Seed dispersal in the dung of large herbivores: implications for restoration of Renosterveld shrubland old fields

Abstract

Species-rich, winter-rainfall, microphyllous Renosterveld vegetation in the Western Cape Province of South Africa has largely been transformed for production of wheat and wine. Remaining fragments thus have high conservation value. Abandoned old fields adjacent to natural vegetation fragments could potentially be restored as corridors and habitat for indigenous flora and fauna. We hypothesised that indigenous antelope maintained in a matrix of natural vegetation and abandoned field could play a role in restoration of Renoserveld via seed dispersal.We collected dung of indigenous ungulates in an abandoned field at various distances from natural Renosterveld vegetation, in order to assess the potential of large herbivores to contribute to restoration of plant diversity through seed dispersal. Emerged seedlings from the collected dung represented 29 forb, 13 grass, four sedge, four geophyte and one shrub species. The most abundant emerging seedlings were lawn grass Cynodon dactylon (38%), alien pasture grasses (31%) and indigenous geophyte Romulea rosea (12%). Whereas seeds of annual forbs and grasses were dispersed, only one shrub species was dispersed at very low density. We concluded that large herbivores could retard the rate of recovery of Renosterveld vegetation because viable seeds of herbaceous plants, particularly alien annual grasses and lawn-grasses were more abundant in the dung than the shrub, geophyte or perennial tussock grass species that characterise this vegetation type.

Facilitative interactions between an exotic mammal and native and exotic plants: hog deer (Axis porcinus) as seed dispersers in south-eastern Australia

“…However, these effects are not restricted to exotic plant species and may also facilitate native plants (Williams et al 2000). In particular, endozoochory may facilitate the re-establishment of plant species that have been displaced from habitat fragments (Cosyns et al 2005;Shiponeni and Milton 2006) in situations where plant community conservation is constrained by seed availability (Bakker and Berendse 1999). However, the benefits of endozoochory for native plant communities will depend on the composition of native plant species being dispersed.…”

Towards an integrated ecological restoration approach for abandoned agricultural fields in renosterveld, South Africa

“…An examination of seed dispersal has shown that dispersal of native species into abandoned agricultural fields does occur, but seeds struggle to germinate on arrival. 11,12 In areas where grazing is allowed, the few native species that manage to recruit are grazed by animals whilst they are still young. 6 If not grazed, environmental factors, e.g.…”

“…4 Besides, grazing has also been reported to disperse seeds of invasive alien grasses rather than those of native shrubs. 12 Secondly, natural succession will only be successful where remnants of renosterveld are close to the abandoned agricultural fields so as to allow seed dispersal to take place. Seed dispersal is reported to be taking place, but is unfortunately spreading invasive alien grasses.…”

Effects of domestic livestock on the vegetation of the Knersvlakte, South Africa

“…The only other comparable studies in South Africa were carried out at the Succulent-Nama-Karoo interface (MILTON & DEAN 2001) and in the Renosterveld (SHIPONENI & MILTON 2006). As the role of endozoochory was unknown and many mesembs were regarded as unpalatable (Ute Schmiedel, personal communication 2007), this study aimed at obtaining a first insight into the general practicability of a respective study in the Knersvlakte.…”

“…As my study revealed that there are many endozoochorously distributed species with even a high number of mesembs, and that the applied methods were practical, further studies could use a more systematic sampling approach. The dung could be sampled, for example, along transects that are narrow enough to be able to survey the full width and long enough to get a sufficient amount of dung as it was done by SHIPONENI & MILTON (2006). They additionally sampled over a longer period of time to account for differences in flowering times.…”