Targeted Vegetation Survey of Floodplains and Lower Slopes on the ...

CCA08 Far North Coast <strong>Targeted</strong> <strong>Vegetation</strong> <strong>Survey</strong>
1.3.4 Coastal Quaternary geology
A new classification <strong>of</strong> Quaternary deposits was
undertaken for the coastal zone <strong>of</strong> NSW (Troedson
et al. 2004). Quaternary deposits were divided into
three depositional classes: alluvial, estuarine <strong>and</strong>
coastal barrier s<strong>and</strong>. The depositional classes were
also differentiated into Holocene <strong>and</strong> Pleistocene
deposits. Holocene sediments are deposits in the active
depositional coastal zone <strong>and</strong> have accumulated over
the last 10,000 years following post-glacial marine
transgression (Troedson et al. 2004). Pleistocene barrier
s<strong>and</strong>s were deposited during times <strong>of</strong> high sea-level
before 10,000 years ago.
Alluvial plain depositional systems occur on the
l<strong>and</strong>ward section <strong>of</strong> the coastal plain. They are most
extensive in the estuarine deltaic plains <strong>of</strong> the main
coastal rivers <strong>and</strong> extend into non-tidal narrow valleys
<strong>of</strong> coastal catchments (Troedson et al. 2004). Estuarine
depositional environments occur in waterbodies <strong>of</strong>
brackish to marine salinity <strong>and</strong> under some tidal
influence (Troedsen et al. 2004). Coastal barrier
systems are located on the seaward side <strong>of</strong> the coastal
plain <strong>and</strong> comprise wind-blown <strong>and</strong> marine-deposition
s<strong>and</strong>s (Troedsen et al. 2004).
1.3.5 Climate
Climatic patterns are controlled by the progression <strong>of</strong>
high- <strong>and</strong> low-pressure systems across the continent.
Seasonal patterns <strong>of</strong> temperature <strong>and</strong> rainfall are
driven by the north–south migration <strong>of</strong> high-pressure
systems. The effects <strong>of</strong> tropical cyclonic activity <strong>and</strong>
l<strong>and</strong>forms both also have an impact on the climate
<strong>of</strong> the region. Longer term trends in rainfall <strong>and</strong>
temperature are influenced by the El Niño–Southern
Oscillation (ENSO), which determines the circulation
<strong>and</strong> strength <strong>of</strong> trade winds directing moisture across
eastern Australia (NRAC, 1996b).
Summers are hot <strong>and</strong> winters warm. Annual mean
maximum temperatures vary from 26°C at Casino,
which is inl<strong>and</strong>, to 23.3°C at Yamba, on the coast. The
mean summer maximum is 31°C at Casino, <strong>and</strong> the
mean summer minimum is 25.9°C at Alstonville, close
to but not on the coast. Cooler temperatures occur at
higher altitudes along the Nightcap, McPherson <strong>and</strong>
Border Ranges <strong>and</strong> at Mount Warning (NRAC, 1996b).
Rainfall is highest in summer–autumn <strong>and</strong> lowest
in winter–spring. The northern coastal fringe <strong>and</strong>
hinterl<strong>and</strong> ranges receive high annual rainfall (mean
annual rainfall at Byron Bay is 1707 mm; at Ballina
1654 mm). Rainfall increases to over 2000 mm per
annum on the McPherson, Nightcap, Burringbar <strong>and</strong>
Border Ranges. The intensity <strong>of</strong> rainfall is extreme,
<strong>and</strong> the potential for erosion is high. Annual rainfall
decreases from north to south along the coast; it is
1456 mm at Yamba. There is a dry rainshadow, with
average annual rainfall less than 800 mm, north <strong>and</strong>
south <strong>of</strong> about Casino (which itself has a mean annual
rainfall <strong>of</strong> 1098 mm) (Temperature <strong>and</strong> Rainfall data
from Bureau <strong>of</strong> Meteorology website).
1.3.6 <strong>Vegetation</strong>
The vegetation <strong>of</strong> the study area has significant
biodiversity values <strong>and</strong> many notable features. It is
located in the McPherson Macleay Overlap, contains
remnants <strong>of</strong> the Big Scrub rainforest, supports three
areas <strong>of</strong> World Heritage Rainforest, <strong>and</strong> contains the
Border Ranges, which is one <strong>of</strong> Australia’s 15 National
Biodiversity Hotspots.
The McPherson Macleay Overlap is an area <strong>of</strong> very
high biodiversity. The overlap contains species <strong>of</strong>
both temperate <strong>and</strong> tropical areas as a result <strong>of</strong> a
combination <strong>of</strong> climatic <strong>and</strong> geographical influences.
The study area is home to the Big Scrub, which was
once the largest expanse <strong>of</strong> subtropical rainforest in
Australia, but has been largely cleared <strong>and</strong> now less
than 1% remains. The Big Scrub was a rich area for
flora with a high level <strong>of</strong> species endemism. The study
area contains the Focal Peak, Sheild Volcano <strong>and</strong>
Main Range Groups <strong>of</strong> the World Heritage Gondwana
Rainforests <strong>of</strong> Australia.
1.3.7 Previous studies
Previous regional surveys focusing on public l<strong>and</strong> <strong>and</strong>
forested environments include the North East Forest
Biodiversity <strong>Survey</strong> (NEFBS) (NPWS 1994), the
vegetation surveys <strong>of</strong> the Comprehensive Regional
Assessments (CRA) (NPWS 1999), <strong>and</strong> the vegetation
surveys <strong>of</strong> the Natural Resource Audit Council
(NRAC) (NPWS 1995). The NRAC vegetation
surveys targeted vacant <strong>and</strong> reserved Crown L<strong>and</strong> in
the Clarence, Richmond <strong>and</strong> Tweed River Catchments
(NPWS 1995). The NEFBS flora project surveyed <strong>and</strong>
analysed the distribution <strong>of</strong> vascular plants throughout
the forests <strong>of</strong> north-eastern NSW (NPWS 1994),
<strong>and</strong> 205 sites sampled during the NEFBS lie within
the study area <strong>of</strong> the present study. The CRA surveys
were done as part <strong>of</strong> the data-collection component
<strong>of</strong> a regional assessment <strong>of</strong> forests in north-eastern