Influence of grazing and vegetation type on post-fire floristic and lifeform composition in Tasmania, Australia

摘要

Fire and herbivory are important disturbances in vegetation globally. These disturbances are widely applied in combination for conservation and livestock management. Little is known regarding the relative effects on species composition of post-fire grazing, grazing by itself, burning by itself, the absence of both of these disturbances or of the variation of their influences between vegetation types. At seven sites in Tasmania, Australia, in sedgeland, heathy forest and grassland, the covers and heights of tracheophytes were measured before and for 2 years after the commencement of a fire experiment that nested grazing within burning. Burning followed by grazing, largely by native vertebrates, tended to result in greater changes in species and lifeform composition than either grazing by itself or burning by itself. Heathy forest and sedgeland responded primarily to fire rather than grazing. Heathy forest shifted to a new state with burning while sedgeland began a return to its pre-burn state. Grazing after burning most strongly affected the lowland tussock grassland, while also strongly influencing the height of highland tussock grasslands. Intact canopies in eucalypt forest after fire prevented a return to the original understorey while grazing animals turn tussock grassland into lawn after fire. In all cases, the effects of grazing after burning are incremental rather than strongly synergistic.