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Impacts of grazing by vertebrate herbivores on the flower stem production of tall alpine herbs, Eastern Central Plateau, Tasmania
journal contribution
posted on 2023-05-16, 12:54 authored by Kerry BridleKerry Bridle, James KirkpatrickJames KirkpatrickSome species and genera of tall herbs that are widespread both in Tasmanian and in mainland Australian alpine vegetation are dominant or codominant over large areas in the Australian Alps, while being typically subordinate species in Tasmania. This difference has been attributed to the impact of vertebrate herbivores, which are abundant in the Tasmanian high country but rare in or absent from the higher altitudes in the Australian Alps. The present study tests the hypothesis that lack of dominance (>50% cover) of tall alpine herbs in Tasmanian alpine and subalpine areas could be at least partially caused by grazing of their reproductive parts. Both in experimental plots and a clipping experiment, tall herbs produced more flowering stems under lower grazing/clipping pressure. In the field, the greatest reduction in flowering occurred under a grazing regime of sheep plus rabbits plus native herbivores. There was no consistent difference in the number of flowering stems between rabbit-grazed and rabbit plus native-grazed areas. However, there was a significant negative relationship between the number of flower heads and wallaby scats and a non-significant positive relationship between the number of flower heads and rabbit scats, suggesting that wallabies, not rabbits, were largely responsible for flower head depletion. Many species had more flowering stems in rabbit plus native vertebrate-grazed areas than in ungrazed exclosures. Therefore, it seems possible that the effects of vertebrate herbivory on flowering may have contributed to the lack of tall alpine herbfields in Tasmania.
History
Publication title
Australian Journal of BotanyVolume
49Issue
4Pagination
459-470ISSN
0067-1924Department/School
School of Geography, Planning and Spatial SciencesPublisher
CSIRO PublishingPlace of publication
Collingwood, AustraliaRepository Status
- Restricted