Tree mortality is a fundamental process governing forest dynamics, but understanding tree mortality patterns is challenging because large, long-term datasets are required. Describing size-specific mortality patterns can be especially difficult, due to few trees in larger size classes. We used permanent plot data from Nothofagus solandri var. cliffortioides (mountain beech) forest on the eastern slopes of the Southern Alps, New Zealand, where the fates of trees on 250 plots of 0.04 ha were followed, to examine: (1) patterns of size-specific mortality over three consecutive periods spanning 30 years, each characterised by different disturbance, and (2) the strength and direction of neighbourhood crowding effects on sizespecific mortality rates. We found that the size-specific mortality function was U-shaped over the 30-year period as well as within two shorter periods characterised by small-scale pinhole beetle and windthrow disturbance. During a third period, characterised by earthquake disturbance, tree mortality was less size dependent. Small trees (,20 cm in diameter) were more likely to die, in all three periods, if surrounded by a high basal area of larger neighbours, suggesting that sizeasymmetric competition for light was a major cause of mortality. In contrast, large trees ($20 cm in diameter) were more likely to die in the first period if they had few neighbours, indicating that positive crowding effects were sometimes important for survival of large trees. Overall our results suggest that temporal variability in size-specific mortality patterns, and positive interactions between large trees, may sometimes need to be incorporated into models of forest dynamics.
An often overlooked aspect of urban housing development is the composition of the space between buildings; the streetscape. The pressures of suppressing suburban sprawl have seen housing developments respond by increasing residential density within more centralised city sites. Medium-density housing typologies are often used as urban infill in response to the challenge of accommodating an increasing population. A by-product of these renewed areas is the creation of new open space which serves as the fundamental public space for sociability to develop in communities. Street space should emphasise this public expression by encouraging social exchange and interaction. As a result, a neighbourhood owes its liveliness (or lack thereof) to its streets. The issue of density when applied to the urban housing landscape encompasses two major components: the occupancy of both the private realms, constituting the residential built form, and the public spaces that adjoins them, the streets. STREETSCAPE: dialogues of street + house. Continual transition between the realms of public and private (building and street space) enact active edges, giving way to public stimulation; the opportunity for experiencing other people. The advent of seeing and hearing other people in connection with daily comings and goings encourages social events to evolve, enhancing the notion of neighbourly conduct. Within New Zealand, and specifically in Christchurch as considered here, the compositions of current streetscapes lack the demeanor to really encourage and facilitate the idea of neighbourly interaction and public expression. Here lies the potential for new street design to significantly heighten the interplay of human activity. In response, this research project operates under the notion that the street spaces of urban residential areas are largely underutilised. This lack is particularly evident in the street. Street design should strive to produce spaces which stimulate the public life of residents. There exists a need to reassert eminence of the street as a space for vibrant neighbourhood life. This thesis employs design as a tool for researching and will involve using numerous concept generators to trigger the production of multiple scenarios. These scenarios are to explore the ways in which the streetscapes within medium-density urban communities could respond in the event of (re) development.
Implementing seismic risk mitigation is a major challenge in many earthquake prone regions. The objective of this research is to investigate how property investment market practices can be used to enhance building owners’ decisions to improve seismic performance of earthquake prone buildings (EPBs). A case study method adopted, revealed the impacts of the property market stakeholders’ practices on seismic retrofit decisions. The findings from this research provide significant new insights on how property market-based incentives such as such as mandatory disclosure of seismic risks in all transactions in the property market, effective awareness seismic risk program and a unified earthquake safety assessment information system, can be used to enhance EPBs owners seismic retrofit decisions. These market-based incentives offer compelling reasons for the different property market stakeholders and the public at large to retain, care, invest, and act responsibly to rehabilitate EPBs. The findings suggest need for stakeholders involved in property investment and retrofit decisions to work together to foster seismic rehabilitation of EPBs.
