Soils in old-growth treetops can store more carbon than soils under our
feet

Date:
December 16, 2021
Source:
American Geophysical Union
Summary:
Canopy soils that form on tree branches contain three times more
carbon than soils on the ground in Costa Rica, potentially serving
as an important carbon sink around the world.



FULL STORY ==========================================================================
New research reveals a previously underappreciated way old-growth
forests have been recycling and storing carbon: treetop soils. Branches
in forest canopies can hold caches of soil that may store substantially
more carbon than soils on the ground beneath them, and scientists are
just beginning to understand how much carbon canopy soils -- which exist
on every continent except Antarctica - - could store.


==========================================================================
The new research on these unique soils, being presented on Wednesday,
15 December at AGU Fall Meeting 2021, marks the first attempt to quantify carbon capture by canopy soils. The work highlights another way old-growth forests are rich, complex ecosystems that cannot be quickly replaced by replanting forests.

Tree branches collect fallen tree leaves and other organic material
over hundreds of years, like the ground does. On top of the branches,
the plant litter decomposes as it accumulates, forming a carbon-rich
layer that can be several inches thick. The researchers climbed up into
the rainforest canopy in Costa Rica, instruments in hand, to find out
just how much carbon canopy soils can contain.

Active carbon, a short-term storage pool of organic carbon, was three
times higher in canopy soil compared to soils underfoot, the researchers
found.

"We knew these would be really organic-rich soils, but we didn't expect
the extremely large amount of carbon compared to mineral soils," said
Hannah Connuck, an undergraduate researcher at Franklin and Marshall
College who will be presenting the study results.

The researchers are still calculating the total concentration of organic
carbon at their research site, but other research has found canopy
soils to have up to 10 times higher concentrations of organic carbon,
according to soil scientist Peyton Smith, a study co-author and Connuck's
soil science mentor at Texas A&M University.

Connuck and Smith also measured how much carbon dioxide was being released
by microbial organisms living in the canopy soils, which is critical
for knowing whether soils are storing or releasing carbon overall. They
found that even though the microbes were releasing higher volumes of
carbon dioxide than ground soils, their rate of carbon storage was rapid
enough to compensate, likely making canopy soils a net carbon sink that
has not been considered in carbon models yet.

"It could be a substantial carbon sink, and we need to account for it,"
Smith said.

Like other soils, canopy soils take a long time to form, and therefore
take a long time for a forest to recover if an area of old growth is cut
down. The soils also host unique microbiomes, including highly diverse microbial organisms and canopy-specific plants like epiphytic orchids.

"It's a good argument for keeping primary and other old-growth forests
around, rather than harvesting and replanting with secondary growth
forests," Connuck said.

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


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Link to news story: https://www.sciencedaily.com/releases/2021/12/211216150334.htm

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