Fencing is not enough to reinstate regeneration: Evidence from a large fruited canopy tree Beilschmiedia tawa

Fencing forest fragments to limit the effects of herbivores is a common method for restoration, but recent studies have suggested that fencing alone is insufficient for fragment recovery. The endemic New Zealand canopy tree tawa (Beilschmiedia tawa (A.Cunn.) Kirk) is suffering recruitment failure in forest fragments throughout its northern range. We sought to determine the role of fragmentation and fencing on B. tawa seedling survival and to identify the factors driving recruitment failure in this species. The main factors that affected B. tawa seedling survivorship were desiccation and herbivory. Fragmentation had a negative effect on the survivorship and growth of potted B. tawa seedlings. Fencing neither influenced survivorship nor diminished mortality by desiccation. However, small roofed enclosures positively affected seedling survivorship, potentially by diminishing desiccation. Our results are consistent with other studies where desiccation has been deemed a key factor of tree mortality in fragmented forests. As a single management strategy, fencing appears to be insufficient to positively affect B. tawa regeneration and other complementary activities are suggested.