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The autecology of lonicera japonica in a restoration context

This thesis concerns the autecology of Lonicera japonica in relation to ecological restoration in Hamilton. It addresses three groups of questions, relating to L. japonica's place in the plant community, its reproduction and spread, and its impacts on other plants. L. japonica's role in the plant communities of natural areas and restoration sites and its variation with environmental factors were studied quantitatively through vegetation measurement and soil analyses at plots established at a naturally regenerating site in Hamilton. Its role under varying disturbance regimes and physical conditions was studied qualitatively and semi-quantitatively at eight other locations. A simple model relating stem diameter to age was developed to assess the age and demography of L. japonica populations. L. japonica's potential to spread was assessed through trials to establish seed and fragment viability, examination of climatic records, and the identification from the literature of potential vectors. Impacts of L. japonica on other species were assessed first through a consideration of the frequency at which plants of differing characteristics are invaded, and second by characterising its impacts upon those plants. The thesis concludes with recommendations for further research and for the management of the plant in restoration areas. Through the field work it was found that L. japonica is more widely dispersed both within and across natural areas and restoration sites in Hamilton than had been detected from initial site visits, to the extent that it was difficult to detect patterns and relationships at the chosen scale of investigation. It exhibits a tolerance for low pH and wet conditions greater than found in studies overseas, and neither those factors nor soil fertility are likely to limit its spread in restoration and natural areas in New Zealand. However at light levels found ii beneath typical native canopy cover the plant's vigour is greatly reduced, and this offers the most promising avenues for control. L. japonica disperses readily via stem fragments incorporating nodes and sets plentiful fertile seed. Though the viability of that seed is short, propagation by this means is possible in Hamilton and may become significant in relation to future restoration work. In good light conditions L. japonica forms dense mats that smother vegetation of low stature and prevent natural succession in canopy gaps, as well as compromising the health of restored areas. In locations with mature canopy L. japonica may survive over lengthy periods on the ground, with restricted vigour, or in canopy-entering clumps that have grown with the host; either form will expand rapidly if light conditions improve. However because of their growth form and trunk texture even mature tree ferns may be killed by L. japonica. Novel elements that have emerged from this study are the plant's tolerance of a wider range of environmental conditions in New Zealand than reported overseas, its potential to spread by seed in local conditions, and an emerging synergistic relationship with another invasive liane, Ipomoea indica. The latter two issues are worthy of further study.
Type of thesis
Pudney, K. J. (2009). The autecology of lonicera japonica in a restoration context (Thesis, Master of Science (MSc)). The University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/3267
The University of Waikato
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