Development of soil chemical and microbial properties in reclaimed and unreclaimed grasslands in heaps after opencast lignite mining

Understanding changes in soil chemical and microbial properties under different vegetation types on post-mining sites is an important step in developing management practices to enhance ecosystem functions. Changes in soil carbon (C), nitrogen (N) and phosphorus (P) stock, pH, bulk density and microbial properties (microbial biomass, respiration and ergosterol content) were studied in chronosequences on reclaimed and unreclaimed grasslands on heaps after lignite mining in the northwest of the Czech Republic. Reclaimed sites were established by applying topsoil and seeding cultural grasses and legumes. Unreclaimed sites were only levelled and spontaneously colonized by grassy vegetation dominated by bushgrass (Calamagrostis epigejos (L.) Roth). Topsoil application created more favourable conditions for organic matter accumulation in soil. The C and N contents in the soil of reclaimed sites increased with age, while no significant changes occurred in unreclaimed sites. The results indicated a high potential for C sequestration in reclaimed grasslands with topsoiling, estimated at up to 1.6 t ha y−1. The P content did not change with age in either reclaimed or unreclaimed sites. Microbial biomass and respiration increased with chronosequence in both sites. However, respiration did not differ between reclaimed and unreclaimed sites, while microbial biomass was significantly higher in reclaimed sites.