Arctic Soils

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Arctic Soils


Electron micrograph of the Ebola Zaire virus. This was the first photo ever taken of the virus, on 10/13/1976. By Dr. F.A. Murphy, now at U.C. Davis, then at the CDC.

By Tia Chung-Swanson

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The insertion code consists of:

Double brackets: [[ Filename: PHIL_1181_lores.jpg Thumbnail status: |thumb| Pixel size: |300px| Placement on page: |right| Legend/credit: Electron micrograph of the Ebola Zaire virus. This was the first photo ever taken of the virus, on 10/13/1976. By Dr. F.A. Murphy, now at U.C. Davis, then at the CDC. Every image requires a link to the source. Closed double brackets: ]]

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Introduce environment. Give key information relevant to the microbial ecology of the environment.


Detailed Environmental Description

Global distribution of soils based on thickness of permafrost layer. Dark purple is continuous permafrost. From the International Permafrost Association.

In the first soil classification system, created in the 1890s, there were five natural soil zones: tundra, podzol, chernozem, desert, and laterite.[2] Arctic soils were classified in this system as tundra soils. Even with the limited knowledge from the 19th century, it was clear that cold-climate zones were unique because of the much more relevant layer of permafrost. Permafrost is soil that remains permanently frozen for the entire year, which is topped by an active layer that thaws each summer and then freezes again for the winter.[3] Today, arctic soils are classified as gelisols within the soil taxonomy created by the Natural Resources Conservation Service. A gelisol is defined as a soil that has either “permafrost within 100 cm of the soil surface,” or “gelic materials within 100 cm of the soil surface and permafrost within 200 cm of the soil surface.”[4] Since permafrost is frozen year-round, it stores a large amount of organic matter that does not get degraded. Arctic soils are particularly interesting at the moment due to anthropogenic climate change. When permafrost melts from the rising temperatures, the microbes stored in that soil activate and they can use all the newly accessible nutrients. They release CO2[5] and possibly other greenhouse gases, like CH4, and N2O.[6] This permanently increases the thickness of the active layer, which has implications for the biogeochemical cycling that the Arctic and other gelisols are capable of.

Overview of Microbial Ecology as it is known

Alpha diversity of bacterial phyla, bacterial classes, archaeal phyla, and fungal phyla. From a meta-analysis from Malard and Pearce, 2018.

Arctic soils are dominated by Proteobacteria and Acidobacteria. The next most common phyla are Bacteriodetes and Actinobacteria, but the proportion of these two varies by study site.[7] The proportion of cyanobacteria is very low compared to other nutrient-rich soils like molisols due to the much thinner active layer of Arctic soils.
The archaeal phyla are much less consistent, though there are consistently very few members from the Parvarchaeota phylum. Fungal phyla are dominated by Ascomycota and Basidiomycota. [7]

Expansion topic 1-3

How you expand upon the basics will depend on your environment. Pick a couple or three of interesting subtopics and describe them in detail. Include some current research, with at least one figure showing data.

Key Microbial Players

In all of your systems there will be at least a couple of key microbial players. Describe these in detail. Where do they fall on the tree of life? Are they cultured? What do they do in general and as it relates to your target environment?

Nitrogen fixing Proteobacteria, including Rhizobiales, Burkholderiales, Xanthomonadales, and Myxococcales dominate and do all of the nitrogen fixing in Arctic soils. These orders belong to Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Deltaproteobacteria respectively. Despite the low percentage of Cyanobacteria in these soils, Cyanobacteria are still critically important because they are responsible for most of the CO2 and N2 uptake.[7] Nitrogen fixers are so important that one study found that Arctic microbial communities are actually N-limited, rather than C-limited like most other soil microbial communities.[6]



Authored for Earth 373 Microbial Ecology, taught by Magdalena Osburn, 2020, NU Earth Page.