The effects of tree canopies on invasive<i> Lantana camara</i>: a follow-up study 18 years later

Abstract

Lantana camara is primarily a bird-dispersed invasive plant species that has spread quickly across South Africa in disturbed areas. We re-examined the distribution of Lantana at Rodger and Twine’s (2002) study site (R&T) in a highly grazed communal area and an adjacent conserved area in 2019. R&T found that Lantana was more common in the communal area than in the conserved area. Glyphosate herbicide was sprayed to suppress Lantana from 2016 to 2019 in the conserved area only. We re-examined the bird-dispersal hypothesis by surveying subcanopy and intercanopy environments. We found more Lantana in the subcanopy than in the intercanopy. There were more Lantana plants in the conserved area, but there were virtually none in the communal area. Most concerning was the apparent resprouting of Lantana despite herbicide application. We used sequential aerial photographs and found that there has been an increase in woody cover in the conservation area since 2013, which may exacerbate the problem with this invasive plant. We conclude that it is not communal grazing per se that causes the encroachment of Lantana, and that it has more do with the woody cover of native plants, as concluded by R&T.