Arboricultural Assessment and Report.

Transcription

1 1 Eric Ave BLACK FOREST 5035 ABN: Phone: Mobile: Fax: treeaware@bigpond.com Arboricultural Assessment and Report. Prepared for Mr. & Mrs. W. Tait Site located at 7 James Street, Clarence Park SA 5034 Regarding Significant Tree: Schinus molle var areira: Pepper Tree Prepared by Andrew Nichols Adv Dip Arb, Adv Dip Hort. Page 1/17

2 1 Eric Ave BLACK FOREST 5035 ABN: Phone: Mobile: Fax: treeaware@bigpond.com CONTENTS Page No. 1.0 Executive Summary Introduction Terms of Reference Limitations & Constraints (Caveat Emptor) The Site The Tree: Schinus molle var areira: Pepper Tree Tree Discussion Hazard Assessment Legislative Requirements Recommendations 14 Appendix A: Site Plan 15 Appendix B: References 16 Appendix C: Limitations and Disclaimer 17 Page 2/17

3 1.0 EXECUTIVE SUMMARY 1.1 This report describes the inspection and hazard assessment of the Schinus molle var areira: Pepper Tree located at the rear of the property at 7 James Street, Clarence Park owned by Mr. & Mrs. W. Tait and Family. 1.2 It has been proposed to redevelop the property by partial demolition of the existing lean-to at the rear of the dwelling and construction of an addition. 1.3 It has been observed that the tree is suffering advanced decline and senescence. The main leader is almost completely dead and many lateral branches display thin, sparse and pale foliage. 1.4 There are many large burls on the main stem. Generally, burls or burrs (however formed) do not pose treats to trees. However in this situation, the accumulation of many large burls around and within the main stem union has created a potential for compromise to the structural stability of the main union. 1.5 It has been determined that the trees safe useful life expectancy is less than 15 years and the remedial options for the tree are severely limited, problematic and unsustainable and as such, felling and removal appears warranted prior to the commencement of development. 1.6 Due to the fact that the tree is classified as a significant tree under the legislation contained within the SA Development Act 1993, it is a requirement of the Development Regulations that an application be submitted to the Unley City Council prior to undertaking any works, to seek approval for the felling of the tree. This report may be submitted along with the Development Application. 2.0 INTRODUCTION 2.1 The results of the inspection of both the site and tree are presented. A brief assessment of the current condition of the tree is made, the findings of the inspection are interpreted, and the best course of action to pursue to abate any problems identified is recommended. 2.2 The report provides a brief description of the tree, including an accurate circumference when measured at one metre above ground level, the approximate height and radius crown spread (measured at the widest point). 2.3 The recommendations made take into consideration the comments and the location of the tree, and provide an overall hazard rating. 2.4 The hazard rating provided is used to prioritise the works identified in the recommendations. 3.0 TERMS OF REFERENCE 3.1 Written and verbal instructions were received on the 11 th March The instructions requested a report on the condition of the tree identified growing in the centre of the rear garden of the property situated at 7 James Street, Clarence Park. 3.3 The clients are concerned about the rapidly declining condition of the tree. As they proposed to redevelop the site, their request includes that a determination of the Safe Useful Life Expectancy (SULE) of the tree be made. 3.4 The instructions also request: An assessment of the tree's characteristics and physiology. Page 3/17

4 3.4.2 An assessment of the condition of the tree An assessment of any factors that may be influencing the tree's health or stability An analysis of the hazard presented by the tree and failure potential of the tree or any part of it Recommendations for any action required to manage the tree. 4.0 CAVEAT EMPTOR 4.1 This is a stage 1 'Ground report'. The tree was inspected from the ground only. A climbing inspection was not performed. 4.2 The report is limited by the time of the inspection. The inspection was conducted in March at the time of new bark formation in the phenological period. (Growth Cycle) 4.3 The report reflects the tree as found on the day of inspection. Any changes to site conditions or surroundings, such as construction works or landscape works, may alter the findings of the report. 4.4 The report is based on the inspection and the material available at the time of inspection. 4.5 No soil samples were taken for laboratory analysis. 4.6 The inspection period to which this report applies is two months from the date of the report. 4.7 The roots were not inspected below ground. 5.0 THE SITE 5.1 Refer to the site plan (Appendix A). 5.2 The tree is surrounded on all sides by open soil and is located in the centre of the rear garden. It is approximately 9.5 metres east of the rear of the dwelling. (see Figure 1) Figure 1 shows the tree at the rear of the dwelling when viewed from the west. Page 4/17

5 5.3 James Street is located in the suburb of Clarence Park within the Council boundaries of the City of Unley which in turn is located in the south-eastern suburbs of Adelaide; being approximately 5 Kms south east of the Adelaide Central Business District. 5.4 The local tree character is of small to large sized trees with exotic and native species represented. 6.0 THE TREE 6.1 Schinus molle var areira: Pepper Tree 6.2 The tree is an over-mature/senescent Pepper Tree approximately 16 metres tall, with a stem circumference of approximately 3.84 metres (when measured at 1 metre above ground level). The crown spread was approximately 10 metres radius to north, south, east and west giving the tree a symmetric rounded shape and form. (see figure 2). 6.3 Roots Figure 2 shows the tree in the rear garden when viewed from the south. Note the dead central leader. (Highlighted) There are no surface roots visible, however it should be expected that a tree of this age and size would have developed an extensive root system that may occupy all available space on this property and extend onto the properties to the north and east There is no major evidence of damage to structures by root intrusion but I am informed by the Client that some significant cracks have developed in the internal walls of the eastern side of the dwelling adjacent to the tree. It is not clear if the tree is responsible for these cracks but as trees contribute to soil drying, it may be possible. (Engineering advice should be sort to confirm this assertion. Page 5/17

6 6.3.3 A strip of brick paving is located adjacent to the dwelling and it is observed that some of the pavers are lifted and kinked. I did not lift the pavers but it is suspected that tree roots may be responsible for this minor damage and it does indicate the potential spread of the trees root system. (see Figure 3) 6.4 Butt and Stem Figure 3 shows the kinked pavers within the path at the rear of the dwelling adjacent to the tree The substantial main stem rises as a single trunk from the ground to a point approximately 2.2 metres above ground level from where it divides with 3 main stems resulting. The northern stem rises a further 3 metre from where it divides again A large diameter horizontal branch emanates from the northern side of the tree and is oriented to the north-west over the dwelling. Another large diameter branch extends over the shed to the south The main stem union is surrounded by large irregular shaped burls or burrs with one large pronouncement emanating from the base of the union. (see Figures 4 & 4a) The scaffold system and crown are predicated on this union. Figures 4 & 4a show the large burl pronouncements surrounding and within the main stem union. Page 6/17

7 6.4.4 There are other large burls situated in various locations on the main stem and scaffold branches. (see Figures 4b & 4c) Figures 4b & 4c show other examples of burls on the main stem and scaffold branch unions The significance of these woody excrescent growths are discussed within Section 7.0; Tree Discussion Some small emanations of epicormic regrowth are noted in various locations over the main stem and scaffold system. This regrowth is also in very poor condition with thinning foliage and masses of dead twigs present. 6.5 Crown The foliage within the crown is generally very pale, thin and very sparse. The large amount of foliage on the ground indicates that defoliation has been sudden and rapid. Indeed, it appears every portion of the crown has been affected. In some areas the foliage is completely absent and on other branches it is still reasonable dense. The image below shows a silhouette of the branch to the south. It is obvious that the foliage is very thin. In good health, it would not be possible to see through the crown at all. (see Figure 5) Figure 5 shows the branch to the south and it is obvious that the foliage density is well below average. Page 7/17

8 6.5.2 There is evidence of branch dieback through out the crown. Of most concern is the main central leader which is almost completely dead.(see Figure 5a) 7.0 TREE DISCUSSION Figure 5a shows the apex of the main central leader. It is observed that it is almost completely dead. 7.1 There are a number of serious issues associated with this specimen that require further detailed explanation. They concern the trees advanced age and its senescent nature and its Safe Useful Life Expectancy, the implication for structural stability of the main stem union caused by the large burls adjacent and the ineffectiveness of remedial options. Each of these is discussed in turn with a short summary at the end of each section Age & Senescence The natural law that is most important to sustain life is the Second Law of Thermodynamics or energy flow, which states that no system will remain orderly, or survive, unless it receives a continuous supply of energy In animals, aging means that the individual loses its ability to replace damaged tissues. But as a tree ages, it loses its ability to feed and protect the tissues where it stores energy; the tree sheds the parts that are most vulnerable Dr Alex Shigo differentiates betweens trees dynamic mass and static mass. The dynamic mass of a tree is the sum of all the parts that are alive and participating in the capture (photosynthesis) or storage of energy. The static mass is the remainder of the tree, which does not pay its own way and must be protected by living tissue The balance between dynamic and static mass constantly shifts, starting out with little or no static mass in the tree s youth, and Page 8/17

9 ending with very little else. Not only the leaves, but also the bark of a seedling contain chlorophyll, and take part in converting the energy of sunlight into sugar. Practically all the wood cells in the young stem and twigs are alive, so they contain starch granules when extra energy is available. Starch is the only product made from sugar that can be converted back into sugar, to be transported and used As a tree ages, the outer bark and the earliest wood cells (covered over by more recent layers) lose their vitality and die, becoming part of the tree s growing static mass. As long as the dynamic mass can protect it from injury and decay, no-living wood serves as the tree s flexible skeleton. But as the tree ages, it loses its ability to protect all of its static mass. Like dead leaves, dead twigs are easily shed: and often the tree is able to keep decay out of its trunk and large branches by shedding smaller branches that have died. But eventually every tree reaches a point where its rent is more than its income and the tree perishes This Second Law process also has implication for management of older trees. With young trees that have a dynamic mass ratio of 1:1, they can easily tolerate removal of static mass without seriously disrupting the Second Law since enough energy remains to keep the parts and process of the tree system orderly. As trees grow and age, however, the inner and oldest living cells begin to die, and nitrogenous substances move outward toward the cambial zone into the still living cells. When loss of branches occurs by pruning living branches, all of the nitrogenous substances are instantly lost and there is limited or simply not enough energy left to maintain strong defenses, opening the tree to attack by pathogens. The energy reserves of the tree are lost by pruning live tissue In summary, this particular tree has reached a point in its life cycle when it is rapidly approaching a situation of complete loss of dynamic mass. This is shown by the large dead central leader and the overall thinning foliage and branch tip dieback within the crown. Pruning would not assist at all and in fact would certainly accelerate the trees demise by removing remaining parts of the tree that produce energy (ie leaves/dynamic mass) Safe Useful Life Expectancy (SULE) (Barrell-1995) The information derived from the visual inspection of the tree is used to determine the SULE rating. This rating gives an estimate of the expected life span of the tree and takes into account age, life span of the species, local environmental conditions, location, and tree safety. The SULE rating is an assessment of the tree at the time of inspection. This rating may change due to local environmental changes or extreme occurrences such as a storm. Safe Useful Life Expectancy (S.U.L.E.) table. The Pepper tree rating is in Red Category Description 1 Long, life span greater than 40 years 2 Medium, life span from 15 to 40 years 3 Short, life span from 5 to 15 years 4 Remove, should be removed within 5 years 5 Small, Young or regularly pruned, trees that can be readily moved or replaced Unstable Showing imminent signs of structural failure, unstable in the ground, significant trunk damage rendering the tree structurally hazardous Page 9/17

10 In summary, the Safe Useful Life Expectancy of this tree is assessed as: 3; Short life span of 5-15 years. This rating reflects this trees advanced decline and senescence Worthiness for retention on a potential development site The goal of tree preservation or retention is to have trees remain assets to the site for many years to come. It is considered unviable to adapt designs and make allowances for trees that have short life spans or are diseased or structurally compromised. Trees that are selected for retention on construction site should be determined that they will survive construction impacts, adapt to the new environment and continue to perform well in the landscape An assessment of suitability for retention of individual trees is based on tree health, structure, age and species factors. The suitability for retention is expressed as a rating of poor, moderate or good Good = Tree in good health and structural stability that has potential for longevity on the site Moderate = Tree with fair health and/or structural defects that can be abated with treatment: tree will require more intense management and monitoring and may have shorter life span than those in good category Poor = Trees in poor condition or with significant defects that cannot be mitigated; Tree is expected to continue to decline, regardless of reasonable treatments; the species or individual may have characteristics undesirable for landscapes and is generally unsuitable for use areas Mature and over-mature trees are less able to tolerate construction impacts and remain assets than young semi-mature individuals The worthiness of a particular tree for retention also uses the SULE rating as a determining factor It has been concluded that this particular specimen has a poor rating and is unsuitable for retention on a potential development site due to its short life span Burls or Burrs and their structural implications As shown in Section the main stem, scaffold system and some branches of the Pepper Tree are affected by Burls or Burrs. These Burls are a characteristic of this species but I must say I have not seen them so densely arranged or with such contorted shapes and forms. The bracket like formations are very unusual indeed A burl is described as a sound, hard, woody excrescence or protuberance that forms on the bole or branch of trees of nearly all species. It is more or less rounded or horizontally ridged, with no protruding limbs, twigs, stubs or indicators thereof. It is a product of vastly multiplied cell division and growth at point of occurrence, the wood is characterized by wildly contorted grain which may be combined with "bird's eye" - the result of aborted adventitious buds. A true burl is a surface indication that the grain in the wood is contorted into a wavy, curly, or bird's-eye effect- Page 10/17

11 both within the burl and in the immediately surrounding stem wood. (see Figure 6) Burls are considered as a degrader in factory and construction timber logs. Figure 6 shows a cross-section of a burl from a Larch. Note the irregular, random and distorted cell formation. (Hardwood Defects, Howbuck) Burls generally do not represent a major defect however the number and location of them on this Pepper Tree does give rise for concern. With so many large burls accumulated around and within the main stem union it should be expected that some structural defect has developed in this region. There is potential for these burls in this location to have compromised the structural stability or integrity of the main stem union, given their contorted and random nature that does also affect the wood immediately surrounding them. There are no remedial options for this condition Remedial Options There are very few remedial options that will return a senescent tree to good health particularly in this case, as the main leader of the tree is already, almost completely dead. It is my opinion that the only options would be to manage the trees decline to keep it safe until it finally perishes. This process is known as Veteran Tree Management. VTM acknowledges that the tree is at full dynamic/static ratio and mimics the trees natural reduction of its architecture. Here is a brief outline of the principle and practices of Veteran Tree Management Senescence is a normal stage in the trees life cycle. As the tree ages it goes through a process of reducing its mass to allow the reducing energy levels to provide for a smaller more compact tree. This is typical tree architecture shown by ageing trees The works possible with regard to this tree would be to implement an innovative pruning program. The pruning would require the removal of a large percentage of the upper canopy including the dead central leader in line with veteran tree management principles This type of pruning is undertaken with the view to retain and prolong the ultimate life span of the tree whilst reducing its potential to continue to decline and ultimately reduce their potential to drop large limbs. Page 11/17

12 The principle associated with veteran tree management is to preempt what the tree will ultimately try and achieve through natural processes. Over mature trees start the process of old age by slowly reducing their ultimate size by closing down the branch extremities, and producing epicormic growth on the large lateral and scaffold branches closer to the main stem. This allows the trees to reduce the size of their mass thus reducing the amount of energy required to maintain the entire tree system The onset of the decline being shown by the tree (i.e. dying central leader) could be due to a number of factors, most of which will be abiotic, such as natural aging The purpose of veteran tree management is to reduce the large lateral limbs and leaders to an extent and form that can be both adequately managed in the future, and which reduces the potential for large limb failure. If the tree is retained in its current form it will inevitably shed limbs as the decline advances. If the tree retains its current shape and form with long over-extended horizontal limbs any failure could have a significant impact on the targets surrounding it, and ultimately cause significant damage to the tree The potential pruning would aim to reduce the tree to a range of framework branches that accurately reflect the current shape and form of their branching structure. One of the variables that also needs to be considered when pruning is the trees ability to respond and produce new growth. Given the current changes to climatic conditions and the trees advanced state of decline, it would it be unreasonable to expect the tree to respond well It is my opinion that the tree may not have sufficient energy to produce quality epicormic regrowth required to reform the tree crown It is my belief that, as the radical crown reduction required by Veteran Tree Management techniques would destroy the visual notability and amenity of the tree forever and would not reduce the Critical Root Zone, options and rational for Veteran Tree Management are not substantiated in this case The effects of long term drought are also a factor in declining condition. 7.2 Summary of Tree Discussion The tree is an over-mature (senescent) specimen and is in advance decline The tree has a less than 15 year safe useful life span and as such is not worthy of long term retention on the site There are no reasonable remedial options that would allow for the safe retention of the tree. 8.0 HAZARD ASSESSMENT 8.1 A hazard situation requires a tree with a potential to fail, and a target that would be hit if the tree fails to be abated by pruning, removal or other remedial action. A target can be for example, people, vehicles, a structure or animals. 8.2 Targets present: Residential site constantly occupied. Page 12/17

13 8.2.2 Shed and dwelling on the property to the south and west. 8.3 HAZARD RATING Failure potential of the tree, on a scale of 1 (low) to 4 (severe), within the inspection period of the report. 3 High: due to the presence of dying, central main leader and the burls surrounding and within the main stem union Size of part most likely to fail, on a scale of 1 (small) to 4 (large) 3 45cm-75cm: the large diameter central leader and dead wood Target rating of the tree, on a scale of 1 (low) to 4 (severe), within the inspection period of the report. 4 Constant use: The property is constantly occupied. Children use the area to play in. This results in a hazard rating of 10, which is a moderately high score that shows problems with the tree and identifies that abatement of hazards is required. 9.0 LEGISLATIVE REQUIREMENTS 9.1 The tree is a single-stemmed specimen with a stem circumference greater than 2 metres when measured at 1 metre above ground level, therefore fulfilling the criteria contained within section 6A (a) of the Development Regulations 1993, which declares that in the case of trees with a single trunk, that have a trunk circumference of 2.0 metres or more, when measured at a point 1.0 metres above natural ground level are declared as significant trees for the purposes of paragraph (a) of the definition of "significant tree" in section 4(1) of the Development Act Therefore the tree can be declared as significant under the legislation. 9.2 The most appropriate course of action to abate the defects, hazards and short life expectancy identified for the Pepper Tree is felling and removal. This work CANNOT be undertaken without first acquiring consent from the Unley City Council. 9.3 The following points are made in relation to the principles of development control under the significant tree legislation contained within Section 23 (4a)(a)(b) of the Development Act 1993, Part 2 section 6A of the Development Regulations 1993 and refers specifically to Section 177 and 179(a) of the Unley (City) Development Plan consolidated 11 th May The tree is not listed on Table Un/7 of the Unley City Development Plan. Section Definition Findings S177 (a) S318 (b) S318 (c) Does the tree make an important contribution to the character or amenity of the local area? Does the tree form a notable visual element to the landscape of the local area? Does the tree contribute to the habitat value of an area individually or provide links to other vegetation which forms a wildlife corridor? No- due to the very poor condition and rapid decline of the tree it does not make an important contribution to the character or amenity of the local area. No- the tree is not a notable visual element within the landscape as the poor condition of the visible parts of the crown are dominant. No- as a non native tree it does not contribute to habitat value for native fauna. As part of a wider grouping of trees on surrounding properties it may however, provide links to other vegetation that forms a wildlife corridor. Page 13/17

14 S320(a) S320(a)(i) S320(a)(ii) S320(a)iii) S320(a)iv) Significant trees should be preserved and tree-damaging activity should not be undertaken unless: In the case of tree removal. The tree is diseased and its life expectancy is short. The tree represents an unacceptable risk to public or private safety. The tree is shown to be causing or threatening to cause, substantial damage to a substantial building or structure of value. Has it been demonstrated that all reasonable alternative development options and design solutions have been considered to prevent substantial tree-damaging activities occurring? Yes- the tree is assessed as senescent and in decline. It life expectancy is less than 15 years even with costly management. Yes the hazards associated with tree are related to the dead central leader and the potential comprise of the main stem union by multiple burls. Dead wood is considered as a defect due to the ease and unpredictable nature of dislodgement. Yes- there is evidence (cracks in internal walls and disturbed paving) that suggest that the tree may threaten a structure of value. Yes- There is no cost effective techniques or approved methods that will allow long term retention of this dying tree. 9.4 IMPORTANT a development application must be submitted to Unley City Council to seek development consent for the works identified in the recommendations prior to commencement of works RECOMMENDATION 10.1 Having given consideration to all the issues associated with the Pepper Tree, it is my opinion that medium to long term retention is not viable; therefore the tree should be felled and removed prior to redevelopment of the site There would be ample opportunity to replace this tree in a new location within the rear garden once development is complete. There would be sufficient space to enable a tree species of medium height to be replanted. The tree species should be selected to provide a tree that has potential to become a significant tree in the future. It may even be possible to place a Tree Protection and Retention condition on this new tree to ensure its longevity. Andrew Nichols Adv Dip Arb, Adv Dip Hort Arborist Page 14/17

15 APPENDIX A: SITE PLAN (provided by applicant) Schinus molle var areira Pepper Tree Garage and workshop APPENDIX B: REFERENCES Page 15/17

16 Mattheck, C. & Breloer, H. (1994) The Body Language of Trees a handbook for failure analysis HMSO, London. The Development Act (1993) South Australian Legislation. The Development Regulations (1993) South Australian Legislation Unley (City) Development Plan Consolidated 11 th May 2006 Australian Standards 4373 Pruning amenity trees Matheny, N.P: & Clark, J.R (1994) Evaluation of Hazard Trees in Urban Areas. ISA Publications. Matheny, N.P: & Clark, J.R (1998) Trees and Development; A technical Guide to the Preservation of Trees During Land Development. ISA Publications Barrell Jeremy (1995) Safe Useful Life Expectancy Harris, R.W. Clark, J.R. & Matheny, N.P. (2004) Arboriculture: Integrated Management of Landscape Trees, Shrubs and Vines. Prentice Hall Shigo A. (1991) Modern Arboriculture; A Systems Approach to the Care of Trees. Page 16/17

17 APPENDIX C: DISCLAIMER AND LIMITATIONS This report only covers identifiable defects present at the time of inspection. The author accepts no responsibility or can be held liable for any structural defect or unforseen event/situation that may occur after the time of inspection, unless clearly specified timescales are detailed within the report. The author cannot guarantee trees contained within this report will be structurally sound under all circumstances, and cannot guarantee that the recommendations made will categorically result in the tree being made safe. Unless specifically mentioned this report will only be concerned with above ground inspections, that will be undertaken visually from ground level. Trees are living organisms and as such cannot be classified as safe under any circumstances. The recommendations are made on the basis of what can be reasonably identified at the time of inspection therefore the author accepts no liability for any recommendations made. Care has been taken to obtain all information from reliable sources. All data has been verified insofar as possible; however, the author can neither guarantee nor be responsible for the accuracy of information provided by others. END OF DOCUMENT Page 17/17