Pioneers and Perches—Promising Restoration Methods for Degraded Renosterveld Habitats?

Abstract

Areas of abandoned agricultural fields are globally increasing and are also common features in the Cape Lowlands of South Africa. Previous restoration attempts in degraded West Coast renosterveld, a mediterranean-climate shrubland, have attained limited success and therefore novel approaches are needed for this area. The study reports on two restoration experiments, designed to re-introduce key plant functional types back into this critically endangered habitat. The first experiment concentrated on a common pioneer species in renosterveld vegetation, Otholobium hirtum. Although in vitro experiments showed a significantly elevated germination response after scarification, in vivo experiments failed to produce establishment in an abandoned field. The second restoration experiment focused on bush clumps, a sub-type of renosterveld vegetation that is characterized by broad-leaved shrubs with fleshy birddispersed diaspores. The effect of artificial bird perches and their potential to enhance diaspore dispersal by frugivorous birds in two abandoned field communities was tested. Results showed a significant increase in seed dispersal at artificial perch sites. However, in the next fruiting season, and after perch removal, seed germination and establishment in abandoned fields was not successful. The experiments revealed that restoration using early succession species and natural dispersal vectors appear not to produce demonstrable benefits, despite their promising potential and pre-testing of effectiveness. Before launching large-scale restoration programs in abandoned fields of renosterveld, preliminary studies in-field are strongly recommended.