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Urban forest restoration ecology: factors influencing native tree regeneration and practitioner decision-making processes
Abstract
Restoration ecology is a new and growing scientific field in the natural sciences. Typically restoration efforts have been focused in remote and rural landscapes. However, recently there has been a rise in the number of projects aimed at restoring native forests in urban environments. The long-term success of these projects depends on the sustainability of restoration plantings and their capacity to self-regenerate over time. Our scientific understanding of how to effectively restore functional, sustainable urban forests is increasing, yet we know little about mechanisms driving juvenile native tree regeneration and recruitment in these highly altered environments. Furthermore, ecological knowledge alone is insufficient to guide restoration outcomes in cities. Urban forests are socio-ecological systems and project outcomes are also influenced by the values and knowledge of restoration practitioners. In this thesis, I explore these ecological and social drivers of long-term urban forest restoration success in New Zealand.
In chapter 2 I investigate how drivers of juvenile native tree recruitment vary according to plant species successional status and growth stage. The long-term existence of restored forests depends on their capacity to follow the steps of ecological forest succession into maturity. It is crucial this includes recruitment of native tree seedlings into the sapling stage, especially for middle and late successional species. However, it is unclear whether the drivers that promote juvenile recruitment are generally applicable, or if they vary according to plant successional status and growth stage. Using a forest planting chronosequence approach and negative binomial generalised linear models, I investigated what drivers promote recruitment processes of early and mid-late successional native woody juveniles in 79 restored urban forests across nine New Zealand cities. I found that mid-late successional trees respond to different drivers than early successional species and the relative importance of particular drivers varies according to the trees growth stage. The effects of canopy cover appear generalizable across successional status but not growth stage, while the opposite is true for the effects of microclimate. Older forests host greater seedling abundance, and larger forest patch size is important for mid-late successional species. These results indicate that to promote urban forest successional progress and hence recruitment of native tree juveniles, management approaches should vary depending on restored forest age and site conditions.
The third chapter explores how restoration practitioners in Aotearoa (New Zealand) make decisions in their efforts to re-establish native urban forests and why there is a gap between science-based best-practice restoration and on-the-ground implementation. The science- practice gap is well-documented in the applied sciences, but little is known about how it manifests in the urban forest restoration context where there are multiple objectives and many diverse stakeholders involved. To remedy this knowledge gap, we administered an online survey to practitioners involved in urban forest restoration. We found there is a tenuous link between scientific knowledge and urban restoration practice due to breakdowns in knowledge transfer and barriers to implementation. When restoring, practitioners tend to prioritise planting or weed control over other vital elements such as project planning and quantifiable monitoring. Objectives are commonly broad, vague, and focused on restoration of simple structural ecosystem components but not important functional attributes. Results show that practitioners value interactions with ecology experts and fellow practitioners equally to traditional forms of science communication (e.g. journal articles) as sources of restoration knowledge. This chapter suggests that prioritising interactive, interpersonal science communication and encouraging collaboration between scientists and practitioners would help strengthen knowledge transfer. Additionally, providing practitioners with time- saving resources, adequate funding, and guidance to navigate socio-ecological constraints that arise in urban projects will improve restoration outcomes.
This thesis broadens our understanding of social and ecological drivers of urban forest restoration success and highlights opportunities for improving the efficacy of urban restoration efforts. This research allows us to develop restoration ecology theory and refine best-practice methods for restoration of native urban ecosystems in Aotearoa.
Type
Thesis
Type of thesis
Series
Citation
Busbridge, S. (2020). Urban forest restoration ecology: factors influencing native tree regeneration and practitioner decision-making processes (Thesis, Master of Science (Research) (MSc(Research))). The University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/13654
Date
2020
Publisher
The University of Waikato
Supervisors
Rights
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