A lot gone but still hanging on: Floristics of remnant patches of endangered KwaZulu-Natal Sandstone Sourveld

Abstract

Background: KwaZulu-Natal Sandstone Sourveld (KZNSS) is an endangered subtropical grassland type, of which a large proportion occurs within the eThekwini Municipal Area (EMA). Objectives: Examining the flora of KZNSS will allow a more fundamental understanding of the potential variability across remnant patches of this vegetation type, increasing the ability to accurately delimit KZNSS from adjacent similar vegetation types. Method: Floristic data were collected using quadrats and transects for three recognised KZNSS sites (Giba Gorge Environmental Precinct (GGEP), Inanda Mountain (IM) and Springside Nature Reserve (SSNR)), all within the EMA. Alpha diversity (Shannon’s exponential and Simpson’s inverse indices) and beta diversity measures were calculated and compared across all sites. An unweighted pair group method with arithmetic mean (UPGMA) analysis using the Jaccard index and a non-parametric multidimensional scaling (NMDS) ordination were used to assess similarity amongst quadrats across the three sites. Results: One hundred and thirty-one plant species were found to occur in GGEP, 95 in IM and 121 in SSNR. However, of the total 193 species found to occur collectively (i.e. quadrat and transect data combined) across the three sites, only 50 species were common to all these sites. The results of the alpha and beta diversity analyses revealed significant floristic variability both within and across the KZNSS sites sampled, with Shannon’s exponential index being highest in SSNR, followed by GGEP and lowest in IM. The lack of controlled access and unregulated burning regimes appear to have clearly affected the flora at the IM site in terms of species richness and increased evenness, as well as the relatively greater presence of introduced alien species and lower abundances of taxa of conservation concern. The pristine GGEP site had the highest number of species in total, with species being less evenly spread across the site, as well as the highest number of taxa conservation and low abundances of alien species. The main separations in the ordination results can be attributed to quadrat sampling performed pre- and post-burn. Conclusion: The floristic distinction of IM from GGEP and SSNR is attributed here to the intermediate disturbance effect of fire in grasslands which can lead to species loss if burning is too frequent. The implications of these findings are discussed in the context of the delimitation, classification and management of KZNSS

Keywords

• Floristic Delineation