The aim of this study was to determine how carbon and nitrogen mineralization of carob soil (Ceratonia siliqua L.) are affected by the addition of Aleppo pine (Pinus halepensis Mill.) leaf, Kermes oak (Quercus coccifera L.) leaf and their mixtures (containing 2.5% total organic carbon) under the same laboratory conditions (30 days at 28 degrees C). The carob soils were collected from two different sites in the eastern Mediterranean region of Turkey. Carbon mineralization of all soils was determined using CO2 respiration method. Nitrogen (N) mineralization was measured in vitro both in no leaf added soils and plant leaf added soils. Additions of plant leaves in both sites clearly increased microbial activities. No added soils were significantly different from the plant leaf added soils in respect to carbon (C) mineralization at the end of the incubation period, while no statistical difference was observed among the three treatments in which plant leaves were added. The ratios of nitrogen mineralization declined with additions of leaves in both sites. These findings might suggest that carob, Aleppo pine and Kermes oak are in a balanced interaction. (c) 2005 Elsevier SAS. All rights reserved.