Seedling Survival in Forest Re-vegetation Sites within Wellington Peninsula
Transplanting native seedlings is a widely used restoration tool to enhance biodiversity in urban areas. Due to labour and economic needs of this tool, it is crucial to maximise the survival rates of the transplanted seedlings. In this research, I monitored, over a six month period, the status of wineberry (Aristotelia serrata), cabbage tree (Cordyline australis) and lemonwood (Pittosporum eugenioides) seedlings in their initial years after transplanting. The seedlings, up to 4 years old, were located in 11 forest re-vegetation sites in Wellington city, New Zealand. Using mixed effects models to predict the mortality probability of each species, I analyse the relative importance that variables (e.g. soil conditions or grass competition) have in the mortality of the seedlings. Lemonwood seedlings experienced the lowest mortality rates (<2%), independent of age. The models predicting probability of mortality of wineberry and cabbage tree indicate that grass competition and water availability are crucial variables in the mortality of these species during the initial 6 months after transplanting. Combinations of plant size (e.g. height) and certain environmental variables (e.g. soil conditions or slope) crucially affect mortality of wineberry and cabbage trees from one to three years of age. Based on these results, I provide recommendations, such as appropriate planting date and ideal length of maintenance tasks, to maximise survival rates of native plants within the first years after transplanting. A longer monitoring period and similar research of other species are required to assist forest re-vegetation groups in Wellington city achieving more cost- and labour-efficient re-vegetation management.