Rippey & Hobbs: Effects of fire and quokkas on Rottnest Island vegetation 
quadrats, for which the percentage cover and average 
height of each species present was recorded. The 
proportion of bare earth was also noted. 
The three 'groups', burnt and fenced, burnt and 
unfenced, and unburned and unfenced were compared 
with regard to the number of native species, percentage 
cover of native species, and percentage cover of the 
introduced Trachyandra divaricata. Analysis of variance 
was used to test for significant differences amongst 
groups and transects. Logarithmic transformation was 
employed to stabilise the variance for species count data. 
The Kruskal-Wallis rank sum test was applied to the 
percentage cover data of both native species and 
Trachyandra divaricata because standard assumptions for 
ANOVA (in particular normality and homogeneity of 
variance) were violated. 
Aerial photographs 
Photocopies of the following aerial photographs were 
obtained from the Western Australian Department of 
Land Administration to assess vegetation changes on 
Rottnest Island, particularly at the Research Site. 
• aerial photographs of Rottnest Island, 1942: black 
and white 29/9/42, Run 1 YX4140, YX4142; Run 3 
YX 4155, YX4157, YX4159, YX4160, YX4162; Run 4 
YX4136, and a copy of a map derived from these 
photographs: Australian Section Imperial General 
Staff 1943, Rottnest Island, 4 th Australian Survey 
Co, RAE, scale approx: 1:16,000 (4 inches to 1 mile). 
• aerial photographs of Rottnest a few days after the 
1955 fire: black and white Run 1. WA 158. Scale 
1:7920 taken 25/02/1955. These photographs were 
used to assess changes between 1942 and 1955. 
Subsequent vegetation changes were identified by 
comparing these images with aerial photographs 
taken in later years, by superimposing images 
which had been reduced to the same scale by 
photocopying. Photographs were: 8/4/1964 5114, 
WA 854, Rottnest Island (5112-5116) from 12,500', 
Project D60; 18/3/1967 5067 WA 1016, Rottnest 
Road Guide Revision Run 1 (5062-5069) 7920; 14/ 
2/1972 5063 WA 1378 (C) Rottnest Island Run 1 
(5059-5067) 7920 152.56; 1/2/1980 5018, WA 
1857(C), Rottnest Island Run I (5014-5020) scale 
1:10000, Job no 800001; 11/3/1990 WA 2851 (C), 
Rottnest Island Run 1 (50001-5010) Scale 1:15000, 
900890. 
• further series of aerial photographs was used to 
examine changes brought about by the 1997 fire; 
these comprised Rottnest Island, 6/2/1997 Metro 
regional area Run 41, 5002, 5004 and 5006, 1:20,000; 
an enlarged colour photocopy of aerial photograph 
10/01/1998 WA 4044C; Perth regional area Metro 
photography project no 970000, Run 41:5003, Scale 
1:25,000. Computer generated, enlarged images of 
aerial photographs were also obtained: Perth 
regional area Metro Photography 17/02/2000 
Project no 990000, WA 4422C Run 41:5003, 1:25,000; 
14/12/2000 Project no 000001, WA 4544C, Run 
41:5139, Scale 1:25,000. Vegetation distribution was 
related to topography in the Research Site with the 
use of a photocopy of a contour map of Rottnest 
Island produced by the Department of Lands and 
Surveys, Job no 800001, lm contours, from 
photography taken February 1980 and October 1981. 
Results 
Field survey 
The vegetation of the surrounding Acanthocarpus heath 
that had not been burnt consisted almost entirely of three 
native species, Acanthocarpus preissi , Austrostipa flavescens, 
and Thomasia cognata, and the introduced Trachyandra 
divaricata (Table 1). Burning of Acanthocarpus heath 
Table 1 
% cover and frequency of plant species in burnt and fenced, burnt and unfenced, and unburnt areas. 
Burnt and fenced 
% cover % Freq 
Burnt and unfenced 
% cover % Freq 
Unbumt 
% cover % Freq 
Acanthocarpus preissii 
7 
70 
21 
100 
32 
100 
Austrostipa flavescens 
26 
100 
19 
100 
14 
95 
Thomasia cognata 
15 
80 
8 
60 
15 
75 
Olearia axillaris 
8 
60 
0 
0 
Acacia rostellifera 
29 
60 
0 
0 
Solanum symonii 
1 
25 
1 
25 
0 
Lepidosperma gladiatum 
4 
15 
1 
20 
0 
Lepidosperma pubisquameum 
3 
20 
0 
0 
Carex preissii 
0.2 
5 
0.2 
30 
0 
Conostylis candicans 
3 
40 
5 
55 
3 
50 
Rhagodia baccata 
4 
15 
0 
0 
Guichenotia ledifolia 
0.05 
5 
2 
20 
3 
15 
Trachyandra divaricata 
1 
45 
11 
95 
14 
80 
Planted Melaleuca and Callitris 
7 
35 
N/A 
N/A 
Seedlings of ephemerals 
3 
100 
9 
100 
8 
100 
Bare 
8 
23 
11 
TOTAL 
>10(P 
100 
100 
a Acacia rostellifera formed a canopy with an understorey, so that the total coverage shown for burnt and fenced sites is greater than 
100%. The understorey consisted almost entirely of native species, so the understorey was disregarded when calculating percentage 
cover of native species for the statistical analysis. 
53 
