Showing 3 results for Darvishsefat
H. Arzani, M. Jangjo, H. Shams, S. Mohtashamnia, M. A. Fashami, H. Ahmadi, M. Jafari, A. A. Darvishsefat, E. Shahriary,
Volume 10, Issue 1 (spring 2006)
Abstract
Range suitability and its grazing capability are the most important criteria in rangeland analysis and monitoring. Determination and monitoring of factors affecting on range suitability and diagnosis of them are important .All range ecosystem components affect range suitability. Which among them physical and vegetational factors, forage production, water resources and sensitivity to erosion were considered. The objective of this research was to determine range suitability of Lar, Dasht bakan, Ardestan, Siahrood rangelands to design a model for sheep grazing. This study was carried out in four regions, two of them (Siahrood and Lar) located in Alborz mountain chain, Ardestan in center of Iran and Dashtbakan in Zagros mountain chain. According to the results among physical factors, slope remoteness of watering points and sensitivity to erosion had more effect on grazing capability than vegetation factors. In Siahrood watershed aboundancy of poisonous plants, high slope, transient watering points and non resistant formations were limiting factors. High slope, sensitivity of soils and stones to erosion, kind of exploitation in Lar watershed affected range suitability. In Ardestan watershed, low range productivity, presence of invader plants, erosion, remoteness of watering points are major limitation of range suitability. In Dasht Bakan factors including slope, elevation, dispersion of water resources and transient water resources were limited grazing capability. In land evaluation each land utilization type has certain land use requirement and each land unit has certain land qualities. Utilization of rangeland based on grazing capacity, range readiness and recreation of degraded rangeland can improve suitability of rangelands in the studied areas.
O. Rafieyan, A. A. Darvishsefat , M. Namiranian,
Volume 10, Issue 3 (fall 2006)
Abstract
The aim of this study was to detect change of the forest area in the north of Iran between 1994 and 2001. The study area was covered by a 1:25000 topographic map (about 15000 ha) in Babol forests. The forest map of 1994 was extracted from 1:25000 topographic digital map. Landsat 7 ETM+ image dated July 30, 2001 was analyzed to produce the forest map for the end of the period. Since the evaluation of the image quality illustrated it less than ±1DN in the ETM 2, 4, 5, the rectification of the stripping distortion was ignored. There were also duplicate scan lines and sweep distortions in all the spectral bands. Orthorectification was implemented using ephemeris data and digital elevation model. Several spectral transformations such as rationing, PCA, Tasseled cap and image fusion (using Color space transformation and Spectral response method) were performed on the ETM+ data. The sample ground-truth map was prepared using GPS in 3% of the study area. In order to classify the image, hybrid classification method (digital and visual), using original and synthetic bands, was employed. At first the image was classified using maximum likelihood classifier. The most accurate map (overall accuracy and kappa coefficient equal to 94.56% and 0.89, respectively) was converted to the vector format and then it was edited on the basis of various color composites, fused images and other ancillary data. The obtained map showed overall accuracy and kappa coefficient equal to 96.39% and 0.927, respectively. The comparison of the classified map with the forest map of 1994, illustrated that 751 ha of forest area (equal to 8.2% of the previous forest area), were decreased. This includes a 417 ha increase (mostly reforested areas) and a 1168 ha decrease over the study period. The findings indicate the high potential of ETM+ data in forest mapping and change detection over the whole extent of the northern forest of Iran.
E. Abdi, B. Majnounian, A. A. Darvishsefat,
Volume 12, Issue 44 (summer 2008)
Abstract
One of the most important cost factors in forest management, which involves a great deal of investment costs, is road construction. So evaluating forest roads and determining the best one can decrease costs. The objective of this study was to evaluate forest roads using Multi Criteria Evaluation with respect to costs. In Multi Criteria Evaluation method such factors as slope, aspect and soil type were used for suitability map. Then factors were compared in pair-wise comparison in the context of a decision-making process known as the Analytical Hierarchy Process (AHP) to develop weights of map layers. To do this, the opinions of some experts were collected using questionnaires and the results were integrated and factor weights were calculated. Then weights and their factors were entered into Multi Criteria Evaluation (MCE) Module to create final suitability map (factors were standardized before combining). Total costs of each variant were extracted from suitability map. After variant costs were obtained by dividing each variant total cost by its length, unit cost of each variant was calculated. Finally, unit costs were compared and the variant with the lowest costs was determined. The results showed that the slope had the greatest weight followed by soil and aspect. Also, variant 7 had the lowest cost and variant 8 the greatest cost. AHP method has the capability of considering qualitative and quantitative criteria so it is a proper method for weighting. Also MCE method in GIS environment has the capability of combining different factors. As it requires less time and cost, also has a higher precision, it is better to use MCE method in such studies.
