8 
Cunninghamia 
Vol. 1 (1): 1981 
Mean Monthly Rainfall 
Figure 1. Climatic data for Cessnock, New South Wales, approximately 45 km north of 
Mangrove Creek. Data for period 1903-1964 (Hall, 1972). 
THE VEGETATION 
The alluvial flats were cleared in the early days of settlement, but the rest of the 
catchment area still retains much of the original native vegetation, though this has 
been regularly grazed, logged and burnt, particularly on the lower hillsides. 
Only three phototypes could be distinguished: (i) tall open-forest/open-forest, 
(ii) woodland and (iii) cleared agricultural land. The structural formations of Specht 
(1970) are used. Field work enabled the tall open-forest/open-forest type to be 
subdivided into three floristic units, each occupying a distinctive physiographic 
position along a gradient from ridgetop to gully but which, because of the amount of 
intergradation between them, could not be mapped separately at the scale presented 
here (Figure 2). The relationships between the structural units mapped, the 
vegetation communities described, and the geology and physiography are summarized 
in Table 1. Descriptions of the communities arc given below. Site data are given 
in Table 2 and Appendices 1 and 2. 
Eucalyptus deanei-Angophora floribunda TALL OPEN-FOREST 
This community is found in sheltered conditions with relatively fertile soil and 
is restricted to sheltered alluvial valleys or lower hill slopes on exposures of the 
Narrabeen Group, usually on southerly to south westerly aspects. It originally 
occupied most of the alluvial flats of Mangrove Creek down to its junction with the 
Hawkesbury River (Benson, 1974) but has been extensively cleared for agriculture 
and grazing. The original structure of the community was probably tall open-forest 
with very tall straight trees commonly exceeding 30 m in height. Remaining stands 
are now generally less than 25 m high, often composed of a large number of even-aged 
trees which have regenerated following clearing or extensive logging. 
