The document discusses the importance of maintaining a healthy and diverse urban forest. It notes that urban forests provide environmental benefits like reducing temperatures, sequestering carbon, and providing wildlife habitats. Researchers recommend following the "10-20-30 rule" for urban tree diversity - no more than 10% of trees should be the same species, 20% the same genus, and 30% the same family. This ensures biodiversity and genetic diversity within the urban forest. Maintaining a diverse urban forest requires ongoing management, funding, and selecting a variety of suitable tree species.

1. SPECIFIER
UPDATE
ISSUE 18
Contents CASE STUDIES
2 Civic District, Singapore
4 Lonsdale Street
6 Mackay City Centre
8 Calgary Alberta
11 Kent Street Cycleway
EBOOK
14 Conservation of our Urban
Forest Health and
Sustainability

2. The Civic District is the birthplace of modern Singapore
and marks the beginning of the country’s historical,
architectural, and cultural heritage. Plans for the Civic
District enhancement works were revealed during the Draft Master
Plan 2013 exhibition and were completed in phases by the end of
2016.
As part of the enhancement works, a new row of beautiful na-
tive Kayu Arang (Cratoxylum cochinchinense) trees were planted
along Queen Elizabeth Walk at Esplanade Park and in front of the
Asian Civilisations Museum at Empress Place. Complemented with
stepped plazas along the edge of the Singapore River, this area
brings people closer to the scenic waterfront view.
Prior to the establishment of the trees, considerations were made
during the design stages on tree root management solutions that
enable trees to thrive in a complex urban environment where there
is a constant flow of pedestrian traffic.
Leading urban landscaping management solutions provider, El-
mich, introduced Citygreen’s Stratavault solution, an advanced
structural root cell engineered to keep trees healthy by prevent-
ing soil compaction caused by building structures thus providing
Stratavault enlivens Civic District in
Singapore
Installation of soil vault
Continuous, engineered soil vault by Citygreen, supporting pavement.
2 ISSUE 18

3. adequate breathing space for healthy root growth. The root cell
is made entirely from 100% recycled polymers and is a proven
system which builds on the experience gained through trials,
projects, and collaborations with industry innovators worldwide.
The tree root management system features huge openings and a
patented nesting ability for easy installation, higher strength, re-
duced transport costs, and maintenance of large spaces for root
growth and service integration.
Take a walk around the Civic District and experience a feeling of
intimacy with history and lush greenery enhanced with pedestrian-
friendly landscaped spaces for the public.
Project Credits:
Developer/Owner: Urban Redevelopment Authority (URA)
Architect: Architects 61 Pte Ltd / Cox Architecture Pty Ltd
Landscape Architect: Context Landscape Design Pty Ltd
Arborculture Consultant: Arborculture Pte Ltd
Main Contractor: Shanghai Chong Kee Furniture and
Construction Pte Ltd
Completed museum plazaMuseum installation
Continuous soil vault system for healthy trees on the waterfront
CASESTUDY
Citygreen®
SPECIFIER UPDATE 3
CASESTUDY

4. Lonsdale Street transformed into
Melbourne green boulevard –
with benefits to the bottom line
In the heart of Melbourne’s growing southeast corridor lies the
City of Dandenong. In 2010, a comprehensive ‘Revitalising
Central Dandenong’ initiative was launched by the Victorian
government through Places Victoria. Seeking to rejuvenate the
rundown Lonsdale Street precinct, a team of renowned Landscape
Architects, Engineers, and Builders came together to create a fresh
new future for the city.
Five years down the track, the project has proven to be an
overwhelming success, with Lonsdale Street now considered one
of Melbourne’s great boulevards. A green, pedestrian-friendly main
street encompasses the city’s vibrant retail industry with wider
footpaths, various urban furniture, bicycle stands, and – the jewel in
the crown – 251 thriving Pin Oak trees. In line with urban stormwater
best practice, there are also a number of rain gardens which capture
and treat stormwater, which is then reused for irrigation.
Today, the thriving streetscape looks as if it’s always been there,
belying the comprehensive engineering and technology below
ground that made it all possible. Whilst the original design specified
reinforced concrete slabs supported by streel screw piles over a
continuous soil trench, the suspended slab ultimately proved too
expensive due to poor ground conditions. Argot Consultants Pty
Ltd & KLM Spatial were engaged to investigate cost-effective
alternatives to piling, and after seeing several successful projects
in Auckland, New Zealand, Citygreen’s Stratacell product was
selected.
Landscape contractor Sugan Blanchard, of Canteri Bros
Construction Pty Ltd, said, “Argot Consultants Pty Ltd & KLM
Spatial came up with the Stratacell system, which provided cost
and time saving to the project. The main cost saving was on the
reduced thickness of the slab as it was designed as a slab on
ground instead of suspended slab. We had never used this system
before but found it to be easier to install and time efficient, providing
the structural strength to overlying pavement while allowing
uncompacted growth media for trees.”
Landscape Architect, Scott Adams, Director of Taylor Cullity
Lethlean, counts the Lonsdale Street project as one of the firm’s
landmark projects. Adams said, “The Lonsdale Street site proved
to be really challenging, and the Stratacell product was the solution
that got sign off from Argot Consultants Pty Ltd & KLM Spatial
Engineers. Thankfully, the project was completed on time and the
product hasn’t failed despite significant surface traffic. It’s definitely
been successful in generating the result we wanted, with the trees
performing well. As a result, we’ve recommended the product on a
number of subsequent projects.”
Found it to be easier to install and time
efficient, providing the structural strength
to overlying pavement while allowing
uncompacted growth media for trees
4 ISSUE 18

5. Theo Niakolas, Principal Engineer at Argot Consultants Pty
Ltd, echoes this sentiment. “From our perspective, the project
has been a success, and the clear evidence is the health of
the trees. The cells have performed well in terms of providing
support to the hard stand paving above, as expected during
design. No adverse distress of the rigid pavement is evident.
We’ve since suggested the product in other streetscape
projects too numerous to identify.”
Today, Lonsdale Street is unrecognisable, transformed from
a grey, uninviting locale into a green, thriving streetscape for
residents, workers, and visitors to enjoy.
It’s definitely been successful in generating the
result we wanted, with the trees performing well.
As a result, we’ve recommended the product on
a number of subsequent projects.
Highly integrated stormwater management, treatment, and green canopy
CASESTUDY
Citygreen®
SPECIFIER UPDATE 5
CASESTUDY

6. Designed and built over twenty years ago, the CBD
was aesthetically outdated and often subject to minor
flooding and drainage issues. The narrow sidewalk
was also unsuitable for al fresco dining, and failed to offer a social,
multi-faceted shopping experience. Through the revitalisation of
the CBD’s aesthetic and environmental qualities, Mackay Regional
Council sought to resolve these issues, and in turn promote local
and regional economic development.
Dave Watt, formerly Landscape Project Manager at Vassallo
Constructions, said, “The primary goal was to increase public
access and better utilise the area while beautifying it and displaying
some of Mackay’s existing features such as the many art deco
period buildings. The project also enabled the upgrade of services
to the area.”
Ben Ewins, formerly Landscape Architect at RPS Australia Asia
Pacific, said, “Once Mackay Regional Council had confirmed the
preference towards using Hill’s Weeping Fig Trees (Ficus microcarpa
var. Hillii) in the central medians, we identified a disparity between
this species and the prospective available root space and volume.
Ultimately, we needed a solution that would allow the trees to grow
by creating a greater volume of space below the road pavement for
root growth, without encroaching on the proposed civil works.
Ewins said, “To achieve this, we required a sturdy support
mechanism that would facilitate a number of outcomes:
1. Support significant road pavement vehicle loads
2. Prevent compaction of the soil / root zone
3. Achieve a high ratio of support structure soil volume
4. Address the concerns about warranties.”
Mackay City Centre
revitalised with striking
Hill’s Weeping Fig Trees
In August 2014, a significant overhaul of Mackay’s City Centre commenced,
known as the City Centre Revitalisation Project. This tropical CBD resides
along the Pioneer River, and houses the bulk of Mackay’s hospitality and
commercial businesses.
6 ISSUE 18

7. Manager – City Centre Revitalisation at Mackay Regional Council,
said, “This project was a hard sell, because historically there are
problems with underground infrastructure being ripped up by figs
and other big trees. Thankfully, Stratacell allowed us to kill two birds
with one stone – providing a nice big volumetric space for healthy
root growth, and providing a barrier to stop roots going further
and causing damage. Essentially, it provides a giant planter box
underground.”
Watt said, “Citygreen were the specified supplier, because their
products had the capacity to meet the complexities of the project.”
In fact, Citygreen’s Stratacell system was the only product that
delivered the required structural integrity needed for this application.
Watt continued, “Citygreen’s products have been tried and tested
on other projects. The products’ proven success provided us with
confidence that we’d achieve a positive outcome in the required
timeframe, and enabled different construction methods to be
investigated prior to implementing the best procedure.”
Ewins said, “The resulting outcome has been extremely positive
and all trees installed to date are in excellent health. The key benefit
of working with Citygreen was without a doubt their immediate
response times in providing solutions and inputs to what was a
critical situation, which required a fast turnaround. Their expertise,
along with the fast turnaround, was invaluable.”
Watt said, “A positive outcome has been achieved, with both the
public and business owners in the area very upbeat about the end
result. Using Citygreen technologies also provided us with confidence
that there will be no rectification works required and we can be sure of
longevity in this striking-looking project. We’re proud to have played a
part in providing long-lasting satisfaction for the local community and
visitors to the area.”
Rob Guthrie, Principal – Landscape Architecture at RPS Australia
Asia Pacific, added, “The trees are growing, and the system is proving
to work well for us. Citygreen were excellent to work with, providing
lots of helpful information on the product and assisting us to convince
council to proceed. I’d absolutely recommend them to others.”
Carless concluded by saying, “So far, the trees are performing well
with minimal leaf drop. We’re confident we’ll continue to see good
growth rates, without any damage to surrounding infrastructure.
Citygreen were great to work with, with helpful technical people who
gave us lots of information, and were really involved leading up to
construction. I couldn’t fault them, and would definitely recommend
them and this solution to other organisations that have a similar
challenges.”
Magnificent growth, with engineered soil vault
beneath road pavement
Excellent canopy after 2.5 years
CASESTUDY
Citygreen®
SPECIFIER UPDATE 7
CASESTUDY

8. One of the City of Calgary’s 2016 urban construction
projects is Thomson Family Park, on 1236 16th Ave
SW. This park, designed by Ground Cubed and EXP
Engineering, replaces a bowling green with a multi-purpose park
aimed at the widest possible neighborhood demographics.
Along 11th St SW is a broad sidewalk, interspersed with street trees.
These trees will grow through beautiful tree grates and pavers, to
provide shade and visual interest along the street.
Living off the street…
These trees are watered by stormwater that’s fed through catch-
basins and a system of distribution pipes into the StrataVault soil
cells. Heavy solids and particulate matter are filtered out in the
catch-basins to protect the trees as much as possible.
Stratavault installation
The soil cells were installed during May 2016, by Alpha Better
Landscaping. The photograph below shows the compacted
subgrade, with the sub-drain running centrally through the tree-pit.
The clean-out for this drain rises through the cells at the end.
Calgary Alberta uses
Strataflow treepits for
coupling Green with Blue
Thomson Park advanced design for healthy trees and stormwater treatment
Image by Ground 3 Landscape Architects | http://www.ground3.com
8 ISSUE 18

9. Stormwater Distribution
Once the base cells were in place and back-filled with soil, the
distribution pipes could be positioned, running along at 2 parallel
locations through the upper level of the cell matrix.
Stratavault offers very broad openings within the cell matrix, so a
200mm/8” pipe is an easy fit through the system, with no need to
remove any part of the cell structure itself.
Image by Ground 3 Landscape Architects | http://www.ground3.com
CASESTUDY
Citygreen®
SPECIFIER UPDATE 9
CASESTUDY

10. Tree Openings
Another very attractive feature of the Stratavault system, is the ability
to maintain its structural integrity whilst removing sections of the cell
matrix. The pictures show how the contractor was able to create
the root-bole openings to match the position of the rectangular
tree-grate frame above. The system is still completely connected
around the opening, thus maintaining its integrity, and exceeding
the loading standards for downtown Calgary sidewalks.
Thomson Park will be a wonderfully healthy place to rejuvenate and
relax. But the infrastructure itself will also provide a natural means for
green infrastructure to thrive and beautify the area for generations
to come, while reducing the load on the City of Calgary’s municipal
sewer system.
Surely a Win-Win solution…!
Calgary is building beautiful green spaces, using Strataflow design
10 ISSUE 18

11. Stratacell adds green touch
to urban Sydney cycleway
The final section of Sydney’s much-awaited Kent Street Cycleway
is now open – completing a planned network of cycleways through
the heart of the city. Used by around 1700 bike riders each weekday,
the completed cycleway means people now have a safe north-south
route between the Sydney Harbour Bridge and Darling Harbour.
Even in inner city, hostile environment -
excellent growth after 2.5 years
The cells provide an ideal solution for the
installation of trees in highly-developed
urban environments where there is not
much room for construction, providing
growing space for trees and their root
systems without damaging pavements.
The support from Citygreen during the
construction process enabled us to
obtain the best outcome.
Trees at planting
CASESTUDY
Citygreen®
SPECIFIER UPDATE 11
CASESTUDY

12. Between Liverpool Street and Druitt Street, the City of
Sydney – asset owner and local government authority
– sought to add some greenery to a primarily urban
setting. Complete Urban was engaged as the landscape architect
and project manager.
Juan Vargas, of Sydney Civil, said, “Design concepts from the
client required the planting of new tree species in an already
established environment. A solution was required to offer room to
the trees to grow but not affect the infrastructure constructed. The
main issue was the presence of underground services and limited
space available for the planting of the trees.”
Porous paving stones for environmental benefit
12 ISSUE 18

13. Citygreen’s Stratacell system was specified as part of the design,
renowned for its ability to provide the soil volume required and
the room for roots to grow without impeding on or damaging
surrounding infrastructure.
Juan Vargas said, “The project was completed successfully. Whilst
the trees are still in a very early growing stage, no issues have
presented. The cells provide an ideal solution for the installation of
trees in highly-developed urban environments where there is not
much room for construction, providing growing space for trees
and their root systems without damaging pavements. The support
from Citygreen during the construction process enabled us to
obtain the best outcome.”
Trees at planting Sept 2014, compare growth illustrated in
images from 2.5 years later
Ultra-high strength Stratacell 60 system
for intesive loading situations.
CASESTUDY
Citygreen®
SPECIFIER UPDATE 13
CASESTUDYCASESTUDY

14. An urban environment rich with trees is highly valued
for its aesthetic qualities as well as its environmental
benefits, such as reducing summer cooling costs,
carbon sequestration, intercepting airborne pollutants, reducing
storm water runoff and promote habitats for native wildlife. In
the United States, urban forests are estimated to contain about
3.8 billion trees, with an estimated structural asset value of $2.4
trillion (Nowak et al. 2002). Billions of federal, local and private
dollars are being spent annually on management, labor, and the
trees themselves as part of tree revitalization projects, and millions
more are being spent by individual homeowners to improve
their environment and property values. An important criterion for
selecting trees to be planted is diversity: biodiversity and genetic
diversity. Researchers of urban forestry refer to urban biodiversity
as the 10-20-30 rule (Galvin 1999; Santamour 1990).
This rule states that not more than 10% of the urban forest should
be of the same species, no more than 20% should be of the same
genus, and no more than 30% should be of the same family.
Genetic diversity refers to the diversity or genetic variability within
a species. Each individual species possesses genes which are the
source of its own unique features. Similary, human beings are all
the same species but we all look different from each other. A lack
of genetic diversity in individual species of trees reduces the genes
available; as a result, unique features of the species are no longer
present, even its resistance to diseases and thereforeindividuals
looks alike. Genetic diversity is epically important for trees because
of their long live spans and the unpredictability of future pests,
pathogens, climate, and environmental quality. By selecting tree
composition for the maximum biodiversity and genetic diversity,
the trees will have a greater chance of surviving for longer periods.
Unfortunately, the last few decades have seen a movement in
the opposite direction: cultivation in order to achieve uniformity.
Recently, some biodiversity measures have been implemented;
however, despite this multi-billion dollar urban tree economy , little
work has been done to understand urban tree genetic diversity
as an issue of vulnerability, or to examine the long-term impacts
of urban tree genetic diversity on the sustainability of the urban
environment.
Work conducted by Cynthia Morton, PhD and Phil Gruszka, in
2008, compared the level of genetic variation in London Plane
trees already existing in the Pittsburgh area with trees of the same
species currently available from three commercial nurseries. The
genetic diversity was far greater in the older urban tree samples
compared to that of the nursery samples, indicating that the
nursery industry has been selectively cloning to produce new
trees. While cloning trees is in itself a benign practice, doing so on
a mass scale without a proper understanding of the implications
of drastically reducing the genetic diversity of urban forests is ill-
advised and potentially creating an area for natural disaster.
Conservation of our Urban
Forest Health and Sustainability
via Tree Genetic Diversity
by Cynthia Morton and Phil Gruszka
14 ISSUE 18

15. EBOOK
Morton and Gruszka’s initial research led to enquiries for
information about other commonly-grown nursery tree species
and cultivars. The paper entitled “Popularity of tree species and
cultivars in the United States” (Nowak 1992 and updated in 2006)
lists the top ten species sold by nurseries in the United States and
in which major geographic region they are sold. Almost all (eight of
the top 10) of these nursery stock trees are grown throughout the
United States and not just in one or two regions.
In early 2010, Dr. Morton conducted a telephone survey
throughout the U.S. and discovered that most regional nurseries
buy from wholesale growers located in Washington and Oregon.
After this telephone survey was completed, Dr. Morton contacted
the wholesale nurseries in Washington and Oregon and asked
how 5 of the top 10 species of trees were grown. Their response
indicated that almost all were cloned. We can conclude, then,
that selective cloning to produce new trees is currently a common
practice for most nurseries across the United States.
The Morton and Gruszka study found that the genetic diversity was
greater in the older urban tree samples compared to that of the
nursery samples. The existing older urban trees are approximately
100 years old and were originally planted from seeds or seedlings,
representing decades of natural testing for resistance. Clearly,
existing older urban trees are a great resource for increasing
nursery diversity.
Some local groups, such as Tree Pittsburgh have begun growing
trees from seed, but a much larger effort will be required to change
the availability of such trees on a scale needed to supply the entire
country.
Lohr (2013) conduct a survey on plant diversity distributed to
wholesale nurseries in Washington State which showed that most
respondents were aware of the issues, but lacked an in-depth
understanding of them. The respondents reported that lack of
consumer demand was an issue. Those with more education
exhibited a deeper understanding of the risks from low diversity
among landscape plants. In summary, Lohr found that more
education is needed for people in the green industries on why
biodiversity and genetic diversity among landscape plants are
vital.
Morton has sought funding from several federal agencies for a
project that would share cuttings and seeds from tested genetically
diverse hardwoods with nurseries for the development of new and
hardier cultivars. Several large nursery have even written letters
of support for this research, but so far no funding has emerged.
A greater understanding of urban tree genetic diversity will allow
policy makers, city planning and environmental agencies, and the
nursery industry to make informed decisions and recommendations
to improve practices for maintaining a robust tree landscape for
the future.
References:
Bakys, R., Vasaitis, R., Barklund, O., Ihrmark, K., and Stenlid, J.
2009. Investigations concerning the role of Chalara fraxinea in
declining Fraxinus excelsior. Plant Pathol. 58(2):284–292.
Lohr. V.I. 2013. Diversity in Landscape Plantings: Broader
Understanding and More Teaching Needed. HortTechnology.
23:126-129
Morton, C.M. and Gruszka, P. 2008. AFLP assessment of genetic
variability in old vs. new london plane trees (Platanus × acerfolia)
J. Hort. Sci. Biotechnol.83(4):532–537.
Nowak, D.J. and D.T. Sydnor. 1992. Popularity of tree species and
cultivars in the United States. Gen. Tech. Rep. NE-166. Radnor,
PA: U.S. Department of Agriculture, Forest Service, Northeastern
Forest
Experiment Station. 44p.
Nowak, D.J., D.E. Crane and J.F. Dwyer. 2002. Compensatory
value of urban trees in the United States. Journal of Arboriculture
24:194-199.
Poland, T.M. and McCullough, D.G. 2006. Emerald ash borer:
Invasion of the urban forest and the threat to North America’s ash
resource. J. For.104(3):118–124.
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SPECIFIER UPDATE 15

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