Investigating the efficiency of reforestation approaches in restoring rainforest biodiversity and function

Ecological restoration is being increasingly applied to reverse or mitigate biodiversity losses, re-instate ecological functions and increase the provision of ecosystem services in tropical forests. Effective assessment of the success of ecological restoration projects is critical in justifying the use of restoration, as well as improving best practice. However, there is often the assumption that once a degree of vegetation recovery occurs, diversity will increase, which equates with restoration of ecosystem functions. Since very few studies have investigated the interaction between the recovery of habitat structure, biodiversity and ecosystem functioning, this thesis aims to explore these mechanistic relationships to better understand the causal factors behind ecosystem recovery following restoration. Both mammal and dung beetle community composition was clearly progressing towards that of rainforest with increasing restoration age. Restoration increased dung beetlemediated secondary seed dispersal, leaf litter decomposition rates and decomposition multifunctionality (dung and litter decomposition). Functional trait-based metrics provided a clearer pattern of mammal recovery than traditional species-based metrics. Functional diversity metrics were also better predictors of dung beetle-mediated functionality than species diversity metrics, emphasising the need to use a variety of ecologically meaningful diversity metrics when investigating the mechanisms and patterns driving ecological recovery. In terms of vegetation structure, microhabitats were more complex and microclimatic conditions were more stable in restored sites and became more similar to rainforest with age. Faunal recovery was best explained by vegetation structure and microhabitat conditions; whereas functional recovery was explained by a combination of vegetation structure, microhabitat, soil properties and landscape context. These findings suggest that although landscape context and intrinsic site characteristics affect restoration success, they can potentially be mitigated by the establishment of a well-developed, rainforest-like habitat structure and microclimatic conditions within restoration sites. By taking a holistic approach, this thesis demonstrates that ecological restoration of tropical forests leads to the development of a structurally more complex, rainforest-like vegetation structure, a shift to more stable microclimatic conditions and increased availability of microhabitat resources. These successional changes lead to the recovery of functionally diverse, rainforest-like faunal communities and efficient ecosystem functions within a relatively short time frame (10-17 years).