Abiotic disturbance in New Zealand ecosystems: a geomorphological perspective

Abiotic disturbance originating from relatively short duration (geological, geomorphological, hydrological or climatic) events may have an immediate ecological impact within the affected area, and longer term consequences for land surface and ecological stability within the larger drainage basin. The episodic occurrence of abiotic disturbance is analysed using the conceptual framework of the fluvial system, considering concepts such as extrinsic and intrinsic thresholds, recurrence interval, complex response, and magnitude of event. These concepts are illustrated with examples of abiotic disturbance from micro to mega scale events within New Zealand. These include windthrow, landsliding and volcanic eruptions. The major conclusion is that abiotic disturbance as a phenomenon needs to be considered within the wider context of landform, regolith and soil evolution in order to put spatial and temporal changes into perspective. By implication, this will influence the interpretation of ecological stability and instability. Single events of abiotic disturbance, dependent on their magnitude, maintain or change the diversity of ecological sites within a landscape.