Fifteen-year research results of afforestation and plantation on abandoned and marginal agricultural lands have been analysed. The annual growth of different tree species has also been determined performing measurements annually in the first five years and later each 2-3 years. The environmental impacts of afforestation have been assessed in terms of changes in the aboveground vegetation and soil chemical properties. The following tree species were included in the studies: Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.), silver birch (Betula pendula Roth.), common alder (Alnus glutinosa (L.) Gaertn.), grey alder (Alnus incana (L.) Moench.), pedunculate oak (Quercus robur l.), small-leaved lime (Tilia cordata Mill.), and wild cherry (Cerasus avium (L.) Moench syn. Prunus avium L.).

In 15 years tree species such as Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.), silver birch (Betula pendula Roth.), common alder (Alnus glutinosa (L.) Gaertn.), and grey alder (Alnus incana (L.) Moench.) have reached maximum standing volume from 100 m³•ha^-1 (for conifers) to 248 m³•ha^-1 (for broadleaves) on soils with light and medium heavy texture and high density of stocking (2,500- 3,300 trees ha^-1). In Latvian climatic conditions lime (Tilia cordata L.), pedunculate oak (Quercus robur L.), as well as wild cherry (Cerasus avium (L.) Moench.) have reached the standing volume of 18-39 m3•ha-1 in 15 years. It implies that their suitability can be evaluated no sooner than after some 40-70 years. Soil chemical properties have changed during 15 years since forest was established on agricultural lands. In general, the humus content in the active root layer (depth 0-30 cm) has increased and the soil reaction has become more acidic. Changes were observed also in the ground cover vegetation. Before afforestation the trial sites were generally dominated by meadow or fallow plant communities. Shifts in ground cover vegetation are faster on dry lean soils, where in plantations of conifers typical forest bryophytes appear rapidly, but various nitrophyte species prevail on sites of fertile and moderately moist soils.

Keywords: afforestation of surplus and marginal farmlands, plantation of forest tree species, monocultures, mixed plantations, tree species: Pinus sylvestris, Picea abies, Betula pendula, Alnus glutinosa, Alnus incana, Quercus robur, Cerasus avium, Tilia cordata