Vegetation change following exclusion of grazing animals in depleted grassland, Central Otago, New Zealand

  • Published source details Allen R.B., Wilson J.B. & Mason C.R. (1995) Vegetation change following exclusion of grazing animals in depleted grassland, Central Otago, New Zealand. Journal of Vegetation Science, 6, 615-626.


Grasslands in New Zealand have been greatly influenced by anthropogenic activity, including burning (which has induced formation of large areas of grassland) and grazing by introduced livestock and other mammals. In this study in central Otago (South Island), vegetation change following exclusion of domestic sheep Ovis aries and/or European rabbits Oryctolagus cuniculus in depleted semi-arid interior grassland were investigated.

In 1986 at five sites, study plots were established. Each was divided into subplots: one was fenced to exclude sheep, one to exclude rabbits and sheep, and one was an unfenced control open to both sheep and rabbits. Each year (1986-1992) monitoring was undertaken to record plant species height, frequency of occurrence and percentage ground cover.

Overall vegetation exhibited considerable year-to-year variation; at some sites variation between years was as great as, or greater than, that between grazed and ungrazed subplots. This was at least in part attributable to the influence of weather, i.e. at one site changes in vegetation cover and species composition was significantly (statistically) related to rainfall in the early growing season.
During the study period, only two general trends emerged following grazing exclusion: perennials increased in frequency and year-to-year changes declined over time. Total vegetation cover seldom changed as a result of grazing exclusion over the timescale of the experiment.
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