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Changing forests

Researchers find climate shapes initial steps of soil formation in boreal forests

Research

By Kelly Foss

Researchers from Memorial University, the University of Helsinki and other colleagues have found that climate warming is changing the way one key soil formation process is carried out in boreal forests.

Lukas Kohl at Long Pond on Memorial’s St. John’s campus.
Photo: Submitted

“Plant litter decomposition is one of the most important processes in the natural carbon cycle,” said Dr. Lukas Kohl, a recent PhD graduate from Memorial and principal author of a paper recently published in the journal Global Change Biology.

“The foliage produced by plants contains more than twice the carbon as all human carbon dioxide emissions in a given year. While most of this carbon is released back into the atmosphere during litter decomposition, some of it is incorporated into soil organic matter, thus removing it from the atmosphere for centuries and longer.”

Historically, researchers have assumed that chemical differences in plant litter, for example, between leaves from different species, are lost during decomposition, and lead to a similar organic matter composition regardless of the initial input.

1/ Litterfall

Dr. Sue Ziegler, Canada Research Chair in Boreal Biogeochemistry in the Department of Earth Sciences, collecting litterfall in one of the Grand Codroy forest sites.

Photo: Submitted

2/ Provincewide study

A map of three of the four regions of the N.L.-BELT where sampling for the study took place.

Photo: Submitted

3/ Weather reading

A weather station outside of one of the forest study sites in the Salmon River region of the N.L.-BELT, located near Main Brook, N.L. on the Great Northern Peninsula.

Photo: Submitted

4/ In Grand Codroy valley

Initial sample collections made in one of the Grand Codroy forest sites by co-authors and colleagues Sharon Billings, University of Kansas, at left, and Kate Edwards, Canadian Forest Service, at right.

Photo: Submitted

5/

One of the three forest study sites in the Eagle River region of the N.L.-BELT, located near Cartwright, Labrador.

Photo: Submitted

In contrast, recent work has shown these chemical differences are not only preserved during decomposition, but new ones that microorganisms produce are added depending on the decomposition conditions.

The conditions controlling these microbial inputs include nitrogen availability that appears to increase with climate warming.

The chemical changes caused by these indirect effects of climate provide a plausible mechanism for maintenance of soil carbon stocks despite enhanced turnover of soil carbon with the climate warming in these forests.

“In this new study, we demonstrate that such differences occur due to natural variations in climate similar to the climate change that will affect boreal forests over the upcoming decades,” said Dr. Kohl.


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