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Fig. 3 | BMC Ecology and Evolution

Fig. 3

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

Fig. 3

Theron [6] placed metal pins also inside fairy circles and control points in the matrix. A Google satellite image of two marked FCs from July 2009, with arrows pointing to the locations of the metal pins (a). A drone image of the same location, taken in 2020 (b). The FCs have not changed their structure over time. Note the much larger size of FCs as compared to the Euphorbias. FC1 and FC2 have diameters of 12.5 m and 13.3 m, respectively, while the two Euphorbias in the lower right corner are only half that size with diameters being 5.7 m and 5.9 m (b). A Google satellite image from 2009, with the arrow pointing to the marked control point in the matrix (c) and drone image from 2020 of the same control point (d). Ground images of the two marked fairy circles FC1 and FC2 (e, f). Note the absence of large grass tufts around the metal pins. Ground image of the marked control point C1 in the matrix with some stones in the foreground (g). Unlike for the four marked Euphorbia locations, control points had no remains of decaying Euphorbia branches around the metal pins, agreeing with a similar absence of Euphorbia structures in old satellite images from 2009 (c) or drone imagery from 2020 (d). However, control points in the matrix had the same density of larger grass tufts that can be also found under marked, decaying Euphorbias. Another example of a control point in the matrix, which also showed no Euphorbia remains on the ground but only the growth of grasses at low densities that are typical for the matrix vegetation (h)

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