Title:

Are the fairy circles of Namibia caused by Euphorbia species?

Publication Year:
2018
Abstract:

Fairy circles have been documented to occur along the coastline of southern Africa, approximately 50 - 100 km inland. There are many theories concerning the origin of the fairy circles, yet none has been universally accepted. This project investigated the "Euphorbia spp. allelopathy" hypothesis, which states that fairy circles are formed by localized allelopathic affects in the soil, caused by the previous presence of Euphorbia gummifera and E. damarana. In this study a GIS suitability analysis was used to create a prediction model of the occurrence of fairy circles based on rainfall, altitude and land cover. A prediction map was created, and fairy circle distribution has successfully been modelled. Several point pattern tests were performed to describe and compare the spatial pattern of fairy circles with E. gummifera and E. damarana. Voronoi tessellations revealed that fairy circles, E. damarana and E. gummifera all have six neighbours on average. The distance to nearest neighbour showed that fairy circles display a regular spatial distribution pattern with an R-value of about 1.3 to 1.4. Although less-so, E. damarana also displays a regular pattern with an R-value of about 1.2. The pair correlation function revealed a similar pattern for fairy circles and E. damarana. We conclude from the point pattern analysis that despite some differences between the spatial distribution pattern of fairy circles, E. damarana and E. gummifera, many important structural similarities were identified.

Publication Title:

South African Journal of Botany

Volume:
115
Pages:
308
Item Type:
Journal Article
Language:
en