Environmental correlates of coastal heathland and allied vegetation

Abstract

The east Australian coastline supports regionally distinct heathlands and allied structural formations, and of particular interest is the vegetation on Quaternary dunefields and beach ridge plains containing aquifers. Groundwater is abstracted from these aquifers for domestic, industrial and agricultural consumption, and this abstraction proceeds without a sound understanding of plant–water relations. This study examined relationships between the vegetation and a range of simple and complex environmental variables. Aspects of intra-habitat and micro-site environmental heterogeneity were also explored. Watertable depth varied spatially and temporally relative to vegetation type, although differences were not consistently significant. Differences in watertable depth were significant for vegetation samples grouped by topographic position. Plant roots were invariably present at the upper boundary of the aquifer and these were observed at depths of up to 10.5 m. Groundwater was found to have the chemical composition of dilute seawater. Soil properties for the A1 horizon (total phosphorus, total nitrogen and organic matter content) varied with vegetation type and topography, and although mean values were generally higher in wetter habitats, differences were not consistently significant. Ordination identified topography as the more important determinant of vegetation pattern. Intra-habitat and micro-site differences in soil and groundwater properties were detected, and the likely causes of this variation are discussed.

Understanding the characteristics of a groundwater-dependent ecosystem: Eucalyptus parramattensis Woodland at Porters Creek Wetland, NSW.

“…No impact on the health of the Eucalyptus parramattensis trees was observed to result from the short-term change to the water table. Whilst this finding is consistent with Griffith et al (2008), who found that dry heath species could tolerate waterlogging for up to 3 months, the period of possible waterlogging in the current study was very brief (HA1 > HA2 for less than a month in Fig. 9).…”

“…The aquifer associated with Patonga Claystone becomes unconfined north-east of the Wyong River and, consistent with our results, is "generally considered to be low yielding, with moderate to high salinity levels" (Molloy et al 2009, p. 8). This contrasts with the fresh groundwater (< 0.35 ppt) recorded beneath a floodplain supporting Casuarina cunninghamiana forest adjacent to Widden Brook (Chalmers et al 2012), and in a coastal aquifer below Wallum communities of northern NSW (Griffith et al 2008). The order of magnitude difference in groundwater salinity levels between the current study and that of Griffith et al suggests that species that the two studies have in common (e.g.…”

Calling phenology and detectability of a threatened amphibian (Litoria olongburensis) in ephemeral wetlands varies along a latitudinal cline: Implications for management

“…This long calling season may increase their chance of capturing the rainfall peak within that window, which for the study area can occur any time from late spring to early autumn (Chiew & McMahon 2002;Griffith et al 2008). Indeed, calling peaks were highly responsive to peaks in rainfall, which, together with the long calling season duration, are adaptive response to climatic unpredictability and temporary wetland breeding (Wilbur 1987;Jakob et al 2003;Richter-Boix et al 2006;Vignoli et al 2007;Lowe et al 2015).…”

“…Temporarily flooded coastal wetlands of mid-eastern Australia can be characterized by the length of hydroperiod and unpredictable dates of inundation, because of variability in the timing and amount of annual rainfall for the region (Chiew & McMahon 2002;Griffith et al 2008). The climate is sub-tropical with hot, wet and humid summers followed by dryer, cooler winters (Stern et al 2000;Colls & Whitaker 2001).…”

“…Males call in most months of the year but are likely to display seasonality in calling intensity and activity (Hines & Meyer 2011). They breed in wetlands that periodically dry out (Lewis & Goldingay 2005;Shuker & Hero 2012;Simpkins et al 2013), which are strongly influenced by the timing and amount of spring and summer rainfall (Griffith et al 2008;Lowe et al 2015). The risk of reproductive failure for L. olongburensis depends on both the delay or lack of annual rainfall and the length of hydroperiod (Lowe et al 2015).…”