DECOMPOSITION AND NITROGEN DYNAMICS OF FINE ROOTS OF NORWAY SPRUCE (PICEA-ABIES (L) KARST) AT DIFFERENT SITES

Long-term decomposition and nitrogen dynamics of Norway spruce finest (<1 mm in diameter) and fine (<2 mm in diameter) roots were estimated using the root fitter-bag techniques. The seasonal decomposition of th e finest roots was investigated in a 40-year-old high site quality sta nd grown on brown lessive soil at different depths as part of producti vity studies. The fine root decomposition studies were conducted on 8 permanent plots in the Estonia with the aim to describe the site varia tion. The initial material was collected from one of stands (high qual ity site) and incubated at the depth of 10 cm in 1989 (at one site 199 0). The bags were collected once or twice a year except for one site, where the seasonal dynamics was investigated. In all initial and decom posing root samples oven-dry weight, ash and energy content and nitrog en concentration was determined. After five years the finest roots had lost 40% of their initial dry weight, half of it during the first yea r. The initial concentration of nitrogen was 1.29%, the mean concentra tions varied during the incubation from 1.47 to 1.78%. After the first year fine roots had lost 21.0 to 32.7% of their initial dry weight, a fter two years the weight loss was 22.5 to 43.2%. The initial N concen tration in fine roots was 0.73% and in the first years it varied from 0.97 to 1.40% at different sites.