Microbial communities and functionality in degraded tundra soils

In Iceland, unsustainable land use has led to severe land degradation and desertification. Degradation may shape soil microbial communities, which has implications for ecosystem functioning. This study presents for the first time a characterization of the structure and function of soil microbial communities in tundra soils of contrasting stages of degradation in Iceland and shows promise in identifying degradation processes and potentials for recovery. We used shotgun metagenomic sequencing to compare soil microbial communities in a Betula nana heath with erosion spots and a highly degraded desert at two sites, inside and outside the active volcanic zone (Þeistareykir and Auðkúluheiði). The bacterial taxonomic composition of the desert soils with relatively high abundance of Actinobacteria, low respiration (microbial activity) and lower functional diversity reflected a highly degraded state. Heath soils at Þeistareykir had more abundant key ecosystem taxa of the genus Bradyrhizobium, higher taxonomic richness, microbial activity, and functional diversity compared to the heath at Auðkúluheiði, indicating that the heath in Auðkúluheiði is more degraded. Use of the trait-based framework of high yield (Y), resource acquisition (A), and stress tolerance (S) provided a more nuanced picture of the functional microbial roles in each of these soil types.