Autecology of an invading population of the cactus Cereus peruvianus (Queen of the night) in the central Transvaal

Abstract

An autecological study of an invasive cactus ( Cereus peruvianus ) in the vicinity of Zandspruit, central Transvaal showed that the distribution and abundance of the cactus was related to seedling establishment conditions. The plant shows extremely specific establishment requirements and seedlings can only survive in those areas which have fine-textured soils and a high density of shade trees. Selection of these sites appears to be related to available moisture in the soil. In fine-textured subcanopy sites moisture is retained in the first few centimetres of the soil for longer than in more sandy or exposed conditions. Even within the above sites seedling input was extremely variable, further stressing the importance of establishment. It is suggested that the removal of shade trees might be worth testing as an effective and less costly control measure in the long term rather than removing the cactus itself. ’n Outekologiese studie van ’n indringer-kaktus ( Cereus peruvianus ) in die omgewing van Zandspruit, sentraal-Transvaal, het getoon dat die verspreiding en getalle van die kaktus verband hou met die vestiging van saailinge. Die plant toon uiters spesifieke vestigingsvereistes, en saailinge kan slegs voortbestaan in gebiede met fyntekstuurgrond en ’n hoë digtheid van skadubome. Geskiktheid van hierdie terreine hou skynbaar verband met die beskikbare vog in die grond. In skaduryke gebiede met kleigronde word die vog in die boonste paar sentimeter van die grond langer behou as in meer sanderige of blootgestelde gronde. Selfs binne hierdie terreine was die saailinggetal uiters veranderlik, ’n faktor wat die belangrikheid van vestiging verder beklemtoon. Daar word gevolglik voorgestel dat die verwydering van die skadubome as ’n effektiewe en goedkoop langtermyn-beheermetode beproef word.