Some Effects of Fire Frequency on Fynbos Plant Community Composition and Structure at Jonkershoek, Stellenbosch

SYNOPSIS Fynbos vegetation with three differing fire histories was analysed for floristic composition and structure by means of a stratified systematic sample of 100 plots. The three treatments (fire histories) investigated were short rotation burning (about six years), longer rotation burning (about 15 to 20 years) and protection from fire for 37 years. Short rotation burning resulted in a reduction in plant cover, height and biomass, as well as in the elimination of longer lived seed regenerating shrubs. Species diversity was relatively high and short graminoid and herb species dominated the vegetation. Longer intervals between burning resulted in a high cover and large mean plant height in mature 21-year-old vegetation, but species diversity was relatively low and undergrowth species were of much reduced importance. In vegetation protected for 37 years, large shrubs were reduced in importance due to high mortality and low recruitment; as a result undergrowth species showed some signs of recovery, and species diversity increased. Some germination of seed regenerating species was noted, and certain tree species also appeared. The development of true forest does not seem likely owing to shallow soils and summer drought. Vigorous fynbos vegetation would probably be maintained by burning on a 15 to 20 year rotation.