How do sandalwoods (Santalum spp.) affect desert communities: integrating above-ground patterns with below-ground processes

A project undertaken at three Bush Heritage Australia reserves in Western Australia

Project team: Prof David M Watson, Dr Jodi Price and Dr Adam Frew (all Charles Sturt University), Dr Leonie Valentine (University of Western Australia) and Dr Vanessa Westcott (Bush Heritage Australia)

Australia's arid and semi-arid rangelands are undergoing a transformation. After over a century of pastoralism as the predominant land-use, concepts of regenerative agriculture and rewilding are informing a new approach integrating conservation science and holistic management while embracing indigenous knowledge. Central to this re-imagined outback is the idea that profitable land-use need not be extractive; that best practice management should increase soil health and maximise value for native wildlife. One group of plants that hold great promise are sandalwoods, a genus of native parasitic trees that yield a range of products (fruit and seeds as well as highly-prized timber and essential oils) and enhance habitat quality for many native plants and animals.  Despite recent innovations in growing various Santalum species in plantations, the industry remains reliant on harvesting wild plants, potentially diminishing habitat value for native pollinators and the digging marsupials and fruit-eating birds that disperse their seeds. Combining experiments with cross-site comparisons, this pioneering work will identify key interactions with native animals and measure how Santalum affects above and below-ground ecological processes, informing development of more sustainable industry practices.

By integrating comparisons of root parasitic shrubs (Exocarpos and Santalum species) within and between study sites with replicated small-scale litter-bag experiments, this innovative project will:

  1. Describe the suite of ecological processes affected by Santalum spp., identify those animal species dependent on these native parasitic plants, quantify key resources provided (nutritional & microclimatic)
  2. Measure the influence of Santalum spp. on soil health in terms of litter fall, nutrient inputs, carbon assimilation, seed rain, water infiltration, litter-dwelling invertebrates and mycorrhizal occurrence
  3. Determine how seed dispersal, litterfall and altered nutrient inputs interact to affect germination, establishment and, ultimately, plant recruitment beneath parasitic plants

    Integrating these three ecological objectives, the ultimate ecosystem-scale aim of this work is:
  4. Estimate the overall effects of Santalum and Exocarpos spp on successional dynamics, comparing the effects of species, plant density and ecological interactions with soil type and management history.
    In addition to refining on-ground management across Australia's rangelands, these discoveries will promote long-term sustainability of the sandalwood industry.

 


Figure 1. Mature quandong (Santalum acuminatum) at Charles Darwin Reserve.  The dense foliage and high water content of the leaves ameliorate the microclimate beneath the canopy. (David M Watson)

Figure 2. Beneath a quandong, enriched litter accumulates in the shade—ideal conditions for seeds to germinate in this hot, dry environment (David M Watson)

Figure 3. An Australian Sandalwood, Santalum spicatum.  The timber of these native plants is highly prized, large-scale harvesting over the past century reducing their abundance and distributional extent (David M Watson

Figure 4. Litter and woody nuts build up beneath a sandalwood, representing a concentrated source of food for woylies, critical weight range mammals that disperse their seeds (David m Watson)