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Research Papers, Lincoln University

A city’s planted trees, the great majority of which are in private gardens, play a fundamental role in shaping a city’s wild ecology, ecosystem functioning, and ecosystem services. However, studying tree diversity across a city’s many thousands of separate private gardens is logistically challenging. After the disastrous 2010–2011 earthquakes in Christchurch, New Zealand, over 7,000 homes were abandoned and a botanical survey of these gardens was contracted by the Government’s Canterbury Earthquake Recovery Authority (CERA) prior to buildings being demolished. This unprecedented access to private gardens across the 443.9 hectares ‘Residential Red Zone’ area of eastern Christchurch is a unique opportunity to explore the composition of trees in private gardens across a large area of a New Zealand city. We analysed these survey data to describe the effects of housing age, socio-economics, human population density, and general soil quality, on tree abundance, species richness, and the proportion of indigenous and exotic species. We found that while most of the tree species were exotic, about half of the individual trees were local native species. There is an increasing realisation of the native tree species values among Christchurch citizens and gardens in more recent areas of housing had a higher proportion of smaller/younger native trees. However, the same sites had proportionately more exotic trees, by species and individuals, amongst their larger planted trees than older areas of housing. The majority of the species, and individuals, of the larger (≥10 cm DBH) trees planted in gardens still tend to be exotic species. In newer suburbs, gardens in wealthy areas had more native trees than gardens from poorer areas, while in older suburbs, poorer areas had more native big trees than wealthy areas. In combination, these describe, in detail unparalleled for at least in New Zealand, how the tree infrastructure of the city varies in space and time. This lays the groundwork for better understanding of how wildlife distribution and abundance, wild plant regeneration, and ecosystem services, are affected by the city’s trees.

Research Papers, Lincoln University

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.

Images, UC QuakeStudies

Trees alongside the Avon River in Richmond. The river level is high, and the water is grey with silt. One of the trees is leaning towards the river. The photographer comments, "High river levels because of liquefaction in the Avon. Near 373 River Rd, Richmond".

Images, eqnz.chch.2010

Knox Church earthquake repair/rebuild on a walk around Christchurch December 11, 2013 New Zealand. www.stuff.co.nz/the-press/news/christchurch-earthquake-20... All about our ear...

Images, eqnz.chch.2010

The centennial pool demolition is under way. On a walk around the city to catch up on events happening June 18, 2014 Christchurch New Zealand. Swimsuits have been hung on the fence around the Centennial Pool by campaigners against the complex's demolition. The Armagh St facility is being pulled down to make way for the new Margaret Mahy Fami...

Images, eqnz.chch.2010

The centennial pool demolition is under way. On a walk around the city to catch up on events happening June 18, 2014 Christchurch New Zealand. Swimsuits have been hung on the fence around the Centennial Pool by campaigners against the complex's demolition. The Armagh St facility is being pulled down to make way for the new Margaret Mahy Fami...

Images, eqnz.chch.2010

The centennial pool demolition is under way. On a walk around the city to catch up on events happening June 18, 2014 Christchurch New Zealand. Swimsuits have been hung on the fence around the Centennial Pool by campaigners against the complex's demolition. The Armagh St facility is being pulled down to make way for the new Margaret Mahy Fami...

Images, eqnz.chch.2010

On a walk around the neighbourhood, December 3, 2013, Christchurch New Zealand. www.stuff.co.nz/the-press/christchurch-life/avenues/featu...

Images, eqnz.chch.2010

After my visit at the hospital for physiotherapy on my hand I took a walk around the city on my way home. Demolition of the Victoria Square apartments February 12, 2014 Christchurch New Zealand. www.s...

Images, UC QuakeStudies

Students sit outside the InTentCity 6.3 Cafe, which was set up in a tent in the Law car park while University of Canterbury buildings were closed for structural testing. The photographer comments, "The University restarts its teaching, and the techies in e-learning move out of NZi3. The cafe has an outside seating area under the trees".

Images, UC QuakeStudies

A member of the University of Canterbury's E-Learning team in their temporary office in the James Hight building. The photographer comments, "First looks at our new temporary (maybe) office space. Our group will stay here until April or May 2011, then will move to another floor in the Central Library. South view over trees to the hills".

Images, eqnz.chch.2010

What I found on a walk around the city Christchurch November 20, 2013 New Zealand. www.isaactheatreroyal.co.nz/ en.wikipedia.org/wiki/2011_Christchurch_earthquake

Images, UC QuakeStudies

Damage to the garden of a house in Richmond. Liquefaction is visible among the plants and on the driveway, and the driveway is badly cracked. The photographer comments, "These photos show our old house in River Rd. Water and silt have flattened the long grass in the back garden. The growth right of centre is suckers growing from the stump of a prunus tree we had felled last year. The section of fence between us and our neighbour fell down in the Sep 4 quake".

Images, eqnz.chch.2010

Earthquake damaged building on a Walk around the city, May 1, 2014 Christchurch New Zealand. Demolition work on Christchurch's "distinctive" former civic building is under way. The category-2 heritage building was designed by G A J Hart and opened in 1939 as the Miller's department store. It featured the South Island's first escalator, which...

Research Papers, Lincoln University

The increase in urban population has required cities to rethink their strategies for minimising greenhouse gas impacts and adapting to climate change. While urban design and planning policy have been guided by principles such as walkability (to reduce the dependence on cars) and green infrastructure (to enhance the quality of open spaces to support conservation and human values), there have been conflicting views on what spatial strategies will best prepare cities for a challenging future. Researchers supporting compact cities based upon public Transit Oriented Development have claimed that walkability, higher density and mixed-uses make cities more sustainable (Owen, 2009) and that, while green spaces in cities are necessary, they are dull in comparison with shopfronts and street vendors (Speck, 2012, p 250). Other researchers claim that green infrastructure is fundamental to improving urban sustainability and attracting public space users with improved urban comfort, consequently encouraging walkability (Pitman and Ely, 2013). Landscape architects tend to assume that ‘the greener the better’; however, the efficiency of urban greenery in relation to urban comfort and urbanity depends on its density, distribution and the services provided. Green infrastructure can take many forms (from urban forests to street trees) and provide varied services (amended microclimate, aesthetics, ecology and so forth). In this paper, we evaluate the relevance of current policy in Christchurch regarding both best practice in green infrastructure and urban comfort (Tavares, 2015). We focus on the Christchurch Blueprint for rebuilding the central city, and critically examine the post-earthquake paths the city is following regarding its green and grey infrastructures and the resulting urban environment. We discuss the performance and appropriateness of the current Blueprint in post-earthquake Christchurch, particularly as it relates to the challenges that climate change is creating for cities worldwide.