An autoecological study of the central Queensland serpentine endemic plant Neoroepera buxifolia Muell.Arg. & F.Muell. (Picrodendraceae)
thesisposted on 06.12.2017, 00:00 authored by RA Hendry
This thesis reports on autoecological aspects of the serpentine endemic plant Neoroepera buxifolia and provides a general study on the vegetation ecology of the central Queensland serpentine landscape on the east coast of Australia. The first objective of this thesis was to determine if the overlying vegetation could be used as biological indicators of the severity of the serpentine soils. The results supported this theory as negative correlations were found between the relative basal area of the endemic overstorey tree Corymbia xanthope and the soil calcium. The endemic and rare plants increased in abundance with soil nickel and the herbaceous species decreased with soil nickel. The species richness increased with soil boron and decreased with soil nickel. The species abundances also correlated with the landform patterns reflecting differences in soil chemistry. The overstorey tree Eucalyptus fibrosa subsp. fibrosa regulated metal uptake and was not a useful indicator. The endemic shrub Neoroepera buxifolia has a high habitat specificity and is mostly restricted to the perennial and ephemeral creeks within the central Queensland serpentine landscape. It is associated with high soil magnesium and the aim was to determine if the standing volume and height was correlated with the soil magnesium and the soil Mg/Ca quotients. Whilst correlations were found between increased height and soil Mg/Ca quotients, the strongest influence on N. buxifolia was from the extractable soil nickel. No correlations where found between the soil magnesium and the standing volume or height of N. buxifolia. Over 82% of the central Queensland serpentine landscape is covered by mining interests for economic enrichments of nickel, cobalt, iron and magnesium carbonate. iii Successful restoration following mining requires the careful selection plant of species. The suitability of N. buxifolia to be used for phytostabilisation was assessed by determining the bioaccumulation factor of metals. Neoroepera buxifolia was determined to be suitable for phytostabilisation as it is a metallophyte, it does not accumulate metals and the bioaccumulation rates for nickel and cobalt did not exceed a factor of 1. However, N. buxifolia has narrow habitat requirements which would limit its application to high moisture areas such as tailing dams, drains and creeks. Neoroepera buxifolia readily propagated from seed and the seeds did not require dormancy relieving techniques for successful germination. Seeds stored for three months in their fruits had high germination rates and good viability. Vegetative propagation using marcotting and ground layering techniques were also highly successful. The application of auxin promoted the development of the root ball. Propagation using cuttings was not as successful compared to the marcotting and ground layering techniques. The final part of this thesis is an ecological risk assessment which characterised the threats to the endemic shrub N. buxifolia. It was determined that the greatest risks are from climate change, fire, mining, exotic species invasions, livestock grazing and habitat fragmentation. Management actions are required to mitigate and control the threats to N. buxifolia to reduce the risk outcomes and maintain existing populations of N. buxifolia.