Journal of the Royal Society of Western Australia, 86(2), June 2003 
Forest 
Figure 3. Vegetation replacement sequence for Rottnest Island 
forest-woodland-heath system following a fire, in the absence of 
further disturbance. After Noble & Slatyer (1980). 
regenerate and are self-maintaining within an established 
heath environment, although they occur only 
occasionally as understorey species in dense Melaleuca/ 
Callitris or Acacia. The fourth major component of the 
heath, Thomasia cognata (providing some 17% of 
vegetation cover) reproduces from seed alone. For this 
analysis, we classify the species of the heath as DT (seeds 
are dispersed widely so are available at any time, and 
seedlings are tolerant of competition). 
A sequence can be predicted for the development of 
the three vegetation communities following a fire and in 
the absence of further disturbance except perhaps for 
light grazing (Fig 3). All species germinate or resprout 
immediately after fire. Most heath species regenerate 
from seed and rootstock, and reach maturity rapidly. The 
Acacia forms dense scrub 3-4 metres high within 5 years. 
Senescence starts at about 20 years (McArthur 1996b) 
with deterioration from the centre, and the plants die out 
by 40 years, leaving a seedbank in the soil for about 60 
years or more. Melaleuca and Callitris are more slow- 
growing, but as the Acacia declines the forest species 
grow through and dominate until the last survivors die 
off at about 110 years. Thus, immediately following a fire 
and in the absence of further fire or grazing thereafter, all 
species would regenerate in the presence of seed and/or 
rootstock. The heath would dominate briefly before being 
overwhelmed by Acacia (Fig 3). The tree species would 
only grow through the Acacia as the latter thinned out 
and then died by 40 years of age. By about 110 years the 
Melaleuca/Callitris would have died leaving no seedbank, 
the Acacia seeds left in the soil would also have died by 
this time, and only the heath species would persist. 
Materials and methods 
Plant nomenclature is based on Pacskowska & 
Chapman (2000) and information from the Western 
Australian Herbarium. 
Field survey 
On 17"' February 1997 a fire (started by a power pole) 
burnt through about 90 ha on Rottnest Island between 
the centre of the island and the north coast (Fig 4). The 
vegetation consisted of Acanthocarpus heath, apart from a 
small zone of coastal heath at the northern extremity 
(which is not considered in this survey). Several 
plantations adjoining the burnt area were protected from 
the fire by firebreaks, and the only trees burnt were two 
Melaleuca lanceolata. The burnt area and the immediately 
surrounding Acanthocarpus heath that was not burnt will 
be referred to as the Research Site. Within five months 
the Rottnest Island Authority had fenced 70% of the 
burnt area into six separate plots, using 1 m high fencing 
reputed to be quokka-proof for at least 8 years (C 
Hansen, Environmental Officer, Rottnest Island 
Authority, personal communication). Some quokkas 
were able to jump the fence but were removed 
periodically (C Wright, Environmental Manager, Rottnest 
Island Authority, personal communication). The entire 
fenced area was planted with Melaleuca lanceolata and 
Callitris preissii seedlings, of local provenance, over the 
ensuing four years at a density of about one plant per 
20 m 2 ; a few Pittosporum ligustrifolium were planted but 
none survived (C Hansen, Environmental Officer, 
Rottnest Island Authority, personal communication). 
In August 2001, four sites were selected where the 
surrounding unbumt vegetation was in close proximity, 
and had a similar aspect to the area that had been burnt, 
within and outside the fenced plots. Further sampling 
was not possible because much of the burnt unfenced 
area surrounding the plots was taken up by fire breaks 
and vehicle access tracks. Three 25 m x 2 m transects 
were established at each site to compare the surrounding 
heathland that had not been burnt with the vegetation 
that had been burnt, both fenced knd not fenced (Fig 4). 
Each of the 12 transects consisted of five 5 m x 2 m 
Figure 4. Rottnest Island: area burnt in 1997 showing fenced 
plots, adjacent plantations and positions of transects. 
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