FINE-ROOT MORPHOLOGY AND UPTAKE OF P-32 AND S-35 IN A NORWAY SPRUCE (PICEA-ABIES (L) KARST) STAND SUBJECTED TO VARIOUS NUTRIENT AND WATER-SUPPLIES

An investigation of fine (< 1 mm in diameter) and small (1-2 mm in dia meter) roots in the organic soil layer was carried out in a Norway spr uce forest stand with different treatments of water and nutrients, inc luding control (C); ammonium sulphate application (NS); nitrogen-free fertilization (V); irrigation with liquid fertilization (a complete nu trient solution) (IF); NS followed by artificial drought (ND); V follo wed by artificial drought (VD). In order to evaluate the vitality and function of the fine roots, the following approaches were used: i) cla ssification of fine roots, based on morphological characteristics; ii) nutrient uptake bioassay, using P-32-phosphate and S-35-sulphate; iii ) nutrient concentration in fine roots and its relation to nutrient up take. The NS treatment showed effects on the fine and small roots, wit h a decrease in amount of living roots, and a decrease in the total am ount of fine and small roots. The VD treatment resulted in increased a mounts of living small roots, while the ND treatment showed the opposi te, as compared with the V and NS treatments, respectively. The uptake of P was negatively related to the P supply, with a higher P uptake f or C and NS fine roots than for IF and V fine roots. The specific root length (SRL, m g(-1) DW) decreased for NS fine roots and increased fo r IF fine roots, indicating a further increase in uptake for NS roots and a decreased uptake for IF roots if calculated on a root length bas is. So far, the NS and IF treatments maintain a considerable increase in above-ground biomass with a significantly reduced root biomass and standing crop.