Neal Enright

Projected effects of climate change across many ecosystems globally include more frequent disturbance by fire and reduced plant growth due to warmer (and especially drier) conditions. Such changes affect species–particularly fire-intolerant woody plants–by simultaneously reducing recruitment, growth, and survival. Collectively, these mechanisms may narrow the fire interval window compatible with population persistence, driving species to extirpation or extinction. We present a conceptual model of these combined effects, based on synthesis of the known impacts of climate change and altered fire regimes on plant demography, and describe a syndrome we term “interval squeeze”. This model predicts that interval squeeze will increase woody plant extinction risk and change ecosystem structure, composition, and carbon storage, especially in regions projected to become both warmer and drier. These predicted changes demand new approaches to fire management that will maximize the in situadaptive capacity of species to respond to climate change and fire regime change.

Significant climate changes are evident across Australia with declining rainfall and rising temperature, in conjunction with more frequent fire. Significant species loss and range contractions have been predicted, however the validity of these predictions is uncertain with critical gaps remaining in our understanding of the intrinsic capacity of species to respond to climate change. We quantified genome wide adaptive genetic variation in populations of Banksia attenuata, a prominent woody plant of multiple vegetation types in southwest Australia, evaluated the impact of declining rainfall, rising temperature and shortened fire intervals on population adaptive genetic variation. We characterised candidate genes associated with rainfall gradients, temperature, and fire interval through environmental association analysis. Population adaptive genetic variation was significantly impacted by shortened fire intervals, while declining rainfall and rising temperature have not had detectable influence so far. Candidate genes associated with rainfall and high temperature are diverse, with polymorphic alleles present in populations, while genes associated with specific fire intervals are fixed in one allele. Gene annotation further revealed four genes with function in stress tolerance, regulation of stomatal opening and closure, energy use, and morphogenesis with adaptation to climate and fire interval. B. attenuata, and perhaps other species with similar life history and distribution, may tolerate some further change in rainfall and temperature through evolutionary adaptation based on their adaptive genetic variation. However, the capacity to survive future climate change may be compromised by change in fire regime, and the capacity to survive more frequent fire and further environmental fluctuations is uncertain.

Floristically rich and ecologically complex, Mediterranean-type ecosystems are rapidly being cleared for urban, horticultural and industrial development. A prime example is Banksia woodland, an ecosystem restricted to the Swan Coastal Plain in Western Australia. In order to compensate for the clearing of Banksia woodland due to urbanization, land developers are required to attempt biodiversity offsets whereby topsoil from newly cleared landscapes can be moved to degraded land with the aim of restoring Banksia woodland. Yet the science and practice of restoration ecology is not sufficiently advanced to know for certain that this aim can be achieved. Assessing the efficacy of a spectrum of restoration techniques will provide new insights for the restoration of endangered plant communities, and critically, a test of the feasibility of biodiversity off setting. The topsoil was subjected to three site-scale treatments: altering topsoil depth, ripping & herbivore exclosures. Additionally, six plot-scale treatments were applied to explore germination effect (three smoke water-related, topsoil heating) and competition effect (herbicide & artificial shade installation) on native seedlings’ emergence and survival. Significantly fewer seedlings emerged from ripped (17.01 ±1.03 SE) than unripped plots (37.99 ±2.05 SE). Species richness was similar across all treatments with a total number of native plant species emerging from the transferred topsoil of 129 in the first year and 115 in the second year. Mean survival rates of native perennial seedlings were very low (year I = 11.1% & year II = 1.2%). The maximum average survival was recorded under artificial shade (41% ±12.2 SE).

Delayed seed release (serotiny) is a syndrome of adaptive significance in a randomly fluctuating environments such as fire-prone and arid ecosystems. Selective forces involving fire, rainfall and seed predators have been suggested as factors influencing serotiny. Callitris preissii is a conifer in the Cupressaceae found only in Australia and New Caledonia and it is regarded as “fire sensitive”. It has excellent potential for erosion control of sandy, alkaline coastal sites and has been used in revegetation in many region in Western Australia. We compared the degree of serotiny among different populations and related this to fire history, climate and seedling predators.The relative ages of cohorts of closed cones were determined on trees in populations ranging from arid interior sites to islands with much higher annual rainfall. The individuals with the greatest serotiny grow at inland sites (Kalgoorlie and Lake Grace), while the plants with the lowest serotiny were recorded at island sites. Seedling recruitment after fire at Boorabin National Park burnt in 2007 was dense and at Cape Le Grand National Park near the south coast of Western Australia a patchy fire produced many seedlings in burnt areas. However in both areas seedlings were absent from unburnt sections. The strong serotiny at these sites ensures an abundant seed rain after fire kills adult plants. The weaker serotiny at the island sites might be thought to relate to the possibility that there is interfire recruitment of the plants.

Global importance of fire: Disturbance regime is a fundamental driver of plant community composition and structure, and of species coexistence. Fire is one of the most common causes of recurrent landscape scale disturbance, and has shaped evolution and adaptation in many taxa globally (Bond & Keeley 2005). Altered fire regimes are a significant component of global environmental change and have been implicated in species losses and invasions. Climate change is predicted to result in decreased precipitation and increased temperature across many fire-prone regions, resulting in longer fire seasons and increased fire likelihood, while reduced productivity may lead to increased fuel limitation and less fire in other situations (Moritz et al. 2012).

Global change, population growth and urbanisation are ever-increasing pressures on biodiversity and ecosystem function. Given that conservation of existing natural fragments will not be sufficient to maintain extant biodiversity or meet conservation goals, there is a major need for the practice of ecological restoration whereby degraded lands are managed to increase and maintain indigenous species. However, technical capacity lags and research on restoration tools is vitally needed. One increasingly common restoration tool is topsoil transfer, moving quality topsoil and its associated soil seed bank (SSB), nutrients, and soil fauna to degraded areas. To assess the capacity of topsoil transfer, several key aspects of the SSB were examined parallel to a real-world topsoil transfer in south-west Australia. We evaluated restoration values of topsoil transfer, by investigating plant functional traits, SSB similarity to extant vegetation, exploring mechanisms to improve restoration outcomes, and what influence the process of topsoil transfer has on germinable seed. Glasshouse germination was monitored over 13 weeks from 24 pre and 24 post-transfer soil samples. Treatment included soil depth and smoke plus heat combined. Topsoil transfer resulted in significant seed dilution, equal mixing through the soil profile relative to pre-transfer soils and a marked change in species composition (including lack of perennial species). Smoke and heat failed to stimulate additional germination post-transfer. Topsoil transfer, while successfully translocating native seeds, influences restoration success through dilution and lack of perennial species, thus suggesting a need for topsoil transfer to be supplemented by other restoration techniques, and therefore limiting its cost effectiveness.

The effects of climate change, particularly altered rainfall patterns, are apparent across Australia. In Southwestern Australia, a biodiversity hotspot, decreased annual rainfall is causing concern for the persistence of native flora. The ability of Australian species to rapidly select for drought tolerance in response to decreased rainfall is largely unknown, yet this knowledge is required to develop future management and conservation strategies. This research aims to determine whether seed-banks of selected species can potentially mitigate effects of a drying climate through rapid selection and adaptation. It is hypothesised that the seed-bank of a species can increase resilience to climate change by providing a range of genetic material for rapid selection. Eight locations where fire was followed by a wet, dry or average winter were identified at Eneabba, Southwestern Australia. At each location, seed was collected from five serotinous, fire-killed species; Banksia hookeriana, Banksia leptophylla, Hakea costata, Hakea polyanthema and Beaufortia elegans. Seed was germinated, and divided into three drought treatments: 100%, 75%, and 50% mean winter rainfall equivalent. Post-spring, seedlings will be harvested and dry-weight of roots/shoots determined. A larger proportion of seedlings descended from plants recruited post-fire in dry winters are expected to exhibit tolerance to drought treatments than those descended from plants recruited in average or wet winters. This experiment is part of a broader study on evolutionary adaptation in Western Australian species, which aims to determine the ability of species to rapidly evolve in response to climate change, and assist in informing approaches to adaptive conservation management.

Background/questions/methods: The main urban areas of Western Australia (WA) are located on the Swan Coastal Plain - the 400 km long sandy landform between the Indian Ocean and Darling Scarp that encompasses the main habitat for endangered Banksia woodland. This floristically rich but poorly understood Mediterranean-type ecosystem is being rapidly destroyed by urban, horticultural and industrial development. In order to partially ameliorate the damage being inflicted on Banksia woodland vegetation WA land developers have been required to purchase offsets of, often degraded, land to where topsoil from construction sites can be moved to help rehabilitate the damaged areas. The aim of this project is to restore Banksia woodlands by optimising germination and survival of native species from the soil seed bank contained within transferred topsoil. The project is a part of an offset program associated with the development of the Jandakot Airport 25 km south of Perth city. In the first year, key research questions are focused on enhancing germination by varying depth of returned topsoil, ripping, fencing, weed control and experimental additions of smoke. Subsequent work will examine the survival and persistence of germinants including treatments such as provision of artificial shade. Assessing the efficacy of a spectrum of novel restoration technologies will provide new insights for environmental management of endangered plant communities. Results/conclusions: Preliminary results will be presented at the conference.

Background/question/methods: Understanding directions, rates and causes of recent trends in biodiversity is vital to planning conservation actions. State of Environment Reports turn to map statistics and aggregated indices to infer general trends, while empirical data are considered too patchy or inconsistent to contribute to an overview. Using examples from Australian heathlands, we asked what further insights on the status of biodiversity can be gained from available empirical studies. We reviewed a selection of long-term ecological experiments of 10-30 years duration. We aimed to identify major drivers of ecosystem dynamics, determine trends in different biota and diagnose causes of change. Results/conclusions: The studies were continental in coverage and identified land clearing, fire regimes, climate processes and disease as major influences on heathland dynamics. Fire regimes are the most ubiquitous driver, but the mechanisms and nature of fire-driven changes vary among biota and across the continent. Land clearing caused severe historical losses of biodiversity in the south-west and continues to threaten coastal heathlands. Plant disease is driving the most rapid recent declines, primarily in southern Australia. Observed sensitivities of heathland biota to climatic factors signal potential losses of diversity under future climates. All of the studies advanced understanding of heathland dynamics. Concordance between studies with varied approaches suggests robustness of inferred trends. We conclude that long term ecological studies are under-utilised in conservation reporting and planning. Further investment in them will greatly strengthen capacity to detect and interpret trends in biodiversity. Similar insights could not be achieved with any certainty by short cut methods.

The length of inter-fire intervals plays a central role in determining species composition in plant communities across the world. Recently, extremely short intervals have been identified as a threatening process for the ongoing persistence of species in a number of vegetation types. A variety of methods were used to determine a minimum fire-return interval suitable for the maintenance of biodiversity in the species-rich and fire-prone northern sandplain shrublands of Western Australia. Several species considered vulnerable to high fire frequency were selected for demographic analysis with space-for-time substitution used to determine key life-history attributes such as time to produce adequate seed for self-replacement. Community-level resilience was captured using pre- and post-fire plot comparisons in recently burnt vegetation that was re-burnt by experimental fires. The stability of each site was measured in terms of resemblance to pre-fire composition at 12 months after fire. The effect of post-fire rainfall on seedling mortality was also examined as a factor independent of fire interval length. The results were combined to identify a minimum return interval that has provided land managers with a sound ecological basis for determining an appropriate prescribed burning regime for the community.