Alaskan tundra - Maëlle Villani
In Arctic regions, soils are composed of a permafrost layer (i.e., ground that remains below 0°C for at least two consecutive years) surrounded by an active layer (i.e., ground that thaws in summer and freezes in winter). Climate change is thawing permafrost, leading to a release of carbon into the atmosphere estimated at 120–195 Pg by 2100. The release of carbon into the atmosphere as greenhouse gases (CO2 and CH4) contributes to a positive feedback effect on warming climate and deeper permafrost degradation. Another consequence of climate change and permafrost degradation is the shift in vegetation in Arctic and sub-arctic tundra: we are facing a shift in vegetation from sedges to shrubs, called “shrubification”.
Graphic summary of the research - Maëlle Villani
Shrubs have different concentrations of mineral elements (Si, K, Ca, P, Zn, Mn, Cu, Mo, and V) than sedges. With the return of foliar vegetation to the top soil, the concentration of these mineral elements in the topsoil would be different with the vegetation shift. This change in topsoil mineral element concentrations could influence organic carbon decomposition. For example, these elements can act on the growth and the environment of decomposers (microorganisms and fungus). However, the influence of vegetation shift on the recycling of these mineral element and their concentrations in topsoil in the context of permafrost degradation remain poorly quantified.
This recent study quantifies the influence of permafrost degradation associated with a vegetation shift from sedges to shrubs on topsoil and plant mineral element concentrations (Si, K, Ca, P, Zn, Mn, Cu, Mo, and V) in sub-Arctic tundra soils. To do this, we investigate foliar vegetation (two sedges and two deciduous shrubs) and topsoil mineral element composition across a natural gradient of permafrost degradation at a typical sub-Arctic tundra at Eight Mile Lake (Alaska, USA).
Results show that vegetation shift is influencing topsoil mineral element composition i.e., mineral elements that are key players for the rate of organic carbon decomposition and nutrient availability for vegetation. For example, we find a lower Si concentration in topsoil covered with shrubs, which can decrease organic carbon decomposition because Si is a promoter of decomposer growth.
What happens in Arctic does not stay in Arctic and we will also be affected by this amplification of warming climate.
Studying all parameters that can impact carbon cycle in permafrost regions is very important because this region contains twice as much carbon as there is currently in the atmosphere. All carbon released into the atmosphere is then amplifying warming climate all around the world. What happens in Arctic does not stay in Arctic and we will also be affected by this amplification of warming climate.
Do you want to read more about this interesting research? Have a look at the full article here!
Written by Maëlle Villani