Measuring the health of trees with the speed of sound

measuring health of trees

Trees can be deceiving – while they may look healthy from the outside, inside often tells a very different story. Wood rot in living trees causes overestimates of global carbon pools, timber loss in forestry, and poor tree health. Wood decay is of particular concern in the tropics, with tropical forests estimated to harbor, “96% of the world’s tree diversity and about 25% of terrestrial carbon, compared to the roughly 10% of carbon held in temperate forests.”

But how can foresters and researchers see into a living tree to measure wood decay? Surprisingly, with sound. A recently published article in Applications in Plant Sciences details methods using a sound wave technology called sonic tomography, tested on more than 1800 living trees in the Republic of Panama.

Greg Gilbert, lead author of the article and Professor and Chair of the Department of Environmental Studies at the University of California, Santa Cruz, said, “We don’t yet know where internal decay and damage rank as a cause of tree mortality. Most of the decay is hidden–the tomography now allows us to see how many apparently healthy trees are actually decayed inside.”

Sonic tomography sends sound waves through tree trunks, with the longer it takes for a sound wave to traverse a trunk indicating more decay in the wood. Based on the velocity of sound, the tomograph makes a color-coded image of a cross section of the trunk.

Sonic tomography can also be used for urban forestry. In fact, Gilbert and his colleagues, together with the Smithsonian Tropical Research Institute will collaborate with Panama City to use tomography to evaluate the health and associated risks of Panama’s urban trees.

Learn more about innovative tree solutions for urban forests here.



Perth councils take action to stop 90% of trees dying before maturation

trees dying before maturation

In a frightening statistic, more than 90% of trees planted by Perth councils in an attempt to cool hot suburbs will die before maturing. The three main causes of death include:

  1. Defective root systems, due to gradual changes in nursery technologies over the past 50 years
  2. The practice of ‘hydrozoning’, a watering technique used in parks and reserves which prioritises turf and recreational areas over trees
  3. Increasing infill and resulting ‘hardscaping’ which has led to a decrease in soil quality

Recognising the seriousness of this mortality rate, Perth councils are pouring cash into greening, and slight adjustments have been made which will hopefully achieve big results.

Standards Australia has this year released a new Australian Standard aiming to improve the quality of root health in trees. Hydrozoning plans must also be adapted to better care for trees, and lastly soil health must be improved with planning for trees occurring at the same time as planning for infrastructure, allowing for the required volume and quality of soil (mindful of Perth’s already sandy soil).

Arbor Centre Principal, Rob Bodenstaff, said, “You need to engineer in a tree, not expect it to tolerate everything else we do. We do have solutions to all this stuff. It’s not high-level science … you can drought-proof trees and suburbs. Within the same budget we could get far better outcomes. If nothing happens, we’ll have constant celebration of trees being planted and the constant disappointment of realising they have failed.”[1]

Learn more about innovative tree solutions for urban forests here.


New trees for Melbourne in response to climate change

trees in response to climate change

Climate change is undeniable with rising temperatures and drier conditions causing many of Melbourne’s established elm and plane trees to struggle. Melbourne City Council and Melbourne University recently teamed up, releasing a report advising which trees to plant to better cope with climate change.

Dr Dave Kendal studied tree inventories from 200 countries and selected 875 species suitable for warmer temperatures and sub-tropical climates. Lord Mayor Robert Doyle said the council commissioned the study after a startling discovery was made when scientists studied temperatures across Melbourne’s greater metropolitan area. “We found that the centre of the city is 5 degrees Celsius hotter than the outskirts,” Cr Doyle said.

In a bid to cool down Melbourne, 3000 new trees have been planted each year since 2012. With this new insight, council will focus on diversifying the urban forest, introducing Australian native species that thrive in sunny, warm climates such as hoop pines, Queensland brush boxes, and Moreton Bay figs. New exotic tree species that cope with warm temperatures and droughts, such as the Algerian Oak, and flowering tree species, will also be planted.

The city’s urban forest strategy costs $1.5 million each year, but Cr Doyle said it was a worthwhile investment. “We are doing a 100 years policy, our grandchildren and great grandchildren will enjoy the urban forest of Melbourne just like we have,” he said.

Learn more about innovative tree solutions for urban forests here.


Do trees have friends? Absolutely, says German forest ranger and author

do trees have friends?

Peter Wohlleben, a German forest ranger and best-selling author, has learned many secrets about trees. His latest book, ‘The Hidden Life of Trees: What They Feel, How They Communicate – Discoveries From a Secret World’ has been a runaway success.

In the book, he details the wildly complex and intriguing secret life of trees. And, yes, he believes trees have friends!

Wohlleben says trees, “…can count, learn and remember; nurse sick neighbors; warn each other of danger by sending electrical signals across a fungal network known as the ‘Wood Wide Web’ – and, for reasons unknown, keep the ancient stumps of long-felled companions alive for centuries by feeding them a sugar solution through their roots. These trees are friends. You see how the thick branches point away from each other? That’s so they don’t block their buddy’s light. Sometimes, pairs like this are so interconnected at the roots that when one tree dies, the other one dies, too.”

Despite the book being a best seller, it has been controversial with some German biologists who question his use of language to describe life in the forest. Wohlleben says, “I use a very human language. Scientific language removes all the emotion, and people don’t understand it anymore. When I say, ‘Trees suckle their children,’ everyone knows immediately what I mean.”

With a new appreciation of trees key to our planet’s survival, Wohlleben’s work is nothing short of inspirational.

Buy the book here or read more about urban forests for the future here.


Restoring the Urban Environmental Cycle [INFOGRAPHIC]

restoring the urban environmental cycle

Ongoing scientific research provides overwhelming evidence to reinforce the numerous benefits and advantages that trees can bring to the urban environment, in terms of both their social and environmental impacts:

  • Water flow and quality:

    Trees and soils improve water quality and reduce the need for costly storm water treatment (the removal of harmful substances washed off roads, parking lots, and rooves during rain and snow events), by intercepting and retaining or slowing the flow of precipitation reaching the ground.

  • Individual wellbeing and public health:

    Urban trees and forests make the environment a more aesthetic, pleasant, and emotionally satisfying place in which to live, work, and spend leisure time. Urban trees also provide numerous health benefits; for example, reducing ultraviolet radiation and its associated health problems, and enabling hospital patients with window views of trees to recover faster.

  • Community wellbeing:

    Urban forests make important contributions to the economic vitality and character of a city, neighbourhood, or subdivision – improving the sense of community optimism.

  • Noise abatement:

    Properly designed plantings of trees and shrubs can significantly reduce noise by 50% or more.

  • Wildlife and biodiversity:

    Urban forests help create and enhance animal and plant habitats and can act as reservoirs for endangered species.

  • Local climate and energy use:

    Trees influence thermal comfort, energy use, and air quality by providing shade, transpiring moisture, removing air pollutants, and reducing wind speeds.

  • Real estate and business:

    Landscaping with trees can increase property values and commercial benefits. One study found that, on average, prices for goods purchased were 11% higher in landscaped areas than in areas with no trees.

restoring the urban environmental cycle infographic

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