干旱区生态环境知识资源中心

The present native and exotic woody vegetation of the rainshadow region of Central Otago, in eastern South Island, New Zealand, is described. Fourteen present-day associations of woody species are related to a gradient in elevation and climate, and to the degree of disturbance by fire and mammalian grazing since human settlement. A few closed-canopy forest remnants remain only in the montane zone, while more modified forest relicts are scattered across a wider range of environments. Remaining woody plant associations have originated as secondary successions following fire, and range from exotic-species-invaded lowland associations on semi-arid basin floors to prostrate, native-species-dominated associations on mountain tops. Indigenous short-tussock grasslands and seral shrublands are being invaded by exotic trees and shrubs, especially in lowland environments. Dwarf and prostrate low shrub associations on the range tops may have replaced tussock grasslands since the commencement of pastoralism, where taller tussock-shrubland communities were destroyed by fires soon after human settlement. The region’s vegetation is not at equilibrium, and taller, woody communities tend to develop following removal of fire and grazing. Biodiversity restoration goals for deforested eastern South Island regions such as Central Otago should include long-term succession to indigenous woody communities in representative areas of all land environments.