Biology Reference
In-Depth Information
also the understorey and ground layers. A woodland
remnant can be a large patch of trees (plus understorey
and ground cover) extending over tens or even hundreds
of hectares or it can be as small as a single paddock tree.
Remnant native vegetation is critical for the
persistence of biodiversity: for birds it is three times
more important in terms of the number of species it
supports than planted vegetation and it also supports a wider array of declining
woodland bird species.
1
In this chapter we discuss some of the key features of a good remnant and how
these features influence wildlife. These features include vegetation condition, patch
size, and adjacency to other areas of vegetation (including plantings; see Chapter 3).
We discuss native woodland remnants by their various vertical and horizontal
layers and structural classes, and consider why each one is important for
biodiversity using examples from our research over the past decade to illustrate key
topics. We outline management actions that can maintain existing areas of good
remnant vegetation or improve them for biodiversity. Although our focus is on
what we consider to be a 'good' remnant, we stress that
any
remnant native
vegetation on a farm is good for animal and plant biodiversity because it will
support at least some native species.
Most of this chapter explores issues associated with patches of remnant
native vegetation. Scattered paddock trees and native pastures are also
important elements of remnant native vegetation, but we discuss them in
Chapter 4.
All of the natural layers of
woodland remnants are
important - the ground
cover, the understorey and
the overstorey trees
Vegetation condition
For the purposes of this topic, vegetation condition is measured as the degree to
which a remnant varies from 'reference sites' that are relatively unmodified stands
of the same vegetation community.
2
The reference concept is based on the
assumption that ecosystems approaching conditions that prevailed prior to major
periods of modification (e.g. European settlement) will generally reflect the
conditions to which native plant and animal communities are best adapted.
3
Attributes that are used to assess vegetation condition in the context of
biodiversity are those elements of remnant native vegetation that represent
important habitat for wildlife and are indicative of ecosystem function. These can
include (among many things) the number of large hollow trees, the volume of
fallen timber, the cover of understorey shrubs, and the presence of regeneration.
It is important to assess the condition of a particular remnant relative to an
equivalent vegetation community. For example, if good vegetation condition was
based on the amount of shrub cover in a remnant, then naturally shrubby
vegetation communities such as Red (or Mugga) Ironbark forest would always be
