Post-fire effects of invasive exotic plants on seed banks, regeneration, soil chemistry and selected soil microbial populations in the Silvermine Nature Reserve, Cape Peninsula, South Africa

[摘要] ENGLISH ABSTRACT:The fires, which occurred during January 2000 on the Southern Cape Peninsula, Cape Province, SouthAfrica, focused attention on the importance of sound, informed management of exotic plant invaders infynbos, especially at the urban interface. The fires also highlighted the relative lack of knowledge aboutthe combined impacts of fire, exotic plants and the exotic-clearing programme on soil seed banks andregeneration.This study examines soil borne seed banks, regeneration, soil chemistry and micro biota in different postfireenvironments, focusing on three components of exotic plant management: The post-fire effects ofstanding invasive exotic plants; stacks of slashed exotic plant material which were deliberately burnt andstacks reduced to heat scars by a wildfire.The primary hypothesis addressed is that post-fire vegetation regeneration patterns, seed bank diversityand seed bank abundance are linked to pre-fire vegetation characteristics and, in particular, to thetreatment of exotic plant species. It is also hypothesised that soil microbe population sizes are linked topre-fire vegetation and soil chemical composition.Differences in soil seed banks, soil micro biota and vegetation regeneration patterns occur in differentpost-fire environments. High volumes of (live or dead) woody exotic biomass negatively impact upon postfireindigenous species diversity and abundance, both above and below-ground. Soil seed banks andabove-ground regeneration decline with increasing fire intensity, wildfire burnt stack treatments showingthe largest declines followed by wildfire burnt standing exotics, control burnt stacks, wildfire burnt clearedareas and wildfire burnt Mountain Fynbos treatments. Persistent indigenous seed banks are found undersome exotic dominated stands. Heat damage, associated with high woody exotic biomass, affects seedsof all species into deep soil layers. Depth of burial is a more important determinant of seed survival duringfires than seed size.Soil microbial populations are variably affected by exotic plants, their management and increases in fireintensity. The most drastic microbial population changes are in post-fire treatments of high exotic plantbiomass. Soil chemistry affects microbial population sizes as does seasonal climatic changes.In this thesis vegetation, seed bank and microbial responses to various exotic plant managementpractices are shown and management recommendations are made.Keywords: exotic plants, fire, Fynbos Siome, microbes, post-fire succession, soil seed banks.

[发布机构] Stellenbosch University