EVALUATION OF URBAN TREES SELECTION

FOR SUSTAINABLE PARKING LOTS

Dayang Zahidah Binti Abg Mohamad Othman

Master of Environmental Science

(Land Use and Water Resource Management)

2015

Faculty of Resource Science and Technology

EVALUATION OF URBAN TREES SELECTION

FOR SUSTAINABLE PARKING LOTS

DAYANG ZAHIDAH BINTI ABG MOHAMAD OTHMAN

This dissertation is submitted in partial fulfilment for the requirements of Master in

Environmental Science (Sustainable Land Use and Water Resource Management)

Faculty of Resource Science and Technology

UNIVERSITI MALAYSIA SARAWAK

2015

I

ACKNOWLEDGEMENT

I would like to express my sincere appreciation to my supervisor, Prof. Dr. Hamsawi Bin Sani

for his guidance, advices, knowledge, suggestions and had guided me patiently in the

preparation of this study and report.

My special recognition goes to my mother, Puan Dyg Hjh Rabiah Abg Abd Karim, my

siblings; Abg Zahiden, Abg Mohd Idris, Abg Yusuf and Dyg Halimatun Saadiah for giving

me support and encourage me to finish this project.

Special thanks and appreciation are recorded to Puan Durie Austin, Encik Mohamad Norizam

Bin Ahmad and Encik Mustaffa Nor Bin Ramssay from Dewan Bandaraya Kuching Utara

(DBKU). Special thanks also to Encik Anis Bin Bujang, Encik Musa Liau and Encik Mohd

Saupi Sahari from Unit Landskap, UNIMAS.

Countless thanks to Heida Mohd Kamel for helping, guiding and support me. Thank you also

to Mohamad Firdause Bin Abol Hassan, Abg Hj Amir and Halimah Abg Somaili who has

helped me, supportive and concerns about my project. Not forgetting to all my friends and

families for their supportive and companionship.

II

Table of Contents

Acknowledgement ……...…………………………………………………..

I

Table of Contents …………………………………………………………... II

List of Figures …………………………………...........…………………….

IV

List of Tables ……………………………......................……………….…..

V

Abstract ……………………………………………………………………..

VI

CHAPTER 1 INTRODUCTION................................................................

1.1 Problem statement.........................................................................

1.2 Objectives......................................................................................

1

2

3

CHAPTER 2 LITERATURE REVIEW....................................................

2.1 Urbanization..................................................................................

2.1.1 The Kyoto Protocol On Climate Change....................

2.1.2 Effect of the Urbanization...........................................

2.2 Parking Lot...................................................................................

2.3 Benefits of urban trees.................................................................

2.4 Parking lot and trees.....................................................................

2.5 Parking lots trees planting instruction..........................................

2.6 The important of species selection for sustainable parking lots...

2.7 Parking lot shading provision.......................................................

2.8 Minimum space requirement for trees planting............................

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CHAPTER 3 MATERIALS AND METHOD...........................................

3.1 Study sites....................................................................................

3.2 Identification and management of tree species.............................

3.3 Visual Assessment of tree health.................................................

3.4 Interview with relevant authorities...............................................

3.5 Data Analysis................................................................................

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III

CHAPTER 4 RESULTS AND DISCUSSIONS…………………..……...

4.1 Assessment of tree species at parking lots....................................

4.2 Parking lots...................................................................................

4.2.1 Chancellery And University House (CAUH)................

4.2.2 Faculty of Applied and Creative Art (FACA)………...

4.2.3 Development Office (DO)............................................

4.2.4 Sarawak State Library (SSL)……………………….....

4.2.5 Parking Lot at Jalan Masjid (Padang Pasir)…………...

4.3 Species description of the trees planted…………………………

4.3.1 Pongamia pinnata..........................................................

4.3.2 Tabebuia heterophylla ……….………………..……...

4.3.3 Samanea saman..............................................................

4.3.4 Carpentaria acuminata ………………..………….....

4.3.5 Peltophorum pteocarpum ………………………...…...

4.4 The design and location of the trees.............................................

4.5 Interview with relevant authorities ……………………….…….

CHAPTER 5 CONCLUSIONS AND RECOMENDATIONS..................

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CHAPTER 6 REFERENCES...................................................................... 59

IV

List Of Figures Page

Figure 1 Roadside trees reduce nearby indoor air pollution by more than 50%

(Maher et al. 2013).

11

Figure 2 Tree planting diagram (Service et al. 2008). 15

Figure 3 Trees can create a continuous canopy for maximum rainfall

interception (Service et al. 2008).

19

Figure 4 Know where power lines and other utility lines are before planting

(Service et al. 2008).

20

Figure 5 TruPulse Rangefinder/Hypsometers 23

Figure 6 CAUH and FACA 26

Figure 7 Development Office (DO) 26

Figure 8 Sarawak State Library (SSL) 27

Figure 9 Padang Pasir (PP) 27

Figure 10 Overall percentages for conditions of trees health status at the

selected parking lots.

32

Figure 11 P. pteocarpum with large surface roots at Padang Pasir. 41

Figure 12 The view of parking lots at CAUH with P. pinnata species. 45

Figure 13 The view of parking lots at DO with P. pinnata species. 45

Figure 14 The view of parking lots at FACA. 47

Figure 15 The design and location for T. heterophylla at FACA. 48

Figure 16 The sign of termite surface feeding on the T. heterophylla at FACA. 48

Figure 17 T. heterophylla are being covered by Lichen and mosses. 49

Figure 18 Rows of C. acuminata at Padang Pasir. 49

Figure 19 P. pteocarpum have been cut down at the middle row or parking lots. 51

Figure 20 The parking area at SSL cannot be used due to the roots of S. saman. 52

Figure 21 The parking lots at SSL with cars under the shades of S. saman.

52

Figure 22 Perodua Kembara hits by tree during heavy rain. 58

V

List Of Tables Page

Table 1 Tree Condition Classification 22

Table 2 The number of tree and year planted at the parking lots with

respect to tree species.

28

Table 3 The number of tree at the parking lots with respect to

diameter breast height (DBH) ) classes, height classes and

crown size classes.

29

Table 4 Condition of health status for all the trees surveyed at the

selected parking lots.

30

Table 5 General characteristics of the species at the selected parking

lots.

40

Table 6 The affect of trees species selection to the parking lots. 42

Table 7 The schedule of maintenance for the trees planted in

UNIMAS.

52

VI

Evaluation Of Urban Trees Selection For Sustainable Parking Lots

Dayang Zahidah Binti Abg Mohamad Othman

Master of Environmental Science

Faculty of Resource Science and Technology

Universiti Malaysia Sarawak

ABSTRACT

The increments of urban population have led to an increased need of facility. One of the facilities required is

parking lots to meet the increased use of vehicles. The larger car park surface has led to an increase in

temperature in the city making it hotter. Therefore, tree planting is necessary to achieve the sustainable

environment. However, to achieve a sustainable level, only suitable trees can be planted in the parking lots.

Through the results of the study, selection of species like Pongamia pinnata is very suitable for planting to get

the cooling and shading effect in the parking lots. Thus the pollution level will be decreased and the impacts of

parking lots will be reduced. Besides the types of trees, sufficient planting space both below and above ground

is to be taken into account because it affects the rate of tree growth and surface parking situation event if the

right species of trees were planted.

Key words: Parking lots, species selection, trees, sustainable

ABSTRAK

Pertambahan bilangan penduduk bandar telah menyebabkan peningkatan keperluan fasiliti. Salah satu fasiliti

yang terlibat adalah tempat letak kereta untuk memenuhi pertambahan penggunaan kenderaan. Tempat letak

kereta yang luas telah menyebabkan peningkatan suhu di bandar. Oleh itu, penanaman pokok adalah perlu

untuk keseimbangan alam sekitar yang mampan. Namun demikian untuk mencapai tahap mampan, hanya pokok

yang sesuai boleh ditanam di kawasan letak kereta. Hasil kajian, pemilihan pokok Pongamia pinnata, amat

sesuai ditanam untuk mendapat kesan penyejukan dan rimbun di kawasan tempat letak kereta. Justeru kadar

pencemaran dan kesan negatif tempat letak kereta dapat dikurangkan. Selain daripada jenis pokok, luas

kawasan penanaman perlu diambil kira kerana ia mempengaruhi kadar pertumbuhan pokok dan keadaan

permukaan tempat letak kereta walaupun spesis pokok yang ditanam adalah betul.

Kata kunci: tempat letak kereta, pemilihan spesis, pokok, mampan

1

CHAPTER 1

INTRODUCTION

Sustainable development can be defined as development that meets the needs of the

present without compromising the ability of future generations to meet their own needs and

that increases the quality of life in the present and the future (Kates et. al 2005)

Sustainable, development, present life and future generation are all related to the

saving of the environment. In other words we must preserve the environment for the future

generations while meeting our needs at present.

When the human population increases, the areas for residential development,

industrialization and urbanization have becomes larger that lead to forest depletion, increases

the pollution and many other negative consequences are related to our environment. In order

to bring the concern on the importance of preserving the environment, some of the things that

we can do are having trees in the city, either by creating urban parks or having trees along the

road as well as in the parking lots. Trees are important for the benefits of healthy environment.

For this report, we shall be looking at trees at parking lots.

Parking lot is places which serves as storage for vehicle while the owner spend time in

their workplace, home or even study places. But parking lots also reflect the lifestyle trends of

the people. For example, Universiti Malaysia Sarawak (UNIMAS) have now provided more

parking lots because of the increased number of students and staff that bring their vehicles to

the university.

2

Parking lot is often viewed as important by the developers, building owners because of

its function that can attract the people to the building or parks. But at the same time, large

surface of parking lots can contribute negative impacts to the environment.

Large surface parking lots can contribute to drainage and flooding problems, increase

urban heat islands, become visual eyesores, and encourage people to abandon mass transit,

thereby accentuating air quality problems (McPherson, 2001).

Whenever a certain area is converted into parking lots, it just mean that the open space

with large area. Usually parking spaces are made of concrete or tar surfaced. With tropical

climate, the area will be very hot most of the time. To overcome this matter, trees can be

planted to provide shade, cooling effect and esthetic value. Thus the selection of trees to be

planted is critical, otherwise the function of the trees at parking lots are becoming a problem

instead of solution.

1.1 Problem Statement

There is no one perfect tree. The reason is because there is no one homogenous urban

environment or site. With thorough understanding of the environmental variables, together

with the condition of the planting site, we are able to make appropriate tree species selection

for the purpose of sustainability. In this report, we shall be looking the purpose of planting

trees at parking lots. Are the trees at parking lots serving the purposes without causing damage

to the parking area thus causing the high maintenance? The findings should be used as

yardstick to improve the selection of the trees suitability for parking lots that serve the purpose

as well as for easy maintenance and safety reason.

3

1.2 Objectives

a) To identify the trees species presently at parking lots.

b) To evaluate the suitability of planted species at selected parking lots.

c) To assess whether the trees provide sufficient shading at parking lots.

CHAPTER 2

LITERATURE REVIEW

2.1 Urbanization

The word utban has a several meaning which related to a variety of condition such as

population density, land cover or cultural practices (Andersson, 2006). Urbanization has been

occurring since the early century, from the age of the Greek until nowadays. With the rapid

urbanization, this has contributed to the growth of small town and cities into a developing

metropolitan within a short period of time. So, urbanization is defmed as the urbanization

concept to be the process of becoming urban, relocating into the cities and changing from the

agriculture based to the city concept (Mondal, 2014). Several factors have been leading the

urbanization and this has contributed to the city growth and expansion. The cities have been

attracting the people from the rural areas as they offer more favorable and better environment

compared to the rural areas.

As mentioned by Mondal (2014), mostly people tends to move away from the rural

areas are due to the factors of employability, better standard of living, educational prospects

and available facilities . Mondal also stated that the rural areas have also undergone the

transformation as they have been adopting the cities culture, changing their rural culture (Day

& Bassuk, 1994). The transformation shows that the utbanization has rapidly growing within

the present community. Based on the findings from the World Urbanization Prospect, The

2005 Review done by the United Nation, the utbanization have taken its peak at the twentieth

century. From on 12% in 1900 to 49% in 2005 it have exceed rapidly increased and the

4

fllsat ~lUtMakluIlatAkademii lTNIWRSm MALAYSIA SARAWA~,

continuation of the urbanization have made and expectation of the population living in the

cities to be 60% of the global population in 2030 (Day & Bassuk, 1994).

2.1.1 The Kyoto Protocol on Climate Change

The Kyoto conference was the beginning, not the culmination, of the first serious

international attempt to address greenhouse emissions and the prospect of climate change.

Kyoto was not the last word but rather only a stage in working toward genuinely binding

international agreements. That has disappointed those people who had hoped for dramatic

action. But it was consistent with the advice that scientists are still far from a reliable grasp of

the planet's climatotogy, just as its diplomats and politicians are far from a consensus on

dealing with it. The climate is not the only factor that will affect the quality of life on this

Earth in the 21 st century. The population of the world is also rising rapidly. While its rate of

growth has slowed over the last several decades, it is still rising several times as fast as the

CO2 concentrations in the atmosphere.

The world's economic output in recent years has been raising half again as fast as its

population and there are few people - certainly not President Clinton -who are prepared to

slow down productivity in order to protect the climate. Global warming, population increase

and economic expansion are all related teach other. "It is our solemn obligation to move

forward with courage and foresight to pass our home on to our children and future

generations." Clinton said at the National Geographic Society in October. But because of all

that a restless and creative humanity does from day to day, our children and future generations

5

are going to live in a world very different from the present one. A changing climate will be

only one of those differences (Anderson, 1998).

2.1.2 Effect of the urbanization

Urbanization can contributed to only positive effect with its own certain limit.

Extensive and uncontrolled urbanization may cause an adverse effect. The unplanned and

extensive urbanization can threat the sustainable growth of economic development, social

development and environmental protection. In order to avoid the situation, relevant issues

must be managed such as the necessary facilities and policies implemented in considering of

the benefits of the city.

Resulting in the negligence of any factors, scene likes overpopulation, pollution and

environment degradation can be observed (World Urbanization Prospect 2014). From the

overpopulation, rise the issues of accommodation and this will leads to the growth of slums in

major cities. The last issues will be the uncontrolled pollution, uncontrolled deforestation and

rising in the climate temperature. This is mainly contributed by the excessive vehicles and also

the industries within the cities.

2.2 Parking Lot

Facility is defined as something that is built for specific purposes and will make

certain activities, actions and operations easier (Appleton et aI., 2009). Examples of the

facilities that are provided in the cities or urban areas are parking lot.

6

Also known as car park, this facUity is very important within the city area. This is the

cleared space with the intention to park the vehicles. Building or complex that have their own

attraction and needs within the community will require immense space to ensure the vehicles

will be able to be place properly without any worry of blocking the traffic and causing any

unwanted difficulties on the traffic condition.

In America, the parking lots are related to the increase-in urbanization within the state

and the urban estimation of the urban coverage are in between 2 to 5% and rapidly growing

especially with the development on the residential development, industrial and leisure malls.

Besides that, parking lot is also a space which has no attraction and hostility, with the ability

to reduce the land value and also cause the congestion, undermine the walking distance,

abundant and also a subtle subsidy toward the automotive industry. However, if the parking

lot is still under development or insufficient, this will contribute the cars parked on the street,

obstructing the traffic that leads to congestion and also obstructing pedestrian traffic on the

access roads (Davis et. al 2008).

This problem is usually solved by providing appropriate space for the vehicles to park.

On the other hand, the requirement for the parking space is not directly decided in a quick

manner. A commercial area dealing with the public will require enough parking spaces during

the peak hours or occasions where at this time the parking lots provided are not enough to

cater all customers. However, during normal seasons most of the parking spaces are empty,

especially at the shopping mall. Hence, in most cases the town planners tend to provide more

padcing lots than the actual number required in order to avoiding the parking space shortage

7

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during festive seasons. Thus, the final factor will be the perspective of the personnel that often

wrong about the space availability (Davis et. al 2008).

To the developers, parking space is often viewed as being essential to the market

success ofcommercial buildings. Therefore, city planners must balance this commercial need

fur parking with other community desires which are more compact urban form, a more

pedestrian-oriented urban design and not to forget an improved environment (Wolf &

Resources, 2004).

Large surface parking lots can contribute to drainage and flooding problems, increase

urban heat island, become visual eyesores, and encourage people to abandon mass transit,

thereby accentuating air quality problems (McPherson, 2001).

The interaction of air, water, sunlight and living things with the land can be considered

as being changed or altered by the developed landscaped which are covered with paving,

building and other land treatments. Therefore many cities in recognition to this problems, are

exploring new approaches to reducing impervious cover in new and existing urban areas.

Road and parking areas for vehicle pose a distinct set of concerns aside from the other

environmental consequence due to the production and use of automobiles. From the recent

decades, scientific study shows that the effects of vehicular use areas in human environments

have grown dramatically. Therefore additional studies have begun to explore solution and

mitigations to improve environment (Wolf & Resources, 2004).

As cities grow and expand their land use, ~ot surprisingly the existing tree and

,.-W.atic)ll cover is replaced by urban infrastructure. Actually healthy trees and vegetation

8

....

generate many benefits. The benefits from the environmental are includes [ower energy use,

reduced air pollution greenhouse gas reductions, decreased storm water runoff and also

improved ecosystems (Wolf & Resources, 2004).

In urban areas, heat island effect occurs where materials that have heat absorbing

properties, such as asphalt are prevalent. Heat island can be created by paved surfaces in two

ways. The first is through the accumulation of heat in excessive volume. More of the sun's

energy is traps by city building caused by darks materials and the enclosed canyons. As higher

reflection means cooler temperatures, the reflection rate of paving compared to natural

surfaces is important. The hottest, black pavements have solar reflectance of 5 to 10 percent.

While for lighter pavement, the solar reflectance rates are 25 percent or higher. For soils and

various types of vegetation, the reflection values range from 5 to 45 percent. From recent

research done, it indicates that urban areas are 2 to gOF hotter in summer due to the increased

absorbed beat. The lower moisture content of paving and building materials is the second

cause of heat islands. No moisture is available to dissipate the sun's heat through evaporation

due to those materials are watertight (Green Parking Lot Resource Guide, n.d.).

The absorption and retention, then admittance of heat by urban materials can produce a

dome of elevated air temperatures 5° to 15°F greater over the city, compared to adjacent rural

areas. Heat island effects have been detected in cities as small as 1000 population (Wolf &

Resources, 2(04).

Tree canopy cover reduces urban heat island effects (Akbari, 2002). Tree planting is

one ofthe most cost effective means of mitigation urban heat island. Vegetation canopies can

cool paving by direct shading of the ground surface. They also cool parking areas indirectly

9

order

i)

through transpiration of water through leaves. Exposed solid also help through evaporation of

water. Approximately 1°F of temperature reduction is associated with each additional 10

percent oftree canopy cover (Simpson, et al. 1994).

2.3 Benefits of urban trees

To exist as a nation, to prosper as a state, and to live as a people, we must have trees.

Theodore Roosevelt

The cultivation oftrees is the cultivation ofthe good, the beautiful, and the ennobling in man.

J. Sterling Morton

In the sustainability debate, trees play an important role, not least because the forest

industry "invented' the principle of ecological sustainability more than three centuries ago. In

to preserve ecologically healthy and economically usable ecosystem for future

generations, foresters realized that they needed to replace cut trees. Urban trees provide

important services for humans and the environment similar to their counterparts in forest. The

services provided by urban trees are as follows:

producing oxygen and storing carbon through photosynthesis,

ii) providing habitat to the urban wildlife

iii) cooling the urban environment and moisturizing the air

iv) providing shaded areas on hot days,

v) absorbing air pollutants with their leaves and thus cleaning the air ofharmful particles

vi) accelerating water percolation and thus mitigating foods

vii) greening the city and thus contributing to the overall well-being ofcity residents.

10

In many urban areas, poor air quality is a common problem where it can lead to human

health problems and reduced visibility. Besides that, it can also damage the landscape

materials and ecosystem processes. But with the help of urban forest, this problem can be

reduced. By reducing air temperature, and directly removing pollutants fi:om the air, the urban

forest can help to improve the air quality.

The air that human breathe can be freshen by trees through releasing oxygen as

byproduct of photosynthesis. But the net annual oxygen production are varies where it

depends on the tree species, the tree size, health and location. For example, about 260 pounds

of oxygen can be produced by annually from a healthy 32 foot tall ash tree. For every year, a

typical person need 386 pounds of oxygen, therefore a healthy ash trees with two numbers

and medium sized can supply the oxygen required for one person over the course of a year

(McPherson & Geiger, 2005).

Despite that, trees also can emit volatile organic compounds that can contribute to

ozone fonnation (Nowak, 1993). Integrative studies have revealed that an increase in tree

cover leads to reduced ozone formation as illustrated in Figure 1 (Maher et a1. 2013).

Figure 1: Roadside trees reduce nearby indoor air pollution by more than 50% (Maher et al. 2013).

11

a

2.4 Parking Lots and Trees

In urban areas, the trees playa bigger role as they can provide their greatest benefit by

reducing the impacts of parking lots. According to a study by the Center for Urban Forest

Research, parking lots can occupy up to around 10 percent of land in the cities where the act

as miniature heat islands and are sources of motor vehicle pollutants. By shading cars and

lowering parking lot temperatures, trees can reduce evaporative emissions of hydrocarbons

(HC) that leak from fuel tanks and hoses (Scott et al. 1999). Ozone formations are due to

hydrocarbons (HC) emissions where 15% to 20% of total motor vehicle of HC emissions is

contributed by parked cars. Therefore one of practical strategy that communities can use to

meet and sustain mandated air quality standards is parking lot tree planting (McPherson &

Geiger, 2005).

There are a lot of benefits having landscaping in and around parking lots such as

improves appearance, prevent soil erosion and reduces carbon dioxide through photosynthesis.

Besides that, planted areas also reduce storm water drainage problems, reduce the detrimental

effects of wind and noise and enhance human comfort by providing heat reducing shade.

Especially in hot days, trees also provide welcoming shade in parking lots. Trees not only

shade cars but also pedestrian walkways, reduce glare, screen views and muffle noise.

The amount of solar radiation that is transmitted to dark paving surfaces can be

reducing by trees trough reducing the surface temperatures. The type of trees can affect the

ount of radiation transmitted through a tree canopy, where the ranges are 6 to 30% in the

::summer and 10 to 80% in the winter. In Davis, California, trees at the parking lots can reduce

~.Mlalt temperatures by as much as 36 OF, while to the vehicle cabin the temperatures are

12

emission reduction

reduces by over 47 of and the fuel tank temperatures by nearly 7 of (Wolf & Resources,

2004).

Automobiles are major sources of reactive organic gases (VOCs). While most vehicle

emission is in the form of tailpipe exhaust, it is estimated that approximately 16 percent are in

the form of evaporative emissions when vehicles are not operating. Thus idle vehicle

emissions may be more severe in locations where vehicles are concentrated and where

temperatures are high. The cooler the car, the lower the rate of gasoline evaporation in from

leaky fuel tanks and worn hoses. Trees cool air temperatures in parking lots, reducing ozone­

fonning hydrocarbons that are emitted by cars (Scott et al. 1999).

Studies in Sacramento, California suggest that 50 percent shading of paved areas

would reduce hydrocarbon emissions city-wide 1 to 2 percent, equivalent to about 0.84 metric

tons per day. While this effect seems modest, these reductions are equivalent to agency

goals for non-transportation air quality improvement (such as waste

burning and vehicle scrap practices) (McPherson 2001).

Tree canopy cover, scientifically assessed as the amount and distribution of tree leaf

area, is directly associated with the urban forest's capacity to produce community benefits.

Increasing a city's canopy cover is a direct way to increase benefits afforded by trees: climate

CODtrol and energy savings: improvement of air, soil and water quality: mitigation of storm

runoff: reduction of the greenhouse gas carbon dioxide: provision of wildlife habitat;

increased real estate values and human psychological well-being (Maco & McPherson,

13

Therefore, planting trees at parking lots also creates more pleasant and attractive

parking environment and increases tree canopy cover that can making communities greener

and healthier places (McPherson & Geiger, 2005).

2.S Parking lots trees planting instruction

There are several tree planting techniques for planting trees at parking lots. The

following are steps to be taken when planting trees at parking lots. The steps of planting trees

are illustrated in Figure 2.

i) Remove containers, wrappings, wires and ties.

ii) Make the planting hole 2 to 3 times the width ofthe root bait Set ball on finnly packed

soil to prevent settling.

iii) Trunk flare can be avoided by keeping much away from base of tree.

iv) Keep mulch 1 to 2 inches back from trunk.

v) Gently pack backfill, using water to settle soil around the root ball. Use topsoil for back

filling.

VI) Use two opposing, flexible ties - when staking is necessary. Ties should be placed on the

lowerhalfof the tree and allow trunk movement. Be sure to remove ties within one year.

14

I

mulch 1102

Figure 2: Tree planting diagram (Service et al. 2008).

15

2.6 The important of species selection for sustainable parking lots

Trees face many urban challenges starting with the construction process. Topsoil is

generally removed during at the beginning of parking lot construction. Then the sub grade is

compacted followed by layers of crush and run stone, and asphalt or concrete that are spread

and also compacted. The resulting soil mix under the pavement is not penetrable to roots due

to mechanical impediment if municipal compaction specifications are adhered to. Low

available oxygen also limits root growth. Due to root damage and soil volume restriction, trees

planted near pavement often suffer. Due to the lateral growth of shallow tree roots, sidewalk

can crack and heave, creating 'lips' or 'subtoe' spots which are caused by uneven

displacement of adjoining section of concrete. In urban forestry, the root versus pavement

contlict is one of the most pervasive problems in urban forestry. Thus due to limited

municipal funds, removal and or replacement of trees and repair of paved surfaces will take

longer times to proceed. In addition where injuries occur as a result of pavement hazard, city

governments may be found liable in damage suits. Therefore selecting appropriate trees for

PJdring lots and other paved areas is challenging.

While other has a narrow range in which they will grow well, it is important to note

some trees are adaptable to a fairly wide range of environmental conditions. List of tree

presented complete with information about adaptability. Under near optimal

.1iti4>DSwith pH of6.8 and consistently moist but well drained soil, all trees can grow well.

fiiSf!v.!!r it is not easy to find these conditions in the urban environment. Therefore the trees

..tIIltftnli'l be planted must he tolerate broader, less ideal conditions while still providing the

These kinds of trees don't prefer poorer condition but still can grow adequately in

16