Post-fire succession at Pella, a South African lowland fynbos site

Abstract

Pyric succession was studied in sand plain lowland fynbos vegetation that was 1 to 19 years post-fire age. Species richness and cover in the 39 plots sampled increased from 1 to 3 years post-fire. There was no significant difference in percentage live cover in communities of 5 to 19 years post-fire age. Species richness was greatest in 5-year-old stands and was significantly higher than 19-year-old communities. Percentage litter cover increased linearly with increasing post-fire age. The number of geophyte and annual species was greater in the older communities than in the immediate post-fire phase. A descriptive model of pyric succession is presented in which Restionaceae are the dominant elements in mature communities. About 30% of the species are common to pre- and post-fire communities. About 45% of the species were found only in the pre-fire stands and about 25% were exclusive to post-fire vegetation only. Most of the differences in patterns of succession between these lowland communities and mountain fynbos are ascribed to the relative aridity of the lowland environment and consequent slower growth rates. The stated policy of a burn every 12 or so years for mountain fynbos is too frequent for sand plain lowland fynbos. Plantsuksessie na vuur was in 1-jarige en 19-jarige plantgemeenskappe in sandvlakte-Iaaglandfynbos bestudeer. In die 39 afgemete persele wat bestudeer was, het die rykheid van soorte en plantbedekking toegeneem van die 1-jarige tot die 3-jarige fases na die vuur. Daar was geen statistiese betekenisvolle verskil in die persentasie plantbedekking tussen die 5-jarige en 19-jarige plantgemeenskappe na die vuur nie. Soorte-rykheid was die hoogste in die 5-jaar-oue gemeenskappe en was betekenisvol hoer as in die 19-jarige plantgemeenskappe. Die persentasie plantafval het lineer toegeneem met toenemende ouderdom na vuur. Daar was meer geofiete en 1-jariges in die ouer plantgemeenskappe as in die onmiddelike fase na die vuur. ’n Teoretiese model van plantsuksessie na vuur word voorgestel waarin Restionaceae die dominante elemente in volwasse gemeenskappe is. Ongeveer 30% van die soorte kom voor by plantgemeenskappe van beide die fases voor en na die vuur. Ongeveer 45% van die soorte was aangetref slegs in die voor-vuurse gemeenskappe en ongeveer 25% was eksklusief by die na-vuurse plantegroei aangetref. Die grootste deel van die verskille in suksessionele patrone tussen laagland- en bergfynbos word toegeskryf aan die relatiewe ariditeit van die laagland omgewing en die gevolglike stadiger groei tempo’s. Die beleid van beplande brande ongeveer elke 12 jaar vir bergfynbos is te gereeld vir sandvlakte-Iaaglandfynbos.