Nitrogen mineralization in volcanic soil under grassland, shrub and forest vegetation in the Aegean region of Turkey

Net nitrogen mineralization of a grassland-, Quercus coccifera shrub- and Pinus brutia forest-site within the Aegean region was investigated continuously through a year by field and standard incubation methods. Seasonal fluctuations resulting from field incubation are marked in grassland and shrub, but less pronounced in the forest. They are mainly associated with the changes in soil moisture being at minimum in the mediterranean summer. The annual yield of N mineralization is high in grassland and shrub (7.5 and 6.6g.m-i), but low in the forest (2.8 g.m-1), where nitrification is inconspicuous. The reasons for this surprising phenomenon are discussed. N-mineralization is highly elevated in all sites under the favourable conditions of standard incubation (potential mineralization) and the seasonal differences as well as those between the sites are largely diminished