The effect of different fire regimes on plant diversity in southern African semi-arid grasslands at Honeydale research farm, Eastern Cape, South Africa

  • Published source details Uys R.G., Bond W.J. & Everson T.M. (2004) The effect of different fire regimes on plant diversity in southern African grasslands. Biological Conservation, 118, 489-499


Fire may be an important component in managing grasslands for grazing mammals and maintaining grassland diversity. However, the effects of fire in southern African grasslands are poorly understood. In this study, the effects of long-term burning treatments on biodiversity in semi-arid grassland in South Africa was investigated.

Study site: The effects of long-term burning treatments on biodiversity in semi-arid grassland was investigated at Honeydale (550 m.a.s.l), the University of Fort Hare’s research farm, located 5 km east of the town of Alice (Eastern Cape).

Burn treatments: Plant diversity was examined under a range of burning treatments in a randomly allocated, replicated block design. The treatments were:

1) annual, biennial (i.e. two years between fires), triennial, quadennial winter burns;

2) annual, biennial, triennial and quadennial spring burns;

3) no-burn.

Each treatment was replicated in two 10 m x 10 m plots for 26 years. During burning, a back burn was lit on the down wind side of the plot and a head burn lit on the opposite side. The head burn was carried across the plot by the prevailing wind, until it met the back burn.

Sampling: The importance-score method was used to sample biodiversity, providing estimates of species richness and abundance. A series of concentric nested sub-quadrats (1, 2, 5, 10, 20, 50 and 100 m²) were used, measuring from the smallest to largest sub-quadrat size. Each plant species was awarded a score depending on the first sub-quadrat in which it was encountered. Thus, the first encounter of a common species should be in the smaller sub-quadrats (the 1 m² quadrat holding a score of 7) whereas of a rare species in the larger quadrats (the 100 m² quadrat holding a score of 1). Average species richness was calculated for each treatment for the 1 and 100 m² quadrats.

Species richness suggests that there is a small increase in diversity in southern African semi-arid grasslands with decreasing burn frequency. Comparing species compositions, no-burn treatments had different communities to burn treatments, with more woody species being present. When no-burn was removed from the analysis, the communities separated out according to block and the no burning regime. Also, the sod-forming grass Cymbopogon plurinodis decreased with increasing fire frequency, whereas the bunch grass Themeda triandra increased with increasing fire frequency.

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