Biology Reference
In-Depth Information
9.
Many exotic species such as tree lucerne are so invasive that they can choke an
entire tree planting which, over time, can result in the planting being
dominated by a single species.
Establishing suitable plant species goes beyond simply selecting those species
that are generally local to a given area. There is also a need to consider suitable
microclimatic conditions for particular plants. For example, different species of
trees, understorey shrubs and ground cover plants grow better on ridges and rocky
slopes than on valley floors. Establishing tree and understorey species in
appropriate places can influence not only rates of growth, but also rates of
mortality and ultimately the success of a revegetation program.
The understorey layer of plantings is a critical vegetation layer for native biota.
For example, understorey cover is an important part of the suitability of plantings
for native bird species such as the Grey Fantail, Rufous Whistler and the White-
plumed Honeyeater
3
as well as the use of these areas for feeding by the Squirrel
Glider. Plantings with a dense midstorey wattle layer often do not support the
hyper-aggressive Noisy Miner - a native honeyeater that is notorious for driving
away many small native woodland birds
21
(see Box 2.7 in Chapter 2). Establishing
an understorey in plantings is therefore important, otherwise revegetation
programs risk creating more habitat for the Noisy Miner with detrimental
additional impacts on other native birds.
22
The value of the understorey layer in plantings highlights the value for
biodiversity of using mixtures of tree and shrubs in revegetated areas.
9, 19
Indeed, this is a general principle not only for planted vegetation in temperate
woodland environments
1
but also replanted areas in Australian tropical forest
landscapes (e.g.
23
).
0
1
5
20
80
% cover
Acacia
in midstorey
Figure 3.16:
Relationships between the occurrence of the Noisy Miner and the density of wattle trees in the
understorey of a planting.
