Determinants of inselberg floras in arid Nama Karoo landscapes

Abstract

Aim This study investigated the relationship between inselberg floras in floristic and functional terms and their correlation with environmental variables at macro‐scale and landscape level. Location Four inselberg landscapes in Namibia’s arid Nama Karoo in southern Africa were selected. Methods Plant surveys were undertaken over a 3‐year period and species composition, growth form and dispersal spectra were used as measures for floristic and functional composition. Canonical correspondence analysis (CCA) was employed as the main tool to explain the perceived patterns. Results Regarding floristic affinities, inselberg floras formed distinct groups per study area and thus geographical position, with strong correlations between inselbergs within a particular study area. Neither growth form nor dispersal spectra closely resembled the pattern that emerged in the ordination of floristic composition. The influence of geographical position lessened when functional rather than floristic measures were introduced in the analysis. Main conclusions (1) On landscape and macro‐scale, floristic composition of inselberg floras was largely determined by geographical position, geology, elevation, habitat diversity, rock outcrop in the surrounding and surface area of inselbergs. (2) Environmental variables operating at landscape level had greater influence on functional composition than on floristic composition. (3) Stochastic variables were more important in shaping the flora of these arid Nama Karoo inselbergs than deterministic processes such as niche relations and competition.

Vegetation Heterogeneity and Life-Strategy Diversity in the Flora of the Heterogeneous Landscape of Nizanda, Oaxaca, Mexico

“…The comparison of growth-form spectra also reveals important differences, because SV climbers were much more numerous, whereas forbs prevailed in savannahs. It is frustrating that biological spectra in Nizanda's flora can only be compared against a handful of studies, simply because they are not available or because they do not report comparable species classifications (e.g., Burke 2001;Matallana et al 2005;Zhu et al 2005;Çakan and Karataş 2006). Unfortunately, floristic research is being increasingly excluded from many research funding and publication priorities.…”

Biogeography of Platberg, Eastern Free State, South Africa: Links with Afromontane Regions and South African Biomes

“…This long-distance dispersal by wind allows for crossing mountain valleys, from one isolated peak or inselberg to another. Pollination by wind allows for gene flow between disparate areas (Cowling & Lombard 2002), which have different geology, soils, moisture availability and climate (Burke 2001(Burke , 2002Linder 2003). The effects of wind to influences floristic composition and species richness over long distances and connect different regions is seen on the granite inselbergs in West African (Porembski et al, 1996), Namibian (Burke 2001), and Mulanje (Burrows & Willis 2005), basalt lavas of Platberg (Brand et al, 2010) …”

The Grassland vegetation of Platberg, eastern Free State, South Africa

“…The Korannaberg near Excelsior (also in the eastern Free State) is the only other inselberg where a phytosociological study was performed, by Du Preez (1991,1992), Du Preez and and Du Preez, Bredenkamp and Venter (1991). Studies of the grassland vegetation of inselbergs in Africa are limited to studies in west Africa by Porembski and Barthlott (1995), Porembski and Brown (1995), Porembski et al (1996) and Porembski et al (1998), in central Atlantic Africa by Parmentier et al (2006), and in Namibia by Burke (2001Burke ( , 2004. The lack of data of inselberg vegetation can be attributed to the physical difficulty of accessing inselbergs.…”