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Fig. 2 | BMC Ecology and Evolution

Fig. 2

From: Revisiting Theron’s hypothesis on the origin of fairy circles after four decades: Euphorbias are not the cause

Fig. 2

The original study site of Theron [6] in the far south of the Giribes Plains. In this plot “Gir-1” Theron marked several Euphorbia damarana with metal pins. Drone image taken at the site which is situated on a plateau (a). In this plot E. damarana is the only dominating shrub species and FCs are very large. Genuine fairy circles are characterized by having no vegetation growth inside the circle, as the Google satellite image from July 2009 shows (b). By contrast, decaying Euphorbias are characterized by dark and smaller circles where the dead branches of the shrubs lead to filled circles that clearly differ from the bright vegetation-free FCs. The arrows in the 2009 satellite image point to ground-truthed and GPS-mapped locations of four metal pins that Theron inserted at the four Euphorbias E1-E4. A drone image from March 2020 of the same marked Euphorbias (c). Despite the decay of the shrubs, none of the four marked Euphorbia locations developed into a fairy circle without vegetation. Also, the peripheral ring of larger grasses around the shrubs disappeared between 2009 and 2020, while the fairy circles still have this distinct ring (c). Zoomed drone image of the marked Euphorbias E1 and E3, with arrows pointing to the metal pins and their visible shadows (d). Already this drone image shows dark grass tufts growing at the metal pins of decaying Euphorbias. Ground photographs of the four marked shrubs show clearly with arrows that many large grass tufts were growing directly in the center of former Euphorbia locations and that the shrub remains had thus no phytotoxic effect (eh). All four locations had various amounts of dead Euphorbia branches concentrated on the soil surface around the metal pins, confirming the former presence of Euphorbias and alike satellite image interpretation from 2009 (b)

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