Rippey & Hobbs: Effects of fire and quokkas on Rottnest Island vegetation 
Figure 1. Location of major fires on Rottnest and Garden Islands 
since 1955. 
During the latter half of the 20 th century, the cover by 
forest and woodland was further reduced, to 7% by 1974 
(White & Edmiston 1974), while heath became 
increasingly widespread. The primary management 
objective over this period was the provision of tourist 
amenities, as the island was an A Class reserve with the 
gazetted purpose of public recreation, with about 500 000 
visitors per annum by the end of the century. 
Maintenance of the quokka population was another 
concern, as quokkas were endearing to tourists and also 
a declared threatened species. Fires were rapidly 
controlled if they occurred. A small fire on Garden Island 
in 1991 was studied in some detail (McArthur 1996a,b; 
McArthur 1998). A restricted fire on Rottnest Island in 
1997 and the subsequent response of the vegetation is 
discussed in this paper. Fig 1 shows the positions of the 
four major fires on Rottnest and Garden Islands over the 
past fifty years; all fires occurred at the height of summer 
(end of January or during February). 
Attributes of dominant plant species on Rottnest Island 
Melaleuca lanceolata/Callitris preissii low forest, Acacia 
rostellifera scrub and Acanthocarpus heath have dominated 
the Rottnest Island flora at various times. Noble & Slatyer 
(1980) suggested that successional changes in plant 
communities subject to recurrent disturbances can be 
predicted by examining the vital attributes of the 
dominant component species. Applying their criteria, 
Heath I r 
iUlUl it t UtU toltd l tfUmi l faMMUtoUrt lull MmUHUIKI l. l I .| I M »U mmi .H im I I II »iiHi/ i 
A cacia _! 
Figure 2. Vital attributes of the three dominant communities (r 
representing the time at which the species reaches reproductive 
maturity, 1 the end of the lifespan, and e the time at which all 
propagules, plants and seeds become extinct). After Noble & 
Slatyer 1980. 
Melaleuca/Callitris would be classified as Cl (seeds are 
stored in the tree canopy not the soil, and germinants are 
intolerant of competition). Reproduction of Melaleuca/ 
Callitris is solely propagule-based. These are 
bradysporous species with seeds stored in the capsules 
or cones in the canopy. The seeds are short-lived and 
there is no seedbank in the soil (McArthur 1996a). The 
trees are killed by fire, but dense germination in the 
vicinity of burnt parent trees can follow burning (Baird 
1958; McArthur 1998; White & Edmiston 1974). They 
regenerate in open conditions, being unable to compete 
with conspecific adults. The trees take up to 10 years to 
reach sexual maturity (C Hansen, environmental officer, 
Rottnest Island Authority, personal communication), and 
their life span is about 110 years (McArthur 1998), 
although one Callitris preissii of about 140 years has been 
recorded (Powell & Emberson 1981). Fig 2 gives these 
vital attributes in diagrammatic form. 
Acacia rostellifera falls into Noble & Slatyer's category 
of SVI (seeds are stored in the soil, but the species also 
reproduces vegetatively; germinants are comparatively 
intolerant of competition). The species germinates from 
seed and also resprouts after fire from underground parts 
up to 50 m distant from the parent plant (Storr 1963). 
Acacia rostellifera seeds are hard-coated and have a 
prolonged dormancy, in common with the great majority 
of Acacias (Simmons 1981). Successful regeneration 
requires open conditions such as follow disturbance, 
especially fire. The shrubs have a lifespan of about 40 
years (Powell & Emberson 1981; McArthur 1996a), but 
become senescent on the islands after about 20 years 
(White & Edmiston 1974; McArthur 1996b). 
The heath species Acanthocarpus preissii and Austrostipa 
flavescens, which together with the introduced 
Trachyandra divaricata make up two thirds of the 
vegetation cover in the heathland surrounding the burnt 
zone, are capable of regenerating vegetatively or from 
seed. Trachyandra is a rhizomatous herb, growing to 
0.35 m, with ribbon-like leaves. These three dominant 
species are widespread on Rottnest Island and for the 
purposes of this analysis we assume that there is a 
constant supply of propagules from the surrounding 
heathland. Acanthocarpus, Austrostipa and Trachyandra are 
considered tolerant of competition as they continue to 
51 
