Estimating the Value of Conservation Function of Soil Nutrient in Forest Ecosystems

Considering the very long process of soil formation and its key role as one of the most important agricultural inputs, its protection is very crucial. One of the most important services and functions of forest ecosystems is preventing the soil erosion and increasing the holding capacity of its nutrients. This function is very important especially in high slopes and mountain areas. Because the soil erosion control services, as well as, many other forest ecosystem services, have no market to determine their value, recent years, some new methods has been developed to estimate these values. In this paper the value of soil conservation function have been estimated in a part of the Caspian forests of Iran. Significant point in this valuation is the spatial estimation of the value in each watershed. Initially the current status of erosion and sedimentation were evaluated in natural condition using the MPSIC model. Then, two scenarios have been developed, if convert natural forest to destructed forest or convert it to the eroded pasture. I in every scenario the status of erosion and sedimentation and their change in comparison to natural condition were evaluated. The value of forest ecosystems in the maintenance of soil nutrients in each scenario has been estimated by using replacement cost method. Finally, the map of soil nutrient conservation value for each basin was prepared by using geographic information system. Results show the average soil conservation value per hectare of the study area in scenario one (conversion of natural forest to destructed forest) is IRR 34 Thousand ($ 34) and in scenario two (natural forest conversion to eroded pasture) is IRR 252 Thousand ($ 25), which represents key role of forest ecosystems in controlling soil erosion. According to some factors such as soil type, slope and therate of erosion rate, the value differ from minimum IRR 212/72 to maximum IRR 401/84 Thousand per hectare, under the fivdifferent catchment basin area. This difference shows the strong relationship between structure and function of ecosystem. Also the spatial valuation can provide more accurate information for managers and planners to protect the natural resources and to develop more precise programs for the area.