Soil microbial communities links to alternative steady vegetation states (HISTECO WP3)

In this study, the objective was to identify factors that governed the transformation of a sub-arctic vegetation into two contrasting trajectories, or 'alternative steady states', in response to historical reindeer herding. A productive graminoid-dominated vegetation, induced by intensive grazing intensity, has been suggested to represent an alternative state for the slow-growing dwarf shrub vegetation typical for subarctic tundra ecosystems. Microbes are important symbionts for plants and crucial for nutrient and carbon cycling in northern ecosystems. However, the soil microbial communities seem more resistant to disturbance compared with plant communities, which could create a discrepancy in how above- and belowground communities and soil carbon sequestration change through time after disturbances. For understanding the recovery of dwarf shrub vegetation from disturbance, we studied the extent of which the soil microbial community compositions remained stable or were transient after a disturbance. We sampled four types of plots at old reindeer herding sites 1) controls (dwarf shrub), 2) recovered, 3) shifted, and 4) graminoid plots. Samples were collected in August 2021. Soil microbial community compositions were characterized using high-throughput sequencing with fungal (fITS7-ITS4) and bacterial primer pairs (515F–806R). Two DNA extractions were done per soil sample and combined before PCRs and sequencing.