ROOT DISTRIBUTION IN A NORWAY SPRUCE (PICEA-ABIES (L.) KARST.) STAND SUBJECTED TO DROUGHT AND RAMMONIUM-SULFATE APPLICATION

Results of the spatial distribution of fine roots are reported from a Norway spruce (Picea abies (L.) Karst.) in SW Sweden stand subjected t o drought (D) and ammonium-sulphate application (NS). The sampling was carried out by excavating monoliths in segments of 0.5 x 0.5 x 0.1 m to a depth of one meter. Root data also included in the study were obt ained by excavating whole trees and soil coring. The data suggest a fa irly deep distribution pattern of fine roots (< 1 mm in diameter) in t he study area compared with other forest sites in SW Sweden. The weigh t fraction of living fine roots in the LFH-horizon amounted to 53, 36 and 55% of the total fine-root biomass and 12, 30 and 32% of the total fine-root necromass (dead fine roots) in the control, D and NS-treatm ent areas respectively. Drought seemed to result in a redistribution o f fine roots to deeper mineral soil horizons. Ammonium sulphate applic ation led to the reverse, viz, a concentration of fine roots to the LF H-horizon. A significantly smaller fine-root necromass was indicated i n the LFH-horizon of the control areas compared with both the D and NS -treatment areas, suggesting a high mortality of fine roots in these a reas. A heavy dry matter fraction accumulates in roots > 1 mm in diame ter and in stumps. These root fraction, were frequently found between the trees, although the stump constitutes an important fraction in ter ms of dry weight.