Microbial Communities of Mt. Prindle, AK — Permafrost soils!

Sophie Weaver
Technical summary: Permafrost and microbial functional diversity

Climate change is amplified in high latitudes, making areas with discontinuous permafrost especially susceptible to thaw. With the thaw and resulting processing of previously frozen soils through microbial decomposition, increased release of CO2 and CH4 into the atmosphere will occur. Permafrost currently stores approximately twice as much carbon as is in the atmosphere, making permafrost thaw and microbial processing an important topic of research in light of climate change. These authors asked (1) how are microbial communities and their functional composition and abundance affected by permafrost thaw and (2) what environmental shifts due to permafrost thaw (i.e. vegetation) might be leading to these changes. This study was carried out in Interior Alaska, where discontinuous permafrost creates an ideal location to study the impacts of permafrost thaw on soil biogeochemical cycling. They used GeoChip analyses to measure microbial functional genes present in minimally thawed, moderately thawed, and extensively thawed permafrost soil samples. They found that microbial community functional gene abundances (especially for C and N cycling genes) were highest at the moderately thawed sites and were associated with higher vascular plant growth. They found that along the thaw progression, microbial functional gene richness declined, but microbial community diversity actually increased. These results suggest that microbial communities and vascular plant growth might be correlated due to warming soils and permafrost thaw. As permafrost thaws, microbial decomposition and nutrient cycling will likely increase in these soils, and vascular plants could benefit from this, changing the tundra landscape and vegetation and suggesting that microbial and plant communities may co-evolve.

Non-technical Summary: What’s going on below this patch of vegetation??
Every environment surrounding us contains communities of microorganisms that perform important processes. These processes cycle elements, like carbon and nitrogen, throughout the biosphere (think – water cycle but more complex!). Soils, for example, are incredibly diverse environments that not only harbor plant growth, but are also home to millions of microbes. Soils have many characteristics that help define the community of plants and microbes that will be able to live there. Some soils are located in climates that are so cold they are continuously frozen for more than two years. This extreme soil habitat is called permafrost, and has its own unique microbial communities. When we think of climate change, we often picture starving polar bears and rising sea levels, but permafrost is also damaged by warming temperatures! As permafrost thaws, the plants growing on these soils can be impacted by increasing soil moisture and temperature. Microbial communities can also change, as some microbes are better fit to survive in the new, thawed,  conditions. So what might happen to these microbes that currently live in permafrost habitats that are starting to thaw? A study in central Alaska discovered that as permafrost thaws, plant growth changes, and the amount and the function of microbial communities present also changes! These scientists discovered that microbes found in more thawed soils had more abundant genes involved in the cycling of carbon and nitrogen, meaning that these microbes were better fit to process the carbon and nitrogen available in their environment. This change in soil conditions not only caused a change in microbial community, but also impacted the growth of the plants nearby! So what does this mean for microbes? As the Earth’s temperature continues to rise, more permafrost is expected to thaw, and microbes in Alaska are going to have to adapt in order to survive in novel soil conditions or they will be replaced by other microbes that are better fit for an unfrozen soil environment. While these microbes will likely benefit from thawing permafrost, the loss of permafrost will have huge implications for climate warming and plant growth, Microbes will contribute to climate change by increasing the prevalence of greenhouse gases (carbon dioxide, methane) in the atmosphere. The importance of microbial contributions to climate change should not be underestimated!

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