree hollows (greater than 6 PNTs per 3 ha), and a high biomass of acacias (20–50% of stand basal area). Leadbeater's possums also occurred at low frequencies and densities in old-growth-regrowth forest ecotones, and in mature and multi-aged forests with an understory of eucalypts and acacias. Models of trends in habitat availability predict a massive decline over the next 30 years, followed by a population bottleneck lasting until the year 2075. Survival of Leadbeater's possum during the bottleneck will depend on protection of refuge habitats, particularly patches of mature, multi-age and old-growth forest. Recovery after the bottleneck is expected to depend on the extent to which current silvicultural practices can be modified to guarantee recruitment of PNTs within timber production forests.
Article
The management of multi-aged E. delegatensis forests in highland Tasmania is described. An area of 372 500ha is managed primarily for production of sawlogs, although the harvesting of pulpwood will assume increasing importance in future. Two major management problems are the failure of regeneration on grassy and especially, frost-prone sites, and the dieback of trees of all ages where cessation of regular burning has resulted in the development of understoreys of rainforest species. Options of management in overcoming these problems by adoption of alternative practices to clearfelling are discussed in relation to the silvicultural characteristics of the species. Differing objectives of management for State forests, corporately-owned forests, and other privately-owned forests are defined. Prescriptions for wood production, protection forest, and maintenance of environmental quality are given in each case. Likely future developments are discussed. -Authors
Article
The management of mountain ash forests in Victoria has entered a new era which will require more detailed scientific knowledge of the effects of management practices on ecosystem processes. The professional challenge is clear and goes beyond the mountain ash forests to encompass much of the remaining 4700 000ha that constitute the public estate of forest of commercial importance for wood production in Victoria. This paper is concerned with the effective management of the 150 000ha of mountain ash forest controlled by the Department of Conservation, Forests and Lands. These forests occur on high quality mountain land, are close to major population centres and generate massive benefits to the community, including production of water, formation of soil, production of wood, conservation of indigenous flora and fauna, and the provision of aesthetic, recreational and educational opportunities. Timber production from these forests has the potential to make an increasingly important contribution to the economy of Victoria. The paper reviews the ecological and silvicultural knowledge that provides the scientific basis for the development of management systems to achieve the interdependent objectives of ecosystem conservation and sustainable use of all goods and services, especially sawlog production. -from Authors
Article
On 8 January 2003, over 80 fires were ignited by lightning strikes across the remote forested and alpine areas of north-eastern Victoria and Gippsland. While most of the fires were rapidly controlled, a small number could not be contained and eventually merged to cover about 1.1 million ha. Of the 1 million ha of public land burnt, 440000 ha of State forest containing more than 87000 ha of commercially-valuable alpine ash (Eucalyptus delegatensis R.T.Baker) stands were fire affected. Of these, around 7500 ha were initially assessed as being fire killed and considered economically suitable and accessible for salvage harvesting. Wood utilisation plans for an estimated 600 000 m³ gross of sawlog were developed to reflect resource availability for an intended two-year salvage program. Roads were identified and scheduled for upgrading to cater for the anticipated ten-fold increase in log truck traffic. The Victorian Government approved and supported a salvage program based on a formal business case put forward by Forestry Victoria (now VicForests). The salvage of fire-killed E. delegatensis stands was based on existing geographic management units and organisational structures, supported by additional staff to cater for the significantly increased planning and operational requirements. A limiting factor was the availability of harvesting and haulage contractors. The scale and environmental impact of the program were very different from those of normal operations. This led to the development of specific salvage harvesting prescriptions, using internal and external expertise with an emphasis on soils, water quality, and flora and fauna. A marketing plan catered for harvesting arrangements, resource allocation and distribution, financial considerations, and declining resource quality with time due to gradual surface drying and cracking of the boles. A communication strategy was critical in the early stages of the program, particularly with Local Government. The key issue with the community and other government organisations was the impact of increased log traffic on local roads. As of 31 December 2004 over 2190 ha had been harvested for a total of 201500 m³gross of sawlogs and 304 000 m³ gross of residual logs. Operations to recover sawlogs have extended through 2005 and 2006. The challenge of harvesting while optimising protection of fire-regenerated seedlings was well met by the use of mechanised harvesters. Monitoring for gaps in regeneration in harvest areas and in E. delegatensis logging coupes with regeneration less than 20 y old is ongoing. Areas requiring retreatment are mechanically disturbed and sown with seed collected from outside the fire area.
Article
There is increasing recognition that natural disturbance is a dominant force in forest development. This paper sets out to review natural disturbances and their effects in forests in Australia, and to determine whether or not the effects of management of forests for all of their benefits can be contained within the known effects of natural disturbance.The history and evolutionary significance of fire in Australia is reviewed, and the differing fire ecologies of two representative species, Eucalyptus regnans in the south-east (which is killed by fire and regenerates prolifically from seed after fire) and Eucalyptus marginata in the south-west (which survives all but the most severe fires and regenerates from both shoots and seeds) are outlined. The development of E. regnans following stand-replacing fire can be defined as highly resilient (returning quickly to the pre-disturbance state) and that of E. marginata as resistant (difficult to move from the pre-disturbance state).The topic of forest management in relation to disturbance is discussed within the context of forests of mountain ash (Eucalyptus regnans), the world's tallest flowering plant, in south-eastern Australia. These forests in their natural state are essentially even-aged or at the most include two to three age-classes, the result of regeneration following stand-replacing bushfires. They produce timber of high value, and current land planning and management prescriptions allow for about one-half of the forest area to be managed for timber production on a sustained-yield basis. The silvicultural system is clear-felling, followed by burning to give stand-replacing conditions. Mountain ash regenerating from this system is one of the fastest growing tree species in the world and at its best has a volume increment of 50 m3 ha−1 year−1 and net primary production of 35 t ha-1 year-1 over the first 10 years. There is no definitive evidence of a loss of diversity of plant species in timber production forests. The greatest problem is to manage land for timber production and for the diversity of fauna which depend on nesting hollows in large dead or living trees. However, all of the species found in older forests can be found in regrowth forests which have been burned or logged over the past 50 years and which include large dead or living trees with nesting hollows.There has been speculation that harvesting mountain ash forests by clearfelling and regenerating them following slash-burning will lead to a loss of nutrients and a consequent loss of productivity. Nutrient cycling in mountain ash is shown to be resilient to disturbance. Rapid uptake of nutrients by the regenerating forest, immobilization of nutrients by microorganisms, and increased rates of nitrogen fixation are processes which lead to the conservation of nutrients following stand-replacing fires. There is no evidence of productivity decline following bushfire or timber harvesting.Another concern about forest harvesting is that there will be a reduction in carbon storage. The break-even point for E. regnans plantations yielding short-lived products (e.g. paper) is 37 years and for E. regnans forests grown for sawn timber, 60 years. Harvesting forests on rotations of 80–120 years will therefore result in an increase in carbon storage; however, it would take several rotations to restore carbon storage equivalent to that of old-age forest.Much of the literature on disturbance illustrates the difficulties of dealing with traditional and sometimes deeply entrenched concepts of how plant communities develop and the nature of the end-state of development. Development of mountain ash forest fits within Egler's model of initial floristic composition; there is no stable and self-perpetuating end-point, the climax is probably no more than the state where species change is immeasurably slow, and maximum diversity and productivity are maintained by random periodic disturbance. Does this set of conclusions provide the basis for management of the forest? The management of diversity in heath is discussed as an example; the issue is less contentious than in forests since no commercial product is harvested. Coastal heath on soils of poor fertility in Victoria also follows the model of initial floristic composition; diversity and productivity are maintained by fire, decreasing markedly within 20–50 years of disturbance. Management can use fire to maintain a mosaic of regenerated heathland to accommodate the range of responses of fauna and flora to disturbance, thereby maximizing diversity.The solution of maintaining diversity through an intermediate level of disturbance is well-established in the ecological literature; through disturbance, an equilibrium is never reached and higher diversity is maintained. In the managed forest, management dictates the disturbance regime (frequency, size and intensity) which must be fitted to the attributes, or life histories, of the organisms to be managed.This paper presents the view that timber harvesting in Australian forests is ecologically sustainable and that the effects of management can be contained within the framework of those caused by natural disturbance. Given that each plot in the forest differs from all other plots and that none is at steady state, a solution for the management of diversity is to use the whole of the forest estate (parks, stream reserves, catchment reserves, old-age forest, forests of different ages resulting from past fires and logging) so that diversity of the estate, rather than diversity of each plot, is maximized.
Article
Thesis--University of Melbourne. Includes bibliographical references (v. 1, p. 82-84). pt.1. Germination and seed dormancy.
The autecology of Eucalyptus regnans. F.Muell
  • D H Ashton
Ashton, D.H. (1965) The autecology of Eucalyptus regnans. F.Muell. PhD thesis, University of Melbourne, Melbourne, 235 pp.
The ash forests of south-eastern Australia. Australian Forest Profiles. A series from the National Forestry Inventory about forest types and major issues relating to them
  • P Attiwill
Attiwill, P. (2002) The ash forests of south-eastern Australia. Australian Forest Profiles. A series from the National Forestry Inventory about forest types and major issues relating to them. Bureau of Rural Sciences, Canberra.
Seed Crop Assessment Kit for Mountain Ash Seed requirements for the Bogong North Complex Bushfire. Recommendations Flowering and seed forecast of two ash species in Central Victoria
  • O D Bassett
  • Victoria
  • O D Bassett
Bassett, O.D. (1996) Seed Crop Assessment Kit for Mountain Ash. Department of Natural Resources and Environment, Victoria. Bassett, O.D. (2003) Seed requirements for the Bogong North Complex Bushfire. Recommendations. Internal report 6 March 2003, Department of Sustainability and Environment, Victoria. Bassett, O. (2005) Flowering and seed forecast of two ash species in Central Victoria. Report prepared for VicForests (unpublished).
Analysis of seed crop data for VicForests salvage coupes—Report 1. Consultant's report for VicForests following the
  • O Bassett
Bassett, O. (2009a) Analysis of seed crop data for VicForests salvage coupes—Report 1. Consultant's report for VicForests following the 2009 Victorian bushfires (internal report).
Eucalypt Sowing and Seedfall. Native Forest Silviculture Guideline No
  • P Fagg
Fagg, P. (2001) Eucalypt Sowing and Seedfall. Native Forest Silviculture Guideline No. 8, Forestry Victoria, Department of Natural Resources and Environment, Melbourne, Victoria.
Examination of possible reasons for poor germination of E. delegatensis seed sown in winter 2007 after the great divide fire. Forest Regulation Unit
  • P Fagg
Fagg, P. (2008a) Examination of possible reasons for poor germination of E. delegatensis seed sown in winter 2007 after the great divide fire. Forest Regulation Unit, Department of Sustainability and Environment, Melbourne, Victoria (internal report).
The Victorian Great Divide Fires
  • D Flinn
  • K Wareing
  • D Wadsley
Flinn, D., Wareing, K. and Wadsley, D. (2009) The Victorian Great Divide Fires, Dec. 2006–Feb. 2007. Fire and Emergency Management, Department of Sustainability and Environment, Melbourne, Victoria, 137 pp.
Mountain Ash in Victoria's State Forests
  • A Flint
  • P Fagg
Flint, A. and Fagg, P. (2007) Mountain Ash in Victoria's State Forests. Silviculture Reference Manual No. 1, Department of Sustainability and Environment, Melbourne, Victoria, 97 pp.
The Silviculture of Eucalyptus delegatensis. Part 1 —Germination and Seed Dormancy
  • R J Grose
Grose, R.J. (1963) The Silviculture of Eucalyptus delegatensis. Part 1 —Germination and Seed Dormancy. Bulletin No. 2, School of Forestry, University of Melbourne, Melbourne.
Seed crop monitoring in mountain ash forests Silvicultural systems project internal paper no
  • M Harrison
  • R Campbell
  • M Mccormick
Harrison, M., Campbell, R. and McCormick, M. (1990) Seed crop monitoring in mountain ash forests. Silvicultural systems project internal paper no. 2, Department of Conservation and Environment, Victoria.
Bushfire recovery— forest values (silviculture). 2007 regeneration report
  • C Jewell
  • M Lutze
  • P Fagg
  • M And Ryan
Jewell, C., Lutze, M., Fagg, P. and Ryan, M. (2008) Bushfire recovery— forest values (silviculture). 2007 regeneration report. Department of Sustainability and Environment, Melbourne, Victoria (internal report).
Measures of site occupancy by victorian mixed species forest regeneration
  • M Lutze
Lutze, M. (2004) Measures of site occupancy by victorian mixed species forest regeneration. Master of Forest Science thesis, University of Melbourne, Melbourne.
Discussion paper on ecological stocking Bushfire recovery silviculture report
  • M Lutze
  • C Slijkerman
  • P Fagg
  • M Lutze
  • W Notman
  • R Patrick
  • J Cleaver
  • E Harper
  • K Doherty
Lutze, M. (2011) Discussion paper on ecological stocking. In: Slijkerman, C., Fagg, P., Lutze, M., Notman, W., Patrick, R., Cleaver, J., Harper, E. and Doherty, K. (eds) Bushfire recovery silviculture report. 2009 black saturday fires. Department of Sustainability and Environment, Melbourne, Victoria (internal report).
Site Preparation. Native Forest Silviculture Guideline No. 6, Forests Service, Department of Conservation and Natural Resources
  • M Lutze
  • P Geary
Lutze, M. and Geary, P. (1998) Site Preparation. Native Forest Silviculture Guideline No. 6, Forests Service, Department of Conservation and Natural Resources, Melbourne, Victoria.
Seed Supply and Forest Recovery after the Carey State Forest Wildfire
  • M Lutze
  • D Terrell
Lutze, M. and Terrell, D. (2000) Seed Supply and Forest Recovery after the Carey State Forest Wildfire. Forest Research Report 374, Department of Natural Resources and Environment, Melbourne, Victoria.
Forest Recovery after Bushfire. Native Forest Silviculture Guideline No. 17, Forests and Parks Division
  • M W Poynter
  • P C Fagg
  • O D Bassett
  • C Slijkerman
  • M Lutze
Poynter, M.W., Fagg, P.C., Bassett, O.D., Slijkerman, C. and Lutze, M. (2009) Forest Recovery after Bushfire. Native Forest Silviculture Guideline No. 17, Forests and Parks Division, Department of Sustainability and Environment, Melbourne, Victoria.
07 great divide fire recovery (forest values) 2008 regeneration report
  • C Slijkerman
  • M Lutze
  • P Fagg
Slijkerman, C., Lutze, M. and Fagg, P. (2010) 2006/07 great divide fire recovery (forest values) 2008 regeneration report. Department of Sustainability and Environment, Melbourne, Victoria (internal report).
Bushfire recovery silvicul-ture report—2009 Black Saturday fires
  • C Slijkerman
  • P Fagg
  • M Lutze
  • W Notman
  • R Patrick
  • J Cleaver
  • E Harper
  • K Doherty
Slijkerman, C., Fagg, P., Lutze, M., Notman, W., Patrick, R., Cleaver, J., Harper, E. and Doherty, K. (2011) Bushfire recovery silvicul-ture report—2009 Black Saturday fires. Department of Sustainability and Environment, Melbourne, Victoria (internal report).
Regeneration Silviculture for Victoria's Eucalypt Forests
  • R O Squire
  • B D Dexter
  • A R Eddy
  • P C Fagg
  • R G Campbell
Squire, R.O., Dexter, B.D., Eddy, A.R., Fagg, P.C. and Campbell, R.G. (1991b) Regeneration Silviculture for Victoria's Eucalypt Forests. SSP Technical Report No. 6, Department of Conservation and Environment, Melbourne, Victoria.
The Victorian Alpine Fires—Jan Fire Management, Department of Sustainability and Environment
  • K Wareing
  • D Flinn
Wareing, K. and Flinn, D. (2003) The Victorian Alpine Fires—Jan.– Mar. 2003. Fire Management, Department of Sustainability and Environment, Melbourne, Victoria. P. Fagg, M. Lutze, C. Slijkerman, M. Ryan and O. Bassett