Heat stress and tree death won’t daunt Northbourne’s tree planting

Genevieve Jacobs 25 January 2019 131

An artists’ impression of how the eucalyptus mannifera will look surrounding the light rail route. File photo.

Despite death, decline and heat stress, Transport Canberra senior management say they remain confident that the eucalyptus mannifera specimens planted along Northbourne Avenue are the right choice for the light rail zone and will eventually thrive.

That claim has been disputed by an expert regional silviculturist who remains adamant that the trees are “doomed” and that planting advanced trees to satisfy public expectations demonstrates “a very basic lack of knowledge”.

Marcus Sainsbury, who is the senior manager design planning and environment for Transport Canberra wouldn’t put an exact number on the trees that are dying or likely to die along the Northbourne alignment although he conceded the long run of extremely high temperatures had been very stressful for the newly planted four-metre trees.

“There are two categories – the ones that are in permanent decline and ones that are under stress,” he said. “It’s fair to say that in general terms the industry would expect a 5 per cent loss of mature trees planted, and we’re confident that we are under that at the moment.

“Clearly some of the trees have died and by the same token, some of the trees under stress have made a recovery. We are monitoring the ones under stress and seeing how they go, maintaining a watering regime for the stressed trees over the past few weeks.”

Paradoxically, heavy surface watering can create shallow root systems and unsustainable growth because the trees aren’t anchored deeply. Mr Sainsbury says this is a fair observation but believes that the “bespoke” planting environment installed for each tree will solve any problems.

“We’ve used 30 cubic metres of growing medium for each tree, and that level of soil preparation was never undertaken in the past. Previous trees were sitting on a clay pan which meant that the roots spread out in shallow systems. But the manniferas have provision for deep-root watering, where the water is channelled down to the base of the tree pit to promote root growth.”

Mr Sainsbury says the growing environment should also prevent compression from construction traffic, parrying the suggestion that it’s a compromise to plant them out at this size rather than planting smaller trees.

It’s there that he differs considerably from independent silviculturist Peter Marshall, who runs TerraPreta truffles at Braidwood and has over 40 years of forestry experience. He believes more trees are doomed because of “this concept of growing a tree to be long and thin and whippy and putting it in to create an instant forest.

“It’s a construction zone with soil compaction and concrete in the soil so the PH will be very high from the leftover lime. The position is very exposed and there’s a massive swing in temperatures at ground level from day to night.

“Had they planted little dollar seedlings of the same species they would have grown a metre in every year, at an astonishingly lower cost. This nursery-grown stock is four metres tall now, but they’ll possibly die under the stress of exposure, while the tubestock would get there quickly, with a much better root architecture and stability.

“Where is the survey that says the public want tall saplings that then die? Have they made this up in their own heads?”

Marshall is also critical of the species choice, saying the eucalypts risk shedding limbs as a matter of course. “High-temperature limb breakage is an ecological adaptation. A water column in the trunk literally explodes and detaches itself, which creates a hollow nesting place for birds and animals, whose manure then fertilises the tree. That’s a great ecosystem adaptation, but a massive disadvantage in an urban environment.”

In stark contrast, the tree planting process is characterised as “careful and deliberate” by Marcus Sainsbury. “Back in May 2017, we established a landscape trial plot that replicated in exact detail the planting arrangements for Northbourne. We are not watering the trial plots trees at all now and the regime has shown that those trees are doing really well”

Peter Marshall argues that deciduous trees, perhaps Mexican oaks from a very similar climate but with a much stronger root and branch structure would have been a better choice amidst Canberra’s magnificent tapestry of trees. But Marcus Sainsbury is adamant that the manniferas are the right choice and will thrive.

Do you think mature eucalypts were the right choice for the Northbourne corridor?


What's Your Opinion?

Please login to post your comments, or connect with
131 Responses to Heat stress and tree death won’t daunt Northbourne’s tree planting
Tony Williamson Tony Williamson 5:24 pm 29 Jan 19

Eucalypts dont like being moved.......At least if they survive they will continue to look like trees not a bunch of twigs that leave a big mess every year

Margaret Brauer Margaret Brauer 5:20 pm 29 Jan 19

Gum trees belong in the bush ,put some decent trees there !!

Meredith Robson Meredith Robson 5:17 pm 29 Jan 19

Mike Yup, the trees are dying already ☹️

Craig Elliott Craig Elliott 5:05 pm 29 Jan 19

Typical public service....they Probably asked one of the big 4 for advice as they can't think for themselves....SES that is

    Ali Geez Ali Geez 5:59 pm 29 Jan 19

    it was ACT public service that were responsible for light rail

    Craig Elliott Craig Elliott 7:20 pm 29 Jan 19

    Ali Geez .....yeah...but the big 4 have been supporting for over a decade

Christopher Mawbey Christopher Mawbey 4:53 pm 29 Jan 19

So what if they die.

The contract will stipulate replacement until they live.

Ian Champ Ian Champ 4:36 pm 29 Jan 19

Why would we believe any science based advice that the trees are in trouble in this day and age when we can simply believe any nonsense we choose.

Ian Jeffrey Ian Jeffrey 4:10 pm 29 Jan 19

Canberra was well when it it was looked after By the National Capital Development Authorities since then local Government took over it a shambles.

    Ashley Wright Ashley Wright 6:49 am 30 Jan 19

    Ian Jeffrey love your rose coloured glasses.

    Mine say most of the issues we have these days are as a result of the NCDC. Including the issue of moving people from a to b. The good old NCDC didn’t believe anyway would ever need to leave their own little town centre and would live, work and play nearby.

Jacqui Owen Jacqui Owen 3:55 pm 29 Jan 19

Trees that cool the corridor would be appropriate

Dorinda Lillington Dorinda Lillington 3:46 pm 29 Jan 19

NO. I think that any horticulturalist will know that young native tube stock does so much better than mature ones. Although any Eucs planted in tube stock would appear small and not have the immediate visual effect they would have had a better chance to establish with strength and would over time attain the same height as the mature ones planted any way. It is the contractors responsibility to replace any ones that die and of the same height. This project has made me cringe since I saw the first tree fall. If the Government can make this a money making venture great but I fear that this project is only going to suck money out of Canberra's population. But if I can be proved wrong then go for it. Are the fares going to reflect the real price that they need to be to cover the cost? I don't think so.

Peter Major Peter Major 2:57 pm 29 Jan 19

Wait till they put roots through the concrete and drop limbs on passengers and trams.

ACT planning at its finest 🤣🤣🤣🤣

They didn't learn from the last fiasco.

    David Brown David Brown 3:06 pm 29 Jan 19

    Peter Major What did they use so much concrete? In Europe they use sleepers. Less cost, less noise, quicker to lay and easier to maintain when something goes wrong.

    Peter Major Peter Major 7:36 pm 29 Jan 19

    Good ACT ineptitude. More money than sense

Robert McMahon Robert McMahon 2:57 pm 29 Jan 19

They were looking crook well before the heat.

Anthony Grice Anthony Grice 2:55 pm 29 Jan 19

Root system will destroy the road

Christine Jack Christine Jack 2:10 pm 29 Jan 19

No. Eucalyptus trees should not be planted in suburbs, what are they gonna do when one falls on a tram, Think 🤔

Erica Rushton Erica Rushton 2:02 pm 29 Jan 19

No. They make a huge mess.

Lynne Audsley Lynne Audsley 1:57 pm 29 Jan 19

Maybe they were put in when they were, as advanced trees and grasses, to give the impression that the light rail was closer to fruition than it actually was... 🤔And while we are at it, what are all those copper spaghetti type pipes all along the ‘nature areas’ of the light rail stations?

    Ashley Wright Ashley Wright 8:58 pm 29 Jan 19

    Lynne Audsley it was always the plan. The trees were put in at an advanced stage to help soften the visual impact faster. And you know what I personally don’t think it looks too bad. Certainly shits on what I saw in Sydney the other day with their new extension. That was plain awful.

    Lynne Audsley Lynne Audsley 9:30 pm 29 Jan 19

    But why plant them so early, with no obvious plan for watering over summer, and still construction going on? Surely all construction and beautification is on the same schedule?

    Ashley Wright Ashley Wright 6:53 am 30 Jan 19

    Lynne Audsley they did have a watering plan. A truck has been spraying the grasses and shrubs on a daily basis, another truck has been hand watering the trees.

    The biggest issue is the record breaking extreme heat we have had, and the length of time it has hung around for. Or where they meant to have somehow foreseen that too?

    And may I point something out in the article it clearly mentions the failure rate is LOWER than what they had planned for!

Justin Sev Justin Sev 1:55 pm 29 Jan 19

What is with that native/mondo/whatever grass that is planted on the line with the trees? It either looks dead or is an ugly metre long weed.. quality landscaping indeed

Fortress Epiphany Fortress Epiphany 1:50 pm 29 Jan 19

Whoever decided on those trees has NO CLUE !!! As an ex-staff member of what was the Melbourne & Metropolitan Tramways Board, I can assure you (and them) that leaves on tram track cause safety issues, constant skidding and other problems. Even dropping sand, as trams need to do to create enough resistance to stop in many conditions will not be enough to deal with the constant skidding on wet leaves. Pity no one asked any old school tram drivers what driving a tram actually involves. It will be like Melbourne’s Victoria Parade, with it’s gorgeous, but hazardous autumn leaves except gum leave fall all year around. What do you think Doc Rutherford 😃

    Paul Rutherford Paul Rutherford 5:20 pm 29 Jan 19

    I don’t know what eucalyptus leaves are like - never saw many along Melb tramlines. They may be oily but modern trams with electromagnetic breaking may not skid uncontrollably like the old W class trams did. But having to use an emergency brake in a tram full of passengers isn’t fun. But l reckon the tram will be great. Add some character to the boredom of the inner north 😎

    Tony Williamson Tony Williamson 6:44 pm 29 Jan 19

    Leaves on the rails WILL cause problems.....steel wheels on steel rails dont grip very well and then you add oily eucalypt leaves into the mix. Government at any level dont consult anyone that has any true knowledge on the subject at hand

    Colin Wilson Colin Wilson 9:06 pm 29 Jan 19

    Ann Chaplin “No Clue” pretty much sums up the ACT Greens/Labor Government.

    James Forge James Forge 10:06 pm 29 Jan 19

    Colin Wilson pretty well sums up every ACT government since the late 1980’s

Trish Roberts Trish Roberts 1:50 pm 29 Jan 19

No, of course the trees weren't the right choice. Aren't they called "brittle gums"? Who will be the first person they drop a limb on?

Pixie Longsocks Pixie Longsocks 1:46 pm 29 Jan 19

I don't understand why the big, established trees were cut down only to be replayed by younger versions thereof. What was the point?

    Steven Worthington Steven Worthington 7:02 am 30 Jan 19

    There were also issues with the trees not having a deep root base that was caused by ground watering. It meant that they would fall over more easily in storms and high wind. The new trees have systems in place to water them deeper to encourage deep roots. Kinda protecting us and the tram lines from potential damage. My understanding is that this also isn't the first time they have replanted Northbourne over the years.

    Pixie Longsocks Pixie Longsocks 11:17 am 30 Jan 19

    Fair enough, makes sense with respect to construction logistics. However, Eucalyptus have shallow root systems regardless of watering systems and gain their tenuous stability from their tap roots. So whilst a water system may have been installed to promote deeper lateral roots I don’t see how this would significantly improve the tree stability. I assume science says it does.

Mark Bowell Mark Bowell 1:35 pm 29 Jan 19

Next to electricity cables who is the dumb ass who ok’d that

CBR Tweets

Sign up to our newsletter

Region Group Pty Ltd

Search across the site