Copyright is owned by the Author of the thesis.  Permission is given for 
a copy to be downloaded by an individual for the purpose of research and 
private study only.  The thesis may not be reproduced elsewhere without 
the permission of the Author. 
 



Tree Collections of Auckland: 
Biodiversity and Management 

A thesis presented in partial fulfilment of the requirements for the degree of 

Master of Applied science 
in Landscape Management 

at Massey University, Palmerston North, New Zealand 

Presented by Penelope Frances Cliffin 

2001 



Abstract 

Recent developments in New Zealand environmental legislation and 

government policies are based on an economic world-view where landscape is 

portrayed as a ·natural' resource. This paradigm largely ignores the human­

made urban landscape where the highest proportion of population live. our 

national legislation pays little attention to urban vegetation in general and 

exotic tree collections in particular. Research therefore has a vital role in 

highlighting the character and values of urban vegetation , and in analysing the 

current models used to manage its continued existence. This study examines 

the importance of charting and managing biodiversity and focuses on 

managed amenity and scientific tree collections in the Auckland region . 

This regional study seeks to characterise the biodiversity of tree collections in 

Auckland , and describe how landscape management can best contribute to 

their biological and human-use values. The literature review establishes the 

importance and values of trees and urban vegetation as critical to the fabric of 

human lifestyles and the ecology of the city. It then reviews the basis for the 

preservation of biodiversity in managed plant collections. Management 

principles and systems are reviewed along with the legislative context in 

Auckland. No mandate is estab lished for exotic plant collection managment 

under the Resource Management Act, 1991 (RMA1991 l. Management of this 

resource is found to lack the focus and funding from which natural and rural 

biodiversity benefit under the RMA and other national legislation. 

A biodiversity survey of thirty-eight collections of trees characterises the 

biodiversity in the collections, and a survey of twelve tree collection managers 

provides data about the goals, practices and tools used in the management of 

those collections. 

Results reveal the diverse and unique flora of Auckland tree collections, and 

establish a baseline for comparison over time. The regional mix of native and 

exotic species found in Auckland collections is compared with other national 



plant surveys, and demonstrates differences consistent with regional climatic 

character and a differing research focus. The largest collection of trees and the 

most specialist genera collections were found at the Auckland Regional Botanic 

Garden, while the university of Auckland provides the most extensive range of 

scientific plant-collection facilities. There is evidence of sequential open space 

acquisition for tree collections in the Auckland region . comparison of best 

management practices put forward in current literature with current practices 

of collection managers in Auckland reveals some significant issues. There is 

little evidence found to suggest strategic plant acquisition goal setting. It is 

also of concern that only half the collection managers used computerised plant 

record systems such as inventories and specialised database systems. Only one 

third of the managers had management plans, and therefore documented 

collection goals. There was no significant difference in the use of best 

management practices between the private and publicly owned collections. 

well-managed collections are characterised by high or specialist tree species 

diversity, clear strategic goal setting and management planning, computerised 

plant record systems, adequate resources, appropriate staffing and the use of 

monitoring tools. 

Discussion of these research results leads to three recommendations. Firstly, 

the management of specific sites is discussed in light of a proposed model for 

plant collection management. secondly, management policy for the regional 

urban Forest is recommended. Lastly, the finding that Auckland 's exotic tree 

collections are a valuable resource worthy of protection, currently having little 

status under the law, leads to the recommendation for the empowering of a 

national body <central agency> with a mandate for the national coordination of 

botanic gardens and plant collections. 

This research therefore charts aspects of Auckland 's urban biodiversity with 

reference to current legislation and management models. Its findings and 

recommendations are of importance to reviewers of national environmental 

legislation, regional policymakers and tree collection managers. 

ii 



Acknowledgements 

I wish to acknowledge the help and support of many people in the research 

and writing of this thesis; Marion MacKay for her guidance and direction in her 

role as supervisor; Massey university Agricultural Research Foundation for 

provision of funding to conduct this research ; Nancy Beck and the staff of the 

School of Landscape and Plant science at UNITEC for their personal and 

academic support; Keith Hammett, John Adam, Mike Wilcox, Ewen Cameron, 

Beverley McConnell, Bryan Gould, Lance Goffart-Hall and members of the Royal 

New Zealand Institute of Horticulture for guidance in the initial focus of the 

research ; the tree collection managers of Auckland who contributed to the 

surveys; Margaret McClure for editorial assistance; Yongmei Li for data entry 

and Meer Hay for publishing support; and lastly to my family, Peter, Alice and 

Tim for their support and patience. Thank you all. 

i ii 



Tree Collections of Auckland: 
Biodiversity and Management 

Table of Contents: 
Abstract . .. ... .. ... .. .... ............ ... .... ... ... ..... i 

Acknowledgements ...... . ... . ..... ............. ... ..... . iii 

Table of contents ....... .. . .. .. . . .... . .................. iv 

List of Figures ....... . . .................................. v 

List of Tables ......... . . .. .......... ... . ........... . . ... vi 

List of Appendices ........... .. ..... .... ... ... ...... .... . vi 

Chapter 1: Introduction ............................ . ..... 1 

1.0 An overview of Chapter 1 ........... .. .. . ......... .... .. 1 

1.1 The Human use Values of Trees ..... .. . . .. . .... . .......... 1 

1 .2 The Biological Values of Trees ........ ....... . .... . ..... . 12 

1.3 Plant Collections and Botanic Gardens .. . ....... . .. . .. . .. . 16 

1.4 The Auckland Research context ........ . . .. .......... .... 23 

1.5 Landscape Management ......... . ................. . ... 28 

1.6 Management Process : strategic, operati onal and Implementa ti on .. 45 

1.7 Management Context: Legislation and Policy .. . ... .. ... .. . .. . 68 

1 .8 conclusion to Chapter 1 .............. . ..... . . .... . . ... 88 

1.9 The Research Question . . ....... . . ........ ... ... ....... 90 

Chapter 2: Methodology ............... .. .. .... . ........ 92 

2.0 Introduction ............ .. ... . .... .. .... . .......... . 92 

2.1 Research Paradigms ... . ... . ...................... . ... 93 

2.2 Review of Two Research Tools .... . .. . ... . . .. . ........... 97 

2.3 Research Quality Issues .... . .. . .. ... ......... . ... . ... . 105 

2.4 conclusion . ... .... . .......... .. .. . ... ..... ... ... .. . 106 

Chapter 3: Results: Biodiversity survey ..... . .. .. .. ....... 107 

3.0 Introduction .... . .. .... ... . .. . . . . ................ . . 107 

3.1 Diversity of Auckland Tree Collections ........ .. .. ... . . .. . 107 

3.2 Tree Character : origins, sources and Trade Availability ..... .. .. . 119 

3.3 Collection Character: Age , Types and Distribution ............. 122 

Chapter 4: Results: Management survey ... . .... .. ... . ... . 126 

4 .0 Introduction .......................... . . . .......... 126 

4 .1 Tree Collection ownership ..... . .. ............. . ... .... 127 

4.2 Collection Age ... . . .. . . .... .. ... . . .......... . ... .. . . 125 

iv 



4.3 Collection Goals ... . . .. . ..... . . . ... ... . .. . .. ...... .. . 128 

4.4 Management Plans . . .... . . .. .... . . .. .... . .. . ... . ..... 131 

4.5 Tree Types ..... .. .. . .... .. .. ....... ... . ...... ... ... 139 

4.6 Information systems . . ... . ... .... . . . .. . . ...... .. . .. .. 140 

4.7 Biodiversity Indicators .. . . . ................ .. .. . ..... 145 

4.8 Collection Threats . . .. . . ....... . . .. . . . . . .... ... . .... . 151 

4.9 Professional consultants .. ...... . ........ ..... .. . ... . . 153 

4.1 o Policy and Legislation . ................. .... . ... ... . . 154 

4.11 conclusion .. . . . .... . ... . .. ... . .... .. .. .... ........ 155 

Chapter s: Discussion .. ... ... . . .. . .. . . . .. . ....... .. .. . . 157 

5.0 Introduction ...... . ... . . . . . .. ... .. . ....... . .. ... ... 157 

5.1 Tree Biodiversity in Auckland ... . .. . .... . .. .... ..... ... 158 

5.2 Plant Collection Management Model ... . . .. .... . ....... . . 164 

5.3 Regional Planning: the Geography of the Urban Forest ... ... ... 177 

5.4 National Planning: a Legislative Mandate .... ............... 179 

5.5 summary of Recommendations ...... ..... ...... . ...... . 180 

5.6 conclusion .. .. . . . . .. .. . ......... . . .. . . . . . .. . . . ..... 181 

Appendices .. . .. . ..... . . . ........... . . .. ............ . 182 

Bibliography . . .. . .... .. ...... . . ... . .. .. . . . .. . ..... ... 281 

List of Figures 
Figures Title Page 

Map 1.1 The urban Forest of Auckland (Bradley, 2000> 24 
Figure 1.1 Management Cycle (Gilbert et at. , 1995> 29 

Figure 1.2 Management cycle (Grev, 1996> 30 
Figure 1.3 Information systems in the Management cycle 

(Chua, Lowe, & Puxtv, 1989> 31 
Figure 1.4 Revised Management cycle Model 33 
Figure 1.5 Management Model for a Plant Collection (MacKav, 1996> 38 
Figure 1.6 The outdoor Recreation 'Systems Management Model ' 

Uubenville and Twight, 1993> 40 
Figure 1.7 outline of a Typical Management Plan (Bromley, 1994> 61 
Figure 3.1 Number of Species in Auckland Tree Collections 109 
Figure 3.2 Origin of Tree species in Auckland Tree Collections 120 
Figure 3.3 species Availability in Nursery Trade 121 
Figure 5.1 The Revised Tree Collection systems Management Model 166 

V 



List of Tables 
Tables 
Table 1.1 

Table 3.1 

Table 3.2 

Table 3.3 

Tab le 3.4 

Table 3.5 

Table 3.6 

Table 3.7 

Table 4.1 

Table 4.2 

Table 4.3 

Table 4.4 

Table 4.5 

Table 4.6 

Table 4.7 

Table 4.8 

Table 4.9 

Table 4.10 

Table 4.11 

Table 4.12 

Table 4.13 

Table 4.14 

Table 4.15 

Table 4.16 

Table 4.17 

Table 4.18 

Appendices 
Appendix 
Appendix 1 

Appendix 2 

Appendix 3 

Appendix 4 

Appendix 5 

Appendix 6 

Appendix 7 

Title Page 
Types of Botanic Gardens and Arboreta (Given,1994) 17 

Total Number of Taxa in Auckland Tree Collections 108 

Most common ly Represented species 
in Auckland Tree Collections 110 

Burstall and Sale's (1984) List of Auckland 's Great Trees 111 

comparison of Genera in Mackay's National 
survey (1990l with Auckland Collections 115 

Numerically Best Represented Genera 
in Auckland Tree Collections 117 

Numerically Best Represented Families 
in Auckland Tree Collections 119 

Tree Collection types 123 

Age of Auckland Tree Collections 127 

Presence of Collection Goals 128 

Goals of Auckland Tree Collections 129 

Management Plans in Auckland Tree Collections 131 

Factors which Lim it Effectiveness of Management Plans 133 

Public Input Mechanisms for Auckland Tree Collections 135 

Elements of Auckland Tree Collections 136 

Tree Types in Auckland Tree Collections 139 

Plant Record systems for Auckland Tree Collections 140 

Information Provided by Plant Record systems 143 

Plant Record Update Frequency for Auckland Tree Collections 144 

Species Diyersity of Auckland Tree Collections 146 

Tree Health of Auckland Tree Collections 147 

Tree Maturity Stages in Auckland Tree Collections 148 

Species Rarity in Auckland Tree Collections 150 

Primary and secondary Threats to Auckland Tree Collections 151 

Professional consultation for Auckland Tree Collections 153 

Effect of Policy on Auckland Tree Collections 154 

Title Page 

Personal communications contact List 182 

The Nature of Auckland 's original Vegetation 183 

ARBG Plant Records Database Fields 185 

Auckland Regional Parks Map 187 

survey Questionnaire and Accompanying Letter 188 

summary species Data List and Locations 195 

Full Species Data List 226 

The Urban Forest of Auckland- Enlarged Foldout <Bradley, 2000) 

version Showing collection Locations at Back cover 

vi 



Chapter 1: Introduction 

1.0 An overview of Chapter 1 

This research project seeks to investigate the biodiversity of managed amenity 

and scientific tree collections in the Auckland region, and to examine their 

botanical significance and the adequacy of the management systems applied 

to them. 

Chapter One is a review of literature relevant to this study. This begins with 

establishing the value of trees in the urban environment, then introduces the 

concept of biodiversity and how plant collections can be used to conserve 

biodiversity. Then the specific Auckland research context is described, 

highlighting the need for management of landscape resources. Next is a review 

of current management theory and external influences on management 

systems, such as the legislative environment. The chapter provides the reader 

with definitions of terms used, establishes existing background knowledge, 

and describes current theoretical frameworks used to examine the way plant 

collections and landscape management are understood. Lastly, this chapter 

poses the specific research question to be addressed by this project. Appendix 

1 provides a contact list for all personal communication referenced in this 

thesis. 

1.1 The Human use Values of Trees 

1.1.0 Introduction 

According to Nadel et al. <1977, p. 85) : 

trees reach up and link man with the sky. In a city they transcend the noise, 

confusion and disorder. Silently, they provide a resting place and refuge 

from the chaos of urban life. In the quiet early morning hours of dawn, in 

the rush of late afternoon business, city trees proudly stand protecting us 

from the loss of our humanity 

Trees embody many different values, some inherent and some ascribed to 

them by humans, termed human-use values (Given, 1994; Loxton, 1991; O'Neill, 

1993; Phillips, 1993; stone, 1996l. 

INTRODUCTION 1 



1.1.1 symbolic values 

From ancient times trees were given symbolic status in human art, mythology 

and literature. This can be seen in the role of trees in the imagery of major 

Eastern and western religions, such as the tree of life and knowledge in 

Judaism, ·sacred groves· in ancient Greece and Italy set aside as temples, and 

tree worship of Ficus religiosa in Pakistan !Bell, 1997; Bernatzky, 1978; Nadel et 

al. , 1977; westoff, 1983 l. Many nations select plants as national symbols, for 

example the New Zealand silver-fern emblem. The fern was used as an example 

of the symbolic value of native fauna by then Prime Minister Jenny Shipley in 

her endorsement of the Draft Biodiversity strategy in 1998 !Department of 

conservation and Ministry for the Environment, 1998l. 

As well as these positive images of vegetation there are also examples of 

negative imagery. Forests represent the primeval or mythical world, and are 

one of the archetypal landscapes of the western world , which humans have 

gradually sought to convert into the cultural landscape !Bell, 1997; Schama, 

1995). Forests have also been seen as a place of hiding for enemies and evil 

spirits and as somewhere posing the threat of becoming lost mwyer et al., 

1991; Westhoff, 1983l. A range of these different views of vegetation can be 

expected to have a place in the psyche of even the most modern city dweller, 

and to influence his or her attitude to urban trees !Arnold, 1993; schama, 1995l. 

1.1.2 Psychological and Physiological Benefits 

Another benefit of vegetation which is well supported in the literature is the 

positive physiological and psychological benefit of nearby nature, with trees 

playing a major role <Honeyman, 1992; Kaplan , 1992; Miller, 1988; Phillips, 1993; 

Relf, 1992; Schroeder, 1990; Ulrich, 1983; Ulrich & Parsons,1992l. 

Interaction with nature has a number of direct positive physiological effects on 

the human body. Research has centred on people suffering from symptoms of 

stress, such as high blood pressure, muscle tension and increased heart rate. 

Research reviewed by Ulrich and Parsons !1992> gives evidence of stress 

recovery indicators such as reduction in blood pressure, muscle tension and 

normalised heart rate after exposure to natural environments. studies on brain 

INTRODUCTION 2 



waves by Ulrich (1981l indicate that nature scenes elicit a wakeful , relaxed state. 

Particularly interesting is a study by Heerwagen (1990l on heart rate 

comparisons of people visiting a dentist. A nature scene mural in the waiting 

room was shown to reduce stress symptoms for the visitor. 

The positive effects of gardening projects on interpersonal and community 

wellbeing in American housing estates are documented by Lewis (1992) . 

Neuberber (1992) reports on benefits of horticultural therapy for sufferers of 

mental illness in Germany. Browne (1992) reports her research into how 

important 'landscaped grounds' are to potential rest home residents. Ninety 

nine percent of respondents considered th is either ·essential' or 'important' in 

their preference criteria for selecting a rest home. some of the benefits 

reported were aesthetic enjoyment, motivation for physical exercise, social 

interaction and opportunity for self-expression in the gardens. McDonald and 

Bruce (1992) review research showing that in institutions for geriatric and 

handicapped people, human interaction with plants heightens self-esteem, 

increases purposeful behaviour, creativ ity and self-expression, and helps in 

adjustment to new environments (Hill & Relf, 1982; Inman & Duffus, 1984; Isaacs, 

1986; Watkins, 1982l. Providing views to nature for prison inmates is known to 

reduce admissions to prison hospitals (Moore, 1982; west, 1985). 

Models such as Ulrich 's Information Processing Model (1981 ; 1986) enable 

preference predictions to be made about a particular landscape scene. Trees 

are a very clear content preference in landscape scenes whether it be in 

regional work, such as done by Fabos & McGregor (1979) in Australia , or on 

localised urban scenes research by Kaplan (1985l. urban dwellers value natural 

features such as trees, grass and water (Schroeder, 1982). urban ratepayers 

value tree programs highly compared with other municipal services in Detriot, 

e.g. tree lined streets were very popular (Getz et al., 1982) with residents. Trees' 

aesthetic qualities, provision of shade and effect of increasing property values 

were considered their most important contributions to urban environments in 

that study. In a study by Schroeder (1990) trees rank highly in preference 

factors for parks, and Hull (1992) found that thirty percent of residents 

identified the urban forest as the most significant urban feature that was 

INTRODUCTION 3 



damaged in a hurricane in Charlston, and listed a range of psychological 

benefits for having trees in the city. A New Zealand study <Kilvington & 

Wilkinson, 1999) on community attitudes to urban vegetation in Christchurch, 

found that psychological and physiological benefits, such as stress relief and a 

sense of peace, were the most commonly identified values of urban vegetation 

by focus group participants. From the sample of studies reviewed above, it is 

clear that psychological and physiological research has demonstrated the 

positive effect of plants on people, and has led to better understanding of 

human preferences for landscape and vegetation. 

1.1.3 Recreation Values 

Most tree collections are sited within parks and gardens which also provide 

space and facilities for one or more forms of active or passive leisure or 

recreational pursuits. This defines them as sites with recreational value 

<Cobham, 1990). Recreation is a recognised role of botanic gardens <Given, 

1984), and is an important reason why many people visit botanic gardens (ARC, 

200m. Clark and Stankey (1979) propose the Recreation Opportunity Spectrum 

<ROS) which seeks to explain a continuum of recreational experiences, ranging 

from primitive or wilderness experiences where the environment is pristine, 

and little management is required, through to sophisticated cultural 

experiences where the site is likely to be highly designed, developed and 

managed. This spectrum represents the range of experiences the recreational 

user has to choose from, and also a relationship between the biophysical site, 

management and the visitor's choice. This continuum has similarities to the 

landscape spectrum proposed by MacKay (1996), in both content of the 

continuum and the level of management input ascribed for the continuance of 

different types of recreation landscapes. The biophysical attributes of the site, 

the services on the site and the social setting, all influence the visitor's choice 

to come to the site Uubenville and Twig ht, 1993), along with factors such as the 

distance and ease of transport to the site uubenville and Twight,1993; Miles & 

Seabrook, 1977). 

Biophysical site qualities such as scenic quality, favourable climate and 

opportunities for participatory activities are factors which attract visitors 

INTRODUCTION 4 



(Miles & Seabrook, 1977). Recreational use often conflicts with biological 

resource values (Lemons, 1987), and so must be considered in landscape 

management systems. This is where resource monitoring reviewed in section 

1.6.6, such as resource carrying capacity and limits of acceptable change are 

useful to gather evidence of recreational use effects on the environment. 

Recreation values can clearly be seen as part of the human use being managed 

in a tree collection . Therefore the conflict between human use and the 

biological resources must be understood and actively managed . The 

recreational impacts of visitors to a collection need to be accounted for in any 

management model considered in this research . 

1.1.4 Historic Values 

Gardens are increasingly being recognised as an important reflection of 

cultural and social history (Goulty, 1993). Garden design traditions developed 

within distinct geographic and cultural situations (Barnett, 1993; Bradbury, 

1995; Goulty, 1993). Individual t rees have been planted throughout history to 

commemorate special visits, events or people (Heritage Victoria, 1999). Certa in 

tree species were introduced at particular times and these dates can help 

identify historical periods (Banks, 1988). Knowledge of gardens in general, and 

trees as major structural elements, may, through interpretation, give us access 

to the knowledge of history, a depth of understanding of the contemporary 

cultural landscape and how landscapes reflect cultural values moisset,1980; De 

Lambert, 1986; Goulty, 1993). 

Protection and management of historic cultural landscapes is evident in 

countries with many centuries of cultural history, such as in Britain, where 

historic gardens receive protection and funding through the National Trust. 

The historical significance of landscapes and trees is less well conceptualised 

and valued in New Zealand . This lack of recognition is apparent in the Historic 

Places Act (1993), where there is no protection provided for gardens and trees 

except in association with a building. Many Australian states are similar to New 

Zealand, but the state of Victoria provides protection for different kinds of 

landscapes, including gardens and individual trees e.g. the 'Federal Oak' in 

INTRODUCTION 5 



Melbourne <Heritage Victoria, 1999>. Tree collection heritage values are 

therefore unlikely to be managed effectively under the Historic Places Trust, 

unless an historic buiding is associated with the site. 

1.1.s Economic Values 

Economic values of trees include direct monetary values such as those gained 

from plant products and crops, such as timber, paper, food , medicines, eco­

tourism profits and contributions to real estate values <Barbier et al. , 1994; 

Groombridge, 1992; McNeely, 1988; Miller, 1988; Phillips,1993>. 

Trees also have indirect values of, such as maintaining the options for future 

generations to directly utilise plant species for purposes as yet not realised, as 

described by Given (1994l. The non-saleable products of ecosystem functioning 

include the release of oxygen, absorption of carbon and pollutants such as 

sulphur dioxide, cooling and shading effects, run-off and erosion control 

(Bradley, 1999>. These indirect benefits are sometimes termed ecosystem 

services, and are (generally unacknowledged) subsidies to economies <Costanza 

et al., 1997; Falke, 1992l. The New Zealand Biodiversity strategy <Department of 

conservation and Ministry for the Environment, 2000, p. 3l states: 

that New Zealand bases much of its economy on the use of biological 

resources and benefits from the services of healthy ecosystems. 

In the current western economic paradigm of ·user-pays' arguments that seek 

to demonstrate economic value or utility of natural resources, are perhaps 

seen as more persuasive than moral or aesthetic arguments (Groombridge, 

1992l. Economic techniques are essential tools in valuing natural resources 

(Contanza & Daly, 1992; Falke and Kaberger, 1992; Mykletun, 1990; Wagner et al., 

1998l. Methods which seek to calculate economic values to natural resources 

include opportunity or alternative cost approaches, cost benefit analysis 

(Hampicke, 1994; Moll, 1995), contingent valuation, revealed preference surveys 

and travel cost analysis Uakobsson & Dragun, 1996>. 

one example of an alternative cost method is the calculation of energy 

INTRODUCTION 6 



equivalents for urban ecosystems services such as reduction in storm water 

run-off, temperature reduction from tree canopies, and improvements in air 

quality. These energy equivalents can be compared to the cost of alternative 

services such as extending storm water reticulation systems and air 

conditioning or filtering costs and are therefore useful complimentary bio­

physical estimates to a monetary analysis (Bradley, 1995; Falke, 1992). 

A particularly difficult issue in economic valuation is the importance of 

acknowledging intrinsic or existence value of natural resources. contingent 

valuation methods ask users about their willingness to pay for recreation 

opportunities or to accept compensation for giving up the right to that 

recreation or use. This method is gaining support, with 1600 documented 

works reported , may provide a more holistic approach to economic valuation 

Uakobsson & Dragun, 1996). 

There are several different valuation models in use for placing economic value 

on individual trees, such as used by the Royal New Zealand Institute of 

Horticulture (Flook, 1996), the Arboricultural Association (1990) in Britain, the 

Australian Institute of Horticulture (1997) , the council of Tree and Landscape 

Appraisers with the International society of Arboriculture (1995) in the USA. 

These systems all award points on the basis of qualitative criteria and then 

award a dollar value rate per point scored. In student comparative studies at 

Waikato Polytechnic, valuation systems have been found to give very different 

values for the same tree !Collett, 1997). Each system of valuation gave a relative 

measure of values between trees evaluated by that system, but the dollar 

values generated were inconsistent. 

Auckland City council prepares evaluations of trees scheduled in its district plan 

(Auckland City, 1999a), which give numerical scores without converting the 

score to a dollar value (Auckland City arborist Bryan Gould , personal 

communications, February 200m. Monetary values can be calculated for species 

with commodity values and ecosystem function values, but there is still no 

reliable evaluation system available to measure additional amenity and social 

values in monetary terms mobson, 1998). 

INTRODUCTION 7 

.. 
<' 



1.1.6 Aesthetic and Design Values 

Trees add beauty to our environment through graceful shape, foliage, 

fragrance, flowers and fruit as well as their ability to define and articulate 

space, and to enhance or control views (Phillips, 1993; Thomas, 1983l. 

vegetation is the landscape architect's unique material palette, making 

landscape design distinct from other design professions. Trees are the largest 

structural plant elements in that palette. They are long-lived and provide the 

main framework for planting design. Their selection and placement must 

therefore be designed following principles of landscape design such as 

balance, proportion, scale and unity. Size and form must be considered to 

avoid long-term problems such as view obstruction. Visual control includes 

being able to provide privacy; enframe, create focal points, emphasise and 

screen views and buildings; and therefore control movement of viewers 

around a site (Booth & Hiss, 1991 ; carpenter & Walker, 1990; Clouston, 1990; Grey 

& Deneke, 1978; Hackett, 1979; Robinson, 1992). 

Choice of plant material will depend on a combination of the following four 

criteria. Firstly the functional goals for the site and the three dimensional 

effect required for the particular use. secondly the physical constraints of the 

site must be considered e.g. soil type, climate, management practices. Next, all 

the plants selected for a design should contribute to the overall theme or 

effect to be created . This must be done in sympathy with the architecture, site 

and location (Barnett, 1993l. Using trees from local and nearby flora contributes 

to establishing a local theme or identity, e.g. the iconic pohutukawa used to 

symbolise Auckland 's coastal identity (Auckland City, 1999bl. 

Lastly, the aesthetic goals of the designer are brought to bear. The form or 

overall shape and size of the tree, colour (from its leaves, bark, seasonal flowers 

and fruit) and texture (surface characteristics of the tree, determined mainly 

by leaf size and arrangement) are each considered in relation to the whole 

(Booth, 1983; Robinson, 1992l. 

INTRODUCTION 8 



The individual (specimen) appeal of trees is seen by some, as a handicap to 

designers using trees effectively at an urban scale. Arnold (1993, p. 1l suggests 

that: 

the most persistent problem confronting every designer who works with 

trees is their seductive appeal. The remarkable aesthetic power of trees 

distracts artists so much that their potential for building dense organic 

compositions has been replaced by an over-refined, precious reverence for 

individual trees 

Although Arnold 's comment may be critiqued as limiting the design use of 

trees, he does express the different approach requ ired when using trees at an 

urban or city scale, compared with a residential or garden scale. Reverence for 

the individual or specimen value of trees is important for designers to 

consider. At the city scale however, the bold framework approach he 

advocates is more effective in providing a link between open space and 

providing a sense of hierarchy of transport corridors or carriageways. 

Signature tree species of differing scale may convey this hierarchy. Auckland 

City (2000l describes eight street typologies within its boundaries, for which it 

selects different types of street tree to suit different functions e.g. heritage 

areas have street planting which allow the buildings to be clearly viewed, 

pedestrian areas have small scale trees to keep with the intimate human scale. 

commercial areas have large scale trees to balance the scale of the buildings. 

The anomaly here is that the street design cross-section does not allow enough 

width to give large trees enough space to grow properly. Queen street is an 

example of this where the Platanus orientalis are etoliated due to lack of light 

and damaged due to physical contact with the shop canopies. A new 

streetscape design is being proposed for Queen street in conjunction with 

plans for light rail transport system, which provides unimpeded tree spaces 

!Cumming, 2000l. 

Arnold (1993) advocates using large trees in single species grid formations in 

urban areas. Large trees give an appropriate scale to large buildings in the city. 

Using a large number of the same species of tree provides linking or unifying 

INTRODUCTION 9 



elements amongst mixed architecture, and grids of trees add to that unity. 

Grids or avenues also create a sense of movement and linkage of open spaces 

such as parks and plazas. Fredrick Law Olmsted's park systems recognised the 

increased visibility and accessibility afforded by linkage of urban open space 

<Smith & Hellmund, 1993). The wide, treed boulevard was the design form he 

advocated to achieve this linkage, along with walking trails and greenbelts, 

together encouraging use by pedestrians <Bella, 1987). The public use of the 

tree collections surveyed would therefore be enhanced by creating linkages 

such as advocated by Olmsted (Smith & Hellmund, 1993l. 

1.1. 7 Engineering values 

The biological values and ·ecological services· which vegetation provides in 

natural areas are often utilised by engineers, architects and landscape 

designers in urban areas. Additional engineering functions of vegetation in 

general and trees in particular are well documented in landscape architectural 

texts from authors such as carpenter & Walker <1990) , Jackman (1986), Motloch 

(1991) and Robinette (1972). 

Erosion control is afforded both by canopy cover interrupting the impact of 

the rain on soil, and by the reinforcing nature of plant root systems in the soil 

structure. Plants also absorb large quantities of rainwater, contributing to the 

balance of the hydrological cycle. Noise abatement by plant material is not as 

efficient as more solid barriers to deflect sound waves, but visual screening 

using plants does give psychological relief from the effect of noise pollution, 

as well as effective control of glare e.g. for houses along motorway margins 

<Robinette, 1972). Climatic control may be achieved by the use of tree wind 

breaks, designed to deflect and/or filter strong or cold winds, or to channel 

cooling summer winds to lower high temperatures. Deciduous plants provide 

effective shade from summer sun, while allowing winter light to penetrate into 

outdoor spaces and indoor rooms. Air filtering and oxygen production values 

of trees are also available to urban designers to contribute to the air quality 

benefits of the Urban Forest (Beckett et at., 200m. 

INTRODUCTION 10 



1.1.8 Amenity Values 

somewhere in-between aesthetic, social and recreational values is the ill­

defined or rather broad term ·amenity value·. Cobham (1990> lists a range of 

values of land used for amenity purposes which include leisure and recreation , 

visual beauty, historic and cultural interest, habitat, social and economic values. 

The Resource Management Act (1991) also gives a broad definition, ·natural and 

physical qualities and characteristics of an area that contribute to people's 

appreciation of its pleasantness, aesthetic coherence, and cultural and 

recreational attributes·. 

For the purposes of this research the term amenity value will be considered a 

general term encompassing a wide range of landscape values. It provides a 

useful term to describe the values of the surveyed tree collections sited in 

parks. 

commentary 

This section has clearly shown that trees influence people, especially in the city 

(Arnold, 1993; Honeyman, 1992; Kaplan, 1992; Miller, 1988; Phillips, 1993; Relf, 

1992; Schroeder, 1990; Ulrich, 1983; Ulrich & Parsons,1992L Urban vegetation is 

a critical component of the fabric of urban lifestyles, and is understood as 

many things, including open space, scientific collection , ecological service, 

historic artifact or economic asset. People can also be seen to have a 

fundemental influence on the landscape as they constantly design, use and 

manipulate their environment (Laurie, 1986; Meinig, 1979; Relf, 1992). There is a 

large body of research which seeks to provide models for landscape 

assessment of both human-use and biological values (Daniel & Vining , 1983; 

Fabos & McGregor, 1979). In the next section on the biological values of trees, 

biodiversity and its conservation are considered, with a focus on scientific 

plant collections and botanic gardens as tools to conserve biodiversity as key, 

and well-described collection types in the biodiversity literature reviewed. 

Plant collection research in New Zealand is then reviewed to establish the 

context in which this study sits. 

INTRODUCTION 11 



1.2 The Biological Values of Trees 

Plants are an essential part of the ecological systems and biological cycles 

which constitute the complex web of life on Earth (Chapman & Reiss, 1992; 

Folke, 1992; McNeely, 1988; White et at. , 1984). As plants take in carbon dioxide 

and water to photosynthesise their own food, they release oxygen as a by­

product and accumulate carbohydrates. Plants therefore provide oxygen and 

food for the animal kingdom (Chapman and Reiss, 1992). Forests play a crucial 

role both globally, in climatic regulation, (Given, 1994) and locally in terms of 

temperature, humidity, wind control and providing habitat for animals 

(Bradshaw et at., 1995). They also provide the carbon sink which regulates the 

levels of carbon dioxide and oxygen in the earth 's atmosphere (Chapman and 

Reiss, 1992; Dobson, 1998). These biological roles are sometimes termed 

·ecosystem services' (Costanza & Daly, 1992, p. 37; Costanza et at., 1997, p. 253). 

Deforestation of land for agriculture and urban development reduces the 

buffering capacity of natural ecosystems and cycles and therefore threatens 

the stability of the Earth 's climate (Given, 1994; Groombridge, 1992). Global 

warming and ozone depletion are examples of human effects on 

environmental stability. Limiting deforestion and vegetation clearance, and 

planting more trees is considered a key strategy in attempts to regain 

environmental equilibrium (Dobson, 1998; Given, 1994). Plants therefore 

maintain the biosphere as a functioning system and provide the material basis 

for human life (Folke, 1992; Groombridge, 1992; McNeely, 1988). 

1.2.1 The concept of Biodiversity 

Biodiversity is a contracted form of the term 'biological diversity', and has been 

identified as a key indicator of biological quality moc & MOE, 2000; RMA, 1991 

section 2l. 

Biodiversity can be understood at three different levels: The first is in terms of 

genetic variability within a species. A plant taxonomist or systematist would 

usually describe biodiversity in terms of the number of species in a 

monophyletic taxon i.e. genetic variability (Eldredge, 1992). The second is in 

INTRODUCTION 12 



terms of the number of species in any given area. An ecologist would be 

interested in the number of species and the relationship between species in a 

particular ecosystem. A taxonomic plant collection or botanic garden curator 

may view biodiversity in terms of the number of species and cultivars within a 

plant collection , but must also consider genetic diversity within the collection. 

All three levels of diversity are important concepts in conserving overall 

biological quality (Groombridge, 1992>. 

Biodiversity is important to the health of the environmental setting, and is a 

required consideration for management of State lands in New Zealand 

mepartment of conservation and Ministry for the Environment, 2oorn . Human 

actions on the landscape in industry, horticulture, agriculture, housing and 

forestry all tend to reduce species and ecosystem biodiversity. Worldwide 

research clearly indicates that plant species biodiversity is declining at an 

alarming rate (Given, 1994; Groombridge, 1992). Native forests have been 

cleared all over the world in the wake of western colonisation, and present day 

tropical forests are still being cleared at a rapid rate (Given, 1984). Modification 

or destruction of natural plant habitats is the main cause of plant biodiversity 

decline, followed by direct collection or harvesting (Groombridge, 1992). Plant 

collections are one way of conserving plants under threat. New Zealand has 

been suggested as a potential botanical Noah's Ark, for conserving threatened 

temperate and subtropical floras (Given 1986/1987). 

New Zealand relies heavily on exotic plants and animals for its world trade 

(Hammett, 2000). Plant conservation strategies, including plant collections, seek 

to ensure the maintenance of plant biodiversity for biological and ecological 

reasons as well as human uses such as food , fibre, timber, fuel and medicinal. 

Other values of vegetation such as aesthetic and the future option values of 

plants, are covered in section 1.1. Preservation of diversity of garden plants is 

reliant on the plantsmanship and horticultural knowledge and skills of home 

gardeners, landscape planting designers, plant collection managers the nursery 

industry (Given 1986/1987; Hammett, 2oorn. Design trends to have fewer types 

of plants in gardens to give a minimalist or modernist look, encourage 

nurseries to stock a more limited range of plants (Bradbury, 1995>. Keith 

INTRODUCTION 13 



Hammett (2000> describes this as a trend towards "more and more of less and 

less". This trend poses a threat to the continuing availability of a wide range of 

garden plants. An analysis of availability of the trees found in this study will be 

undertaken to assess current species availability. Trade availability becomes 

important to tree collection managers when replanting programmes are 

undertaken, especially when historic values of the collection dictate direct 

replacement of existing species. 

1.2.2 Plant conservation Management 

conservation of species biodiversity is concerned with maintaining viable 

populations of species. For short-lived plant species in the wild, population 

viability is a serious issue, due to the necessity for frequent seed production 

cycles for the continuance of the species. Fifty plants is considered a minimum 

number for a viable breeding population (Given, 1986/1987). For the amenity 

tree species considered in this study, population viability is not such a serious 

issue, as the trees are long-lived, and vegetative propagation is possible. 

However this type of reproduction does lead to a decline in genetic variability, 

and therefore to vulnerability problems inherent in monocultures, such as 

susceptibility to pests and diseases, may become a threat (Given, 1986/1987). In 

order to maintain biodiversity, two approaches to maintaining viable 

populations of species are well established: 

In situ conservation is used to conserve viable plant species populations in their 

natural ecosystem environments. The habitats must often be protected in 

order to ensure their continued existence. New Zealand 's National Parks and 

Protected Natural Areas scheme seek to preserve a range of threatened habitat 

types, so as to conserve our plants species in situ. 

In contrast, ex situ conservation maintains plant species in cultivation. Botanic 

gardens and plant collections form a major part of world's ex situ plant 

conservation efforts <Given, 1986/1987; Groombridge, 1992). conservation of 

rare and endangered plants, the habitats of which are already seriously 

depleted or under threat, are often managed from an ex situ approach. New 

Zealand is considered an ideal location for ex situ conservation of rare and 

INTRODUCTION 14 



endangered plants around the world , due to its small population, isolation and 

freedom from major pollution (Given , 1986/1987). Other ex situ plant 

conservation approaches include field gene banks and seed banks. Field gene 

banks are areas of land set aside in which collections of viable plants are 

assembled, at a lower cost than, and without the other functions of a botanic 

garden. Field banks are useful for long-lived perennial species such as some 

tree and woody shrub species, with low maintenance requirements and slow 

seed production rates. seeds are collected regularly for propagation of the 

species (Groombridge, 1992l. seed banks are a space-efficient way of storing 

genetic material for the future. Not all seeds are suitable for storing in this way, 

but there are many species which do have seed suitable for long-term storage. 

The Auckland Regional Botanic Garden is planning to start a seed bank in the 

near future (Auckland Regional council, 2001i. 

Horticulture provides useful tools for ex situ plant conservation . An example of 

this is the use of vegetative propagation techniques e.g. hardwood cuttings, 

used to propagate shrubby tororaro (Muehtenbeckia astonm by the Hutt City 

council and the Department of Conservation in Wellington. Plantings of 

Muehtenbeckia astonii were established in traffic islands and street verges in 

the Lower Hutt town centre for conservation purposes me Lange & Silberry, 

1993l. Philip Simpson and Peter de Lange (1993) have documented a history of 

plants saved by people bringing them into their gardens, both in New Zealand 

and internationally. Plants conserved in this way may then be used as 

propagation material to be taken back into the natural environment, once the 

habitat has been protected or restored (Lucas, 1978l. Identification of key sites 

and at-risk species has long been recognised as a crucial conservation role for 

botanic gardens to be involved with internationally (Lucas, 1978l. careful 

collection , identification, recording of species data and plant management 

practices, such as weed control are essential in this type of ex situ conservation, 

to ensure population maintainance (Given, 1994; Hawksworth, 1995). 

Plant collections and botanic gardens are key tools in plant conservation, and 

are discussed in the next section. 

INTRODUCTION 15