The Impact of Edge Effects & Matrix Restoration on Dung Beetle Community Structure & Ecosystem Function
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science (Hons)
Land-use change has become a force of global importance and has gained status as the most important driver of ecosystem degradation. The resulting creation of habitat edges has pervasive impacts on the distribution and persistence of species in forest ecosystems. Responses of species to edge effects can be highly dependent on ‘response’ traits, which may in turn co-vary with ‘effect’ traits that determine rates of ecosystem functioning. Therefore, non-random loss of species due to traits conferring higher susceptibility to extinction may also result in the loss of functionally-important species across a habitat edge gradient. Likewise, response and effect traits may be important in determining reassembly of communities in regenerating habitats, which may provide insight into potential scenarios of functional responses to restoration efforts. To test for potential off-site effects of adjacent matrix habitat restoration on dung beetle communities, I compared dung beetle community structure and species trait composition across Afromontane forest edges adjacent to degraded and regenerating matrix habitat at Ngel Nyaki forest reserve in Nigeria. I also measured dung removal rates across habitat edge gradients to investigate the relative off-site impacts of matrix restoration on dung beetle-mediated ecosystem processes. I found significant effects of adjacent matrix condition on edge response functions in dung beetle abundance, species distributions, and trait composition. Beetle abundances were markedly higher in forests adjacent to regenerating matrix, whereas the largest differences in trait composition were found between degraded and regenerating matrix habitat, indicating the presence of ecological filtering processes in these areas. Furthermore, I found that species traits determined community structural responses to environmental change and this had strong flow-on effects to rates of dung removal. Shifts in trait distributions explained dung removal rates above and beyond total beetle mass, suggesting that neutral processes alone could not explain functional efficiency. In particular, habitat regeneration resulted in the assembly of communities with high total beetle mass and on-average smaller beetles, which was optimal for functional efficiency. In conclusion, the restoration of adjacent matrix habitat was shown to effectively mitigate edge effects on dung beetle community structure resulting in the re-establishment of important associated ecosystem processes.