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CHaPTeR 3 Method of data analysis and collection
For stage 2, however, there is no equivalent, complete floristic map of the coastal parts of the
study area, although work is continuing on developing a mosaic of best-available mapping
for the entire region, including high-resolution mapping for the coastal zone. Therefore, an
alternative method was required for sampling coastal floristic variability to meet regionalscale
survey priorities. The methodology used in this study involved three tiers of gap analysis
and site selection, as described below, in order to address the various scales of variation to be
sampled.
3.2.2 Three-tiered approach to gap analysis
3.2.2.1 Overview
The three-tiered approach to completing site selection for systematic vegetation surveys within
the study area was aimed at addressing regional-scale priorities based on environmental
domain analysis, while subregional priorities were analysed according to canopy diversity,
and local-scale priorities for the coastal zone were studied using environmental stratification
(Sheringham et al. 2008). The three different approaches are described below.
3.2.2.2 Regional-scale survey priorities
As noted above, regional-scale survey priorities were based on intersecting environmental
domain map units with existing systematic survey site locations to identify those areas that
were relatively poorly sampled at this scale. Three measures of survey priority were considered,
with the highest priority given to map units which met all of the following three criteria:
➜ Number of sites per map unit (priority given to units with less than 50 sites)
➜ Number of sites per hectare of each map unit (priority given to units with less than six
sites per 10 000 ha)
➜ Number of sites per extant vegetated hectare for each map unit (priority given to units
with less than 10 sites per vegetated 10 000 ha)
3.2.2.3 Subregional-scale survey priorities
Survey priorities at the subregional scale were identified based on an assessment of existing
site locations intersected with classified SPOT5 satellite imagery (unsupervised) which had
been interpreted for broad vegetation type. Priorities for survey were based on the number
of existing sites per map unit and overall sites per vegetated hectare for each map unit. This
sampling approach was applied to each of the individual classified scenes in an attempt to
maximise the floristic variability sampled throughout the region. Individual scenes were chosen
in preference to the catchment-wide classified image generated from merged SPOT5 scenes
due to the resultant loss of resolution and discernability of individual units across their entire
geographic extent (Siggins et al. 2006).
3.2.2.4 Local-scale (coastal zone) survey priorities
For the purposes of this project, the coastal zone was considered to be that area used for the
New South Wales Comprehensive Coast Assessment (CCA) vegetation and fauna data audits
(NPWS 2003a). The site-selection method for sampling local-scale, coastal variability aimed to
be consistent with the approach used by DECC for the North Coast coastal vegetation survey
(Sheringham et al. 2008), specifically, the inclusion of the Quaternary geology layer produced for
the CCA. While the stratification approach used by DECC also included vegetation formation,
strata-geology and landform relief, these additional variables were already targeted by the
regional-scale and subregional-scale survey priorities used for this project. As such, this third
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