The effects of fire and fragmentation on Blandfordia grandiflora (Christmas Bells) and Acacia baueri (Tiny Wattle)

Gabriel Conroy, Faculty of Science, Health and Education, University of the Sunshine Coast.

Gabriel Conroy at one of the study sites
Photo © Gabriel Conroy

South east Queensland coastal heathlands are highly diverse, and contain many endemic species that are threatened as a result of substantial levels of recent urban development. The impacts of this ongoing urban development on biodiversity include direct habitat loss, fragmentation, the peril of introduced species and alterations to fire, nutrient and hydrological regimes. It is crucial that research occurs into the combined effects of fire and fragmentation upon threatened plant species such as Blandfordia grandiflora (Christmas Bells) and Acacia baueri (Tiny Wattle). Both of these species occupy a unique ecological niche within the coastal heathlands. They also act as important food sources for native insect pollinators as well as bird species such as Lewin’s Honeyeater in the case of Christmas Bells.

Whilst many coastal heath species are reliant on fire, human influences have led to the indelible alteration of fire regimes.  Both of my research species are dependent on fire for regeneration and are ephemeral in the above-ground heathland landscape mosaic which leads to the creation of complex metapopulation dynamics.  Metapopulations are populations of the same species that are geographically separate but linked by dispersal mechanisms, such as pollination or seed dispersal in the case of plants. Historically, heathlands have been naturally fragmented in the landscape, however further fragmentation may yield profound ecological and genetic consequences in terms of the survival of threatened heath species. Utilising a metapopulation approach to my research will reveal the conservation management implications of landscape-level processes such as fire and fragmentation on Christmas Bells and Tiny Wattle.

Blandfordia grandiflora (Christmas Bells)
Photo © Gabriel Conroy

Blandfordia grandiflora (Christmas Bells) is an iconic heath species that is classified as ‘endangered’ under the Queensland Nature Conservation Act 1992. This species was previously more common and was harvested intensively for the wildflower trade.  Christmas Bells are an erect perennial herb that flowers from December through to March for 1-2 seasons after fire and when flowering they are both conspicuous and beautiful.

The perianth of the flower is most often red with yellow semi-circular lobes, although significant variation has been observed and it appears that the 'traditional' form of Christmas Bells may have been so heavily harvested that it is now more common to encounter flowers that are mostly yellow in colour.  Christmas Bells are endemic to Queensland and New South Wales coastal heathlands where they are restricted to wet, sandy or peaty soils.

Their original distribution has become greatly reduced from land usage change, clearing and harvesting. It is undoubtedly important to preserve such a visually striking, taxonomically unique and ecologically significant species.

I always derive great inspiration for my research from a quote I stumbled upon in the QLD herbarium by the late, great pioneering conservationist Thistle Y. Harris: 

'It is always a delight to the nature-lover to come upon a posse of Christmas Bells, flaunting their red and orange heads in the sunlight'
     - Thistle Y.Harris BSc., Australian Wild Life, Volume 1, 1934.

Acacia baueri (Tiny Wattle)
Photo © Gabriel Conroy

Acacia baueri (Tiny Wattle) is a perennial, spreading shrub that can grow up to 50cm, although it is highly unusual to encounter specimens larger than 30cm. It is currently classified as ‘Vulnerable’ (Queensland Nature Conservation Act 1992) and appears to thrive in a post-fire environment due to the reduced competition from larger, more vigorous species. The Tiny Wattle has bright yellow flower clusters which can occur throughout the year, and are followed by slender curved seed pods which may provide a food source for foraging marsupials.  Unfortunately there is currently very limited knowledge of the ecology of this species which is restricted mainly to the infertile, sandy soils of heathlands within 20km of coastline and on coastal islands from Bundaberg to Sydney.

The overall aims of my project are to investigate the effects of fire and fragmentation on the ecology and demography of Acacia baueri and Blandfordia grandiflora and to integrate spatial, ecological, fire and genetic data in order to ascertain the viability of the research species via the use of metapopulation models and population viability analysis (PVA).  To do this, I have divided my SE Qld study area into two distinct zones. The first spreads north of Noosa and up to Fraser Island, and the second extends south of Noosa and throughout the Sunshine Coast.  The northern zone constitutes my unfragmented study area, as this region exhibits fragmentation levels that are much closer to natural levels compared to the highly fragmented southern study area on the Sunshine Coast. 

I have located populations of each species from a variety of sources including herbarium records, DERM literature and personnel, and most importantly the local knowledge of conservation groups and ecological enthusiasts.  Once I have located a population, I conduct extensive fieldwork gathering ecological, demographic and site data for each population which will be incorporated into my computer models and population viability analysis.  In the case of Tiny Wattle, I also collect a small sample of plant material for genetic analysis.  Once I get the genetic samples back to the lab, I use microsatellite primers, which are co-dominant genetic markers that provide invaluable population genetics data regarding genetic diversity and historical gene flow between and within the different populations.  This data can also be integrated into my computer modelling scenarios.

The approach I am taking with this project will provide valuable baseline data about these two threatened coastal heath species and build upon previous multi-species research into threatened coastal heathland species. The metapopulation modelling will allow the assessment of different management scenarios given the manipulation of the models with variable landscape-level processes such as climate change, ongoing fragmentation and fire management scenarios. As such, my research will also provide a solid basis to guide future conservation management practices that will benefit both of these species as well as the overall biodiversity and ecological health of coastal heathlands.