brian g. crane 2013 initial results from a long term study of the effects of root damage on street...
TRANSCRIPT
brian g. crane 2013
INITIAL RESULTS
FROM A LONG TERM STUDY
OF THE EFFECTS OF
ROOT DAMAGE ON
STREET TREES
European Conference of Arboriculture
Planning the green city: relationships between trees and
infrastructures
Turin 26th-28th May 2014
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A THOUGHT
A layman, a mathematician and a scientist are driving through Wales. They see a black sheep:
‘Look’, says the layman, ‘the sheep in Wales are black’
‘No’, says the mathematician, ‘in Wales there is one black sheep’
‘Not so’, says the scientist ‘in Wales, there is a sheep – we know half of it is black’
?
THE ARBORICULTURIST’S BIG QUESTION
But what’s happening here?
We know a lot about how the aerial parts function – because we can see them working and measure what’s happening
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HEALTH WARNING!!!
The data in this presentation has been checked, but further validation is required
before finalisation and publication.
Due to the large database, any amendments and the effect they have on figures
is likely to be limited
RESULTS NOT YET FORMALLY PUBLISHED
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Project Outline and Timings
1994 Record root damage to street trees in the London Borough of Havering
2000/1 Follow-up visit collecting limited data – 1994/2001 data transferred to MS Excel spreadsheet
2013 Full re-survey of aerial parts. Analysis of data
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IMPORTANT BECAUSE:
Thought to be the largest assessment of its kind ever carried out:
Over the longest period of time
Trees are mature
Subject to urban pressures
Large study population
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FIGURES
1994 – 1,168 trees assessed.
2001 – re-survey – results overtaken by 2013 survey
2013 - 1,061 trees assessed.
Period of Time: early 1994 to June/July 2013.
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Approximately 100 trees removed.
Cable installation company paid £250,000 GBP compensation
.....and agreed planting of 3 trees for every one removed
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SOIL !!!!
Yum!!!!
Pore
spaces
Moisture
Tree soil Minerals
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To the (Urban) Landscape
Below Ground!!!!!!
Welcome!
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LONDON BOROUGH OF HAVERING
Outer London Borough
Main period of development in surveyed areas – inter-war
Main areas surveyed:
RomfordHornchurchHarold HillElm Park
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Original trenches generally about 500 -
650 millimetres deep (350 + millimetres
cover, 100 millimetres pipe diameter
and 100 + millimetres granular levelling
fill).
Re-excavated trenches between 1.4 and
3 metres long
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Rooting depth‘...from numerous studies involving comprehensive root
excavations the indication is that typically as much as 90% of the tree root length occurs in the upper metre of soil’. (Roberts, R., Jackson, N. and Smith, M. 2006 Tree Roots in the Built Environment)
‘Overall temperate broadleaved trees have 82% of their roots in the upper 50 centimetres of soil...’ (Jackson, R.B., Canadell, J., Ehleringer, J.R., Mooney H.A., Sala, O.E. and Schultz, E.D. 1996. A global analysis of root distribution for terrestrial biomes. Oecologica, 389-411).
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Dated: 2003
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1994
SURVEY
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Necessary to upload tree location data without GPS locations and add these later
Crown condition. Almost all the crowns
of existing trees were in good condition.
This was assessed on leaf cover, leaf
size and extension growth.
Almost all the trees had been managed
by heavy crown reduction on a regular
basis. Heavy crown reduction was
assessed as existing when a tree
showed reduction back to cuts of 150
millimetres or more.
Assessment of suitability for
follow-up survey with ground-
searching radar – if woody
plants near enough for roots to
confuse radar, site not selected.
In 46% of eligible sites the street
tree was the only significant
vegetation.
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2013 SURVEY
Applies to both tree AND each
root
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Remarks 1994 Root diameter
Distance from trunk
Depth Root Severed Y/N
Root matrix value
Total weighting
Phone pole adjacent-wires in crown. Adjacent to cross over - Large surface buttress roots.
18 210 15 Y 2 2
Adjacent to cross over - Water pipe between tree street lamp adjacent and Encom trench.
32 250 15 Y 2 2
75 190 20 Y 6 11
16 190 20 Y 2
19 190 15 Y 2
8 190 15 Y 1
8 200 20 Y 0
4 200 5 N 0
Link ID
Road Location Date of Inspection
Species Height Trunk diameter at 1.5 metres
Crown radius
Age
1 Alan Gardens O/S 6/8 18/10/1994 Acer pseudoplatanus
10 44 6 M
2 Alan Gardens O/S 4/2 18/10/1994 Platanus x hispanica
10 80 6 M
3 Alan Gardens Flank of No 1 18/10/1994 Platanus x hispanica
12 55 8 M
3
3
3
3
3
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ROOT DAMAGE MATRIX
Complete spreadsheet 4414 lines, 67 columns
Root diameter
Distance from trunk
Depth Root Severed Y/N
Root matrix value
Total weighting
Weighting class
18 210 15 Y 2 2 VL
32 250 15 Y 2 2 VL
75 190 20 Y 6 11 H
16 190 20 Y 2
19 190 15 Y 2
8 190 15 Y 1
8 200 20 Y 0
4 200 5 N 0
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ROOT DAMAGE MATRIX
Root size (diameter
at cut end)
Overall severed root diameter or numbers
Weighting Total weighting
Weighting class<1
metres from trunk
1 to 1.5 metres from trunk
>1.5 metres from trunk
<9 millimetres
Less than 100 millimetres in total *
1 1 1 1, 2 Very low
<9 millimetres
Between 100 and 500 millimetres in total*
2 4 4 3 to 5 Low
<9 millimetres
Over 500 millimetres in total*
4 2 1 6 to 7 Moderate
10 to 24 millimetres
Per root 3 2 2 8 to 11 High
25 to 49 millimetres
Per root 6 4 2 12 - 21 Very high
50 to 79 millimetres
Per root 10 8 6 >21 Extremely high
80 to 99 millimetres
Per root 12 10 8 C1 if roots present C2 if no roots
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DATA HANDLING
Remove invalid entries (unlocated or misidentified trees, data entries which appeared to be incomplete)
Develop single-line entry for each tree using root damage matrix
Merge spreadsheets
Check continuity of entries
Interrogate data
Sample re-check data with GIS entries
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Tilia x europaea planted in
mid 1800s. Roots cut down to about 1 metre
depth in 1970s. Tree still growing
with good vigour
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AcerAesculusAilanthusBetulaCarpinusCrataegusFagusFraxinusLaburnumMalusPinusPlatanusPrunusPyrusQuercusRobiniaSorbusTilia
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Tilia
Acer
SPECIES BREAKDOWN
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Control 1 (only unsevered roots found)
Control 2 (no roots found)
Extremely heavy
Very heavy
Heavy
Moderate
Light
Very light
7.5%
27.6%
13.8%18.5%
9%
6.2%
10.3%
7.1%
TO SHOW DEGREES OF DAMAGE RECORDED
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THIS BOROUGH DOES NOT HAVE A PUBLISHED TREE OR
URBAN FORESTRY STRATEGY
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FACTORS AFFECTING STREET TREE LOSSES IN URBAN
AREAS
Changing fashions (e.g. replacement of larger species with smaller)
Disease outbreaks – particularly common in monocultures)
Pressure from individual householders
Subsidence claims
Removal of declining stock (overmaturity)
Cost of management
Highway and utility works
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Mature Acer pseudoplatanus. Roots cut
down to about 1 metre
depth for theatre car-parking in
1970s. Tree still growing with good
vigour
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Trees remainingMissing trees (ad-justed)Vehicle crossoversAbiotic removals
Class Number Percentage of total
Trees remaining 696 65.6Missing trees (adjusted)
284 26.7
Vehicle crossovers 77 7.3Abiotic removals 4 0.4
Overall results – Missing trees have been adjusted to show effects of vehicle crossovers and ‘abiotic’ removals
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0
100
200
300
400
500
600
700
800
900
1000
Series1
Class No %
Small trees original population 117
Missing small trees 65 55.6
Large trees original population 935
Missing large trees 286 30.1
Differences in losses between smaller, short-lived and larger, longer-lived genera
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0
10
20
30
40
50
60
Series1
TO SHOW AVERAGE d.b.h. INCREASE BETWEEN 1994 AND 2013
d.b.
h. c
entim
etre
s
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0
100
200
300
400
500
600
700
800
Series1
Class Number PercentageControl trees 363Control trees missing 102 22.9Control trees crossovers 19Non-control trees 698Non-control trees missing 286 32.2Non-control trees crossovers 61
Control/non-control tree survival – adjusted by subtracting ‘crossovers’ from ‘missing’ totals.
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To show losses expressed as % age of each damage grouping
Perc
enta
ge
0
5
10
15
20
25
30
35
40
45
50
Series1
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Average %age loss over all damage
ranges %age loss - control trees
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Extremely heavy damage
Very heavy damage
Heavy damage
Moderate damage
Light damage
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WHERE NOW?
Try to establish reasons for tree removals in localised areas using Freedom of Information Act
Re-check data – interrogate using Access database – increase parameters
Prepare, peer-review and publish full paper
Examine funding for ground-searching radar analysis of selected sites – first attempt to secure funding was unsuccessful
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My sincere thanks to:
David Cutler Professor of Plant Science and Research Fellow, Royal Botanic Gardens, Kew
Francesco Ferrini Professore di Arboricoltura urbana e di Parchi e Giardini, Dipartimento di Ortoflorofrutticoltura - Università di Firenze , Italy
Edward F Gilman Professor, University of Florida, Environmental Horticulture Dept
Tom Smiley Arboricultural Researcher, Bartlett Tree Research Lab, Charlotte NC
Gary Watson Senior Research Scientist Morton Arboretum Adjunct Professor, University of Illinois
Jeremy Barrell Registered Consultant, Arboricultural Association, Chartered Arboriculturist, UK
Dave Shandley Mobile GIS Services, UK
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THE ENDThank you for your attention
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