Laser technology measures biomass in world's largest trees

Date:
October 15, 2020
Source:
University College London
Summary:
Laser technology has been used to measure the volume and biomass
of giant Californian redwood trees for the first time, records a
new study.



FULL STORY ========================================================================== Laser technology has been used to measure the volume and biomass of
giant Californian redwood trees for the first time, records a new study
by UCL researchers.


==========================================================================
The technique, published in Scientific Reports, offers unprecedented
insights into the 3D structure of trees, helping scientists to estimate
how much carbon they absorb and how they might respond to climate change.

Professor Mat Disney (UCL Geography), lead author on the study, said:
"Large trees are disproportionately important in terms of their above
ground biomass (AGB) and carbon storage, as well as their wider impact
on ecosystem structure.

They are also very hard to measure and so tend to be underrepresented
in measurements and models of AGB.

"We show the first detailed 3D terrestrial laser scanning (TLS)
estimates of the volume and AGB of large coastal redwood trees (Sequoia sempervirens) from three sites in Northern California, representing some
of the highest biomass ecosystems on Earth." The research contributes
to an aspect of climate change research with increasing focus.

Professor Disney add: "Big questions within climate science in response
to rising CO2 levels are whether and where more trees should be planted
and how best to conserve existing forests. In order to answer these
questions, scientists first need to understand how much carbon is stored
in different tree species." Estimating the size and mass of very large
trees is an extremely difficult task. Previously, trees could only be
weighed by cutting them down or by using other indirect methods such as
remote sensing or scaling up from manual measurements of trunk diameter,
both of which have potentially large margins of error.



========================================================================== Working with colleagues at NASA, and with support from the NASA Carbon Monitoring System programme, the researchers used ground-based laser measurements to create detailed 3D maps of the redwoods. NASA's new space
laser mission, GEDI, is mapping forest carbon from space, and the GEDI
team are using Professor Disney's work to test and improve the models
they use to do this.

The trees scanned include the 88-metre tall Colonel Armstrong tree,
with a diameter-at-breast height of 3.39 m, which they estimate weighs
around 110 tons, the equivalent of almost 10 double-decker buses.

The researchers compared the TLS estimates with other methods and
found that their estimates correlated with those of 3D crown mapping, a technique pioneered by American botanist Stephen C. Sillett that involves expert climbers scaling giant redwoods to manually record fine details
about their height and mass.

Professor Disney's team found that their AGB estimates agreed to within
2% of the records from crown mapping. Crucially, they also found that
both these 3D methods show that these large trees are more than 30%
heavier than current estimates from more indirect methods.

The researchers recommend that laser technology and 3D crown mapping
could be used to provide complementary, independent 3D measures.

Assistant Professor Laura Duncanson (NASA Earth Sciences & University
of Maryland), last author on the study and member of the NASA GEDI
science team, said: "Estimating the biomass of large trees is critical
to quantifying their importance to the carbon cycle, particularly in
Earth's most carbon rich forests. This exciting proof of concept study demonstrates the potential for using this new technology on giant trees
-- our next step will be to extend this application to a global scale in
the hopes of improving GEDI's biomass estimates in carbon dense forests
around the world."

========================================================================== Story Source: Materials provided by University_College_London. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Mathias Disney, Andrew Burt, Phil Wilkes, John Armston, Laura
Duncanson.

New 3D measurements of large redwood trees for biomass and
structure.

Scientific Reports, 2020; 10 (1) DOI: 10.1038/s41598-020-73733-6 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201015084517.htm

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