THE EFFECTS OF NITROGEN ADDITION AND REMOVAL ON NORWAY SPRUCE FINE-ROOT VITALITY AND DISTRIBUTION IN 3 CATCHMENT AREAS AT GARDSJON

Investigations were carried out on the impact on root vitality and dis tribution of fine roots, in catchments subjected to increased nitrogen deposition (G2 NITREX), decreased nitrogen and sulphur deposition (G1 ROOF), and ambient levels of nitrogen and sulphur deposition (F1 CONT ROL) at Lake Gardsjon basin, southwestern Sweden. Root studies were ca rried out on sequential cores and ingrowth cores. The fine roots were separated into three vitality classes. Estimated root variables displa yed a high variability between samples from the same area and year, in dicating a high heterogeneity within the catchments. Year-to-year chan ges in the amount of fine roots of different vitality classes which oc curred in all catchment areas, were probably related to natural variat ions in climatic conditions. The bulk of the fine roots (living + dead roots less than 1 mm in diameter) was found in the FH layer (45-82%). Signs of an increased percentage of living fine roots in the organic soil layer in the G1 ROOF catchment suggest that growth conditions for fine roots are improved by reducing N and S deposition. Results from the G2 NITREX catchment suggest that increased nitrogen deposition may reduce the total amount of fine roots.