The present research was carried out in three black alder plantations in Estonia in 1998-2002. The above-ground productivity and the efficiency of nitrogen and phosphorus use in a plantation in reclaimed opencast oil-shale mining area in Sirgala were analyzed and compared with two plantations growing on fertile mineral soils. The activity and diversity of microbial communities in the soil-root interface and in bulk soil were investigated. The above-ground productivity of the plantations was comparable (14.3 to 17.2 t ha(-1) yr(-1)); nitrogen use efficiency (116.5 kg kg(-1)) was highest in Sirgala. Although initial phosphorus content in oil-shale mining detritus is low, the availability of phosphorus was highest in Sirgala. Alders created a favorable environment for microbes at their soil-root interface in oil-shale mining detritus. A planting density from 2,000 to 2,500 trees per hectare is recommended for establishing plantations of black alder on exhausted oil-shale opencast mines.