Invasive Species Compendium

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Abstract

Alien and indigenous plant species diversity of homegardens of a rural settlement in the eastern Kalahari, South Africa.

Abstract

Background and aims - The green infrastructure of rural settlements is represented by various land-uses which are of potential importance for the maintenance of biodiversity. Especially homegardens play an important part, but regardless of the knowledge that is available on the floras of urban environments, this feature has never been specifically quantified for South Africa, or any other southern Africa country. The aim of this study is to describe the contribution of homegardens towards the urban green infrastructure of a rural settlement in South Africa in terms of plant diversity and to provide a baseline for future research on urban floras of larger or culturally different urban areas. Methods - A grid provided 118 suitable sampling points for 20Ă—20 m sample plots. Each sample plot consisted of five transects of twenty points each. At each of the 100 points the closest tree, shrub, forb and grass was recorded within a 0.5 m radius. For the purposes of this descriptive study, the frequency data was converted to presence-absence data. Key results - The four land-use types of Tlhakgameng is habitat for 460 species, in 302 genera and 96 plant families. Of these species 56% are alien to Thlakgameng. The two most dominant families were the Asteraceae and Poaceae and the most dominant genera Acacia and Eragrostis. The five most dominant species for the study area were all indigenous. A total of 27 South African endemic and eight Red List species were recorded from the settlement. Homegardens had the highest gamma diversity which was mainly alien species cultivated for their uses. Food plants and ornamentals made up the majority (68%) of the garden flora. Most of the alien species originate from Asia and the Americas, some of which are counted with the 41 declared invaders and weeds recorded from the study area. Conclusion - This study confirms that rural settlements, like urban environments, are floristically diverse. The results of this study revealed that homegardens have the highest species richness as compared to other types of land-use in a rural settlement. The majority of the species found in homegardens were cultivated horticultural floras, and indigenous and alien weeds. Homegardens also provide a refuge for endemic or threatened species. The various needs of households in Tlhakgameng seem to sustain the growth of a rich and diverse mixture of multipurpose species in homegardens.