LAUSR

Abstract Various alder species may be used in the reforestation of post-mining barrens in order to supply developing mine soils with nitrogen, increase their organic matter content and biological activity. The objective of this study was to compare the effect of green alder (Alnus viridis) and black alder (Alnus glutinosa) on chemical and microbiological properties of sandy mine soils. The samples of O horizon and mineral soil (0–5 cm) were taken under the equal-aged green and black alder stands growing on extremely poor sands and measured for the contents of organic C (Corg) and total contents of N (Nt), P (Pt), K, Ca and Mg. In the mineral soil, additionally available and water soluble P (Pavl and PH2O) was measured. The measured microbial properties included microbial biomass (Cmic), basal respiration rate (RESP), N mineralization rate (Nmineralization) and the activities of urease (URE), alkaline and acid phosphatase (PHOalk and PHOacd, respectively). The O horizon under black alder contained significantly more nutrients (Nt, Pt, K), harbored higher microbial biomass and exhibited higher basal respiration rate than the O horizon under green alder. In the mineral soil differences between the two alder species were less pronounced. The contents of Corg, Nt, Pt, K and Ca were similar under both alder species. The Cmic and RESP values also did not differ between the alder species. Nevertheless, higher Nmineralization, PHOacd and PH2O content under black alder suggest that this species increases N and P availability in the mine soils to a greater extent than green alder. We conclude that although both alder species contribute to development of mine soils the positive influence of green alder is less compared with black alder.