Vegetation Changes after 10 Years of Grazing Exclusion and Intermittent Burning in a Themeda triandra (Poaceae) Grassland Reserve in South-eastern Australia

Abstract

Changes in the vegetation composition of a remnant Themeda triandra Forsskal grassland in south-eastern Australia were documented following the replacement of stock grazing with intermittent burning at 3–11-year intervals. The vegetation was initially sampled in 1986, 1 year after stock were removed, and then 10 years later in 1996. Most frequently encountered grassland species were abundant in both surveys, although there was little correspondence between species richness at the quadrat scale in 1986 and 1996. Total floristic richness increased slightly over the 10-year period, owing to the proliferation of tall forbs with wind-blown seeds, including exotic thistles and colonising native forbs. Unfortunately, most native ‘increasers’ were ‘weedy’ species which are not typical or common components of species-rich temperate grassland remnants in southern Victoria. Thus, replacing grazing with intermittent burning has not resulted in the flora becoming more similar to that of high-quality, species-rich grassland remnants, but instead, has promoted a group of ruderal colonisers. The ability to identify factors contributing to particular botanical changes was hampered by the design of the management regimes implemented over the past decade. Suggestions are provided to overcome these difficulties, incorporating principles from adaptive management.