CAPACIDAD Y NIVEL DE SERVICIO EN RAMPAS ESPECIALES.

Effective assessment of the success of ecological restoration projects is critical in justifying the use of restoration in natural resource management as well as improving best practice. Ecological restoration projects are increasingly focussing on creating stable, resilient, functioning ecosystems, however there are very few studies that investigate the response of both functioning and biodiversity of restored sites. In addition, there is often the assumption that increasing species and or functional diversity equates with restoration of ecosystem function, but there has been little research empirically demonstrating these mechanistic relationships in situ.

The overall objective of this thesis is to assess how several components of diversity from different levels within a trophic system respond to restoration, whilst simultaneously looking at the responses of ecosystem functions that relate to nutrient cycling and forest succession (Figure 1.2), and investigating the relationship between biodiversity and ecosystem functioning within a restoration context. In achieving this objective, the thesis addresses four principal research topics:

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Figure 1.2 Simplified outline of the contribution of mammals, dung beetles and decomposition processes to the nutrient cycle affecting plant biomass in tropical forest systems

1.9.1Chapter 2: Assessing responses of mammal diversity to tropical forest

restoration: a functional approach

Faunal recolonisation following ecological reforestation is a major component of ecosystem recovery due to the ecological functions that they mediate. Mammals play an integral role within rainforest ecosystems as consumers, seed and spore dispersers and as predators and prey. Changes in mammalian community structure following ecological reforestation are therefore likely to have consequences for the integrity and stability of the system. This chapter examines: (1) whether small mammal species diversity increases with time since restoration; (2) whether functional diversity increases with restored forest age; and (3) whether restoration forests are converging in species composition and functional diversity on the ‗old-growth‘ forest condition?

1.9.2Chapter 3: Measuring the success of reforestation for restoring dung beetle

diversity and associated ecosystem functioning

Functional trait information and diversity indices complement traditional taxonomic based indices and when used together with assessments of ecological functions, can

20 provide comprehensive evaluations of the success of restoration projects. By directly measuring the response of dung beetle mediated ecosystem functions and dung beetle diversity to ecological restoration of tropical forests, the mechanistic link between biodiversity recovery and functional recovery is examined, using individual functions and an index of multifunctionality. This chapter examines: (1) whether increasing time since restoration leads to an increase in species diversity and a more rainforest- like community structure; (2) increasing time since restoration leads to an increase in functional diversity and functional efficiency; and (3) the relationship between biodiversity and ecosystem functioning in ecologically restored sites.

1.9.3Chapter 4: Investigating Responses of leaf litter decomposition rates to

tropical forest restoration and microhabitat conditions

Conversion of forest to agriculture is widespread and is known to cause substantial deterioration in soil properties. Therefore, the restoration or reforestation of tropical forest on degraded land requires the restoration of ecosystem processes that recover suitable soil conditions. Leaf litter decomposition is one of the major pathways of nutrient cycling, crucial for restoring soil condition, and as such provides an indication of nutrient cycling and soil quality, as well as the soil and decomposer subsystem. This chapter examines: (1) whether leaf litter decomposition rates increase with time since restoration started; (2) how the successional stage of restoration affects key biophysical parameters associated with leaf litter decomposition (mean temperature and humidity, variability in temperature and humidity, mean woody and leaf litter volume, soil pH and soil bulk density); and (3) the relationships between biophysical parameters and decomposition rate.

1.9.4Chapter 5: Determining the biophysical drivers of biodiversity and

ecosystem functioning recovery through ecological restoration

There are many factors that affect the successional trajectories of restored forests. All of these factors interact and influence the habitat characteristics of restored forests and, in turn, the recovery of biodiversity and functionality. This chapter looks at the responses of key biophysical characteristics to ecological restoration and explores the relationship between these characteristics and the recovery of biodiversity and functionality. Of particular interest is the relative importance of landscape and site variables (e.g. distance to mature forest, soil properties) that are independent of

21 restoration, compared with habitat structure and microclimatic conditions (e.g. canopy cover, understory density, litter volume) that are affected by restoration, on biodiversity and functional recovery. This chapter examines: (1) how biophysical parameters (habitat structure, microhabitat conditions, soil properties and landscape context) respond to ecological restoration; (2) the effect of biophysical parameters on biodiversity and ecosystem functioning; and (3) whether restoration-dependent characteristics (i.e. habitat structure, microhabitat conditions) are more important than restoration-independent characteristics (i.e. soil properties, landscape context) in driving patterns of biodiversity and functionality recovery.

Each of the data chapters of this thesis have been written for publication: Chapter 2 is in preparation for submission to Restoration Ecology. Chapter 3 has been published in the Journal of Applied Ecology. I intend to submit Chapter 4 to Forest Ecology and Management, and Chapter 5 to Ecological Applications in due course. Therefore, this thesis is made up of stand-alone chapters linked by a common theme of the responses of biodiversity and ecosystem functions to tropical forest restoration. Chapter 6 summarises the key findings resulting from each chapter and highlights future research needs.

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Chapter 2