摘要：This research was carried out in natural Alder ( Alnus subcordata C. A. Meyer) stands for evaluation effects of Alder trees on restoration of forest soil in North forest of Iran. The soil samples and different parts of Alder such as leaves, barks, roots and nodules were collected from three altitudes zone in Alder and birch stands. Mineral amount of plant and soil sample were analyzed in laboratory by standard methods. Results of mineral analysis in deferent parts of Alder revealed that the amount of nitrogen and phosphorus in leaves significantly more than bark and root. Generally the fallen leaves of Alder remained in the soil as a source of nitrogen. Amount of nitrogen in nodules was significant higher than roots. Nitrogen analysis of soil profiles in two Alder and birch stands also showed that mean amount of nitrogen in Alder stand was significantly more than birch stand. Overall, the results indicated the positive role of Alder trees in restoration of soil fertility by nitrogen fixation.
