The effect of fire frequency on the structure and floristic composition of a woodland understorey

Abstract

AbstractA long term study site which had not burnt since 1968 was partly burnt in August 1974 and the entire area burnt again in August 1980. The two wildfires, in the same season and with similar intensity, allowed a study of the effect of the frequency component of the fire regime on the floristic composition and structure of a shrubby woodland understorey. In 1982, 2 years after the last fire, that part of the site burnt twice in 12 years had significantly more plant species, higher shrub density and greater cover than that which burnt once only. Of the species found only on the single‐fire part of the site, all were obligate seedling regenerators, while the larger number of species found only on the twice‐burnt part were predominantly vegetative regenerators. The results have implications for vegetation managers: areas burnt too frequently may lose obligate seedling regenerators, while an area remaining unburnt for too long may lose some vegetatively regenerating species, as well as short‐lived obligate seedling regenerators. This highlights the necessity for research in different vegetation types to assess adequately these limits to their ‘natural’ frequencies. Such research would form the basis for informed management decisions.