مجله پژوهشهای محیط زیست
سال یکم شماره 2 (پاییز و زمستان 1389)

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.

Forest planning is accomplished by a decision-making process that is spatially and temporally hierarchical. Main decisions at the strategic and landscape levels are about the determination of forest functions and forest classification for these purposes. This could be archived by ecological evaluation. Developing of specific model for ecological capability evaluation is a important tool for this goal. In this study a specific model for ecological capability was developed. Ecological parameters consisting of physical and biological parameters were studied. Then produced data were digitized. Model was run for three classes of commercial forests and a class of conservation and protected forest. Results showed that 3842 ha (47%) of studied forest classified as conservation and protected forest.

The most valuable wetland ecosystem in Kurdistan province is Zaribar Lake in the west of Iran near Marivan city. It is surrounded by forest in north of Zagros that belong to Irano-Anatolian Hotspot in the world. These forests are valuable for conservation of water and soil, prevention from soil erosion, preparing suitable weather condition and Ecotourism, because of attractive places such as Zaribar Lake and Bashmagh border (border of Iran and Iraq). The purpose of this study is evaluatingforest surrounding Zaribar Wetland for ecotourism. In this study, 151 micro ecosystems identified and evaluated for ecotourism besed on specific model that made for this study. After evaluating ecological capability, socio economic resources such as present land use, income from land use, infrastructure, rate of unemployment, transmittal of live stock etc, final map of ecotourism capability prepared. At the end from total area of the study area (8236.5ha) 10.84% capable is for Intensive recreation class2, Intensive recreation class3 with 12.32%, extensive recreation class1 with 10.56% and 0.81% for Extensive recreation class2.

The large scale water resource development projects have in many cases recognized as the sources of diversified complex environmental impacts. Proper assessment of these impacts requires devising novel approaches to deal with the multiple aspects of the impacts per se, as well as to apply rather quantitative techniques to make more reliable and less uncertain synthesis of the overall consequences of the project activities on both the integrity and health of the surrounding environment. Analysis of the significance of the environmental impacts is a multiple criteria decision making problem and makes the core of the conventional environmental impact assessment methods. However, these conventional measures of significance analyses are proved to be inadequate for dealing with imprecise, vague and uncertain nature of the linguistic assessments of the ecological, social and cultural impacts. A new numerical method called the fuzzy outranking sorting technique for ELECTRE TRI (ELimination Et Choix Traduisant la REalite) is proposed and applied in this research for the purpose of environmental impact significance assessment of the Ardebil Dam, Drainage and Irrigation Development Project in Northwestern Iran. The basic idea behind the research was to develop a methodological framework in order to assist the environmental impact analysts in reducing, as much as possible, the intrinsic imprecise and uncertain traits of the multi-expert judgment based methods currently used in the analysis of environmental impacts of the projects. Compared to the compensatory MCDM techniques, ELECTRE TRI provides the advantage of using a fuzzy approach in the analysis of the vague and poorly determined set of judgment data and helps in more credible assignment of values to a set of predefined categories with respect to a set of impact criteria. Results of the Fuzzy ELECTRE TRI based analyses are compared with a conventional method, which has used for the environmental impact assessment of the same project. It is argued that due to its multiple criteria and fuzzy characteristics, the ELECTRE TRI method is capable of producing more reliable inputs for the decision making process compared to the conventional additive techniques.

Nowadays, the changes emerged from human activities in a dynamic environment and the predominance of the man on landscape has caused a fragmented natural environment. It has led to improving and a shift from concentration on ecological concept of isolation to the linkages and from site conservation to an ecological conservation network. Therefore, the new concept of landscape ecology with combination of science and emphasizes on spatial patterns has been entered into environmental planning and designing. Hence, a concept such as designing urban ecological network has received more attention by the environmental scientists. The present study was conducted to study the urban ecological network of Tabriz city. At the first stage, the present status of the urban ecological network of Tabriz was investigated by Mosaic model. As a result, natural and artificial ecological layers were identified. Then, the layers were analyzed by network analysis technique. This helped us to determine the network structure and enhance it at city scale.

During the past 50 years, due to dam construction, many rivers globally have been changed and diverted river basins. Some 40-80 million people were forced to move from their dwelling places. This had many serious socio-economic, cultural and environment impacts. Iran has also in the area of the large dams particularly for many of the people residing in the nearby reservoirs, socio-economic impact have been to a large extent. The present study will review the impact of the Gotvand Olia (upper Gotvand) on the river of Karoon.In this relation geographical,environmental,economic and socio charactristics, the coefficient and review of the variables will be also analyzed and the results presented. Furthermore, in order to strategize using the SWOT grid and with various socio-economic and cultural variations will be qualitatively and quantitatively analyzed.

Earth movement is one of natural hazards which affects sustainability of our environment. In this research, on slopes facing Hamedan city (W. Iran), the hazards of natural movements have been studied by Brunsden (1994) methods, using GIS (Arc GIS 9) in scale of 1:25000. The hazard been classified in 3 groups of A, B and C. The results indicate that 64% of slopes facing Hamedan city is unstable to relatively unstable, which this hazard should be considered in development planning of the city.

Floods are generally categorized as the most important hazard causing enormous social, economic and human loses. Land use changes caused by man's interference resulted to an increase of flood severity and frequency during recent decades. In this research Environmental impacts of land use changes on surface runoff and subsequently flood flows, have been studied in the Dough river watershed. Curve number (CN) method was employed to estimate maximum discharge in two different cases: present land use as well as the proposed land use based on land capability. The study revealed the significant role of land use changes in increasing flood flow as a result of increased surface run off in the basin, particularly in dry soil condition. Changing the present land use to a proper condition based on land capability, may decrease maximum discharge to 70 %, 50% and 20% respectively in moderate, sever and very sever wet soil conditions, also pick discharge will be decreased to 20% in the basin. Here, the important effects of land use policies in severity of heavy floods especially when the soil is dry are apparently clarified. In the case of wet soil condition with high amount of rainfall (with longer return periods), the effect of land cover decreases though still plays its moderating role in diminishing the severity of heavy floods. Obviously, climatic and physical elements like heavy rains, the extent and the size of the watershed are also responsible for causing floods in this region, but anthropocentric activities like degradation of forest and rangelands, incorrect animal husbandry, mismanagement of natural resource, irrational allocation of land to settlements and construction of unsuitable structures and facilities multiplies the impacts and severity of floods. Remote Sensing (RS) and Geographical Information System (GIS) techniques have been extensively used to provide necessary information and maps.