Spatial distribution of below-ground biomass and total biomass production was studied in a young grey alder stand growing on a nutrient-poor sandy soil. The stand was repeatedly irrigated and fertilized every year. Roots and root nodules were sampled at 4 years of age by excavation of 200-litre cubes of soil down to a depth of 40 cm. Coarse roots (diameter > 1 mm) and root nodules were mainly found close to the tree trunk while fine roots (less-than-or-equal-to 1 mm) were more uniformly distributed horizontally in the soil. The root system was shallow with 90% of the biomass found in the upper 20 cm of the soil. This distribution was probably favoured by water and nutrient supply from above in combination with a nutrient-poor soil and no contact with a deep ground water table. A low shoot/root ratio of 1:2 could be explained by a slow establishment and initial growth and thus small trees at the time of below-ground sampling. The above-ground woody biomass production increased with increasing stand age and was 0.2 and 0.6 kg oven-dry weight m-2 yr-1 at 4 and 5 years of age, respectively.