| چکیده انگلیسی مقاله |
IntroductionEcological vulnerability is a common term that can be used in different hierarchical levels (animate, population,community, ecosystem, and landscape). Ecological vulnerability evaluation has lots of applications inenvironmental sciences such as EIA, risk assessment and environmental monitoring. This represents theimportance of the evaluation. This paper aimed at assessing ecological vulnerability of the protected area ofTouran (in East of Iran) using a combination of three methods of overlay, i.e., reciprocal effects matrix, AHP,and EA.So far, a large number of researches have been published about these methods around the world and Iran, aswell. Some works in Iran are "Degradation Model" and Jabbarian's work which has innovations in objectifyingecological vulnerability assessment with reciprocal effects matrix approach. We can also point to zonation ofenvironmental vulnerable and sensitive areas in west of Fars Province with method of fuzzy logic approach andAHP.Different methods have been used around the world to assess ecological vulnerability. Some of thesemethods are FAHP and compound the methods of AHP and GIS and also Multiway Data Analysis (MDA) fordetecting relations between indicators, Reciprocal of Fractal Dimension (SPCA) and compounding ecosystemsensitivity and landscape pattern.More diverse indices have been used in the field of ecological vulnerability, so far. Some of these indices areecological Sensitivity (ES), Natural and Social Pressure (NSP), Ecological Recovery Capacity (ERC) and theothers related with landscape such as Reciprocal of Fractal Dimension (FD), Isolation (FI) and Fragmentation(FN). In this paper, indices of Ecological Sensitivity are used because these data are available in Iran.Materials & MethodsProtected complex of Touran is in southeast of Shahroud City, southwest of Sabzevar City and in the north ofgreat plain of Kavir in Semnan Province (from 55 to 57 E and from 34° 44' to 36° 22' latitude).For calculating ecological vulnerability, first of all the reciprocal effects m atrix must be prepared. In thismethod, a matrix of ecological factors in which if the points of an ecological factor effects on other factors theyare given figure of one and otherwise figure of zero. In the next steps, the summation of rows and columns andthe degree of importance of ecological factors is calculate based on following equation.nij j i1S ( X X )Where Sij is the degree of importance of ecological factor, Xi is the number of ones in the row of i and Xj is thenumber of ones in column of j. Then by comparing the degrees of importance of ecological factors, table of AHPof ecological layers was made for identifying the degree of preferences of layers. In fact, using reciprocal effectsmatrix, process of preferences turned into objective method in AHP.Extent Analysis Method used for calculating preferences degree of layers, the preferences for some of thelayers would be negative; so simple AHP was used for calculating preferences degree of ecological factors. TheExtent Analysis Method was used in FAHP for scaling classes of layers.In the Extent Analysis Method after supplying hierarchy decision tree, pairwise comparisons wasaccomplished; then, using Extent Analysis Method these qualities converted into quantitative values. Numbersused in this method is Triangular Fuzzy Numbers. In this method for each row of pairwise comparisons matrix, value of Sk which is Triangular Fuzzy Number, is calculated. njminjk kj ij S M M111 1(1)Where k is the number of rows and i and j are alternatives and indices, respectively. After calculating S k s,magnitude degrees of them are obtained into each other. Generally if M1 and M2 are two Triangular FuzzyNumbers, magnitude degree of M1 into M2 is calculated as:( ) ( )( ) 11 2 1 21 2 1 2V M M hgt M MotherwiseV M M ifM M (2)Magnitude degree of a Triangular Fuzzy Number into K Triangular Fuzzy Numbers is calculated by thisequation:V M M M V M M and and ( ,..., k ) ( ) ... 1 2 1 2 ( ) 1 k V M M (3)Also calculating weight of indices is obtained from pairwise comparisons matrix, thus:( ) min 1 W x ( i k ) V S S (4)After scaling classes of layers and calculating preferences degree of layers, the obtained values are applied inmaps by GIS and using weighted overlay. Ecological vulnerability map of the area was provided. Ecologicallayers used in this work are elevation and aspect with five classes and slope with eight classes gotten from 50meter DEM, climatology with one class supplied by revised De Martonne, land use with seven classes,vegetation density eith six classes, soil depth with five classes, erodibility of soil with five classes, water erosionwith three classes, and finally wind erosion also with five classes.Results and DiscussionThe most effective factor in ecological vulnerability that obtained through reciprocal effects matrix and AHPmethod (Fig. 1) was erodibility of soil.This factor affects extremely other factors such as soil depth, watererosion and wind erosion. The weight of this factor in AHP was obtained about 0.371. The climatology andelevation factors are lower than the erodibility of soil. They are with preference degrees of 0.161 and 0.137,respectively. In the end of the list both layers of soil depth and vegetation density are affected by other factors,with preferences degree of 0.16.Finally, the map of ecological vulnerability was obtained by weighted overlay of the layers and also byapplying scales of classes for each layer. It is remarkable that location of the areas in sensitive geological zones,zones of deep soils, arid and warm climate, and wind erosion zones is determinant in vulnerability degree ofthose areas. These layers are converted into raster format and then overlaid by their weights; finally the map ofecological vulnerability was obtained as a result raster layer. For better land management, the area was classifiedby natural breaks method (Fig. 2) into four classes of resistant, subsensitive, sensitive, and vulnerable. Fig. 2. The map of ecological vulnerability for protected area of TouranConclusionsAccording to vulnerability map of the area, western parts are more vulnerable relative to other areas.Furthermore, most of the areas are placed in class of sensitive. Therefore, the protected area must be recognizedin different managerial levels for more conservational acts. |