Comparative water relations of indigenous and invasive Australian Proteaceae in fynbos

Water-use efficiency (WUE) as reflected in the leaf carbon stable isotope ratio was compared between co-occurring indigenous fynbos proteoids and invasive Australian hakeas H. sericea, H. gibbosa and H. suaveolens. At the driest site, H. suaveolens was slightly more WUE than several co-occurring proteoids; there was no significant difference between hakeas and proteas at the other sites. Transpiration rates of shoots and of whole trees were compared between Hakea sericea and Protea repens growing on Stellenboschberg northeast of Cape Town. Both measurements showed no real difference between the species and it is concluded that differences in water relations are not responsible for the highly competitive growth rates of hakeas in fynbos. It is hypothesised that hakeas may be able to vegetatively outcompete proteoids as a consequence of monopodial architecture and some ability to prevent shade-limitation of photosynthesis. A rough estimate of water loss due to transpiration and interception by H. sericea stands indicates that this species may have a significant effect on catchment water loss relative to open-canopy proteoid fynbos. This effect would be due not to transpiration rates of individual trees but to consistently high densities of mature hakea stands.

Grantor dc:publisher.institution

Department of Biological Sciences

Year dc:date.issued

1998

Author dc:creator

• Bergh, Nicola G

Advisor dc:contributor.advisor

• Midgley, Jeremy J

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/26049

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/26049