A floristic comparison of three Northern Coastal Forests differing in disturbance history

Abstract

Background: The impacts of disturbance history on the floristics of Northern Coastal Forest (NCF; South Africa) are unknown.
Objectives: This study compared the floristics of three remnant patches of NCF (in KwaZulu-Natal) with contrasting disturbance histories: a primary forest with low levels of disturbance (Hawaan), a primary forest with high levels of disturbance (Umdoni) and a secondary forest (Twinstreams) that was rehabilitated with presently low disturbance levels.
Method: Transects and quadrats were used to assess species composition and diversity at each site.
Results: Collectively, 688 species, 400 genera and 113 families were found, but only 21.95% of the species were shared by the three forests. The most speciose families were Fabaceae >Asteraceae > Rubiaceae. The species richness was highest at the disturbed primary forest and notably lower at the primary forest. Diversity indices exhibited a similar trend. Cluster analyses and ordinations indicated that the secondary forest was intermediate between the two primary forests, with the disturbed primary forest and secondary forest being more similar.
Conclusion: The disturbed and secondary forests maintained a NCF floristic affinity. The dissimilarity between Hawaan and other forests is most likely the product of differing disturbance histories and rehabilitation efforts. The findings suggested that NCF patches are likely to be different in richness, but not in structure and affinity. Anthropogenic related pressures and disturbance appear to be major causes of floristic differences amongst patches. This leads to higher levels of richness by accommodating opportunistic, atypical and alien species, and
possibly the creation of novel NCF types.