Antioxidant properties of soils and associated vegetation in the polar urals

The increase in global air temperatures and climate aridization, associated with climate change, contribute to the biodegradation of soil organic matter (SOM) which is crucial for the ecosystems in cold and humid environments. SOM of the high-latitude mountain systems might be more vulnerable to temperature growth compared to that of plain landscapes due to higher soil drainage and solar irradiation. Thus, it is important to study the biochemical processes underlying the conservation of biomolecules of organic residues in these environments. Even though antioxidants might in principle contribute to stabilization of SOM, at the moment there is no established theory about the sources of soil antioxidant activity (AOA) and the mechanisms of its realization. In particular, in the relevant literature there is no data on the AOA of cryogenic soils. In this study we assess the antioxidant activity (radical scavenging activity and the ability to inhibit the initiated lipid peroxidation) of soil extracts from mountain tundra and meadows in Polar Ural (Russia) in model biological substrate. We show that SOM from sites with closed vegetation is less susceptible to oxidative degradation due to the high content of amino acids, organic forms of C and N including their water-soluble fractions, and low C/N ratio. On sites with scarce vegetation, soils exhibit low AOA and are vulnerable to the increase in temperature and aeration. Decreased AOA, low productivity of tundra plant communities, and the occurrence of large bare spots (up to 70% of the habitat) make these ecosystems most sensitive to climate change.