Belowground functional diversity and resilience of health clinic gardens in South Africa
Urban soil ecosystems are one of the last uncharted territories of ecology. Knowledge is limited on this hidden underground world. Soil organisms play an essential role in ecological food webs; however, the effect of urbanization on these mechanisms is largely unknown. Research indicated that there is high redundancy of soil organisms within functional groups. This contributes to high response diversity within these ecosystems which is important for the continued resilience of these systems when facing stress and disturbances. Moreover, a high functional diversity is essential for the maintenance of ecosystem services.
In South Africa, Health Clinics were established under the auspices of the National Department of Health to render accessible equitable and integrated quality health services. Recently a project was initiated in the North-West Province to characterize the biological diversity of their clinic gardens. These gardens are modelled according to cultural Tswana tshimo garden design (characterized by specific microgarden types) and represent ‘pockets’ of social-ecological memory. Initial studies focussed on the plant diversity of these gardens. The aim of the current pilot study is to determine the functional diversity of soil micro- and mesofauna in the microgardens of each clinic and how this compares to natural grassland soil community composition. This will indicate the effectiveness of these soils as counterparts in building local resilience.
Soil micro- and mesofauna were collected at six clinics in four different microgarden types and in four natural grassland reference sites. Soil samples were collected from the upper soil layer (5 cm) for the micro- and mesofauna and in the plant rhizosphere zone (to a depth of approximately 15 – 30 cm) for nematodes specifically. Soil micro- and mesofauna were extracted from the samples using Berlese-Tullgren funnel extractors. Nematodes were extracted from root samples using an adapted NaOCl method. To further identify more plant-parasitic nematodes additional root and soil samples were subjected to a decanting- and sieving-, followed by a sugar-flotation method. Additionally, for entomopathogenic nematode isolation, an insect-baiting technique was used with Tenebrio molitor as the target insect host.
We hypothesize that (1) there will be high beta diversity between the different microgardens within each clinic; (2) the natural control sites will have a higher number of species and individuals as well as a higher functional diversity in comparison to the clinic gardens; and (3) the clinic gardens will show a higher incidence of pathogenic species.