Seed dispersal in isolated North Canterbury forest fragments. (2016)
AuthorsHenderson, Anna Maryshow all
North Canterbury is one of the most severely degraded parts of New Zealand in terms of deforestation, with a large proportion of the lowland area cleared for agriculture. The fragments of native forest that remain are generally isolated and relatively small. These conditions create the potential for a lack of effective seed dispersal due to insufficient frugivorous bird numbers. This project aims to investigate seed dispersal efficacy in these fragments and identify the primary mechanisms behind any dispersal failure. Bird counts, measurement of fruit removal rates and a seedling/sapling dispersion study have been conducted in five fragments. Bird count results show that while bird abundance and diversity vary greatly between sites, two of the most important seed dispersers (bellbirds and silvereyes) are among the most abundant birds in these fragments. The fruit removal data shows that for my indicator species (Coprosma robusta) all fruit is being removed by the end of the season. No species were found in the seedling plots that were not previously recorded as present in the reserve, but there were some indications of a shift in composition. There was no significant relationship between numbers of fleshy-fruited seedlings and density of frugivorous bird numbers. The fragments were very different from one another in both bird and seedling composition. The implications of these findings for the persistence of the bird dispersal mutualism in forest fragments are discussed. Investigating seed dispersal processes in one of the most modified parts of the country will not only contribute to effectively managing these fragments but also help to inform conservation efforts in small isolated fragments around New Zealand.