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......................................................................................
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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