Abstract: Soil microbes and enzymes could respond to environmental change and stress, which have indicative effects for the recovery of soil ecological function. To investigate the indicative effects of soil microbial community and enzyme activities on changes of reclaimed soil quality in coal waste piles, we collected soil samples from reclaimed coal mine land (3-, 5- and 7-year-old orchards) in Caocun, Huozhou, Shanxi Province. Soil microbial community composition and the activities of four enzymes were measured. The influences of soil physicochemical properties on those parameters were analyzed by path analysis. The results showed that: (1) Soil organic matter, nitrogen and phosphorus concentrations increased with the increases of reclamation years in the three orchards, but the water content and clay content only increased remarkably in 7-year-old orchard. Compared with the local ordinary orchard (CK), soil quality was lower in the three reclaimed orchards. (2) The PLFAs concentrations of different microbial communities andenzyme activities in the three reclaimed orchards increased with reclamation duration. Bacteria, fungi, alkaline phosphatase and urease activities in 0-10 cm and 10-20 cm soil layers increased with the increases of reclamation duration. Both Gram negative bacteria and dehydrogenase activity in 0-10 cm soil layer and actinomycetes and catalase activity in 10-20 cm soil layer significantly increased. Generally, the PLFAs concentrations of microorganisms in different communities and enzyme activities in the three reclaimed orchards were lower than those in the controlorchard. (3) Bacteria, fungi, actinomycetes, Gram positive bacteria, catalase, urease, dehydrogenase and alkaline phosphatase activity all had significant indication for changes of soil properties in reclaimed orchards in coal waste piles, which could be used as microbial indicators for changes in soil quality.

Key words: straw decomposition, biochar, nutrient content, CO₂ emission