Shrub encroachment in grassland environments is observed in many regions worldwide. However, in New Zealand, there is no consensus on the trend and magnitude of this phenomenon, and we lack empirical data to determine what environmental variables may promote shrub invasion. Here, we present a comprehensive study evaluating shrub cover change in a tussock water catchment in eastern Otago, New Zealand.
[First paragraphs...]
A study of the history of the development of grassland in New Zealand is also a study of a prolonged interaction between native and introduced plants in which there has usually been a strong and deliberately guided bias towards the supremacy of the introduced plants. Because much of the native vegetation does not meet the requirements of the farmer, he has tried to replace this with plants that do so.
Fire occurs relatively frequently in beech (Nothofagus) forest in drought prone eastern areas of the South Island, New Zealand. Because beech is poorly adapted to fire, and is slow to regenerate, forest is normally replaced by scrub or grassland. Seeding was investigated as a means of restoring mountain beech (N. solandri var. cliffortioides) forest after fire destroyed 300 ha of forest at Mt. Thomas, Canterbury, in 1980.
Vegetation and soils were sampled at remaining gumland heath ecosystems in northern New Zealand to determine vegetation patterns, environmental controls and major threats to long-term persistence. Classification and ordination techniques identified six vegetation types reflecting differences in drainage, rainfall, altitude, nutrients, and time since fire. Two modal types reflected opposite ends of the main environmental spectra.
Mycorrhizal colonisation of Douglas-fir and Corsican pine seedlings in soil from kānuka and mānuka dominated shrublands in Canterbury was studied using a bait plant technique. Soil cores were collected from 10 sites of each shrubland, transferred to a glasshouse, and sown with seed of both tree species. Mycorrhizal colonisation was examined after 19 weeks’ growth. Overall, seedlings of Douglas-fir were larger than those of Corsican pine, but the amount of Corsican pine seedlings that were colonised (56%) was about twice that of Douglas-fir (29%).
