Effects of season of burn on species populations and composition of fynbos in the Jonkershoek valley

Data from a replicated plot experiment laid out to evaluate the responses of plants to season of burn are analysed. The initial results were published by C.L Wicht in 1948, but the results of subsequent surveys were not published. Plant densities were affected by the month in which the vegetation was burnt. Seedling densities were closest to parent plant densities after fires from January to April. The seasonal trend was strongly influenced by the effects of an unusually dry summer during 1945 and a low winter rainfall in 1946. Species richness and turnover differed after fires in different months. The smallest changes in species composition occurred after fires from December to April. The seasonal trends were also strongly influenced by the rainfall patterns during 1945 and 1946. Four uncommon species (one exotic) were not found again in the post-fire surveys and twenty new species (one exotic), including geophytes, first appeared after the fires. Forty-three species were recorded in all the surveys and a further seven species were not consistently recorded. A total of seventy-four were recorded in the surveys analysed. The highest number of species was found in young vegetation and the numbers declined with age, a pattern which fits the inhibition model of plant succession