Hyrcanian forest ecosystem is considered to be one of the most important natural deciduous forests in the world. Today, these forests are being devastated by human activities. So there have been many plantation establishments with endemic species in degraded forests of this area. But the effects of such conversions on soil C and N stocks and nutrients are still unknown. We investigated the effects of conversion of a degraded natural forest to Alnus subcordata .L, Acer velutinum .Boiss and Cupressus sempervirens. var.horizontalis plantations on soil C and N stocks and nutrients after 18 years. The studied stands are located in the county of Chamestan in the province of Mazandaran, Iran. Some of soil chemical and physical properties including available nutrient concentrations (Ca, Mg, P and K) and total N and organic C stocks in the soil were determined in three soil depths (0-15 cm, 15-30 cm and 30-50 cm). Soil available nutrients were higher under plantation stands compared to the degraded natural forest except for soil available K which decreased under A. subcordata plantation. We expect increasing the soil nutrient improvement with increasing the age of plantation stands. A. velutinum and C. sempervirens had increased soil C and N stocks but A. subcordata decreased soil C stock and increased soil N stock in comparison to the degraded natural forest. These results indicate that conversion of degraded forests with appropriate species can significantly improve soil C stocks, helping to mitigate the negative impacts of the greenhouse effect.
