1Landscape DivisionHighways Department

Hong Kong International Urban Forestry Conference 2020

Acacia Management and BeyondKathy Ng Chief Landscape Architect MLA MSc FHKILA RLA ISA CA ISA TRAQ HKIUD BEAM Pro17 January 2020

This is an abridged version of the original presentation.

Approval from Highways Department (and the original source of photos) have to be obtained for any form of copying, reprinting and reproducing.

2

Government Trees - Urban Areas(exclude Country Parks)

HighwaysDepartment(HyD)

LCSD

around 1.7 million

0.60 M(35%)

ArchSD, WSD, DSD, HD & Others

HyDAround 150 nos.

Stonewall Trees Other departments

.

Note: 1. Data as at March 20192. Source : Controlling Officer’s reply examination of estimates of expenditure, 2018-19, for Special Finance Committee

Chart1

HyD

LCSD

Others

欄1

0.63

0.51

0.53

工作表1

欄2欄1

HyD0.63

LCSD0.51

Others0.53

若要調整圖表資料範圍的大小，請拖曳範圍的右下角。

3

11 km²

Expressways

(total open space in HK - 25 km2)

Slopes

over 10000

HyD SIMAR slopes

+

Highways Department

Chart1

工作表1

欄2欄1

HyD50

LCSD, HD & Others50

若要調整圖表資料範圍的大小，請拖曳範圍的右下角。

4

Urban Forestry

cultivation and management of trees … physiological, sociological and economic well-being of urban society… (Jorgensen, 1970)

…multi-managerial system… wildlife habitats, outdoor recreation opportunities, landscape design, recycling of municipal waste… (Society of American Foresters, 1974)

…longer-term policies and plans for urban tree resources, and is connected to different sectors…

…multidisciplinary …participatory (Konijnendijk et al, 2005)

AcaciaStonewall Trees

Aging trees under stress Eucalyptus

6

Background – Acacia

The Ecology and Biodiversity of Hong Kong (Dudgeon, Corlett, 2004) 7

1950s 2010s Near future

Background - Life cycle of Acacia confusa (台灣相思)

Acacia plantation scheme Senescent stage

• life expectancy is about 50 years

• Health or structural condition of Acacia decline faster at sites with poorer growing condition with shorter life expectancy

• soil erosion control/ vegetation cover

• slope stabilization

• improvement of the fertility of soil

8

Senescent Acacia

May 2018

June 2018

- heavy leaning and poor self-correction

- poor stem taper and high height-to-diameter ratios

- high susceptibility to wind thrown

Declined structural stability

Deteriorating health

9

- high susceptibility to drought, soil compaction and secondary pathogens when injury occurs

Senescent Acacia

10

Low ecological value- exotic species, not provide appropriate fruits for local wildlife

- hinder the natural propagation and growth of native plants - reduction of light, moisture, nutrients and space

- allelopathy

- decline in one-go

Senescent Acacia

Note* Seven typhoons were recorded in 2013 (when compared with four to five in other years) The heaviest annual rainfall record was recorded in 2013 (among 2010 – 2015).

(Source: HyD) Year

HyD’s Maintenance Record on Acacia Removal

35% of all reported tree failure cases - Acacia (Tree Management Office, November 2012)11

Background – Acacia

284 341443

892721

808 863 824

1282

0

200

400

600

800

1000

1200

1400

2010 2011 2012 2013 2014 2015 2016 2017 2018

No. of Acacia trees

12

Objectives

Public Safety Sustainability Biodiversity

Programme Workflow

13

14

1 Planning Ahead

• academia• overseas + local tree experts• Tree Management Office• District Council + public

15

Apple Daily News

2 Prioritization of Risk and Work

16

Acacia tree group survey formPrioritization

Total score

(Moderate priority)

(50-75分)

(Lower priority)(75分)

1.目標評估(Target rating)

2.倒塌風險(Failure potential)

3.樹木大小(Tree size)

4.場地狀況(Site conditions)

5.場地紀錄(Site sensitivity)

Total score 100

2 Prioritization of Risk and Work

3 Implementation

17GEO Technical Guidelines on Landscape Treatment for Slopes

Ilex asprella(梅葉冬青)

Psychotria serpens(蔓九節 )

Psychotria asiatica(山大刀)

Diospyros vaccinioides(小果柿)

Litsea rotundifolia(豺皮樟)

Mallotus paniculatus(白楸)

Sterculia lanceolata(假蘋婆)

Litsea glutinosa(潺槁樹)

Microcos nervosa (布渣葉)

Native trees

Native shrubs and ground covers

Tsing Nam Road, Tsing Yi

18

3 Implementation

Native Planting Schedule (Sample)

Chinese Name Botanical Name Spacing(mm)Trees 餘甘子 Phyllanthus emblica 5000

潤楠 Machilus spp. 5000

豆梨 Pyrus calleryana 5000

桑樹 Morus alba 5000

小果鐵冬青 Ilex rotunda var. microcarpa 5000

假蘋婆 Sterculia lanceolata 5000

大頭茶 Gordonia axillaris 3500Shrubs梅葉冬青 Ilex asprella 500

車輪梅 Rhaphiolepis indica 300

崗菍 Rhodomytus tomentosa 300

野牡丹 Melastoma malabathricum 300

九節 (山大刀) Psychotria asiatica 300

朱砂根 Ardisia crenata 300

梔子 (白蟾) Gardenia jasminoides 300Ground cover腎蕨 Nephrolepis auriculata 200Climber薜荔 Ficus pumila -

Note* Trees in small size (e.g. whips/ light standard trees) will be used to minimize the rootpruning and cost for planting on site

Biodiversity Enhancement

19

3 Implementation

Wong Tai SinPui Man Street

20

3 Implementation – Pilot Scheme

ShatinYuen Chau Kok

21

3 Implementation – Pilot Scheme

22

4 Reuse • Upcycling

23

4 Reuse • Upcycling

24

5 Monitoring, Evaluation and Enhancement

中環蛺蝶Neptis hylas.

珍貴嫵灰蝶Udara dilecta

報喜斑粉蝶Delias pasithoe

蛇目褐蜆蝶Abisara echerius

美鳳蝶Papilio memnon

銀線灰蝶Spindasis lohita

鈕灰蝶Acytolepis puspa

檀方粉蝶Dercas verhuelli

黑邊裙弄蝶Tagiades menaka

白弄蝶Abraximorpha davidii

斑鳳蝶幼蟲Larva of Chilasa clytia

古樓娜灰蝶Nacaduba kurava

白腰文鳥Lonchura striata

珠頸斑鳩Spilopelia chinensis

紅耳鵯Pycnonotus jocosus

戈芬氏鳳頭鸚鵡Cacatua goffiniana

25

5 Monitoring, Evaluation and Enhancement

5 Monitoring, Evaluation and Enhancement

26

Environmental Performance Evaluation and Pathological Assessment of Acacia Slopes

Objectives

• management measures to reduce Acacia failure

• long-term maintenance plan

• strategic replacement planting design

• suitable replacement planting matrix for sustainable management

27

5 Research

Pathological Assessment• Develop sets of parameters for evaluating Acacia slopes→ Determine the needs and priorities for removal of Acacia trees

28

5 Research

Soil Properties Assessment• Collect soil samples→ Analysis and compare data collected from pre-replacement period to post-replacement period

Bird, insect and spider Survey• Conduct surveys on species, biological community found on site→ Determine the effects of replanting on biodiversity at study sites

Microclimate and air quality Assessment• Carbon uptake• Transpirative cooling• Air pollutant update• Air pollutant formation

→ Estimate air quality and climatic effects before and after replanting

29

6 Community Outreach

30

Community

31

Community Bonding

Community

32

Community Bonding

33

Community Bonding

Saw millWood dryer

Correctional Services Department Wood workshop

Community

34

Community Bonding

35

Community Bonding

36

Ecological Corridor Enhancement

Slopes as the ecological corridor - re-connect community + habitatsExisting greenery

HyD Registered Slopes

Node of connection

Mapping of greenery area and HyD SIMAR slopes in Tseung Kwan O

Seasonal distribution, size and type of fruits

(Source: Hong Kong Wildtracks, HKBU library)

Examples of bird species in Tseung Kwan O District

Wildlife habitats + major flows of pedestrians and cyclists

Blow-up Scenario 1 -Tunnel junction

Blow-up Scenario 2 –Along cycling and pedestrian path

Site photos of existing situation

Managing large tree quantity + aging treesover 80% tree over 5m

Proactive Urban Forestry Management- new technology –satellite/aerial photos, VIS, MMS, UAV, LiDAR

• inspection• data collection• analysis • proactive measures• feedback + monitoring

41

UAV inspection of Eucalyptus Tuen Mun Road

Tree Location Survey

Tree Attribute

Survey

Tree Tagging Service

Tree Database

42

43

44

Trial Application

January 2017

March 2018

Tree Health Tracking

January 2017

March 2018

Tree Health Tracking

45

Ultimate Goal

MULTISPECTRAL IMAGESLiDARHYPERSPECTRAL SIGNATURE

AI EARLY WARNINGSYSTEM

HEALTH

DETECTION

Vision

46Thank you

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