In-situ soil greenhouse gas fluxes under different cryptogamic covers in maritime Antarctica

Soils can influence climate by sequestering or emitting greenhouse gases (GHG) such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). We are far from understanding the direct influence of cryptogamic covers on soil GHG fluxes, particularly in areas free of potential anthropogenic confounding factors. We assessed the role ofwell-developed cryptogamic covers in soil attributes, as well as in the in-situ exchange of GHG between Antarctic soils and the atmosphere during the austral summer. We found lower values of soil organic matter, total organic carbon, and total nitrogen in bare areas than in soils covered by mosses and, particularly, lichens. These differences, together with concomitant decreases and increases in soil temperature and moisture, respectively, resulted in increases in in-situ CO2 emission (i.e. ecosystem respiration) and decreases in CH4 uptake but no significant changes in N2O fluxes. We found consistent linear positive and negative relationships between soil attributes (i.e. soil organic matter, total organic carbon and total nitrogen) and CO2 emissions and CH4 uptake, respectively, and polynomial relationships between these soil attributes and net N2O fluxes. Our results indicate that any increase in the area occupied by cryptogams in terrestrial Antarctic ecosystems (due to increased growing season and increasingly warming conditions) will likely result in parallel increases in soil fertility as well as in an enhanced capacity to emit CO2 and a decreased capacity to uptake CH4. Suchchanges, unless offset by parallel C uptake processes, would represent a paradigmatic example of a positive climate change feedback. Further, we show that the fate of these terrestrial ecosystems under future climate scenarios, as well as their capacity to exchange GHG with the atmosphere might depend on the relative ability of different above-ground cryptogams to thrive under the new conditions. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study found that Antarctic soils covered with mosses and lichens have higher levels of soil organic matter, total organic carbon, and total nitrogen compared to bare areas. This results in increased CO2 emissions, decreased CH4 uptake, and no significant change in N2O fluxes. The research suggests that an increase in cryptogamic cover in Antarctic ecosystems could lead to higher soil fertility, increased CO2 emissions, and reduced CH4 uptake, potentially creating a positive climate change feedback loop.