Microbial Biomass, Carbon Stocks, and CO2 Emission in Soils of Franz Josef Land: High-Arctic Tundra or Polar Deserts?

Abstract

The biomass of prokaryotes and fungi, organic carbon stocks, and CO2 emission were studied in the Cryosols and Leptosols of Franz Josef Land. The highest carbon stocks were found in the Eutric Leptosols (Loamic, Humic) formed in the wind-sheltered areas (23.2 kg C/m2 in the upper 50 cm), as well as in Turbic Cryosols (Humiс) that contained organic matter buried by cryoturbation (13.7–20.7 kg C/m2). The number of prokaryotes varied between 0.14 and 2.10 billion cells/g of soil, and the maximum values of their biomass were found in the litter. The fungal biomass varied from tens to hundreds of mg/g of soil depending on the type of soil and biotope. The share of spores was more than a half of the total fungal biomass in 80% of cases. Spores and mycelium were mainly represented by small forms with a diameter of up to 2–3 microns. The length of the fungal mycelium ranged from 4 to 272 m/g of soil. The maximum development of fungi was observed in the lichen biocrusts and moss litters. The fungal biomass decreased exponentially with the depth of horizons, and at the same time the share of prokaryotes in microbial biomass increased by several times. The share of microbial carbon in the total organic carbon was higher in soils of barrens (the most extreme habitats among the studied ones) as compared with the soils of local tundra areas (12.7 versus 2.5%, respectively). The levels of СО2 emission from the surface of undisturbed soils varied in the range of 1.6–91.7 mg C–CО2/m2 per hour and differed by tens of times between barrens and tundra areas. The studied soils are close to the soils of the Arctic tundra when compared by their carbon stocks and CO2 emission values; however, their microbial biomass values and their distribution are close to the soils of Antarctica and hot deserts.