Northern forests store a third of the world’s carbon, acting as sinks for atmospheric carbon dioxide. Forest carbon exchange is the process whereby forests sequester carbon dioxide from the atmosphere via photosynthesis, storing it in their wood, leaves, and roots, and releasing some carbon through decomposition and respiration. This natural cycle in forests is a critical part of the global carbon cycle and is a key factor in the mitigation of climate change.
The carbon cycle in northern forests is affected by the depth of winter snow and its duration. It turns out that other elements of the forest ecosystem play an important role as well. Researchers at the University of Oulu in Finland measured the impact of reindeer grazing and snow depth in Finland’s coniferous forests over a five-year period.
There are areas in northern Finland’s forests where reindeer grazing has been excluded for decades. In these areas, shallow snow increased carbon release. In the same locations, deeper snow decreased carbon release. On the other hand, in areas where reindeer grazed, carbon release remained stable regardless of changes in snow cover.
The researchers theorize that the substantially recovered lichen cover in the ungrazed areas influences soil temperature and moisture conditions. When combined with changing snow conditions, these factors may affect soil decomposers and, therefore, the amount of carbon released.
The essential conclusion of this work is that multiple elements of an ecosystem, such as reindeer grazing, can buffer ecosystem functions, such as carbon exchange. In this case, reindeer play an important role in sustaining the biodiversity of northern ecosystems.
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Reindeer grazing can mitigate the impacts of winter climate change on forest carbon release
Photo, posted December 17, 2015, courtesy of Eco Dalla Luna via Flickr.
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