Technical Feature

  • Home
  • Technical Feature
Tree Care And The Ecovillage Movement

Anybody who knows my work knows I have a great love for the organic grass roots arboricultural projects, that lead into quality arboricultural articles, and into further projects and education to be shared.

Following a request from AA to contribute with feature articles, I see this as an opportunity and this article, my last technical report based feature – heralds the birth of my working as a Conservation Arborist in support of the growing global Ecovillage movement. A movement that I see as the start of a golden age in promoting arboriculture as we start to move away from tree processing into tree culture or Arboriculture.

Now that I am living in an Ecovillage personally, I see the Ecovillage movement as being a catalyst for conservation arboriculture; from a business perspective, with myself at the helm of the Naturaculture Network, I am using this report and project as an educational opportunity for Australian Arboriculture – this is to be discussed in Part 2.

Having recently completed the following professional arboricultural report for Crystal Waters Ecovillage – Crystal Waters Community Trees Report – ‘The Trees on the Green’ – published October 7, 2019, I am running this technical report as a prelude to Part 2 which will also be published in a national Australian Ecovillage community publication. This is an edited version of the original report which can be seen at https:// bit.ly/33qSELo

My goal is to seed Arboricultural values in the global Ecovillage movement which places tree and land care higher in their valuing process than most private or government organisations (bar perhaps Botanic Gardens) that I have experienced. I invite the AA readership to come on this journey with me. In part 2 we will be studying an iconic and ancient community Fig tree as part of the feature article.

Crystal Waters Community Trees Report – The Trees on the Green Following a request from the Landscape Sub Committee for the Crystal Waters Co-op I accepted an unpaid commission to draft this report on the avenue of trees that make up the heart of the Crystal Waters communal area known as the Green.

This report is principally a study on the five main trees that make up the avenue and are of key amenity interest subject to the greatest congregation of people. The report discusses the status of the trees as well as a management plan to integrate new trees over a 40 year window moving forward.

Background – Cassian in the Crystal Waters community

I first came to Crystal Waters in 2009 as a tree inspector working the Energex VTA Program (I helped found the program), when proactively assessing trees likely to fail on to the Electrical High Voltage Network (2007-12 Tin Can Bay to Central West Brisbane).

I returned in 2017 and became a resident where I lived at a number of properties with a number of hosts.

Though I have been moving around the world since then, I regard Crystal Waters as a home and am now part of the growing community passionate about sustainable living. In the long term I wish to invest in CW with a view of keeping a home base. As a qualified professional consulting arborist (30+ years in vegetation management), educator and writer I have been working in S.E. Qld, as a qualified contracting arborist since 1991 and consultant since 2003 (I am currently at Diploma level – Australian Qualifications Framework – Level 5 since 2009 – upgraded to current training package in 2017).

I am a founder member of the Queensland Arboricultural Association (1994+), member, past committee member (1995-98) and past Technical Officer (2014).

There are a total of nine established trees – made up of the Genera Albizia, Tipuana, Grevillea and Jacaranda that make up the treed avenue bisected by the brick pathway known as Bricabrack Lane. The pathway is 83m long by 3m wide, the treed avenue is roughly 110m by 25m.

This is adjacent to a stand of Paulownia trees at the southern end that adjoin the plant nursery area, the Paulowinia trees are in reasonable order following my cleaning them out (dead wood removal) last year (with the ground support of Hayley Buchanan).

The communal hall, deck and cafe is located on the eastern side of the avenue. The gathering of visitors to the Crystal Waters Green is substantially increased on market days (first weekend each month) with a steady flow of locals and visitors attending the Flower pot Cafe, bakery (eastern/western sides of the avenue) and other events. At the northern end of the avenue is the car park and entrance to the Green, another area of focused people gathering.

The reason I have selected the five trees highlighted in Fig. 2 as my key focus is because this is the greatest people traffic area, these trees are the oldest, are the most vulnerable to visitors, with T1, T4 and T5 posing the greatest long term risk to visitors. This is primarily due to stress caused by people pressure (note – all trees are stressed due to decades of soil compaction and biological desertification).

This report is for the CW community, though I have tried to keep it brief – I also intend for it to be published as a Conservation Arboriculture article in The Australian Arbor Age for professional arborists. This report will also be read by professional allied stakeholders (I intend to involve to help fund the avenue’s restoration – the Naturaculture Network), as well as being a future article for other national and global Ecovillages. The content is for both unschooled and professional tree people.

To enable a comprehensive understanding of my recommendations I aim to run an educational power-point presentation (subject to CO-OP approval) on the report to the CW community and will be open to questions to assist this process.

I am in a position to finance the tree restoration process by running a series of workshops (in a similar capacity to Steve Cran’s Permaculture CAP project), hence my interest in drafting this report with a view to project managing this as a Naturaculture project.

Evidence of Genus, Species, Health, Dimensions and Crown Structure – T1 Genus and species.

In the original report is a detailed record on Trees 1-5, in this version the report is briefly summarised.

T1, T3 and T4 – Albizia spp, until flowering time I am unable to get a positive identification on this rare tree (rare in Australia). My own study backed by feedback suggests that this tree is an African species, possibly Albizia amara or Albizia adianthifolia yellow flowered spp), having not seen this tree outside of Crystal waters or in flower, I await flowering time for identification. I am however familiar with this Genus and a number of the local Genera in the family – Fabaceae (Albizia, Caesalpinia, Delonix, Tipuana). The CW trees and African species studied by me online fit the description of being a dominant canopy tree in dry African/Indian deciduous woodland (similar conditions in S.E. Queensland).

T2 – The Rosewood or the Pride of Bolivia – Tipuana tipu from South America is a popular amenity tree with global significance. This tree is regarded as a weed species in Australia and belongs to the same family as the T1 – Fabaceae (https://en.wikipedia.org/wiki/Tipuana).

Observations/Discussion

Background

Discussions with the community indicate that the Avenue was planted in the late ‘80s/early ‘90s placing them at approximately 35-40 years old (since drafting this report leading Permacultural trainer Robin Clayfield confirmed she planted the trees).

When we consider the time frame taken to create the tree cover of Bricabrac Lane avenue it is in all out interests to keep these trees alive and stable for as long as is practically possible. From my perspective with modification to the site the trees lifespans can be extended in the order of decades. I am less concerned with the Tipuana trees long term (they tend to die before they shed crown structure – so when it comes to safety we get plenty of notice) because of their robustness – as I am the Albizia trees which are known to shed live limbs when stressed.

To this effect I will be recommending site improvements to all trees, but the treatment of the Albizia trees are first in the order of priority.

The long term management of the trees require community consideration, with the trees themselves being given the space to make improvement (by giving them friable soil surface area they can better interface with) – this means sacrificing a reasonable percentage of area within the trees root zones for soil restoration. A sustainable management and action plan is in my opinion very necessary to reduce risk, stress on the trees and sustain this very valuable community asset. From what I can see with the Green we have plenty of space that we can share with the trees.

Tree Constraints/ Site Limitations

The constraints that are causing these trees to be in decline need to be understood and recognised by all concerned to enable the reasoning necessary to create change. Personally I would rather see a gradual process that supports the benefits the trees are currently providing extending into another 40 years, rather than a time lag where following tree removal and a greater deserted landscape it takes another 40 years to establish new trees to achieve what we have now. It is normal in most reactive tree management situations (based on a lack of value to be realised in retention over removal and processing) that an avenue such as this be felled then replanted as soon as trees shows symptoms of age.

Imagine if we humans were ‘felled’ as sick 25 year olds rather than be nourished to live out our full lifespans?

Because of non-sustainable tree-management practices trees rarely make it to maturity (the first ⅓ of their lifespans) before the onset of early old age and their removal.

The Constraints On The Trees/Site Are As Follows:

  • Lack of soil oxygen due to Soil Compaction due to decades (pre and post planting) of People Pressure from vehicles, machinery, hooved animals (bullock timber trains, dairy cows) and site visitors (multitudes of feet)
  • Below ground Biological Desertification due to decades of compaction, loss of leaf litter and lawn competition
  • A lack of soil water holding capacity after rainfall, compacted biologically desertified soils (soils low in fungi do not hold water for long) and lawn grasses have significantly greater impacts in times of drought. Wood embrittlement due to drought stress is a factor in major limb failure
  • Limited budget for tree maintenance or removal (from my perspective this is also a benefit – detrimental over-pruning is a common issue where budgets exist)
  • Reduced tree health due to site constraints, the Albizia trees (more particularly) now with advancing signs of decline
  • Expected time frame for another major limb failure – within five years
  • Due to overshadowing/space there are limited options for the successful establishment of replacement trees (replacement planting sites between the existing avenue trees is right within access routes and market stalls), in this case the establishment of Figs is the best practise option
  • ‘Tree time over Human time’ – because human life spans are so short and the processes that make up tree time are much longer – few of us have the understanding to accommodate full tree life expectancy

As stated based on the stress that the trees are under – they are in a stage in their growth cycle where due to the limits imposed upon them they are becoming old before their time. However I see these trees at a switching point in their vitality – whereby (based on stored energy) they can make a comeback (optimise their bodies) with help.

Opportunity for Crystal Waters

Most amenity trees in the urban environment are recoverable, but not so under the reactive land and vegetation management system that is common to most private and public land holders in the world. Proactive tree management means addressing the needs of trees before they go into decline, before they fail or die.

Crystal Waters (as a potential global hub for sustainability) has a great opportunity with these trees, by initiating and being part of a proactive project concerning this Green community hub, Crystal Waters could well be the first Eco-village in the world to save a treed avenue into posterity (this rarely happens in the mainstream globally outside of historical trees in Botanical Gardens).

Discussion and Recommendations Background – Trees and Risk Considering the major limb failure last year (T4), risk needs to be another motivating factor for change, though with my overall recommendations in the long term I am confident that risk can be managed to an acceptable level. In support of the trees it needs to be stated that apart from the 2018 limb failure on T4 in the last 30+ years these trees have no history of recorded risk/ hazard (bar one recent trip hazard incident from a raised brick). Assuming no action is taken considering risk, human occupancy of the site (the number of hours people are under the trees) and the likelihood of a limb failing and falling on a person – I suspect that the trees are barely on the threshold of risk. Based on the current established target level of risk – being 1 in 10,000 or less (Ref: systems of assessing Tree Risk – VALID – Tree Risk-Benefit Assessment and Management and QTRA – Quantified Tree Risk Assessment). Of course with no action taken the trees will continue to decline from people pressure with the likelihood of tree failure escalating and therefore risk of harm.

I intend to organise a workshop to enable an independent risk assessment to be carried out as part of the project management plan

I have for the trees (this I aim to host as a workshop to help raise revenue) should my proposal be accepted by the Co-op.

The steps listed in section 4.0 will collectively reduce risk likelihood well below the risk matrix that professional consulting arborists like myself follow.

People Exclusion Zones – PEZ – reducing targets (on people) whilst reducing people pressure (on trees)

To facilitate the recovery of these trees we need to give a significant amount of space back to them. This means reducing people pressure – people access/congregation (and therefore soil compaction) within the trees root zones (from the trees trunk to the trees driplines) by making designated areas no go zones – PEZ – for people and then making those zones soil restoration areas.

With the goal to make the soil’s friable, to improve on soil health and therefore tree health.

The Bricabrac lane treed avenue roughly measures 110m by 25m (including an extra 15m² to encompass T5) that is an overall area a little under 3000 m².

Currently this whole area is used by people and subject to people pressure, the community need to agree on how much space they are willing to give back to the trees. The brick lane itself takes up approximately 300m², the trees trunks/non treatable structural root zones a further 36m² (4m per tree *9 trees = 36m²). Less the non treatable areas that leaves 2639m² for potential treatment.

Allowing for monthly market stall space is the crux of the issue that will fuel resistance to giving the trees room to breath (as discussed for long term health oxygen in the root zones of woody plants is essential).

If the community is not willing to facilitate space for the trees it will not be viable to make the needed improvements to support the restoration of the trees health. Out of the overall 2639m² of space that the trees need to improve we need to return at least ⅔ of this area to being a healthy friable biologically active soil, that’s 1800 square metres. This area to be comprised of gardens decking or cellular confinement systems. Within this area where people access and market stalls are paramount – we need raised walkways as beneath this zone it is critical that soil friability is improved and sustained.

The community needs to very carefully consider the benefits the trees give versus the costs the trees pose. Which is the greater cost to lose the current avenue and start again from scratch?

This means paying for the trees to be felled and processed, with stumps ground (a cost of up to $10,000 for the three Albizia trees alone), to then carry out soil restoration and treatment with new trees planted followed by 30-40 years of growing time to achieve the current green tunnel that is Bricabrac lane.

The alternative is to retain the current trees but give them the growing space necessary to facilitate the health improvements needed. To do this without great financial cost will mean sacrificing a number of market pitches, if the community are not willing to make that sacrifice then the only solution is to establish raised timber decks or to establish cellular confinement systems over the root zones designated to be restored (this is cheaper than decking though involves changes to the ground surface and financial cost).

Most amenity trees in the urban environment are recoverable, but not so under the reactive land and vegetation management system that is current to most private and public land holders in the world. Proactive tree management means addressing the needs of trees before they go into decline, before they get sufficiently stressed that they fail or die.

As proposed Crystal Waters has a great opportunity with these trees, by initiating and being part of a restoration project concerning the Green Avenue, with being the first Eco-village in the world to do so. As well as project manage such an event I am willing to also draft an article on such a project to share globally. To be true this is my main drive for being in service to the trees and the community, though with my history of project management this project would be in the top 10.

Though for me to be in a position to project manage these trees firstly my vision needs to be understood, then deliberation can arrive at an agreed plan. I am in a position to raise funds for the restoration of the trees by running workshops to cover the cost of materials, labour and arboricultural expertise, though regardless of how this is funded or how the project is designed without gifting the trees a minimum of 1800m² in space then the project is unlikely to achieve success. That advice relates to the replacement trees too, as the existing trees have utilised most of the available resources within the soil.

Soil Inoculation, Nutrient Bed and Plant System establishment (within the Exclusion zones)

Trees as woody plants obtain their nutrition via microbiological association in the trees nutrient absorbing interface known as the rhizosphere – this is literally the ‘stomach lining’ of the tree/soil. The nutrient cycle essential to tree longevity is a natural synthesis that can not be replicated by mankind (people can only sustainably work with the cycle), the rizosphere is retarded/ damaged by fertilizers, herbicides, pesticides, soil compaction and desertification.

The most sustainable strategy for facilitating optimal tree health involves the use of organic cold processed humus.

This is not available in landscape yards, nor from tree processing contractors, the products available from Bunnings are not biologically active (are not a true compost, the microbiology in humus with a very limited shelf life can only be sustainably handled over short time periods). The humus that I use/have access to is farmed sustainably largely from green vegetation (a by-product of tree prunings and removals).

As well as vertically and horizontally inoculating (Soil Inoculation) as a means to decompact soils, I construct Nutrient Beds to house the biologically active medium necessary to (naturally open soils up), to provide nutrition as well as protect the integrity of the inoculated soil medium.

The Nutrient Beds are then capped with a vegative layer – by establishing a Plant System (plant component of an ecosystem) comprised of companion plants that form closed canopies further proofing the system as well as creating high value amenity gardens for site beautification.

The establishment of such systems are self regulating and maintaining as long as people keep off the system. The combined effect of soil inoculation, establishing nutrient beds and plant systems significantly reduces drought stress by holding moisture in the soil. The periodic Irrigation of the plant system helps drought proof trees, hydrated sapwood helps to prevent major limb failure even with the presence of wood decay fungi.

 

Cellular Confinement Systems

The purpose of cellular confinement systems (in our context) is to enable access to restored tree root zones without recompacting soils. Such a system is laid out over geofabric and is made up of a cellular matting filled with angular gravel, another similar load bearing system supports lawn grasses.

In those areas where the community is unable to sacrifice market stall areas as space for trees – cellular confinement is the greatest option, though timber decking is another.

Maypole rigging for the Flamboyant trees (T1 and T4) and propping of lower limb T1 As well as tree health a sustainable management plan must also include risk management.

My main concern is major limb failure, as discussed this relates to the Albizia trees, because of their body language, their stress symptoms and because T4 has already had one major limb failure I am inclined to recommend establishing a fall arrest system to help mitigate further limb failure. This can be seen akin to training wheels for human toddlers. Though the trees are highly stressed young adults – whilst their vitality improves a back-up system brings us a step closer to being well under the acceptable tree risk threshold. Mechanically speaking the trees have recently been demonstrating their prowess to dealing with major wind load – this is evidenced by my study of the trees in response to the heavy August/ September winds.

Generally speaking, where possible, I recommend pruning of trees via volume reduction as a means to reduce limb failure likelihood, however I believe that any pruning on the Flamboyant trees will accelerate their health decline (wounding into heartwood enables oxygen ingress and an acceleration of wood decay, particularly on stressed trees) therefore as a means to help mitigate failure whilst their health levels improve (and therefore their mechanical capacity) I recommend the Maypole rigging system.

This involves setting up fall arrest from a timber pole (power poles are ideal), which is established in close proximity to a trees trunk (not too close to cause damage) yet established to be as central to a trees crown as possible. With fall arrest running from the upper pole to selected crown structure (to be ascertained by me) as a means to arrest structure likely to fail.

Propping T1

I also recommend (in association with our resident builder) to create and install a prop for the lowest limb on T1.

Structurally speaking, I see the retention (without pruning) of this limb as being paramount to the trees overall mechanical capacity to dampen wind load. Propping the limb is likely to buy the tree decades of sustained functionality. Based on experience the removal of this limb is likely to cause upper crown failure in wind events (removal of this limb will also cause major wounding/oxygen ingress) with photosynthate loss and subsequent decay undermining its adjacent trunk – this will seriously mechanically compromise the trees upper crown to deal with wind load.

Note 1.

I recommend removing the line covered flags, setting a pole to attach them to, because of the status of this tree we need to discourage climbing of this tree by our children, that means keeping the adults out too. By the time we have set up the exclusion zones (PEZ) for this tree, we will only have people walking under her, so further reducing risk (and people pressure).

Note 2.

Because of the stress the Albizia trees are already under it is possible that another limb failure may occur post treatment works (the trees will need integration time – up to five years), the goal in the meantime is to mitigate risk through establishing exclusion zones backed with the fall arrest system (Maypole Rigs) discussed.

Note 3.

With regard T5 (no Maypole planned for this tree) I recommend sustaining this trees integrity/reducing risk through establishing an exclusion zone and light pruning.

Replacement Trees

Parent And Child Trees

I see the installation of native Ficus species (Child trees) to engulf host trees (Parent trees) as being the best means to maximise space, whilst utilising the established woody trunks/root plates of the existing trees and compartmentalising them. The restoration of the current treed sites as part of the health management of the existing trees will also facilitate the optimal future health of the replacement Fig trees. By growing Figs on the avenue trees this saves using space between the avenue trees for tree replacements.

The natural precedent of Fig trees growing on and engulfing host trees is a phenomenon that is classic to S.E. Queensland (and the tropics) and is a best practise means to replace local veteran trees with new ones. This strategy is brilliant for stabilising veteran trees (such as the avenue trees) whilst providing an established body for the Fig tree to grow on, as well as being an excellent way to grow a native tree over one listed as a weed species. With consideration of local trees to grow as child trees I recommend two species – Ficus obliqua (Evergreen) the Small leaved Fig and F. virens (deciduous) the white Fig.

As a means to assist the engulfment of the replacement Fig trees I recommend the utilisation of Coir (coconut fibre) tubing, this enables the acceleration of the establishment process as well as help target the root system of the establishing Fig tree/ soil/root area. I recommend installing three Figs per tree (F. virens on the Albizia trees), and three Figs (F. obliqua on the Tipuana

trees). Each tree to have 3 Coir tubes per tree linking the Figs to ground, each tube to be split and filled with leaf litter/humus to accelerate the process. I recommend that the figs be installed low enough to the ground to be irrigated (hosed) once per month during establishment phase.

Key site modifications (Ref: T1 and T3) needed to reduce risk and reduce stress loads on trees

To help accommodate the needed site improvements around T1 I strongly recommend the relocation of the trampoline and potentially the swing set, at least to the edge of the trees canopy. As well as it being important to reduce people pressure within this trees root zone with the long term in mind we also need to reduce people’s exposure to potential risk from this tree. I see the need for T1 to be an exclusion zone for most if not all of its dripline (bar Bricabrack lane as an access route).

Likewise with regard T3 the fire pit needs relocating to beyond the trees canopy. In the long term the constant radiation of the soil/ soils microbiology will significantly reduce the lifespan of this tree.

Conclusion

At the heart of Crystal Waters there is a treed avenue (Ref: T1-T5) in need of human support if the avenue is to have a sustainable future.

This report is a result of a request from Ally Bing of the Crystal Waters Landscape community sub group for professional arboricultural advice.

This report has been drafted as a professional document though is free of charge, it specifically covers five of the main avenue trees but relates to the whole avenue of Bricabrack lane. Personally I elected to take on this work as I see a great opportunity to be in service to the Avenue trees, the community, as well as to cocreate a precedent for Ecovillages globally to take on proactive tree care projects.

For these trees to be integrated into a replacement canopy moving forward action needs to be taken now. The course that

I recommend is for the Committee, the Co-op and the community to discuss and agree on an action plan, a plan that reflects the needs of the trees and the community, that values and integrates the two. It’s my job as an experienced Project Manager interested in championing this cause to help the community see what I see as a long term management plan, to then mediate the steps to bring that into reality. I will assist this process through running a 40 minute presentation with a question and answer session, I suggest doing so via the community Eco-centre.

The management steps I am to initiate to enable a successful outcome are as follows

  1. To achieve the support of the CW Landscape Committee, Markets managers, Co-operative and community, this will involve careful discussion, demonstration and negotiation to achieve the objective of giving the trees sufficient space to better interact with their soil environment, to therefore be able to improve their health and biomechanical status
  2. To share this report with the Stakeholders I have a history with, with a means to gauge the kind of support I can attract for the trees (this was already acted on with the relevant parties at the time of completing the 1st draft of this report)
  3. To plan the engineering components, particularly in association with the Maypoles rigs and prop (T1 and T4)
  4. To Price The Associated Costs Necessary To Gauge Project Cost And Management
  5. With the aim to cover the associated costs through running a number of workshops (to the Australian arboricultural profession and allied professions concerned with tree management) I will ascertain a budget as a means to allocate funds to pay for the works. The number of workshops and trees I aim to service per operational step will feature in an Operations Plan (to be developed)
  6. To gauge from the Co-operative what is willing to be given in support of this proposed project, i.e. use of the Eco-centre and CW accommodation to help keep workshop costs down and to build revenue for the proposed restoration project.

The practical steps I recommend to follow to enable a successful outcome.

  • In association with the Landscape Committee to map out the areas for People Exclusion Zones, Vertical Inoculation, Nutrient Beds, Plant Systems and Cellular Confinement Systems (for market pads and people access walkways
  • Working with the Landscape Committee to relocate the trampoline, swings and fire pit
  • To establish an order of trees to be treated based on priority and workshop funding, to then treat each tree in succession (Maypole Rig, Nutrient Bed, Plant System, Cellular Confinement System, tree pruning and Fig tree planting)
  • To establish a maintenance plan
  • To discuss with the Committee news of any intended development projects that are likely to impact on any of the trees discussed in the report

To help establish a benchmark for Eco Villages globally with a proactive tree management project such as this, I intend to further develop this report as an arboricultural article and an article for the Ecovillage community Australia wide. Should I gain approval to project manage this proposed project subject to funding, I aim to record and promote the restoration process in a series of future articles.

December 26, 2019 / by / in , ,
Grand-Border Stressed/Dying Pines

Non-sustainable vegetation management – modern horticultural practice – an industry-driven tree killer?

My apologies to AA readers for holding back on Part 2 of ‘Conservation Arboriculture in Action’. Part 2 is based on a recent Treepeeps PTY LTD advanced tree – tree planting project. At the time of drafting Part 1 (last edition), I had expected for us to have completed the job soon enough to write the Part 2 article. Not so, in the meantime I am sharing this article on tree decline based on non-sustainable land management.

This article is founded on a report I drafted for a S.E. Queensland council. As a professional arborist I have worked contractually and as a consultant all over the world, Australia, PNG, Vanuatu, America, Canada, Germany, Portugal and the United Kingdom. As a traveller I have also explored much of Europe.

All round the world I have seen the same standard of a collective lack of tree care, with most amenity trees seldom living beyond the first 1/3 of their lifespans.

This is because of environmentally non sustainable land management practices – largely driven by horticulture, with nonsustainable development, agriculture and arboriculture driving home the final coffin nails. Few of us have the awareness or the gumption to speak out, let alone the fortitude to make change.

Even in our profession we have enabled industry to direct our cultural practises to do more damage to trees than benefit them, our limited education (i.e. a lack of biology) is also a reflection of an industry drive.

To achieve sustainability enterprise must balance the environment with economy, there can be no shortcut. The model that is current to land based industry around the world is failing.

The following report is a reflection of the kind of horticulture that kills trees Australia wide.

Project – Mossman Park, Stevens Oval and D’Aguilar Highway, Dalby and Jondaryan S.E. QLD.

Following a request from the VACC Parks and Gardens Coordinator – to assess three treed avenues at Mossman Park, Stevens Oval (Dalby) and D’Aguilar Highway (Jondaryan) – I carried out site/ tree assessments on 18/12/18. The scope of the assessment was to ascertain stress factors (on top of drought stress) likely to be causing tree decline and death. With the three sites in mind approximately ¼ of the Pine trees are dead with more dying.

Status Report

The first site assessed was the avenue of trees on Domingo road adjacent to Mossman Park. The trees are a mix of Pinus spp (Pinus radiata or possibly Pinus taeda), Hoop pines (Araucaria cunninghamiana) and Kauri pines (Agathis robusta), though largely Pinus (as requested this report is concerned with the Pinus spp). Though there has been a recent history of drought there had been rainfall before my arrival on site and the soil was well hydrated.

The Pines stand at (on average) 15m tall with an approximate crown spread of 3-5m. The stem diameters (at chest height) average 40cm and the trunk flare diameters (at ground level) are around 60cm. These trees are largely made up of a single main stems, have symmetrical crowns (trunk, branches and canopy) and are approximately aged 30+ years. The Mossman park avenue is made up of approximately 50 trees.

A question has been raised in relation to the trees condition with the long term in mind, the symptoms that bought these trees into consideration involve scattered dieback in the internal foliage of the trees, leading to complete folial/canopy/upper crown death. Study of the Hoop pines and Kauri pines shows that these trees are also showing stress symptoms.

Evidence of Genus, Species and Health

The Pines – (P. radiata or P. taeda) have fair/poor vitality to none – this is evidenced by stunted foliage, leaf size and leaf colour, leading to death evidenced by scattered dieback in the internal foliage of the trees, leading to complete folial/canopy/upper crown death.

Evidence of Crown Structure (relating to biomechanical assessment)

The crown structure of these young trees is fairly standard for the Genera (Pinus, Araucaria and Kauri) which is generally stable even when stressed in my experience of S.E. QLD. Though the focus of this report relates to tree health.

Observations/Discussion – Site Limitations/Herbicide Concerns

The first study site is where I spent the bulk of my time (my observations of that site form the backbone of this report), study of the second two tree avenue sites validated my observations of the Domingo road avenue. Study of the trees in general revealed that the Pine trees are the most sensitive of the avenue trees to the environmental conditions. Though the other tree Genera reveal symptoms that support the decline in the Pines.

The three avenue sites (ref: Fig. 4. and opening image on page 32, Mossman Park, Fig. 6. Stevens Oval, Fig. 7. D’Aguilar Highway) share identical features/symptoms.

  • The trees are roadside with the bulk of their root systems being in adjacent gullies
  • The growing environments are regularly mown lawns
  • All trees have recent evidence of herbicide application within their structural root zones
  • The avenue trees are surrounded by old agricultural land • The soils are heavily compacted (years of transport vehicle, mower and people access)
  • Crown dieback largely in the Pine trees (ref. Figs 2-7.), but also noted in the Hoop pines (ref. Figs 16-21)
  • Most of the trees have mower damaged exposed roots (ref. selection of Figs 8-12)
  • Large swathes of dead lawn was noted, mostly in gully areas between/adjacent to trees (ref. Figs 13-15).

As well as the major symptoms listed above this report details my other observations and reasoning as to why the VACC Pine trees are in decline.

The avenue sites are by their nature problematic as growing conditions for any tree. The soil compaction and lack of nutrient cycling through the soil profile is known to have a significant impact on tree longevity in itself.

But the sustained use of herbicide application and mower damage on structural roots must be considered, mower injuries are similar (on the impact to trees) as perennial cankers in that as soon as tissue is generated by the tree to close the wound it is damaged on the next round of mowing (the same pattern occurs with canker infection or bird damage).

The wound wood being generated by the tree starts of as cambial tissue which may absorb a measure of the herbicide itself, though it is understood that this usually only occurs with the presence of chlorophyll in plant tissue (perhaps not always present in cambial tissue in stems or roots).

Based on my studies and the evolution of Plant Health Care science (ref: Soil Food Web principles – Dr. Elaine Ingham) the key issue that sustained herbicide use has on soils relates to excess salt.

Bituminous road surfaces are know to leach chemical salts (pollutant runoff is also a factor) that impact on soil health. Trees as woody plants need oxygen and microbial association in soils for sustained nutrient exchange, prolonged lawn environments are known to lead to depletion in essential soil microbiology for woody trees. Though the build up of salts and heavy metals are also a key issue with tree health. Figs. 13-15 are indicative of issues below ground with impacts on turf as well as the trees.

Further to my observations of the trees I make reference to observations of the Hoop Pines (ref. Figs. 16 to 21). Study of the Hoop Pines in all three sites revealed symptoms/perceived stressors that need to be discussed. These involved dieback in shooting epicormic growth (mostly shoots generated following lower branch removal ref: Fig. 16) as well as internal dieback (similar to that of the Pines ref: Fig. 18), comparison to other local Hoop pines in surrounding areas showed me trees without these symptoms. I suspect that this is another indicator of site issues below ground, though I believe that management need to carefully consider herbicide application as being a direct impact.

Discussion with fellow consulting Arborists via the Facebook Australian Arborists Network AAN – Brands such as Roundup, Grazon, Conquest, and chemicals Glyphosate, Picloram, Triclopyr, Metsulfuron-methyl, Dicamba have all been cited as having a direct influence on tree poisoning and death.

It has also been discussed within my circles that Hoop pine deaths are attributed to herbicide application.

Pine nematode Another possible factor in the trees decline which requires consideration and elimination is Pine nematode – Bursaphelenchus vallesianus. Outbreaks of Pine Nematode have been recorded in the Sydney region (2016) and are discussed in this document (since publication the nematode has spread north and is now reputed to be in northern NSW State Forest). Check out: https://www.dpi.nsw.gov.au/biosecurity/ plant/insect-pests-and-plant-diseases/ pine-nematodes? fbclid=IwAR1N6O8TK RIS5S3DjaX-ZgDjyhsANxZQO3E6cRUfkpsRJDPB0k1DGEshDk

Study of the above does provide similarities to the dieback symptoms discussed in this report. The nematode impacts on the trees vascular system by forming air pockets which causes death.

The Pine nematode has been discussed as being present on the following Pines:

  • Aleppo pine (Pinus halepensis)
  • Austrian pine (Pinus nigra)
  • Common spruce (Picea abies)
  • Maritime pine (Pinus pinaster)
  • Ponderosa pine (Pinus ponderosa)
  • Radiata pine (Pinus radiata)
  • Stone pine (Pinus pinea)
  • Scots pine (Pinus sylvestris)
  • Turkish pine (Pinus brutia)

The contacts concerning this matter I made where via the Department Of Primary Industries – DPI NSW and the Department of Agriculture and Fisheries – QLD who I have alerted to the possible issue of a Pine nematode outbreak, at the time of my completion of this report DAF staff where due to make contact.

For a useful conclusion to be reached there is the need for further investigation, I recommend analysis of the soils for salt and heavy metal levels, I also recommend that Council compile a list of all products that are currently being used for herbicide application (as well as frequency of application) as a means to assess/ eliminate the contributing cause of the tree decline/death. Bearing in mind that the herbicide companies downplay the side effects of the products they sell I am more inclined to pay attention to field experience than the ‘literature’ on this topic.

For Analytical services we recommend Southern Cross University Lismore to assess the sites soils for heavy metals and salts www.scu.edu.au/environmentalanalysis-laboratory—eal/

Concerning the possible outbreak of Pine nematode for the record – all pests and diseases are side effects of site issues that impact on tree health, in the case of trees – site issues impact soils which impact tree vitality (principally a lack of soil oxygen, humus for nutrient cycling and allied micro-organisms that compartmentalise disease causing organisms in the soil). Study of the linked Pine nematode document validates this by stating “Control of pine nematode is limited to prevention”. If the Pine nematode is present this will have to be accounted for but not at the expense of treating the site constraints and the factors that have lead to the cause of the most current problem (note – contact with DPI NSW Biosecurity validated my observation that the Pine nematode is an issue only on stressed trees).

Road side avenues of trees are probably the most sensitive and vulnerable to health limitations, tree death is almost always a result of multiple imposition, good management involves removing or reducing stress factors that impact on trees. Non-sustainable horticultural practices are in my opinion the key constraint that require management input.

As a matter of short term and long term soil/tree health I recommend improving on the avenue trees growing environments by establishing Nutrient Beds (comprised of cold processed composted mulch). To help keep people off the Nutrient Bed and accelerate the assimilation of nutrients (activate the soil root-interface) I also recommend the establishment of a Plant System (plant component of an ecosystem), to help proof the nutrient bed and keep vehicles out (exclusion zone). In the course of establishing a plant system I also recommend vertical inoculation of the trees root zone with Soil Food Web grade cold processed compost – humus (this can be done at the time of planting tube stock vegetation).

Trees which have died are best replaced by Hoop pines which are considerably more tolerant of the site constraints.

The use of herbicide in the trees root zones is a practise that needs to be replaced by a more sustainable means.

Likewise to enable wound wood generation and compartmentalisation of exposed sapwood from root damage and likely inoculation by herbicide – lawn mowers need to be kept out of the tree root zones.

If it is not feasible to establish nutrient beds and plant systems I recommend the planting of rings of sturdy vegetation – such as Lomandra hystrix around the structural root zones of trees (as a minimum) to keep mowers/spray crews out. Grass can be cut to the edge of these plants which even deflect brush cutters. The solution to non-sustainable horticulture is sustainable horticulture, practised by old school horticulturists around the world.

Conclusion

In conclusion with thanks to VACC senior management being responsive to recent rapid tree decline this report is a reflection of symptoms presented by the site and the resident avenue trees.

Following rapid death of Pine trees located within three avenue treed sites in the Grand-Border region at Dalby (*2 sites) and Jondaryan (*1), on behalf of VACC I was commissioned to assess the trees with a view to determining reasons for decline in association with drought.

Modern Arboriculture recognises that tree decline/death is generally caused by multiple factors working against the tree as one.

My 18/12/18 assessment has validated this understanding, the combination of soil compaction, lack of nutrition, drought, mower damage, excess herbicide use, the build-up of salt (in the soil profile) and heavy metals, has lead to excessive stress loading on the Pine trees which are the most sensitive to these site limitations. Arboricultural experience supports the symptoms of rapid tree death to herbicide use (this report has recommended that VACC do an audit on brands/types of herbicide used, as well as frequency of application). Likewise the study of information residual to the symptoms  presented by the trees has revealed that there is a recent outbreak of Pine nematode extending North from Sydney, out of responsibility I notified DAF of the issue and an investigation by the department is now underway (advice relating to the management of Pine nematode is available within the document linked on page 36, Observations/ discussion/Pine nematode).

With prevention of such declines I have recommended the review of horticultural practises, as well as cultural improvement of the sites soils, this is with a view to protecting the Hoop pine population which are more resistant to the issues behind the Pine trees decline and death, I have also recommended replacing the dying Pines with Hoop Pines for this reason. If the sites in question do prove to be infected with Pine nematode a protocol has been established by the DPI for its management, this will need to be considered in relation to advise from DAF.

Post-report conclusion For the sake of this technical feature, I have altered names locations and dates in the report, the photographs and content of the report remain true.

Following the drafting of this report DAF made contact with me to confirm that there was no Pine nematode – Bursaphelenchus vallesianus present in any of the soil profiles they sampled concerning the 3 sites (this report I passed on to the client along with my contacts). When we consider the long term economic and environmental costs of managing trees non-sustainably verses via sustainable systems (post establishment) the benefits are multifaceted. The problem is getting tree and people managers to start. To create the precedent for conservation arboriculture we need good local government support, a challenge when we live in a society that makes an economy from being non-sustainable, such as via repetitious herbicide use.

With sustainable tree management in mind Conservation Arboriculture is the solution, though this will save money as opposed to make money – perhaps an anathema to industry, but a great boon to land/vegetation managers. The enterprise of such management and CA will get arborists out of trees and into the soil…

Long live the rhizosphere.

October 6, 2019 / by / in , , , ,
Conservation Arboriculture In Action – Part 1

Though it’s been over three years since I have written for Australian Arbor Age magazine, this article comes straight on the back of my last three-part article that served as an introduction to Conservation Arboriculture.

My whole career has been a steady progression down this path, where I see all trees and their byproducts(when processed correctly) as benefits for the living biological computer that is planet earth. This work is my view on trees through cultural practise as a professional contractual and consulting conservation arborist. This two-part article is a reflection on recent arboricultural projects of mine, carried out with my current professional circle – Treepeeps (run by Mandy Blyss and Tony Aitkenhead) working the Scenic Rim to Greater Brisbane in S.E. Queensland. This article starts with a recent Arb report on the retention of a veteran tree with RNE and flows into a 5 per cent crown reduction as a means to reduce load on a mechanically constrained gum over a Mount Tamborine cabin.

Flooded Gum Assessment

Following a request from the VACC Parks, Gardens and Cemeteries Coordinator to assess a Flooded Gum tree in the centre of Oswald Park, on behalf of Treepeeps Pty Ltd, I carried out a site/tree assessment on March 14, 2019.

The Rathdowney Flooded Gum tree is a local wet sclerophyll woodland species, located close to the centre of Oswald Park beside a footbridge on the edge of a gully.

The Flooded Gum stands at approximately 20m tall with an approximate crown spread of 8m. The stem diameter (at chest height) is 1m and the trunk flare diameter (at ground level) is around 1.2m. This tree is made up of a single main stem, has an asymmetric crown (trunk, branches and canopy) and is approximately aged 30-40 years.

A question has been raised in relation to the trees condition with the long term in mind, the symptoms that bought this tree into consideration involves an extensive lesion on its main stem extending into a lateral branch, exposed desiccated sapwood, early signs of hollowing and effected wound margins.

Evidence of genus, species and health The Flooded Gum – Eucalyptus grandis has fair vitality (historically good), this is evidenced by foliage, leaf size, leaf colour, bark colour and past wound wood generation.

Evidence of Crown Structure (relating to biomechanical assessment) The body language of the Flooded gum indicates stress levels impacting on vitality, this is visible in recent wound wood production surrounding pruning cuts, is also evidenced by a history of past and recent (still green) limb failure. Study of a failed limb (present at the time of assessment) revealed wood embrittlement indicative of dehydration/drought stress.

Observations / Discussion

In a past local consulting role for Toowoomba Regional Council (TRC) in 2015/16, I was involved with the risk management of Gum trees with exactly the same symptoms. Over the period of  several months I gathered extensive data on Gum trees with similar failures and identical lesion symptoms.

In my experience these kinds of wounds/lesions are caused by local Parrots (Galah’s and Rainbow Lorikeets) seeking to create habitation. The birds scribe the outer bark of branch forks into the sapwood with their beaks and return to the same forks to scribe the generating wound wood. This has the effect of perpetuating the injury enabling sustained wood exposure akin to a perennial canker. In fact my research (I assessed over 100 mature Gum trees in association with the TRC project), revealed that the Birds and Canker decay organisms are working together to propagate these injuries.

I first became aware of this issue whilst assessing trees for Arborist Bernard Keays of pre-amalgamation Moreton Bay Shire Council and for Energex in 2007. Prior to this time I did not see these symptoms (as an active tree climbing arborist in S.E. Queensland 1991-2004 I was in a position to) and believe that the issue of wound scribing of branch fork unions has occurred since then because of habitat loss caused by decades of development and loss of habitat trees for the birds.

Coming back to the Rathdowney Flooded Gum – Parrot/canker damage is well recognised with study of the recent limb failure captured for this report. Study of page 8 of the linked report (refer to: https://bit.ly/2YcJIX2) reveals very similar symptoms to the symptoms posed by the Flooded Gum limb failure (Fig. 8-10).

Those symptoms being a lesion from parrot wound scribing, the failure leaving a branch stub (also noted on our Flooded gum), wood embrittlement from dehydration/oxidised tissues and part cross grain shearing and delamination – creating a tear. Though based on study of the failure and consideration of the site/ recent climate I also maintain the tree was drought stressed at the time of failure (another failure criterion).

There is also the site/site history to consider, the tree is located on the top of an embankment with a footpath running through its root zone, the construction of the bridge and footpath may well have originally occurred before the tree was established, though high density human traffic around the trees root zone coupled with lawn maintenance machinery is a sustained load on any top soil (Fig. 3-4). Also with the sustained removal of leaf litter and the inability of the soil profile to cycle humus this is an added ‘nail in the coffin’ that is the trees longevity.

Considering the large trunk injuries (and the energy it’s taken for the tree to occlude them) from major limb removal coupled (Fig. 12) with the health issues discussed I see this tree as being quite reasonably stressed (though not so historically as indicated by lower pruning cuts that are completely occluded).

It is possible that with proactive arboricultural management that the Flooded Gum could well make a recovery. In light of the considerable loss of habitat trees throughout Queensland it falls on us to keep and risk manage every tree we can, especially those that the wild-life is attempting to occupy, as each bird damaged tree we remove puts stress on the birds as well as other non-bird injured gum trees.

Discussion/Recommendations

My advice is to retain and risk managed this Gum tree in the short term, if in the long the tree improves then all well and good. However I do recommend integrating a new tree into the airspace of the Gum, to achieve this I recommend making the Flooded gum a host tree for a strangler Fig (F. obliqua, F. virens, F. watkinsiana etc). In the big picture such a move now will stabalise the Gum in the long term (20 years plus), whilst helping to sustain future habitat within the Gum, as well as allow for continued amenity (note – Treepeeps carries out Ficus establishment as a specialised service). I recommend establishing the Fig on the sloping side of the tree to encourage roots to go downhill into the lawn gully (away from the footpath).

I also recommend improving on the Gum trees growing environment by establishing a Nutrient Bed (comprised of cold processed composted mulch) surrounding the tree from the footpathdown the bank the Gum is growing on. To help keep people off the Nutrient Bed and accelerate the assimilation of nutrients (activate the soil root-interface) I also recommend the establishment of a Plant System (plant component of an ecosystem), to help proof the nutrient bed and keep the public out (exclusion zone). In the course of establishing a plant system I also recommend vertical inoculation of the trees root zone with Soil Food Web grade cold processed compost – humus (this can be done at the time of planting).

With regard the crown/canopy of the Flooded Gum I recommend carrying out a 3-5 per cent canopy reduction. This acts as a 25-30 per cent volume reduction which significantly reduces wind-load/ major limb failure whilst maintaining energy (photosynthesis) production. A good volume reduction only targets outer canopy, inner canopy is retained to help sustain crown harmonics as well as enable retention of future reduction points should the tree need to be reduced lower. This style of crown management is aimed to mirror a trees natural retrenchment process (trees generally shed the outer to sustain the inner). Based on the removal of auxin via the removal of the outer shoots this operation actually helps to facilitate internal canopy growth response, the same can be achieved by removing buds (or nudge pruning to quote UK Arb pioneer – Arborist David Lloyd-Jones), though I often find on my subject trees – that an internal canopy is already being generated. The drawing around the Gum tree (Fig. 13) is an indicator of the line of reduction I suggest. Such an operation is to be done with hand tools, with cuts being small (on average 2.5cm), the aim is to keep cuts out of the heartwood to reduce oxidation of internal tissues and to best work with a trees rapid compartmentalisation of wounding. Such an operation to be repeated five yearly

Conclusion

In conclusion the Flooded gum (a future habitat) tree located at the heart of Jubilee Park (adjacent to the foot bridge) is a veteran tree in need of management to reduce risk, as well as to facilitate a healthier tree in its location for the long term.

The management recommended (cyclical volume reduction and soil restoration/revegetation/public exclusion or RNE – Reduction, Nutrition and Exclusion) requires short term outlay to achieve long term amenity improvement with minimal long-term investment.

Back to main body of the article – since my 2015, three-part piece (Veteran Tree Management via Reduction, Nutrition and Exclusion) I have been consistently engaging with Conservation Arb projects, with a view to build up a body of work worthy of follow up publication. My greatest project is due to commence in Vanuatu this year and has been a rigorous uphill slog to pull off (four years). For me this has been all about holding space in support of a Social Justice mover and maker, I like to think that my articles have always been on topics that are out of the box, Project Vanuatu will certainly be worth writing and reading about.

The Mount Tamborine Tallowood Volume Reduction

Some accuse me of over using the strategy of pruning trees to risk manage them (better that than removal), though the truth is I get more pleasure out of creating nutrient beds and plant systems– the ultimate tree/people driven means to mitigate risk and boost tree health. The public are more used to paying arborists rates for arborists to climb trees that to doctor them on the ground. Though not so with Treepeeps as our legend marketing manager Mandy attracts the perfect clients.

Though in fairness to my artistry I do not recommend pruning non veteranised trees. As with the Mount Tamborine Tallowood Gum – Eucalyptus microcorys I elected to carry out a 30 per cent volume reduction (5 per cent height/spread reduction) because of parrot damage (lesions from beak scribing).

In Part 2, the article will follow through into a study of a Treepeeps restoration project, the soil and trees, the whole package.

July 19, 2019 / by / in , ,
Major Mitchell’s Hollows Artificial Formation Of Tree Cavities – Part 3

A manual of techniques to create simulated natural cavities in Slender Cypress Pine (Callitris gracilis murrayensis): for use by Major Mitchell’s Cockatoo (Lophochroa leadbeateri leadbeateri).

Restore

The deterioration of cavities can reduce their quality to a point where they are no longer suitable for nesting by cockatoos long before they are lost to tree fall or fire (Hurley, 2009; and Saunders et al., 2014). Collapse of the nest chamber roof and walls due to decay and weathering exposes the nest chamber to rain, reducing the insulating quality of the cavity and exposing eggs and nestlings to the risk of drowning from flooding (Hurley, 2006a). The accumulation of wood debris and decayed material can result in cavities becoming too shallow to provide suitable shelter or protection from predators (Saunders et al., 2014).

We used a method similar to that of Saunders, et al. (2014) and Hurley (2009) to restore collapsed cavity floors by placing rounds of timber into the cavity, followed by a layer of coarse chip and finally a layer of fine clean Callitris woodchips ofa texture mimicking that produced by the MMC. Missing cavity roofs or walls were replaced using a Callitris section carved to fit the cavity spout and sealed into place with wedges of timber and silicone sealantand tech screwed.

Another strategy is to replace a collapsed cavity floor by screwing in place a sub floor of wire mesh. On top of this build up a stable cavity floor of Callitris chips to the desired depth (Figure 22).

Cracks in the nest chamber wall were also filled with wooden wedges and silicone sealant; or for larger sections, replaced by affixing sections of timber carved to provide a firm fit (Figure 25)

It is imperative that these sections are well fitted to prevent gaps and are glued and secured in place with long wood screws or coach bolts where necessary.

The collapse of nest chamber floors caused by the progression of heart wooddecay can also result in nest chambers Figure 32 becoming too small or exposing jagged wooden spikes of un-decayed wood (Figure 27 and Figure 28), both of which have been found to prohibit nesting of large cockatoo species. Saundersetal. (2014) did report successful breeding by Carnaby’s Black-Cockatoo, in WA, after restoring cavities by in-filling collapsed nest chamber floors. We further developed this technique for application in Callitris in Pine Plains (Figure 29 and Figure 31).

Nest-box

The creation of and installation of nest-boxes is a last resort action for the conservation of cavity dependent fauna. It is an admission that all other conservation and management action shave failed. Installing nest-boxes creates a Figure 34 requirement for ongoing maintenance and active management of these structures. In conservation reserves where wildfires have removed large numbers of cavity bearing trees it may be necessary to replace some with nest boxes.

Nest-boxes were made from salvaged windfall Callitris logs.

For a safe work environment, a tension tie-down strap was used to secure the log in position when using power tools on each log. A biscuit was sliced from the top and base of each log using a chainsaw to provide a clean surface (Figure 32). Immediately after each cut was made the newly exposed end grain was painted with a log sealer to prevent the ends of the log from splitting (Figure 33). For this we used Mobil Log Seal©. Without an end-grain sealant, once cut, the timber tended to split very quickly (Figure 34). A second thick coating of log seal should be applied. As a further precaution strapping is placed around the top and bottom of each log to further reduce splitting (Figure 35).

Once the ends of the log have been secured the main cuts in the log can be made to create and remove the face plate (Figure 36 and Figure 37). This is best done by first cutting two cross cuts ~ 70 cm apart and not more than 1/4 the circumference of the tree at the height of the cuts. Then make two longitudinal cuts with the chainsaw bar held at a 45° angle for each on either side of the tree starting one at a time from just below one end of the top cut and continuing down to the lower cut (Figure 36). Repeat this on the other side. The angling and depth of the longitudinal cuts should allow the cuts to meet in the middle of the trunk at a right angle all the way along the cuts. The faceplate should naturally fall lose once the final cut is complete (Figure 37).

The wedged shape provides a more robust strThe inside face of the faceplate must be carved so it has internal concave contours to match the curvature and wall thickness of the cavity being carved from the inside of the tree trunk (Figure 44 and Figure 45). The cavity entrance can also be carved from the faceplate (Figure 46) or may be carved out of the nest-box on the oppositeucture to the nest-box by leaving more of the nest-box intact as a single piece (Figure 38). Put the face plate to one side while working on the nest-box proper. To efficiently clear the large amount of material required to form the nest cavity, use a chainsaw to create longitudinal cuts along the internal length of the log (Figure 39). This creates internal slabs that can be further split with a pinch bar and lifted out (Figure 40).

The main cavity, can be worked with two Arbortech blades on separate angle grinders. Once the internal slabs have been removed to create a cavity use the Arbortech© to sculpt the interior walls and floor and deepen the cavity if necessary (Figure 41 and 42).

The inside face of the faceplate must be carved so it has internal concave contours to match the curvature and wall thickness of the cavity being carved from the in

side of the tree trunk (Figure 44 and Figure 45). The cavity entrance can also be carved from the faceplate (Figure 46) or may be carved out of the nest-box on the oppositeside to the face-plate (Figure 47 to Figure 49). These carving tasks are best done with an Arbortech© blade attached to an angle grinder.

Once the interior of the nest-box is nearing completion, the entrance can be made in the log on the side opposite to the faceplate (Figure 47 and Figure 49). It is recommended to carve the entrance to nest-boxes on the opposite side to the face-plate so the face-plate can be placed against a tree trunk and provide further protection from damage by large parrots (Figure 49) (Hurley, 2009).

Use the Arbortech© blade attached to an angle grinder to clean and smooth-off any rough edges to the cavity entrance from both within and outside the nest-box (Figure 50 and 51). Final adjustments can be made to the interior of the nest-box such as carving climbing holds for the birds and ensuring the caulking timbers cover all gaps between the walls and the faceplate. Ply wood fill in the gap created by the kerf width of the chainsaw blade (Figure 52). It is recommended to use timber slats and then glue and screw the face-plate securely in place.

References

Boland, D.J., Brooker, M.I.H., Chippendale, G.M., Hall, N., Hyland, B.P.M., Johnson, R.D., Kleinig, D.A., McDonald, M.W. & Turner, J.D. (2006) Forest Trees of Australia. CSIRO Publishing, Collingwood.

Bond, J. (2006) Foundations of Tree RiskAnalysis: Use of the t/R ration to Evaluate Trunk Failure Potential. International Society of Arboriculture – Arborist News:

Carey, A.B. & Gill, J.D. (1983) Direct habitat improvement – some recent advances. In: Snag habitat management symposium, pp. 80-87. Forest Service General Technical Report Curtis, A., Green, J. & Warnock, B. (2000) Mimicking natural breaks in trees. English Nature, 8:1, 19-21.

DSE (2011) Guideline 8.1.42: Working in the vicinity of hazardous trees. Vitorian Government Department of Sustainability and Environment, East Melbourne.

Fay, N. (2002) Environmental arboriculture, tree ecology and veteran tree management. The Arboricultural Journal, 26:2, 129-136. Forbes-Laird, J. (2008) THREATS: Tree Hazard: Evaluation and Treatment System. Forbes-Laird Arboricultural Consultancy, United Kingdom. FWPRDC (2004) The In-ground Natural Durability of Australian Timbers. Forest & Wood Products Research & Development Corporation, Australian Government, Canberra.

Gibbons, P. & Lindenmayer, B.D. (2002) Tree hollows and wildlife conservation in Australia, 1st edn. CSIRO Publishing, Collingwood. Gibson, M., Florentine, S. & Hurley, V.G. (2008) Age distribution of Slender Cypress-pine (Callitris gracilis) within Pine Plains, Wyperfeld National Park. Centre for Environmental Management, University of Ballarat, D.O.S.A. Environment, Ballarat.

Hurley, V.G. (2006a) Physical characteristics and thermal properties of Major Mitchell’s Cockatoo, Cacatua leadbeateri leadbeaterinest hollows, Wyperfeld NP. Department of Sustainability and Environment, Mildura. Hurley, V.G. (2006b) Survey of Major Mitchell’s Cockatoo in Pine Plains, Wyperfeld NP – Spring 2006. Department of Sustainability and Environment, Mildura.

Hurley, V.G. (2009) A report on installing nest boxes and repair of degraded nest hollows in Callitris Pine for use by Major Mitchell’s Cockatoo (Lophochroa leadbeateri) in Pine Plains, Wyperfeld National Park. Unpublished report prepared by the Department of Sustainability and Environment for the Mallee Catchment Management Authority, Mildura. Hurley, V.G. (2011) Results from the 2010 breeding survey of Major Mitchell’s Cockatoo (Lophocroa l. leadbeateri) Pine Plains, Wyperfeld NP. Department of Sustainability and Environment, Mildura.

Hurley, V.G. & Harris, G.J. (2014) Simulatingnatural cavities in Slender Cypress Pine (Callitris gracilis murrayensis) for use by Major Mitchell’s Cockatoo (Lophochroa leadbeateri leadbeateri). Department of Environment and Primary Industries, Mildura.

Kenyon, P. & Kenyon, P. (2010) Pruning for habitat workshop.

Korpimäki, E. & Higgins, P.J. (1985) Clutch size and breeding success in relation to nest-box size in Tengmalm’s Owl Aegolius funereus. Holarctic Ecology, 8:1, 175-180.

Lonsdale, D. (1999) Principles of Tree Hazard Assessment and Management. HMSO, 1999.

Mattheck, C. & Breloer, H. (1997) The Body Language of Trees. HMSO, London.

Rowley, I. & Chapman, G. (1991) The breeding biology, food, social organisation, demography and conservation of the Major Mitchell or Pink Cockatoo, Cacatua leadbeateri, on the margin of the Western Australian wheatbelt. Australian Journal of Zoology, 39:2, 211-261.

Saunders, D.A., Mawson, P.R. & Dawson, R. (2014) Use of tree hollows by Carnaby’s Cockatoo and the fate of large hollow-bearing trees at Coomallo Creek, Western Australia 1969–2013. Biological Conservation, 177:1, 185-193.

SWA (2011) Draft Code of Practice: Safe Access in Tree Trimming and Arboriculture. Safe Work Australia, Canberra.

Taylor, A.M., Gartner, B.L. & Morrell, J.L. (2002) Heartwood formation and natural durability a review. Wood and Fiber Science, 34:4, 587-611.

VTIO (2010) Draft Climbing Guidelines Victorian Tree Industry Organisaion, Ringwood.

Figure 47: Initial cut into back of nest-box to form entrance.

Figure 48: Marks on inside of nest-box indicating dimension of entrance.

Figure 49: Cavity entrance opened and ready for finishing off rough edges.

Figure 50: Arbortech being used to hollow out and form the cavity entrance.

Figure 51: Arbotech being used to smooth-off and from external entrance features.

Figure 52: Plywood caulking planks tacked and glued into place. Wood glue placed on interior gluing surface ready for attachment of face plate.

Figure 52: Plywood caulking planks tacked and glued into place. Wood glue placed on interior gluing surface ready for attachment of face plate.

Figure 54: This nest box has a metal plate, top and bottom to further protect timber from rotting and splitting. The nest box is resting on the stump of a cut branch.

Figure 55: Note the face plate is facing into towards the tree trunk.

Hurley, V.G. & Harris, G.J., (2015) A manual of techniques to create simulated natural cavities in Slender Cypress Pine (Callitris gracilis murrayensis) for use by Major Mitchell’s Cockatoo (Lophochroa leadbeateri leadbeateri). A report to the Department of Environment, Land Water and Planning, Melbourne.

For more information please send an email to Grant Harris at http://[email protected] ironbarkenviroarb.com

Visit the website www.ironbarkenviroarb.com

December 17, 2018 / by / in
The Tree Assessment

A technique for enhancing the assessment of the structural condition of a Blackbutt (Eucalyptus pilularis (Sm.) using the combination of IML Resi’ PD400, Sonic PiCUS Tomograph (PiT) and Electric Resistance Tomograph (ERT) instruments.

Abstract

A recent health and structural assessment of a street tree in the Ku-ring-gai Municipal area used the combination of IML Resi’ PD400, PiCUS Sonic Tomograph (SoT) and Electric Resistance Tomograph (ERT) to assess the tree for decay and the risks associated with structural decline. The assessment concluded that the tree was of relative sound health and structure based on the combination of three techniques despite the tree showing indications of internal decay. The outcome would not have been the same if the assessment was limited to the PiCUS software (SoT) alone because the ERT identified the presence of adaptive growth which the Resi’ confirmed as sound wood at these locations. This technique shows promise for the assessment of older trees with decay and allows the better quantification of the internal decay based on a combination of factors so that tree risk assessments can be made on an individual tree and quantitative basis.

Introduction

The assessment of trees for their structural soundness is important to identify the risks associated with maintaining a potentially hazardous tree. In addition, trees of structural soundness in urban environments provide a range of other benefits i.e. habitat, aesthetics, carbon sequestration and recreation. The street tree in this report was identified by the Ku-ring-gai Municipal Council as a potential risk to the safety of pedestrians and motorists, with potential impacts to services, adjacent residences and recreational areas. The tree is approximately 18 m high with a diameter at breast height (@1.4m) of 121cm.

The stage of the growth of the tree was considered as mature.

The tree was dominant in the street setting and provides medium wildlife habitat value. On initial visual assessment the tree had a least one, open decay cavity at 3m above ground level (agl), in the northern stem quadrant. There were no visual signs of animal activity. The tree was relatively symmetrical in form with canopy loading in a northerly direction (Figure 1). The crown density was about 90 per cent compared to that for the genus and species when in good condition and of normal vigour.

There were some abiotic impacts including a footpath and roadway to the east and western sides of the tree. There had also been some historical pruning resulting in the regrowth of epicormic into endocormic branching.

Methods

The tree health and structure was assessed using a Tree Risk Assessment methodology as outlined by the International Society of Arboriculture (ISA) Best Management Practices for Risk Assessment 2011. This included a visual tree assessment (VTA) to identify tree characteristics and potential hazards at the ground, in the stem and in the upper canopy.

The basic level 2 assessment identified the presence of an extensive columnar, basal decay interconnecting with an open decay cavity at 3m above the ground (agl) and at the crown union. Pathogenic wood decay from fungal colonisation was suspected however no fruiting bodies were evident. The presence of this external decay escalated the inspection to an advanced ‘level 3’ which required further investigation of the decay.

The advanced Level 3 assessment used PiCUS 3 Sonic Tomograph (SoT) and PiCUS TreeTronic Electric Resistance Tomograph (ERT) (Argus Electronic GmbH, Rostock, Germany) to assess the presence and location of decay in the tree stem as well as the size, shape and characteristics in terms of mechanical properties of the area of interest(Wang and Allison, 2008). While both these techniques are non-invasive the combination of the SoT and ERT methods can help overcome the limitations of either technique being used in isolation and can provide a better conclusion about the trees structural condition.

The SoT and ERT assessments were carried out at the buttress (figure 2a), at the open decay cavity at 3m above ground level (agl) and at the crown union, 4m agl (figure 2b). The IML Resi’ PD400 (IML Instrumenta, Mechanik Labor Systems, GmbH, Wiesloch, Germany) was only used at the crown union (at 4m agl) (Figure 3a). While the first two tools identify the location and extent of decay, the IML Resi’ PD400 resistograph tool confirms the presence of response adaptive growth by comparing the resistance (density) of adaptive growth and stem thickening at these locations against a sample of resistance (density) from solid wood in the same tree. Response adaptive growth is interpreted as the tree’s response to structural weakness, decay, stem movement and increase in wood growth thickening (additional layers of wood) or joining (welding) at branch unions. All measures were taken in January 2018.

PiCUS Sonic Tomographs (SoT)

The SoT method measures internal decay using sound waves with the principle being that sound waves travel slower through decay when compared to solid wood (Gilbert and Smiley, 2004). This is done using a series of sonic sensors (receivers) which are placed around the stem using a series of small pins to record the signals. The pins are tapped manually with an electronic hammer and the velocity of the sound waves and geometry of the sound waves are recorded as a tomogram (graph). The tomogram shows the relative and apparent ability of the wood to transmit acoustic waves while the different colours in the tomograph correlate to mechanical wood quality (modulus of elasticity), a measure consistent with the mechanical structure of the wood at the cross-section of the stem where it is measured.

PiCUS Treetronic Electric Resistance Tomograph (ERT)

The ERT on the other hand uses a low electric voltage to examine the tree and provide a high-resolution electrical conductivity map of the tree’s cross-section (Goncz et. al., 2017). The electric resistance of the wood is influenced by the water content and changes within the wood structure. The resulting tomograms are coded with a blue, green, yellow and red colour range showing blue as areas of low resistance and high-water content (potential decay), through to red showing high resistance and low water content. ERT tomograms are specific to individual tree species as each tree has its own typical electrical resistance distribution. The combination of electrical and sonic tomography in the PiCUS Treetonic system provide a detailed survey allowing more accurate differentiation of various internal defects (Brazee et al., 2011). Both the SoT and the ERT assessments were carried out at the buttress (Figure 4), at 3m above ground level (agl) and crown union 4m agl (Figure 5).

IML Resi’ PD400

In addition to these two methods, resistance testing using an IML Resi’ PD 400 was also used at five positions, at the attachment points of the 1st order structural stems within the crown union. The location of the IML Resi’ PD400 tests are shown in Figure 3a and 3b where each drill location provides a cross-section of the resistance of the wood against the drill bit. The IML Resi’ PD400 instrument assesses resistance to the drill bit of the instrument through the wood and this is then displayed as a graph. The path of the drill bit was selected from cross-sections of the crown union using the SoT and ERT tomographs. Each resistance drill test was compared to a sound wood comparison drill test identified upon the subject tree. This allows a correlation to be made with sound wood and to better identify weakened decaying wood or response adaptive growth.

Where there is higher resistance compared to the sound wood, this indicates wood of a higher amplitude (low moisture content – red in colour on ERT tomograph when integrated with SoT tomograph) and where there is lower resistance this indicates incipient early decay, compromised or decayed wood (higher moisture content – blue in colour on the ERT tomograph when integrated with SoT tomograph). This measure of internal wood resistance is used as an index of wood density at different positions and can be used within the crown union in areas subject to response adaptive growth, to confirm a sound structure.

Strength Retention Formula

In addition to these measures, the t/R ratio is described as the thickness of sound wood in the residual wall(s) of the section of the stem being measured. In this case we compare the ratio of the thickness of the wood of the stem or branch tested, at each location; to the radius of the trunk or branch. 30-35 per cent is the minimum threshold for a tree part (trunk or branch) wall section, to be considered of sound integrity (Mattheck and Breloer, 1994)(see internal red line in figures 6a, 7a and 8a).

Limitations of the t/R Formula

The conventional t/R ratio test is based on field studies of vertical, cylindrical trunks with the decay centrally located and uniform. When the stem is leaning, asymmetrical in shape, or the decay is off centre, the guidelines for shell wall thickness should be used very cautiously. The greater the disparity in shape, away from a cylinder or decay off centre, the greater the inaccuracy. The t/R was used as a guide only in the assessment to assist in the trees risk rating determination. Additional data such as location of decay, presence of response growth, direction of loadings, size and age of tree, wind exposure, etc. are also considered to complement the t/R results and to determine a more accurate likelihood of failure and final recommendation.

Results and discussion PiCUS Sonic tomograph (SoT) and Treetronic Electric Resistance Tomograph (ERT)

At the first location (base of tree), the cross-section of the wood shows approximately 24 per cent of wood was solid on the circumference of the tree stem with some relatively symmetrical, internal columnar decay, representing 76 per cent of the trunk comprised of decay and incipient wood. The results of the SoT and ERT tomograph at location 1 (the tree base) are shown in figure 6. Table 1 gives the key to interpreting figures 6, 7 and 8. The numbers in figure 6 represent the status of the wood according to the SoT and ERT tomograph key (Table 1).

The second test location tomograph’s (Figure 7), show an open decay cavity at 3m displayed, presenting as an asymmetrical open internal, columnar decay. The cross-section of the wood shows 39 per cent of solid wood on the circumference of the tree stem with some asymmetrical internal columnar decay represented by 51 per cent of decay and10 per cent incipient or altered wood. The results of the SoT and ERT tomograph at test location 2 are shown in figure 7a and b. The numbers in figure 7a and b represent the status of the wood according to the SoT and ERT tomograph key (Table 1).

IML Resi’ PD400

The third location showed an internal decay cavity at the crown union at 4m agl. The cross-section of the wood shows 31 per cent of solid wood with 53 per cent of decay and 16 per cent incipient or altered wood. The IML PD400 resi’ tests at this location identified small pockets of response adaptive growth, as shown by the red areas (high ERT resistivity) in the ERT diagram in figure 8b. The results of the SoT and ERT tomograph at test location 3, at the crown union 1st OSS are shown in figure 8. The numbers in figure 8a and b represent the status of the wood according to the SoT and ERT tomograph key (Table 1).

The IML Resi’ PD400 test locations were identified with reference to the ERT and SoT measuring points (mp) as areas of high ERT resistance. At the 1st OSS attachment union each of the five IML Resi’ PD400 results showed wood with good resistance and adaptive growth welds which contribute to stem strengthening at this location (Figure 9).

Figure 9 shows an example of one, of the five, IML Resi’ PD400 resistograph test locations. The IML Resi’ PD400 resonance testing is shown for location 3 (adjacent to ERT mp 12) in the crown union of the 1st OSS. The resulting resistograph identifies generally good resistance (compared to solid wood), potentially indicating response growth (due to branch welds or strengthening wood), with a small pocket of compromised wood at 16-17 cm. The assessment table under the resistograph summarises the resistance measure in cm from the start through to the end of the drill cross-section.

The Final Decision

The determination to retain this tree was based on a combination of the following decision making steps:

  • An analysis of the quality of wood at each defective tree part (Basal SS, open decay cavity 3m agl and crown union SS 4m agl)
  • The risk rating of each defective tree part and whether each reached the failure criteria where t/R was decided upon with evaluation and consideration of: PiT (Volume and location of decay and residual wall thickness and location);
  • ERT (Volume and location of response growth versus decay and location);
  • Confirmation of response growth thickening within the crown union with use IML Resi’ PD400;
  • The subject trees visual body language;
  • The loading on the defective tree parts; and
  • The target trees likelihood of failure, and the impact and consequences of failure

Conclusion

The three scientific decay analysis tools used in this discussion paper included the IML Resi’ PD400, Sonic PiCUS Tomograph (SoT) and the Electric Resistance Tomograph (ERT). Using these results in combination with the other important risk considerations provides a new and insightful basis for determining the soundness of large landscape trees. This is particularly useful where visual assessment alone may ordinarily prove difficult to provide enough information for retention as opposed to removal. In addition, with the PiCUS assessment tool alone the tree would have been likely condemned by most PiCUS operators (Arborists) due to the presence of decay. However, with the introduction of ERT tool used in conjunction with SoT, showed that the strength of the timber in the residual walls of this tree were determined to be of sufficient strength for its size and the amount decay present, and hence the tree was recommended for retention. The use of IML Resi PD400 in association with ERT has confirmed sufficient response adaptive growth in the crown union which identifies areas of high resistance reducing the risk of stem failure and the potential for public risk.

References

  • Bieker, D., Kehr, R., Weber, G., Rust, S. (2010) Non-destructive monitoring of early stages of white rot by Trametes versicolor in Fraxinus excelsior. Ann. For. Sci. 67(2):210.
  • Gilbert, E., Smiley, E.T. (2004) PiCUS sonic tomography for the quantification of decay in white oak (Quercus Alba) and Hickory (Carya spp.) J. Arb. 30(5): 277-281.
  • Goncz, B., Divos, F., Bejo, L. (2016) Detecting the presence of red heart in beech (Fagus Sylvatica) using electrical voltage and resistance measurements. Eur, J. Wood Prod. DOI 10.1007/s00107-017-1225-4. Mattheck, C., Breloer, H. (1994) Field guide for visual tree assessment (VTA) 18(1): 1-23.
  • Nicolotti, G., Socco, L.V., Martinis, R., Godio, A., Sambuelli, L. (2003) Application and comparison of three tomographic techniques for detection of decay in trees. J. Arb. 29(2): 66-78.
  • Wang, X., Allison, R.B. (2008) Decay detection in red oak trees using a combination of visual inspection, acoustic testing and resistance micro-drilling. Arb & Urban For. 34(1):1-4.
  • Note: this technical paper has been shortened for publication purposes and the original full sized paper is available upon request from the author.
December 5, 2018 / by / in
Major Mitchell’s Hollows

Artificial formation of tree cavities – part 2

A manual of techniques to create simulated natural cavities in Slender Cypress Pine (Callitris gracilis murrayensis): for use by Major Mitchell’s Cockatoo (Lophochroa leadbeateri leadbeateri).

Cavity creation techniques

As the decision matrix illustrates there are several techniques available depending upon the size of the tree and the state of any cavities in the tree. Each of the four techniques for creating a cavity ready to use by MMC are described in full detail with images to illustrate each of the key steps in sequence.

Excavate

Excavation involves the creation of an entirely new cavity. This technique is generally only suited to dead wood as it involves removal of a face plate which would cause extensive damage to sapwood if undertaken on a living tree. Also in some dead trees it may be necessary to remove some of the canopy to reduce wind drag in order to increase the longevity of the remaining trunk and cavity (Figure 9). In some cases a natural scar may already exist following the loss of a branch exposing the heartwood. The resulting scar may be used as an entry point to excavate a new cavity.

The first step is to use a chainsaw to cut out a face plate. This is best done by first cutting two cross cuts ~70 cm apart and not more than ¼ the diameter of the tree at the height of the cuts. Then make two longitudinal cuts with the chainsaw bar held at a 900 angle for each on either side of the face plate starting one at a time from just below one end of the top cut and continuing down to the lower cut. Repeat this on the other side. The angling and depth of the longitudinal cuts should allow the cuts to meet in the middle of the trunk all the way along the cuts (Figure 10). The face plate should naturally fall loose once the final cut is complete. The face plate should be set aside for further work later.

Once the face plate is removed, use a chainsaw to make a series of long, deep vertical, parallel cuts into the exposed heartwood (Figure 11). The cavity walls being created should be ≥10 cm thick. Furthermore, check the required blade depth to ensure that no holes are made through to the other side of the tree trunk. This is critical as large parrots, such as Galahs, will chew-out and enlarge even the smallest of holes until they have created a further entrance-sized opening (Hurley, 2009).

Following the chainsaw cuts the resulting slabs can either be prised-out with a pinch bar or horizontal cross cuts can be made to further speed up the removal of the bulk of the trunk’s heartwood (Figure 12). Then use the Arbortech© to clean out the trunk cavity and form contours to the desired dimensions. It is important to leave some rough surfaces or small grooves in the walls of the cavity to provide climbing holds for birds to easily enter and exit the cavity.

If the height of the hole left by the face plate does not match the desired cavity depth it is relatively straightforward to use the Arbortech© to deepen the cavity in the tree trunk. The measurements provided for this dimension should be regarded as a minimum as cavities up to 1.8m deep have been used successfully by MMC at Pine Plains (Hurley, 2006a).

Figure 3: Decision matrix for the selection of the appropriate technique in simulated cavity formation in Slender Callitris Pine (Callitris gracilis murrayensis). Diamonds are decision points and light teal boxes are actions. The dark decision strips represent recording and monitoring activities

It is critical that the proposed nest chamber floor is relatively flat with minimum diameters of 18cm x 19cm. In addition to cavity depth, this is the single most important aspect of the SNC construction (Korpimäki & Higgins, 1985).

Smaller nest chambers will either deter MMC from nesting in them or limit the clutch size laid. A nest chamber with a larger diameter may be used by MMC and may be excavated if the trunk diameter is of sufficient size to accommodate it.

Now, the inside face of the face plate must be carved-out so it has internal concave contours to match the curvature of the cavity being carved from the inside of the tree trunk. The cavity entrance can also be carved from the face plate (Figure 13-14). These carving tasks are best done with an Arbortech© blade attached to an angle grinder.

Refitting the face plate is a critical stage for long-term viability of SNCs. Gaps and/or air flow between the remaining trunk cavity walls and the face plate must be eliminated. The kerf width from the chainsaw creates a 1cm gap between the face plate and cavity walls and requires in-filling. Use plywood strips cut to suit or Callitris lengths custom made to fit each joining surface of the face plate.

Regardless of which timber is used, these infill or caulking strips should be glued and tacked to the joint edges of the trunk and then trimmed with the Arbortech© so that they sit flush with both the external and internal contours of the trunk and cavity. The contouring of theses strips will help to camouflage them from the prying beaks of Galahs and other cockatoos. A standard builder’s glue can be used to bulk up any minor cracks between the jointed surfaces. Tech screws may also be used to strengthen the join between face plate and tree.

Remember to use a standard angle grinder blade to grind off or disfigure the tech screw heads, then paint them matt black and grey. This last action is recommended so as to not to attract undue attention from people or predators. The external surfaces of the caulking strips must also be painted a mottled matt dark-grey and black to protect from the weather. Alternatively thick strips of bark may be attached using silicone glue to cover the caulking strips. Once the face plate has been reattached, fine Callitris wood chips must be placed in the base of the new cavity. One or two handfuls is enough (Figure 15). Following this the face plate should be camouflaged with bark from the same tree the work is being done. Entrances should look as natural as possible Initially allow a half to one full day (4-8 hours) for the excavation of new cavities. With experience a team of two chainsaw operators will be able to an average excavate two cavities per day.

Augment

Cavity formation is normally associated with older mature or senescent trees (Gibbons & Lindenmayer, 2002). It is estimated that Slender Cypress Pine do not reach a sufficient size to support a cavity suitable for MMC (i.e. 50cm DBH) until trees are >80 years of age (Gibson et al. , 2008). A variety of methods involving the exposure of heartwood and manipulation of tree health have been proposed to accelerate cavity development (Gibbons & Lindenmayer, 2002).

The exposure of heartwood provides an entrance for fungi, bacteria and saprophytic insects which cause decay and, in conjunction with the trees adaptive growth response, leads to cavity formation (Mattheck & Breloer, 1997; and Lonsdale, 1999; and Taylor et al., 2002). The rate at which wounding techniques are able to accelerate the processes of natural cavity formation is on a temporal scale unsuited to the rapid provision of cavities for threatened species recovery (i.e. formation will take place over decades). Cavity augmentation involves accelerating the formation of a cavity or improving the function of an existing cavity. Accelerating cavity formation for this purpose is based on many of the techniques required to excavate a cavity in a tree without an existing cavity.

In addition to accelerating cavity formation, cavity augmentation also involves making improvements to an existing cavity. This may be as simple as enlarging the entrance to an existing cavity or may involve more extensive works to enlarge the internal dimensions of a small cavity. Furthermore, augmentation often is in the form of inserting carved timber sections to deflect rainwater from flowing into a cavity or repairing cracks in cavity walls.

The primary augmentation process involves mechanically removing the decay and heartwood associated with wounds caused by natural processes. A pre-existing scar, revealing advanced rotting of the heartwood is slightly enlarged to allow use of Arbortech blades to excavate the rotten timber (Figure 18A and B). Once the rot has been removed to sufficient dimensions for an SNC a face plate is carved from a single piece of timber and glued and screwed in place (Figure 18C).

Augmentation can also include modifications to an existing cavity to improve cavity function. These may be in the form of simply enlarging the entrance or other features of a cavity to suitable dimensions (Figure 19). In some cases augmentation may involve strategically placing a plug of timber to block water from flooding into a cavity(Figure 20 and Figure 21).

Ironbark Environmental Arboriculture Pty Ltd is an interdisciplinary company with expertise in arboriculture, ecology and wildlife conservation. In 2014, in partnership with DELWP, they pioneered the use of chainsaw-carved hollows for threatened species conservation with their work on the Major Mitchell’s Cockatoo. Since this time they have completed a range of targeted hollow creation projects in urban and forest environments, including Musk Lorikeets in the City of Melbourne and Brush-tailed Phascogales in Box-Ironbark forests of Central Victoria.

References

Boland, D.J., Brooker, M.I.H., Chippendale, G.M., Hall, N., Hyland, B.P.M., Johnson, R.D., Kleinig, D.A., McDonald, M.W. & Turner, J.D. (2006) Forest Trees of Australia. CSIRO Publishing, Collingwood.

Bond, J. (2006) Foundations of Tree Risk Analysis: Use of the t/R ration to Evaluate Trunk Failure Potential. International Society of Arboriculture – Arborist News:

Carey, A.B. & Gill, J.D. (1983) Direct habitat improvement – some recent advances. In: Snag habitat management symposium, pp. 80-87. Forest Service General Technical Report

Curtis, A., Green, J. & Warnock, B. (2000) Mimicking natural breaks in trees. English Nature, 8:1, 19-21.

DSE (2011) Guideline 8.1.42: Working in the vicinity of hazardous trees. Vitorian Government Department of Sustainability and Environment, East Melbourne.

Fay, N. (2002) Environmental arboriculture, tree ecology and veteran tree management. The Arboricultural Journal, 26:2, 129-136.

Forbes-Laird, J. (2008) THREATS: Tree Hazard: Evaluation and Treatment System. Forbes-Laird Arboricultural Consultancy, United Kingdom.

FWPRDC (2004) The In-ground Natural Durability of Australian Timbers. Forest & Wood Products Research & Development Corporation, Australian Government, Canberra.

Gibbons, P. & Lindenmayer, B.D. (2002) Tree hollows and wildlife conservation in Australia, 1st edn. CSIRO Publishing, Collingwood.

Gibson, M., Florentine, S. & Hurley, V.G. (2008) Age distribution of Slender Cypress-pine (Callitris gracilis) within Pine Plains, Wyperfeld National Park. Centre for Environmental Management, University of Ballarat, D.O.S.A. Environment, Ballarat.

Hurley, V.G. (2006a) Physical characteristics and thermal properties of Major Mitchell’s Cockatoo, Cacatua leadbeateri leadbeateri nest hollows, Wyperfeld NP. Department of Sustainability and Environment, Mildura.

Hurley, V.G. (2006b) Survey of Major Mitchell’s Cockatoo in Pine Plains, Wyperfeld NP – Spring 2006. Department of Sustainability and Environment, Mildura.

Hurley, V.G. (2009) A report on installing nest boxes and repair of degraded nest hollows in Callitris Pine for use by Major Mitchell’s Cockatoo (Lophochroa leadbeateri) in Pine Plains, Wyperfeld National Park. Unpublished report prepared by the Department of Sustainability and Environment for the Mallee Catchment Management Authority, Mildura.

Hurley, V.G. (2011) Results from the 2010 breeding survey of Major Mitchell’s Cockatoo (Lophocroa l. leadbeateri) Pine Plains, Wyperfeld NP. Department of Sustainability and Environment, Mildura.

Hurley, V.G. & Harris, G.J. (2014) Simulating natural cavities in Slender Cypress Pine (Callitris gracilis murrayensis) for use by Major Mitchell’s Cockatoo (Lophochroa leadbeateri leadbeateri). Department of Environment and Primary Industries, Mildura. Kenyon, P. & Kenyon, P. (2010) Pruning for habitat workshop.

Korpimäki, E. & Higgins, P.J. (1985) Clutch size and breeding success in relation to nest-box size in Tengmalm’s Owl Aegolius funereus. Holarctic Ecology, 8:1, 175-180.

Lonsdale, D. (1999) Principles of Tree Hazard Assessment and Management. HMSO, 1999.

Mattheck, C. & Breloer, H. (1997) The Body Language of Trees. HMSO, London.

Rowley, I. & Chapman, G. (1991) The breeding biology, food, social organisation, demography and conservation of the Major Mitchell or Pink Cockatoo, Cacatua leadbeateri, on the margin of the Western Australian wheat belt. Australian Journal of Zoology, 39:2, 211-261.

Saunders, D.A., Mawson, P.R. & Dawson, R. (2014) Use of tree hollows by Carnaby’s Cockatoo and the fate of large hollow-bearing trees at Coomallo Creek, Western Australia 1969–2013. Biological Conservation, 177:1, 185-193.

SWA (2011) Draft Code of Practice: Safe Access in Tree Trimming and Arboriculture. Safe Work Australia, Canberra.

Taylor, A.M., Gartner, B.L. & Morrell, J.L. (2002) Heartwood formation and natural durability a review. Wood and Fiber Science, 34:4, 587-611.

VTIO (2010) Draft Climbing Guidelines Victorian Tree Industry Organisaion, Ringwood.

Hurley, V.G. & Harris, G.J., (2015) A manual of techniques to create simulated natural cavities in Slender Cypress Pine (Callitris gracilis murrayensis) for use by Major Mitchell’s Cockatoo (Lophochroa leadbeateri leadbeateri). A report to the Department of Environment, Land Water and Planning, Melbourne.

For more information please send an email to Grant Harris at [email protected] ironbarkenviroarb.com or visit the website www.ironbarkenviroarb.com

October 22, 2018 / by / in ,