Scientists record rapid carbon loss from warming peatlands

Date:
July 27, 2020
Source:
DOE/Oak Ridge National Laboratory
Summary:
Scientists have demonstrated a direct relationship between climate
warming and carbon loss in a peatland ecosystem. Their study
provides a glimpse of potential futures where significant stores
of carbon in peat bogs could be released into the atmosphere as
greenhouse gases.



FULL STORY ========================================================================== Scientists at the Department of Energy's Oak Ridge National Laboratory
have demonstrated a direct relationship between climate warming and
carbon loss in a peatland ecosystem. Their study published in AGU Advances provides a glimpse of potential futures where significant stores of carbon
in peat bogs could be released into the atmosphere as greenhouse gases.


========================================================================== Peatlands currently cover around 3% of Earth's landmass and hold at
least a third of global soil carbon -- more carbon than is stored in
the world's forests.

Peat bogs are particularly good at locking away carbon because of the
cold, wet, acidic conditions that preserve meters-deep layers of ancient
plant matter. Scientists have taken a keen interest in these enormous
carbon reserves, questioning how much and how quickly the hotter,
drier conditions in a peatland bog can trigger microbial processes that
release carbon in the form of carbon dioxide and methane into the air, furthering the warming cycle as the gases trap heat in the atmosphere.

Enter DOE's Spruce and Peatland Responses Under Changing Environments,
or SPRUCE project, a unique whole ecosystem manipulation experiment in
the forests of northern Minnesota. SPRUCE uses a series of enclosures
to expose large peatland plots to five different temperatures, with the
hottest of the chambers experiencing an increase of about 16 degrees
Fahrenheit above and deep belowground. Half the enclosures also received elevated levels of carbon dioxide.

This futuristic experiment allows scientists to measure the effects
of conditions this ecosystem has never experienced before, providing a
glimpse of potential future climates.

"Because of DOE's investment in a large-scale experiment, we've been
able to study whole ecosystem warming across a range of temperatures
that can't be extrapolated from historical data," said Paul Hanson, ORNL ecosystem scientist and SPRUCE project coordinator. "In doing so, we have evidence that carbon losses will be anticipated for rapidly changing
peatland systems in the future." Hanson and his colleagues examined
three years of SPRUCE data, tracking changes in plant growth, water and
peat levels, microbial activity, fine root growth and other factors that control the movement of carbon into and out of the ecosystem. Together,
these intakes and outputs make up what's known as the carbon budget.

The study found that in just three years, all warmed bog plots turned from carbon accumulators into carbon emitters -- marking the first time whole- ecosystem plots have been used to document such changes. This fundamental
shift in the nature of the bog occurred even at the most modest level
of warming (about 4 degrees F above ambient temperature), and showed
carbon loss rates five to nearly 20 times faster than historical rates
of accumulation.

Warmer temperatures directly translated into greater carbon emissions,
with the warmest of the experimentally heated plots emitting the most
carbon dioxide and methane. The scientists were surprised to find such
a linear relationship between heat and carbon loss.

"This is a very tight relationship for biological data," Hanson
said. "These results were within the range of hypotheses that we
allowed ourselves to think about, but the sensitivity of carbon loss to temperature was a bit of a surprise." The decline of sphagnum moss, a key species in this ecosystem, contributed notably to the net carbon loss. A previous study by ORNL colleague Richard Norby detailed sphagnum's role
in accumulating carbon in peat and its potentially irreversible decay
as warming dries out bogs.

The SPRUCE data will inform a new wetland model for potential use in DOE's Energy Exascale Earth System Model project, which uses high-performance computing to simulate and predict environmental changes important to the
energy sector. The wetland model accurately predicted the temperature
effects but overestimated the impact of elevated carbon dioxide compared
with the SPRUCE data, which showed no significant ecosystem-level effects
after three years of treatment.


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


========================================================================== Journal Reference:
1. Paul J. Hanson, Natalie A. Griffiths, Colleen M. Iversen, Richard J.

Norby, Stephen D. Sebestyen, Jana R. Phillips, Jeffrey P. Chanton,
Randall K. Kolka, Avni Malhotra, Keith C. Oleheiser, Jeffrey
M. Warren, Xiaoying Shi, Xiaojuan Yang, Jiafu Mao, Daniel
M. Ricciuto. Rapid Net Carbon Loss From a Whole‐Ecosystem
Warmed Peatland. AGU Advances, 2020; 1 (3) DOI: 10.1029/2020AV000163 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200727194713.htm

--- up 1 week, 5 days, 1 hour, 55 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)