The effect of human trampling activity on a soil microbial community at the Oulanka Natural Reserve, Finland

Functional and taxonomic diversities of microbial communities in Arctic soils are governed by the extreme abiotic environment and affected by human activities. We assessed the impact of trampling by humans on biotic and abiotic parameters relevant to soil health at the Kiutaköngäs Trail, Oulanka Nature Park, Finland. Soil was sampled from the 0 to 2 cm, 2 to 5 cm, and 5 to 10 cm layers for four levels of trampling pressure: heavily trampled, medium trampled, low trampled sites, and non-trampled control. Measured and estimated abiotic soil parameters included organic matter, pH, water-holding capacity, and bulk density for each soil sample. Biotic parameters included determination of microbial biomass, CO ₂ evolution and MicroResp®-based community level physiological profiles, and as well as bacterial taxonomic diversity. Results have shown that total organic matter amount might not change significantly under trampling. Nevertheless, absolute substrate utilization, functional diversity, and respiration varied with depth, significantly declining in the immediate subsurface under the trampled sites. On the other hand, the most extreme stress associated with the greatest trampling intensity was associated with an increase in taxonomic diversity but with a proportional decline in Acidobacteria abundance, in line with the increase in pH.