Colonization of Cape fynbos communities by forest species

• Published in: Forest ecology and management 1992-04, Vol.48 (3), p.277-293
• Main Authors: Manders, P.T., Richardson, D.M.
• Format: Article
• Language: English
• Subjects: AFRIQUE DU SUD; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; BOSQUES; COMMUNAUTE VEGETALE; COMUNIDADES VEGETALES; FORESTS; FORET; Fundamental and applied biological sciences. Psychology; PLANT COMMUNITIES; SOUTH AFRICA; SUDAFRICA; Synecology; Terrestrial ecosystems
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/0378-1127(92)90150-8

Forest and mountain fynbos communities intermingle in the southwestern Cape, South Africa, but are distinct in terms of species composition and community processes. Fires occur frequently in fynbos communities, but seldom in the forest communities, which are usually restricted to sheltered ravines or stream banks. Forest species establish in fynbos between fires, and may predominate eventually in exceptional circumstances. We proposed a conceptual model for the development of forest in fynbos and examined processes in the model related to nucleation and the establishment of forest species. Germination and establishment requirements of forest and fynbos species were examined to determine causes of community distinctness. Nuclei of forest species dominated by fruiting species had more seedlings of forest species and more species than nuclei dominated by non-fruiting species. Reciprocal sowings showed that forest and fynbos species have similar germination requirements, but the seedlings establish in their appropriate communities only. Germination studies demonstrated that soil moisture is not the only factor limiting establishment of forest species, and that enhanced soil nutrient levels, litter and a canopy of vegetation influence seedling survival even in wet conditions. Field studies, to characterize the habitats in fynbos vegetation in which forest seedlings are able to become established, showed forest seedlings to be associated with a tall herb layer and vegetation cover greater than 50%. Seedlings were invariably under or within 1 m of a perch, which could be a fruiting forest species or a fynbos shrub. Recruitment of fynbos species is coupled with disturbance whereas recruitment of forest species in fynbos is associated with nucleation and habitat amelioration, and occurs in the absence of fires. The lack of coupling of recruitment of forest species with disturbance results in the exclusion of forest from most areas of the fire-prone fynbos biome.