Ecological Succession Obseiived Duking IIegeneraTioN 
OF Triodia Pungens K.Br. After Burning. 
140 
6.— ECOLOGICAL SUCCESSION OBSERVED DURING 
REGENERATION OF TRIODIA PUNGENS R.Br. 
AFTER BURNING. 
By Nancy T. Burbidge, B.Sc- (Hons.). 
Head 10th March, 1942 : Published Oth December, 1943. 
Certain investigations, into the sheep carrying capacity of the spinifex 
country of the north-west of Western Australia, are being carried out by 
ofhcers of the Institute of Agriculture of the University of Western Aus- 
tralia, at Warralong Station, about sixty miles east-south-east of Port Hed- 
land. The name spinifex is used locally for various species of Triodia R.Br. 
In the course of a taxonomic study of this genus the writer visited the country 
between Port Hedland and Marble Bar during the months May, June and 
July, 1941. Some weeks were spent at Warralong. An area of 400 acres, 
on this property, is being used for certain feeding experiments. The spinifex 
cover has been removed by burning and the plots therefore provide an ex- 
cellent ai*ea for a study of regeneration. Two quadrats (20 x 20 links) were 
mapped in the experimental area and two (50 x 50 links) in adjacent country 
which provided examples of more advanced regrowth. 
The climate is semi-arid with high summer temperatures. Rain may 
fall at any time between December and March. The fails may be spread over 
some months or there may be heavy storms (willy-willies) when the average 
for the year may be exceeded during a twenty-four hour period. The yearly 
aggregates are, however, not notably variable and the climate may be de- 
scribed as one in which dry summers are common, but prolonged droughts 
rare. In 1941 a dry summer w’as followed, in early March, by a violent storm 
which caused record floods in many of the rivers. 
The Warralong experimental plots are situated on the granitic plain to 
the south of the De Grey River. Except for an occasional ridge of stony 
hills due to intrusive rocks the general landscape is flat or very gently un- 
dulating. The soil is a light sandy loam, reddish in colour (Teakle, 1938). 
The vegetation has been described as semi-desert savannah (Teakle l.c.). 
Spinifex {Triodia spp.) is the dominant genus. T. pungens R.Br. is the 
most important species and is frequently the only perennial grass present. 
Small trees and shrubs are present; their relative density varies and appeai^s 
to be dependent on some soil factor which is, as yet, unrecognised. 
T. pungens is the only species of the genus with real pastoral value. It 
is a coarse, tussock-forming, resinous grass very variable in its growth habit. 
At the Warralong plots the general form is a pyramidal tussock varying in 
size up to two metres in diameter and about the same in height. 
The use of fire to improve pasture is, of course, practised in many parts 
of the world. Old fibrous and unpalatable material is bm*nt and young re- 
growth is more easily reached b}^ the grazing animal. In burning spinifex it 
has been assumed, and indeed widely claimed, that the fire burns the tussock 
back to a central butt from Avhich young shoots develop. While this is ad- 
mittedly true in some places, the writer’s observations showed that it is by 
no means ahvays so. Over a wide area fire causes the complete destruction 
of the plants and regeneration takes place by means of seedling establisii- 
ment. 
k 41/43 
