Plant diversity is linked to nutrient limitation of dominant species in a world biodiversity hotspot

This paper investigates the question “What is the role of nutrient limitation of dominant species in maintaining plant species diversity at small spatial scales, particularly in biodiversity hotspots?”

Long-term impacts of prescribed burning on regional extent and incidence of wildfires : evidence from 50 years of active fire management in SW Australian forests

Prescribed burning is advocated for the sustainable management of fire-prone ecosystems for its capacity to reduce fuel loads and mitigate large high-intensity wildfires. However, there is a lack of comprehensive field evidence on which to base predictions of the benefits of prescribed burning for meeting either wildfire hazard reduction or conservation goals. Australian eucalypt forests are among the very few forest types in the world where prescribed burning has been practised long enough and at a large enough spatial scale to quantify its effect on the incidence and extent of unplanned fires. Nevertheless even for Australian forests evidence of the effectiveness of prescribed burning remains fragmented and largely unpublished in the scientific literature. We analysed a 52-year fire history from a eucalypt forest region in south-western Australia to quantify the impact of prescribed burning on the incidence, extent and size distribution of wildfires. Quantile regression identified the longevity of the influence of prescribed fire treatments on wildfire incidence and extent. Anomalies in the frequency-size distribution of unplanned fires were identified through a relative risk mapping using kernel density estimates. Changes in the spatial distribution of fuel age were quantified using patch metrics, while generalized additive models were applied to estimate effects of fuel age patterns on the incidence and extent of unplanned fire

Plant functional traits along environmental gradients in seasonally dry and fire-prone ecosystem

This paper investigates the questions “How does the abundance and richness of plant assemblages with different functional (regeneration and nutrient acquisition) traits vary with fire regime, moisture availability and substrate fertility? What is the role of different functional traits in maintaining plant diversity under changing environmental conditions in seasonally dry and fire-prone environments?

Response of plant species and life form diversity to variable fire histories and biomass in the Jarrah forest of south-west Australia

Frequent fires reduce the abundance of woody plant species and favour herbaceous species. Plant species richness also tends to increase with decreasing vegetation biomass and cover due to reduced competition for light.We assessed the influence of variable fire histories and site biomass on the following diversity measures: woody and herbaceous species richness, overall species richness and evenness, and life form evenness (i.e. the relative abundance or dominance among six herbaceous and six woody plant life forms), across 16 mixed jarrah (Eucalyptus marginata) and marri (Corymbia calophylla) forest stands in south-west Australia. Fire frequency was defined as the total number of fires over a 30-year period. Overall species richness and species evenness did not vary with fire frequency or biomass. However, there were more herbaceous species (particularly rushes, geophytes and herbs) where there were fewer shrubs and low biomass, suggesting that more herbaceous species coexist where dominance by shrubs is low. Frequently burnt plots also had lower number and abundance of shrub species. Life form evenness was also higher at both high fire frequency and low biomass sites. These results suggest that the impact of fire frequency and biomass on vegetation composition is mediated by local interactions among different life forms rather than among individual species. Our results demonstrate that measuring the variation in the relative diversity of different woody and herbaceous life forms is crucial to understanding the compositional response of forests and other structurally complex vegetation communities to changes in disturbance regime such as increased fire frequency

Turner Review No. 8. Ecology and ecophysiology of grasstrees

Xanthorrhoea...is in habit one of the most remarkable genera of Terra Australis, and gives a peculiar character to the vegetation of that part of the country where it abounds’ Robert Brown (1814). Grasstrees (arborescent Xanthorrhoea, Dasypogon, Kingia), with their crown of long narrow leaves and blackened leafbase-covered trunk (caudex), are a characteristic growth form in the Australian flora. Xanthorrhoea is the most widespread genus, with 28 species that are prominent from heathlands to sclerophyll forests. While leaf production for X. preissii reaches a peak in spring–summer, growth never stops even in the cool winter or dry autumn seasons. Summer rain, accompanied by a rapid rise in leaf water potential, may be sufficient to stimulate leaf production, whereas root growth is confined to the usual wet season. Grasstrees are highly flammable yet rarely succumb to fire: while retained dead leaves may reach \u3e1000°C during fire, the temperature 100 mm above the stem apex remains \u3c60°C and the roots are insulated completely. Immediately following fire, leaf production from the intact apical meristem is up to six times greater than that at unburnt sites. For X. preissii, pre-fire biomass is restored within 40 weeks; the mass of live leaves remains uniform from thereon, whereas the mass of dead leaves increases steadily. Leaves usually survive for \u3e2 years. In X. preissii, the post-fire growth flush corresponds to a reduction in starch storage by desmium in the caudex. Minerals, especially P, are remobilised from the caudex to the crown following a spring fire, but accumulate there following an autumn fire. At least 80% of P is withdrawn from senescing leaves, while \u3e95% K and Na are leached from dead leaves. Most stored N and S are volatilised by fire, with 1–85% of all minerals returned as ash. Despite monthly clipping for 16 months, X. preissii plants recover, although starch reserves are depleted by 90%, indicating considerable resilience to herbivory. Analysis of colour band patterns in the leafbases of X. preissii shows that elongation of the caudex may vary more than 5–50 mm per annum, with 10–20 mm being typical. Exceptionally tall plants (\u3e3 m) may reach an age of 250 years, with a record at 450 years (6 m). Fires, recorded as black bands on the leafbases, in south-western Australia have been decreasing in frequency but increasing in variability since 1750–1850. Some grasstrees have survived a mean fire interval of 3–4 years over the last two centuries. In more recent times, some grasstrees have not been burnt for \u3e50 years. The band-analysis technique has been used to show a downward trend in plant δ13C of 2–5.5‰ from 1935 to the present. Grasstrees are most likely to flower in the first spring after fire. A single inflorescence is initiated from the apical meristem, elongating at up to 100 mm day–1 and reaching a length up to 3 m, with one recorded at 5.5 m. This rapid rate of elongation is achieved through leaf (and inflorescence) photosynthesis and desmium starch mobilisation. The developing spike and seeds are vulnerable to a moth larva. Leaf production recommences from axillary buds and the trade-off with reproduction is equivalent to 240 leaves in X. preissii. Flowering and seed production are affected by time of fire. Grasstrees are mainly insect-pollinated. Up to 8000 seeds per spike are produced, although pre-dispersal granivory is common. Seeds are released in autumn and persist in the soil for \u3c2 years. Most fresh seeds germinate in the laboratory but germination is inhibited by light. At any\u3etime, seedlings and juveniles may account for most plants in the population, although there may be up to an 80% reduction within 1 year of seedling emergence, often due to kangaroo herbivory. In the absence of fire, mortality of adults may be 4% per annum. Although few grasstree species are considered rare or threatened, their conservation requirements, especially in regard to a suitable fire regime, remain unknown. Grasstrees are particularly susceptible to the exotic root pathogen, Phytophthora cinnamomi, although recruitment among some species has been observed 20–30 years after pathogen invasion. Much remains to be known about the biology of this icon of the Australian bush