|dc.description.abstract||The loss of native plant species through habitat loss has been happening in NZ since the arrival of humans. This is especially true in Canterbury where less than 1% of the lowland plains are believed to be covered in remnant native vegetation. Rural land uses are changing and farm intensification is creating novel habitats, including farm irrigation earth dams. Dam engineers prefer not to have plants growing on dams. Earth dams are consented for 100 years, they could be used to support threatened native plants. Within the farm conversion of the present study dams have created an average of 1.7 hectares of ‘new land’ on their outside slope alone, which is the area of my research. This new land represents important sites for vegetation restoration in another wise highly modified landscape. My research aims to discover if earth dams could be used as restoration sites for rare, threatened or at risk native plants.
The north and south facing outside slopes of four dams were surveyed to find out which plants have established. Four 5 x 5m quadrats per north or south dam wall were used to identify plant species and ground condition on four dams. Twenty three vascular species were identified from 31 vascular taxa found growing in the quadrats. A combination of dam and aspect had an impact on species diversity in the plots. Only six species were recorded as covering more than 5% of the quadrats. There were significant differences between dam wall aspect in both vegetation height, and ground conditions. Temperature changes recorded over 24 hours were different between the north and south walls of dam 1 and were considered to have implications for planting zones.
Five native rare species were chosen due to nursery availability, and studied in detail, from a list of 44 native plants that were recorded in the area of the Te Whenua Hou dams at Eyrewell, Canterbury. The five species are Aciphylla subflabellata, Coprosma intertexta, Leptinella serrulata, Muehlenbeckia ephedroides, Raoulia monroi. Quadrats were used to identify species growing with the rare species and the ground conditions. There were 94 plots studied across 22 sites, across Canterbury, from Culverden in the north to Ealing, Ashburton District, in the south. Altitude varied from sea level to 481m across the species. Plot vegetation cover was significantly different between species even though ground conditions were not significantly different. Both species diversity and vegetation height were significantly different. There were six species that were found in at least one plot of each of the rare species.
Roots of seven dam species and four rare species were excavated and scanned using the WinRhizo™ programme at Landcare Research/ Maanaki Whenua for quantitative measurements and to evaluate root traits. The root diameter of the rare species was within the range of the dam species, 0.315 mm for Agrostis tenuis to 0.629 mm for Rumex acetosella. The root volumes of the rare species were larger than the dam species. There was significant difference between the specific root length of the rare species and the dam species.
The root diameters imply that the four rare species could be grown on the dams as they all fall within the range of diameters of the established plants. The remaining roots traits imply, that for a restoration site, the dams could be used for the rare species.
A protocol has been proposed for planting novel habitats with target species, based on the steps of this research. This includes direct comparison of novel site and target species natural sites as well as root measurements for site specific comparisons.||en