The many and varied types of savanna country reflect both the
amount of annual rainfall and types of soil. Variation in these two
key factors determines both the dominant trees of a savanna and the
associated combination of grasses (the pasture types) in the
understorey.
The savanna types have been mapped extensively, for example the
Land System Maps of the 1950s and 1960s, and the maps of the
different pasture types. Recently, a generalised vegetation map of
northern Australia has been produced (below).
The savannas range from open forest in the coastal and
sub-coastal regions to woodlands in the semi-arid regions to open
woodlands with scattered low trees in the arid interior. Treeless
grasslands occur on heavier soils and where drainage is impeded.
Most ecosystems in northern Australia are grassy landscapes.
Notable exceptions are the rainforests (the Wet Tropics in north
Queensland and the monsoon forests and vine thickets of Queensland,
Top End and Kimberley), some of the wetland ecosystems and the most
rugged and rocky landscapes of the Kimberley and western Arnhem
Land where the vegetation is sparse scrub or heath.
These environments make an important contribution to both plant
and animal biodiversity of northern Australia, and the health and
management of these landscapes cannot be readily disentangled from
that of the surrounding savanna.
