Increasing Shrubs Reduce The Positive Climate Contribution Of Peatlands
December 26, 2012

From Carbon Sink To Carbon Source, Bogs Lose Effectiveness Due To Increasing Shrub Cover

Brett Smith for - Your Universe Online

Bogs and mires are important ecosystems that also play an important role the storage of global atmospheric carbon emissions.

According to a study in Nature Climate Change, the peat mosses, which are found in boglands and drive the production of peat, are being outcompeted by vascular plants, resulting in bog degradation.

In the study, researchers from the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) closely observed four Swiss bog sites at different altitudes, from 1900 to 6200 feet, over a three-year period. They chose to monitor peat moss activity on an altitudinal gradient in an attempt to predict the various climate conditions in northern Switzerland by 2050.

The research team discovered that an increase of shrub cover and soil temperature has a direct correlation to a reduction of almost 50 percent in the production of new litter via the decomposing effects of peat mosses.

An analysis of the vascular plants that lived alongside the peat mosses showed that they were increasing the amount of soil nitrogen through certain chemical compounds in their leaves. As the plants utilize the nitrogen compounds for their growth through a symbiotic fungal relationship at root level, the researchers found the process becomes even more active as the soil temperature increases.

They also noted that vascular plants release a greater amount of organic matter into the soil through their roots as temperatures increased, stimulating the decomposition activity of microbes in the soil. This increased decomposition activity accelerates the decomposition of old peat. The result of less peat being the reduced storage of atmospheric carbon over time – transforming peatlands from carbon sinks into carbon sources, this contributing to the forces driving climate warming, the report said.

Peat, or Sphagnum, mosses are responsible for the accumulation of peat. They produce a litter that contains antibiotic properties that hamper the decomposing activity of soil microbes. The marshes where peat mosses thrive are excellent at retaining water, making them an ideal place for the tiny plants, which do not have roots. The marshy conditions also create anoxic conditions that reduce the decomposition of plant litter – allowing for peat mosses to dominate the area.

Peatlands have a unique place in the hierarchy of Swiss society, particularly because of the Rothenthurm Initiative. Passed in 1987, the initiative constructed a legal framework to protect the upland moor of Rothenthurm and other moors in Switzerland. An article adopted into the Swiss Constitution that same year was designed to save peatlands from destruction.

Besides being under threat from vascular plants, boglands have been decimated by human activity. Many of them are drained so that they can be used for agriculture or harvested for their peat. The peat drainage causes thousands of years of stored carbon to be released into the atmosphere. Draining of these wetlands occurs most frequently in developing countries like Indonesia and Malaysia.

The drainage can also result in peat fires. Being high in carbon, drier peat readily ignites and can smolder for a long period of time, from weeks to centuries. These fires also contribute to global carbon emissions.

Image 2 (below): Long-term carbon accumulation in peatlands relies on peat mosses (reddish) more than on vascular plants (green). Photo: Luca Bragazza / WSL