Effects of thirty-five years of afforestation with Pinus radiata on the composition of mesic mountain fynbos near Stellenbosch

Abstract

The fynbos vegetation of Biesievlei, Jonkershoek, was surveyed and described in 1945. In 1948 the catchment was afforested with Pinus radiata . This paper presents results of a reassessment of the vegetation in 1984 using the same methods that were used in 1945. Afforestation has reduced the cover of the vegetation (excluding P. radiata ) from 75% to 20%. The total number of species was reduced by 58% from 298 to 126. At least 190 species found in 1945 were not found in 1984, and at least 18 species were added to the list. The mean plant density was reduced from 260 to 78 plants m − 2 . Only stream bank vegetation, comprising mainly large-leaved sprouting shrubs, persisted in a relatively unmodified state. Away from the stream, annuals, geophytes and hemicryptophytes were dominant. Dominant species in the pre-afforestation flora were not resilient to afforestation. Serotinous Proteaceae, woody small-leaved sprouting and myrmecochorous shrubs and large-leaved sprouting shrubs have been virtually eliminated. Certain groups may re-establish after clearfelling, but others, notably various groups of shrubs may have been permanently eliminated. The implications for weed control in conservation areas are discussed.