INITIAL RESULTS FROM A LONG TERM STUDY OF THE EFFECTS OF ROOT DAMAGE ON STREET TREES

1. 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 brian g. crane 2014 brian g. crane 2013

2. 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’ ? brian g. crane 2014

3. THE ARBORICULTURIST’S BIG QUESTION We know a lot about how the aerial parts function – because we can see them working and measure what’s happening But what’s happening here? brian g. crane 2014

4. 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 brian g. crane 2014

5. Project Outline and Timings 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 Full re-survey of aerial parts. Analysis of data brian g. crane 2014

6. 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 brian g. crane 2014

7. Approximately 100 trees removed. Cable installation company paid £250,000 GBP compensation .....and agreed planting of 3 trees for every one removed 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. brian g. crane 2014

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9. Moisture SOIL !!!! Yum!!!! Pore spaces Minerals Tree soil brian g. crane 2014

10. Welcome! To the (Urban) Landscape Below Ground!!!!!! brian g. crane 2014

11. LONDON BOROUGH OF HAVERING Outer London Borough Main period of development in surveyed areas – inter-war Main areas surveyed: Romford Hornchurch Harold Hill Elm Park brian g. crane 2014

12. 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 brian g. crane 2014

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14. 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). brian g. crane 2014

15. Dated: 2003 brian g. crane 2014

16. 1994 SURVEY brian g. crane 2014

17. 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. 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. 2013 SURVEY Applies to both tree AND each root Necessary to upload tree location data without GPS locations and add these later brian g. crane 2014

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19. ROOT DAMAGE MATRIX Complete spreadsheet 4414 lines, 67 columns brian g. crane 2014

20. ROOT DAMAGE MATRIX brian g. crane 2013

21. DATA HANDLING Tilia x europaea planted in mid 1800s. Roots cut down to about 1 metre depth in 1970s. Tree still growing with good vigour • 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 brian g. crane 2014

22. SPECIES BREAKDOWN Acer Tilia brian g. crane 2014

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27. THIS BOROUGH DOES NOT HAVE A PUBLISHED TREE OR URBAN FORESTRY STRATEGY brian g. crane 2014

28. Mature Acer pseudoplatanus. Roots cut down to about 1 metre depth for theatre car-parking in 1970s. Tree still growing with good vigour • 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 • Development brian g. crane 2014

29. Overall results – Missing trees have been adjusted to show effects of vehicle crossovers and ‘abiotic’ removals brian g. crane 2014

30. Differences in losses between smaller, short-lived and larger, longer-lived genera brian g. crane 2014

31. TO SHOW AVERAGE d.b.h. INCREASE BETWEEN 1994 AND 2013 d.b.h. centimetres brian g. crane 2014

32. Control/non-control tree survival – adjusted by subtracting ‘crossovers’ from ‘missing’ totals. brian g. crane 2014

33. To show losses expressed as % age of each damage grouping Percentage Average %age loss over all damage ranges %age loss - control trees brian g. crane 2014

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35. Extremely heavy damage Very heavy damage Heavy damage Moderate damage Light damage brian g. crane 2014

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37. 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 brian g. crane 2014

38. 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 brian g. crane 2014

39. THE END Thank you for your attention brian g. crane 2014