Observations on 7’ heme da australis-Eucalyptus Savannah in Papua 
P. C. Heyligers 1 
Savannahs, vegetation types with a ground 
cover dominated by grasses and an open tree 
storey, are extensive in the coastal lowlands of 
the Central District, Territory of Papua (Fig. 
1 ) . These lowlands were included in a regional 
survey carried out in 1962 by a team of the 
Division of Land Research and Regional Sur- 
vey, CSIRO. 
This paper describes the vegetation of savan- 
nah near Jackson’s Airport, about 12 km east 
of Port Moresby. Emphasis is laid on correla- 
tion with edaphic conditions. The field work, 
in cooperation with the geomorphologist and 
the pedologist of the team, was done in July 
and August 1963. 
The following data pertinent to this area are 
extracted from the survey report (Mabbutt et 
ah, 1965). 
The climate is monsoonal: strong south- 
easterly winds prevail during the dry season 
from May till October, in which monthly rain- 
fall averages 30 mm, and light variable winds 
during the rest of the year with monthly rain- 
falls averaging 160 mm. Table 1 gives more 
detailed information about rainfall, together 
with data on temperature and evaporation. 
The landscape, made up of strike ridges and 
vales, is underlain by fairly steeply dipping 
rocks of Tertiary age. Cherty shale, marl, and 
limestone form the rounded ridges; the vales 
have been cut in less resistant tuff. Relief is in 
the order of 100 m. Lithosols and regosols are 
found on the ridges, brown clay soils and tex- 
ture-contrast soils on the higher parts of the 
flatter land, and dark clay soils and alluvial 
soils near and along drainage lines. The vege- 
tation is savannah, predominantly of the 
Theme da australis-Eucalyptus type, with tall 
grass vegetation and forest along permanent 
streams. 
1 Division of Land Research and Regional Survey, 
csiro, Canberra, Australia. Manuscript received 
September 21, 1965. 
Fires are common throughout the dry season, 
at the end of which most of the ground cover 
has been burnt. Regrowth starts after some 
rain has fallen. Areas burnt early in the dry 
season can have a fair cover at the end of it 
and are liable to burn off again. At the time of 
our investigation, notwithstanding high rainfall 
in June, the dry season was already well ad- 
vanced and fire had destroyed the ground 
vegetation of a part of the area under in- 
vestigation. 
Wild life in the area is very scarce and its 
influence on the vegetation is negligible. Graz- 
ing by cattle is restricted to a few fenced prop- 
erties. 
Two transects were selected for observations: 
transect 1 was located 3 km south of Jackson’s 
Airport near the Rigo Road; transect 2 about 
1.5 km northeast of the airport. Levels were 
taken along each transect and at selected situa- 
tions pits were dug, varying in depth between 
1.0 and 2.5 m. 
TOPOGRAPHIC AND SOILS DESCRIPTION OF 
THE TRANSECTS 
Each transect comprised a fairly straight, 
smooth hill slope attaining 22° to 30° and with 
minor rock outcrop, passing into a shallowly 
dissected foot slope mainly between 0°30' and 
5° and up to 1200 m long, and ended at a small 
strike stream, which on transect 1 has a narrow 
bordering flood-plain. 
Much runoff is as sheet flow: slope wash on 
hill slopes results in small terracettes, and on 
foot slopes leaves a fairly abundant lag gravel 
(Mabbutt and Scott, 1966). 
Each transect had a similar sequence of soils 
(Scott, unpublished data). The hills are occu- 
pied by red regosols, which are deeply devel- 
oped at the lower slope of site 2. On the 
adjacent foot slopes texture-contrast soils are 
found, whilst black clay soils occupy the 
remainder of the flatter country, forming a 
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