Neal Enright

Background
Mediterranean-type ecosystems (MTEs) are experiencing declining rainfall, increasing temperature, and shifting fire regimes as climate changes. While changes in fire regimes and post-fire recruitment are widely reported, evidence for changing plant demographic rates is limited.

Aims
We hypothesised increased time to maturity and decreased serotinous seed stores available for post-fire recruitment due to declining rainfall over recent decades for two fire-killed serotinous shrubs of south-east Australian MTEs, Hakea decurrens and Banksia ornata.

Methods
Fruit and cone production for populations across time since fire chronosequences were measured in the same regions in the 1990s and in 2017.

Key results
Estimated time to 50% maturity increased from 3–15 years and 6–15 years for H. decurrens and B. ornata, respectively, while estimated canopy seed stores were 90% and 50% lower in 2017 than in the 1990s.

Conclusions
Delayed reproductive maturity and decreased total seed stores were significantly related to decreasing rainfall received by 2017 populations over their lifetimes (5–17% less than for stands in the 1990s).

Implications
Shifts in inter-fire rates of seed production and storage, combined with changes to fire regimes and post-fire recruitment conditions due to climate change may already threaten the persistence of some species.

The time interval between fires is a critical component of the fire regime that affects plant species persistence in fire‐prone ecosystems. Fire intervals that are too short or too long may not support regeneration from seed banks or resprouting. Fire intervals that support adequate regeneration may also vary with other factors such as climate, herbivory, and population structure. Using field data on flowering and canopy seed banks, we modelled post‐fire reproduction for woody fire‐killed (obligate seeding) and resprouting species under varying rainfall and herbivory along a 35‐year fire age chronosequence in Banksia woodlands in southwestern Australia. We found that fire‐killed species attained reproductive maturity rapidly after fire with predicted juvenile periods (time to 50% flowering) of 1.5–2.3 years for shrubs and 4 years for trees. Resprouting species had similar juvenile periods to fire‐killed species (1–3.5 years for resprouting shrubs, 4.4 years for resprouting trees). Reproduction varied with rainfall and herbivory with juvenile periods at least doubling under low rainfall or high herbivory for some species. Serotinous species produced cones (woody fruits containing seeds) shortly after flowering commenced, with some evidence of seed bank decline in the oldest sites. While reproduction was clearly correlated with time since fire, plant size was a much stronger predictor. Some species form multi‐cohort populations which can introduce large variation into post‐fire reproductive trajectories, and this should be considered when making decisions about fire intervals that may impact species persistence. This study provides critical information to assess fire interval‐related threats for Banksia woodlands and suggests that woody species of these woodlands are generally tolerant of a wide range of fire intervals. Only the slowest‐maturing, fire‐killed species ( Banksia prionotes , Proteaceae) may require fire intervals > 10 years to reduce immaturity risk under the least favourable growing conditions, and this species often occurs in discrete patches in the landscape such that fire management can be tailored accordingly.

Climate change, with warming and drying weather conditions, is reducing the growth, seed production, and survival of fire-adapted plants in fire-prone regions such as Mediterranean-type ecosystems. These effects of climate change on local plant demographics have recently been shown to reduce the persistence time of local populations of the fire-killed shrub Banksia hookeriana dramatically. In principle, extinctions of local populations may be partly compensated by recolonization events through long-distance dispersal mechanisms of seeds, such as post-fire wind and bird-mediated dispersal, facilitating persistence in spatially structured metapopulations. However, to what degree and under which assumptions metapopulation dynamics might compensate for the drastically increased local extinction risk remains to be explored. Given the long timespans involved and the complexity of interwoven local and regional processes, mechanistic, process-based models are one of the most suitable approaches to systematically explore the potential role of metapopulation dynamics and its underlying ecological assumptions for fire-prone ecosystems. Here we extend a recent mechanistic, process-based, spatially implicit population model for the well-studied fire-killed and serotinous shrub species B. hookeriana to a spatially explicit metapopulation model. We systematically tested the effects of different ecological processes and assumptions on metapopulation dynamics under past (1988–2002) and current (2003–2017) climatic conditions, including (i) effects of different spatiotemporal fires, (ii) effects of (likely) reduced intraspecific plant competition under current conditions, and (iii) effects of variation in plant performance among and within patches. In general, metapopulation dynamics had the potential to increase the overall regional persistence of B. hookeriana. However, increased population persistence only occurred under specific optimistic assumptions. In both climate scenarios, the highest persistence occurred with larger fires and intermediate to long inter-fire intervals. The assumption of lower intraspecific plant competition caused by lower densities under current conditions alone was not sufficient to increase persistence significantly. To achieve long-term persistence (defined as > 400 years) it was necessary to additionally consider empirically observed variation in plant performance among and within patches, i.e., improved habitat quality in some large habitat patches (≥ seven) that could function as source patches and a higher survival rate and seed production for a subset of plants, specifically the top 25% of flower producers based on current climate conditions monitoring data. Our model results demonstrate that the impacts of ongoing climate change on plant demographics are so severe that even under optimistic assumptions, the existing metapopulation dynamics shift to an unstable source-sink dynamic state. Based on our findings, we recommend increased research efforts to understand the consequences of intraspecific trait variation on plant demographics, emphasizing the variation of individual traits both among and within populations. From a conservation perspective, we encourage fire and land managers to revise their prescribed fire plans, which are typically short interval, small fires, as they conflict with the ecologically appropriate spatio-temporal fire regime for B. hookeriana, and likely as well for many other fire-killed species.

Context
The concept of the fire regime is central to understanding and managing fire-prone ecosystems globally, and information on past regimes can provide useful insights into species disturbance adaptations. Although observations from satellite imagery or palaeoecological proxy data can provide direct evidence of past, pre-colonial fire regimes, they may be limited in temporal or spatial resolution and are not available for all ecosystems. However, fire-related plant-trait and demographic data offer an alternative approach to understand species–fire regime associations at the ecosystem scale.

Aims
We aimed to quantify the life-history strategies and associated fire regimes for six co-occurring shrub and tree species from fire-prone, Mediterranean-climate Banksia Woodlands in south-western Australia.

Methods
We collected static demographic data on size structure, seedling recruitment, and plant mortality across sites of varying time since last fire. We combined demographic data with key fire-related species traits to define plant life-history strategies. We then compared observed life histories with a priori expectations for surface, stand-replacing, and mixed-severity fire-regime types to infer historical fire-regime associations.

Key results
Fire-killed shrubs and weakly serotinous trees had abundant post-fire seedling recruitment, but also developed multi-cohort populations during fire-free periods via inter-fire seedling recruitment. Resprouting shrubs had little seedling recruitment at any time, even following fire, and showed no signs of decline in the long absence of fire, likely owing to their very long lifespans.

Conclusions
The variation in life-history strategies for these six co-occurring species is consistent with known ecological strategies to cope with high variation in fire intervals in a mixed-severity fire regime. Whereas resprouting and strong post-fire seedling recruitment indicate a tolerance of shorter fire intervals, inter-fire recruitment and weak serotiny are interpreted as a bet-hedging strategy to cope with occasional long fire-free periods that may otherwise exceed adult and seed-bank lifespans.

Implications
Our findings suggested that Banksia Woodlands have evolved with highly variable fire intervals in a mixed-severity fire regime. Further investigations of species adaptations to varying fire size and patchiness can help extend our understanding of fire-regime tolerances.

Climate change, with warming and drying weather conditions, is reducing the growth, seed production, and survival of fire‐adapted plants in fire‐prone regions such as Mediterranean‐type ecosystems. These effects of climate change on local plant demographics have recently been shown to reduce the persistence time of local populations of the fire‐killed shrub
Banksia hookeriana
dramatically. In principle, extinctions of local populations may be partly compensated by recolonization events through long‐distance dispersal mechanisms of seeds, such as post‐fire wind and bird‐mediated dispersal, facilitating persistence in spatially structured metapopulations. However, to what degree and under which assumptions metapopulation dynamics might compensate for the drastically increased local extinction risk remains to be explored. Given the long timespans involved and the complexity of interwoven local and regional processes, mechanistic, process‐based models are one of the most suitable approaches to systematically explore the potential role of metapopulation dynamics and its underlying ecological assumptions for fire‐prone ecosystems. Here we extend a recent mechanistic, process‐based, spatially implicit population model for the well‐studied fire‐killed and serotinous shrub species
B. hookeriana
to a spatially explicit metapopulation model. We systematically tested the effects of different ecological processes and assumptions on metapopulation dynamics under past (1988–2002) and current (2003–2017) climatic conditions, including (i) effects of different spatio‐temporal fires, (ii) effects of (likely) reduced intraspecific plant competition under current conditions and (iii) effects of variation in plant performance among and within patches. In general, metapopulation dynamics had the potential to increase the overall regional persistence of
B. hookeriana
. However, increased population persistence only occurred under specific optimistic assumptions. In both climate scenarios, the highest persistence occurred with larger fires and intermediate to long inter‐fire intervals. The assumption of lower intraspecific plant competition caused by lower densities under current conditions alone was not sufficient to increase persistence significantly. To achieve long‐term persistence (defined as >400 years) it was necessary to additionally consider empirically observed variation in plant performance among and within patches, that is, improved habitat quality in some large habitat patches (≥7) that could function as source patches and a higher survival rate and seed production for a subset of plants, specifically the top 25% of flower producers based on current climate conditions monitoring data. Our model results demonstrate that the impacts of ongoing climate change on plant demographics are so severe that even under optimistic assumptions, the existing metapopulation dynamics shift to an unstable source‐sink dynamic state. Based on our findings, we recommend increased research efforts to understand the consequences of intraspecific trait variation on plant demographics, emphasizing the variation of individual traits both among and within populations. From a conservation perspective, we encourage fire and land managers to revise their prescribed fire plans, which are typically short interval, small fires, as they conflict with the ecologically appropriate spatio‐temporal fire regime for
B. hookeriana
, and likely as well for many other fire‐killed species.
We extend a recent mechanistic, process‐based, spatially implicit population model for the well‐studied fire‐killed and serotinous shrub species to a spatially explicit metapopulation model. Our model results demonstrate that the impacts of ongoing climate change on plant demographics are so severe that even under optimistic assumptions, the existing metapopulation dynamics shift to an unstable source‐sink dynamic state.

Context
Extinction debt, the time-delayed species loss response to fragmentation associated with habitat clearance, is a conservation concern for management of biological diversity globally. Extinction debt is well defined but difficult to measure owing to the long-term data needed to measure species loss, particularly for communities of long-lived species.

Aims
We aimed to estimate extinction debt for two adjacent threatened communities with contrasting soil fertility in south-western Australia: banksia and tuart woodlands. Further, we assessed what species functional traits are associated with extinction risk.

Methods
Using contemporary (2016) and historical (1992) data on vegetation richness, and patch characteristics dating back to the time of European colonisation (1829), we examined 60 woodland patches using three methods to detect and quantify extinction debt.

Key results
We found evidence of extinction debt in banksia woodland, but not in tuart woodland. We estimated the extinction debt for banksia woodlands as a future average loss of 28% or ~13 species per patch.

Conclusions
Our study demonstrated a delay of species loss consistent with extinction debt in one of two vegetation communities. Despite sharing species and traits, these vegetation communities have responded differently to landscape change over the same timescale and within the same landscape.

Implications
Understanding how vegetation communities, and functional trait types, respond to time-delayed impacts helps land managers to prioritise intervention efforts to pre-empt species decline and extinction through species conservation, and ecological restoration of remnant vegetation patches.

Aims
Responses of ecological restoration projects to disturbances are rarely explored, yet their capacity to withstand and recover from disturbance (resilience) is a critical measure of restoration success. In many plant communities, the soil seed bank (SSB) provides an important source of propagules for species persistence and community resilience to disturbance. Understanding how SSBs develop with time can inform restoration of resilient ecosystems. Here, in fire-prone Banksia woodland restoration following sand mining, we ask: (a) how does the smoke-responsive (dormancy broken by smoke) SSB develop over time; (b) what plant-trait and climate factors influence its development; and (c) what do the data suggest for the resilience of these restored woodlands to fire?

Location
Ellenbrook, Swan Coastal Plain, Western Australia (latitude −31.76, longitude 115.95).

Methods
We used smoke, a key germination cue associated with fire disturbance, to trigger germination of the SSB in Banksia woodland restoration. Using a chronosequence of nine ages between 3 and 26 years since initiation of restoration, we tested how the SSB develops using counts and richness of germinating native and invasive annuals, and native perennial obligate seeding and resprouting species. To understand the contribution of above-ground restored vegetation to SSB development, we compared Sørensen's similarity of the smoke germinable SSB (smoked SSB) and untreated germinable SSB (control SSB) with above-ground vegetation.

Results
Smoked SSB germinant density decreased with restoration age for both native and invasive annuals, but was stable for native perennials. Similarity between smoked SSB and above-ground vegetation was higher for perennial obligate seeders than for resprouters and peaked for perennials at 23 years.

Conclusions
Post-fire regeneration potential of the SSB was evident across the chronosequence, with restoration age influencing the density of native annuals and overall composition of the SSB. The findings for perennial species suggest an increase in resilience to fire with restoration age.

Background
In recent decades, fire has increasingly occurred in the tropical montane rainforests of northern Vietnam. However, there are few studies of the effects of fire on forest composition and recovery in this region, and understanding these effects is critical for effective forest fire management and conservation. Forest plant species richness, structure (density, basal area), and composition were quantified for 133 forest plots randomly located in unburned (> 20 years since last fire) and recently burned (3–9 years since fire) vegetation associated with ten selected wildfires in three provinces of northern Vietnam where fires since 2000 were most frequent. Linear mixed effect models and nonmetric multidimensional scaling (NMDS) ordination were used to explore the structure, richness, and composition of burned and unburned forests and their environmental drivers, and to explore the key drivers of regeneration patterns in burned forest, including time since fire occurrence, fire severity, and distance to unburned forest edge.

Results
Total species richness and diversity, tree species richness, tree density, and basal area were higher in unburned (vs. burned) forest plots, low (vs. high) severity burn areas, near (vs. far) from the closest unburned forest edge, and longer (vs. shorter) time since last fire. Results suggest that while burned forests were recovering on a trajectory back towards unburned forest composition, recovery was likely to be markedly slowed where fires were large (distance from edge effects) and/or of high severity, and forests may shift towards a different state (i.e., composition and structure) where more than one fire affects the same area over short time intervals.

Conclusions
This study provides insights into the effects of fire and other environmental factors on forest composition and recovery in the tropical montane forests of northern Vietnam, crucial for informing policymakers involved in forest conservation and management.

Accelerating disturbance activity under a warming climate increases the potential for multiple disturbances to overlap and produce compound effects that erode ecosystem resilience — the capacity to experience disturbance without transitioning to an alternative state. A key concern is the potential for amplifying or attenuating feedbacks via interactions among successive, linked disturbance events. Following severe wildfires, fuel limitation is a negative feedback that may reduce the likelihood of subsequent fire. However, the duration of, and pre-fire vegetation effects on fuel limitation remain uncertain. To address this knowledge gap, we characterized fuel profiles over a 35-year post-fire chronosequence in California closed-cone pine forests, a system with stand dynamics comparable to stand-replacing fire regimes in other temperate and boreal conifer forests with much longer fire return intervals. We used this system to ask: 1) How do fuel profiles change with time since recent stand-replacing fire? 2) How do trajectories of fuel profiles differ between forests established from different pre-fire vegetation legacies — specifically areas that were forest vs. non-forest pre-fire? We also assessed fuel profiles that supported stand-replacing fire during a large (>90,000 ha) wildfire that burned through our study area shortly after data collection and compared with fuel profiles across the chronosequence. Overall, live and dead surface fuels accumulated quickly, reaching levels comparable to those capable of supporting severe fire after 10–15 years. Canopy fuels peaked at 20 years post-fire but were at levels comparable to those capable of supporting severe fire from 15 years onwards. Pre-fire vegetation legacy drove divergence in post-fire dead surface fuel trajectories, but effects on live surface and canopy fuels were minor. Fuel profiles in California closed-cone pine forests can support subsequent severe fire within 10 years, a fraction of the historical minimum interval between stand-replacing fires (≥30 years) that supports robust post-fire regeneration, but potential for severe fire remains lower for an extended period in areas where pre-fire vegetation was non-forest. Our findings show that the negative feedback of fuel limitation disappears quickly following fire, suggesting that these systems are vulnerable to short-interval severe reburns that could erode forest resilience.

Aims
Responses of ecological restoration projects to disturbances are rarely explored, yet their capacity to withstand and recover from disturbance (resilience) is a critical measure of restoration success. In many plant communities, the soil seed bank (SSB) provides an important source of propagules for species persistence and community resilience to disturbance. Understanding how SSBs develop with time can inform restoration of resilient ecosystems. Here, in fire‐prone Banksia woodland restoration following sand mining, we ask: (a) how does the smoke‐responsive (dormancy broken by smoke) SSB develop over time; (b) what plant‐trait and climate factors influence its development; and (c) what do the data suggest for the resilience of these restored woodlands to fire?

Location
Ellenbrook, Swan Coastal Plain, Western Australia (latitude −31.76, longitude 115.95).

Methods
We used smoke, a key germination cue associated with fire disturbance, to trigger germination of the SSB in Banksia woodland restoration. Using a chronosequence of nine ages between 3 and 26 years since initiation of restoration, we tested how the SSB develops using counts and richness of germinating native and invasive annuals, and native perennial obligate seeding and resprouting species. To understand the contribution of above‐ground restored vegetation to SSB development, we compared Sørensen's similarity of the smoke germinable SSB (smoked SSB) and untreated germinable SSB (control SSB) with above‐ground vegetation.

Results
Smoked SSB germinant density decreased with restoration age for both native and invasive annuals, but was stable for native perennials. Similarity between smoked SSB and above‐ground vegetation was higher for perennial obligate seeders than for resprouters and peaked for perennials at 23 years.

Conclusions
Post‐fire regeneration potential of the SSB was evident across the chronosequence, with restoration age influencing the density of native annuals and overall composition of the SSB. The findings for perennial species suggest an increase in resilience to fire with restoration age.

Seeds are necessary for successful restoration, but few studies track the development of the soil seed bank. Using smoke, we assessed germination of smoke‐responsive plant species across a restoration chronosequence. There was germination across the chronosequence, with composition changing with age. Our data for native perennial plant species suggest resilience of restored Banksia woodlands to fire increases with restoration age.