Why do tall herbs rarely dominate Tasmanian alpine vegetation? Evidence from islands in the Ouse River system

Tall alpine herb field is largely absent from the Tasmanian alpine zone. This absence has been attributed to marsupial grazing. Small islands in the upper Ouse River valley are partly dominated by Craspedia paludicola, a showy tall alpine herb. The herbs dominate on the upstream ends of the islands. The surrounding vegetation on the banks is mainly grassland. The tall herbs are a very minor element of the shore vegetation, occurring on the undercut banks. Grassy islands close to the river banks are grazed and few tall herbs are found there. Craspedia paludicola also occurs in small numbers in damp areas on grassy heaths at other grazed locations, largely within bushes with pungent leaves. The distribution of Craspedia paludicola suggests that it is highly palatable and can thus only survive in larger numbers away from the influence of vertebrate grazers (rabbits and marsupials). It appears that this species requires both disturbance and a lack of grazing to dominate an area.