Development of microbial properties in a chronosequence of sandy mine soils

Soil microbial communities are of crucial importance for the functioning of ecosystems developing in post-mining areas. The objective of this study was to compare the properties of microbial communities in mine soils reclaimed for forestry and in mine soils developing under vegetation from natural succession. Soil samples were taken from a degraded site prior to reclamation (MS), a site after 2 years of lupine cultivation (LUP), reclaimed post-mining sites afforested with Scots pine (R6, R20, R28), post-mining sites with spontaneously developing pine forest stands (S6, S20, S27) and two natural pine forest stands (F30, F100). The examined microbial properties included basal respiration (RESP), microbial biomass (Cmic), Cmic-to-Corg ratio, potential nitrogen mineralization rate (Min_N) and community-level physiological profiles (CLPPs) studied using Biolog® Ecoplates. The lowest Cmic, RESP and Min_N values were determined in soil MS (Cmic = 26.5 mg kg−1, RESP = 1.06 μg C-CO2 g−1 24 h−1, Min_N = 5.2 μg N kg−1 24 h−1). Among the reclaimed mine soils the most biologically active was R6 (Cmic = 89.2 mg kg−1, RESP = 7.28 μg C-CO2 g−1 24 h−1, Min_N = 213.2 μg N kg−1 24 h−1). Cmic, RESP and Min_N gradually increased with soil age in S6, S20 and S27. Cluster analysis of CLPPs revealed a distinct difference between the natural forest soils and the mine soils. Among the mine soils, the least physiologically diverse was MS. In the successional mine soils, the metabolic abilities developed gradually with soil age. The CLPPs of the youngest successional mine soils resembled more the profiles of soil MS than those of natural forest soils whereas for the youngest reclaimed mine soils the opposite was the case. The results indicate that reclamation measures not only boost the gross microbial properties but also promote rapid development of metabolic abilities characteristic of natural forest soil microbial communities.