Chemical and microbial properties of post-mining and post-fire soils afforested with different tree species

Abstract

The effect of tree species on properties of soils revegetated after serious disturbance may depend on the properties of the soil substrate and type of disturbance. We compared the microbial properties of reclaimed mine soils differing in texture (RMS Sands and RMS Loams, respectively), post-fire (Postfire) soils, and undisturbed natural soils (NAT) under three different tree species (black alder, silver birch and Scots pine). The uppermost mineral soil (depth 0–5 cm) samples were measured for the contents of organic carbon (Corg), total nitrogen (Nt) and phosphorus (Pt), dissolved organic carbon (DOC) and nitrogen (DON), pH in H2O and texture. Microbial analyses of the samples included determination of microbial biomass carbon (Cmic), basal respiration rate (RESP), as well as the activities of acid and alkaline phosphatase and urease. Enzyme activities were expressed per soil dry (AcdPho, AlkPho, URE for acid phosphatase, alkaline phosphatase and urease, respectively) and per unit of Cmic as specific enzyme activities (SP AcdPho, SP AlkPho and SP URE for acid and alkaline phosphatase and urease, respectively). The studied tree species differently affected the microbial properties of RMS, Postfire and NAT soils. Silver birch stimulated the development of large microbial biomass with high RESP and URE activity in RMS and Postfire soils. Black alder distinctly stimulated the activity of phosphatases – in particular AcdPho. High activity of phosphatases in the restored soils under black alder resulted from higher N content under this species and the competition for P between the tree species and soil microorganisms. This competition caused lower Cmic in the restored soils under alder despite their high Corg and Nt content. Scots pine had the weakest effect on the microbial properties of the soils restored after disturbance as the values of Cmic, RESP and the enzyme activities were the lowest under this species. Our results suggest that P availability may be limiting factor for the soil restoration under black alder. Therefore, additional P fertilization should be considered when using this tree species in restoration of degraded areas.