Forest succession on abandoned arable soils in European Russia – Impacts on microbial biomass, fungal-bacterial ratio, and basal CO2 respiration activity

Abstract

Soils in a succession row of forest re-growth in the European part of Russia were studied after abandonment of arable land use (7 up to 45 years), and compared to soils of secondary (80–100 yrs), of old-age (>100 yrs) and of mature (450 yrs) coniferous and deciduous forest sites. At each site, two top layers of the podzolic soils were analyzed for microbial biomass (Cmic), basal CO2 respiration activity (BR), metabolic quotient (qCO2), Cmic/Corg and fungal/bacterial ratios. In the uppermost soil layer, Cmic increased significantly (149, 187, 245, 502, 759, and 755 μg Cmic g−1 soil) in the succession row of arable, young fallow, young forests (20 and 45 yrs), and secondary and mature forests, as it was found for BR (0.40, 0.55, 0.76, 1.67, 2.52, 2.34 μg CO2–C g−1 h−1 soil), respectively. Both Cmic and BR were higher in the uppermost soil layer compared to the lower one. In soils of old-age spruce and oak forest, Cmic, BR and the Cmic/Corg ratio were significantly higher compared to the soils of the succession row, while qCO2 was lower. The fungal contribution to total substrate-induced respiration was 58–74%, with a tendency to increase in mature or old-age forests, as compared to young forests and arable soil. Thus, we found evidence that forest succession on abandoned arable sites in European Russia promotes soil microbial biomass and activity up to a level of mature forests, combined with shifts toward a fungal dominated community.