نشریه مرتع و آبخیزداری
سال شصت و ششم شماره 1 (بهار 1392)

Climate change is defined as long term and irreversible changes in the climatic behavior of a region. Many studies have been conducted in different regions of the world on climate change. The results of these studies show considerable changes in climatic factors especially in precipitation and temperature. In this research، the trend of changes in annual and seasonal rainfall and temperature in 24 synoptic stations over a 50-year data period (1956-2005) was investigated in Iran. The Mann- Kendall test and linear regression technique were used to analyze the trend of changes in climatic factors. The results showed both increasing and decreasing trends in annual rainfall at various regions of Iran. Annual rainfall in northern slopes of Alborz and western slopes of the Zagros Mountain as well as in eastern and southeast parts of Iran had a decreasing trend while in the central of Iran the trend of changes was increasing. In southern region of Iran the rainfall had an increasing trend. The results also showed that temperature in most of the studied stations over the considered period was increasing. The highest and lowest changes in temperature were seen in the mean temperature of summer and winter، respectively. Ahwaz and Khorramabad stations had a decreasing trend and over all seasons would go toward more cooling. The temperature trend in Oromiye was decreasing in autumn and summer while Shahrekord and Bandar abbas had the same trend in summer and winter.

Agriculture sector is the main consumer of water in the world. In productive sectors like agriculture، water is considered as a valuable mediatory commodity or production input. Demand for agriculture water comes from consumers› (agriculture products›) behavior. This study aims to evaluate water use optimality in Pomegranate Arbors at the Charkhab village in the Yazd province. The data was randomly collected from 95 people of 153 beneficiaries in the study area. This study surveys water demand variations in the case of one percent change in water procurement expenses in Yazd. Elasticity estimation revealed that pomegranate producers› sensitivity to agriculture water price changes is high. To be specific، one percent increase in the price of agriculture water would decrease water demand by 24. 32 percent amongst pomegranate producers in Yazd. Production elasticity of water input was obtained 0. 0565 which is located in the third part of production region and means over-consumption of water by producers due to its low price. Given high demand for water in this arid area having appropriate polices in water pricing for optimal water consumption is needed.

According to the UNCCD definition، “Desertification” is land degradation in arid، semi-arid and dry sub-humid areas resulting from various factors، including climatic variations and human activities. It has been recognized as a major economic، social، and environmental problem in many countries of the world. The MEDALUS methodology is a practical approach to assess the present status of desertification and evaluate the desertification risk. In this study، a regional model has been developed to desertification assessment and mapping in the SEGZI plain (Eastern Isfahan) based on the MEDALUS methodology. At first step، seven criteria including climate، soil، vegetation cover، ground water، water erosion، wind erosion and policy and management were recognized according to the local condition. Each criterion included several indicators accounting as factor quality determination. These indicators quantified based on their influences on desertification process. For each indicator a score ranging from 100 to 200 were assigned and desertification weighting was finally extracted. The weight of each factor and the weight of desertification status was calculated by geometric mean. Ultimately، desertification status was classified in four levels including low، moderate، severe and high severe. At last the maps of these results was produced by geographical information system. Results showed that 2% of the study area was classified as moderate class، 35% classified as severe and 63% involved high severe class. Climate، policy and management are the most important factors have led to desertification process in this region.

The morphology of a river system is affected by dominant watershed processes including climatic، hydrologic، hydraulic، erosion and sedimentation، geological and topographical characteristics of the river environment and watershed. Understanding the interaction between the river form and dominant watershed processes in river systems is necessary for recognition of river behavior and of importance for developing river environments conceptual models. In this research the aim was to evaluate morphological characteristics caused by dominant watershed processes in the Firoozeh-shahjoob river of north Khorasan and extract equations in order to mathematically link between the river physical features and watershed processes. For this purpose، the HEC-RAS hydraulic model after doing sensitivity analysis and calibration process was used to simulate the relation between dominant watershed processes and river physical factors for 37 reaches of this river. Considering the standard error، level of confidence and coefficient of determination، compared to simple linear models، second order (quadratic) and third order (cubic) models، exponential models were the most suitable ones to extract the mathematical relation between geometrical characteristics and the related dominant processes in this river system.

The study on the livestock dietary and preference value of different species are essential for rangeland management. Therefore، this study was carried out to evaluate the preference indices of 14 plant species in Kahnuj، during two different phenological stages (vegetative growth and after-seed-dispersal). The close observation method was used to measure the preference index for three age classes of Rainian goat (one، three and five years). The results showed that main and interaction effects of goat age، plant phenological stage and the kind of plant species on preference values were significant. Older goat consumed a higher time to graze in the study area. Stipa capensis had the highest preference index and Rhazya stricta had the lowest. The preference index of most plant species was significantly variable between two phenological stages. In addition، in each phenological stage، the preference value of plant species was significantly different. In the vegetative growth stage that annual plant species were abundant، goats mostly focused on these plant species for grazing. However، in the after-seed-dispersal stage in which the annual cover decreased، goats (particularly older ones) focused on shrubs for browsing. As a result، Rainian goat is a grazer in the normal situation and he can be a browser in the hard condition. It was suggested that the cover of Taverniera cuneifolia to be increased in the study area in order to compensate the deficiency of forage in long term. Artificial foraging is useful to reserve the performance of goats (particularly younger ones) in short term.

Nowadays، watershed management practices are undertaken based on selective criteria and/ or a specific purpose such as a decrease in flood risk، soil erosion and the like. In this respect، fuzzy logic has the ability to manage a wide range of options for decision making. This research aimed to use the fuzzy logic theory to priorities watershed management practices considering time and budget constraints in catchments with high sediment production and flood risk. This research was carried out in the Foorg watershed of Darmian town with an area of 11137 ha. All parameters related to soil erosion and flood risk were determined using the standard methods. Fuzzy score for each mentioned factor was then determined. Finally watershed management practices using the fuzzy theory and GIS were prioritized.

The analysis of the relationship between spatial distribution of environmental factors and vegetation types is crucial for understanding mountainous ecosystems. In this research a GIS based approach was used to produce a vegetation map for Sabzkouh protected area in the Chaharmahal-Va-Bakhtiari province. To identify environmental parameters affecting the vegetation cover، 6 primary and secondary environmental parameters including hypsometric، slope steepness، slope direction، annual precipitation، temperature and sun radiation maps were derived from the study area DEM. To investigate the relationship between these factors and the spatial distribution of vegetation cover، quantitative analyses using statistical techniques like Principal Components Analysis (PCA) were undertaken. Then، the spatial distribution of vegetation types was predicted using a multi-logistic regression. Results showed that topographic variables derived from the DEM were very useful for indicating habitats of range and forest types. Although lack of information on the anthropogenic effects led to some uncertainties in the interpretation of spatial pattern of vegetation types، the topographic and climatic variables، derived from the DEM، were considerably effective in modelling the spatial distribution of vegetation types.

Palatability includes plants physical and chemical property that encourages an animal select a plant for grazing. This study is an attempt for intruducing an indicator for determining the palatability of rangeland plants. To do this، the relationship between palatability and forage quality of rangeland plants in Karsanak rangelands of the Chaharmahal-va-Bakhtiari province was studied. First، plant composition based on plant canopy cover and production wasdetermined using of the systematic random sampling method (in each plant type there are 2 transects of 200 m and 15 plots along each transect). Also، the percentage of present each plant in the livestock diet (sheep and goat) was determined using the filming method. Then، the selection index of each plant species by sheep and goat was determined. In the next stage، the forage quality of some plant species was determined by determining the percentage of CP، ADF، DMD and ME. Finally، the relationship between plant quality indices (independent variables) and the selection index of plant species by sheep and goats (dependent variable) was determined using the SPSS software (Ver. 15). Results showed that there is a significant relationship between the selection index of each species (both percentage canopy cover and production) and ADF، DMD، and ME by the sheep (P ≤0. 05). However، such a significant relationship was not found for CP. And، there is not a significant relationship between the selection index of each species (both percentage canopy cover and production) and ADF، DMD، ME and CP by the goat (P ≤0. 05). Considering the results، the quality of forage can be an indicator in determining their palatability.

The present research was done in steppic rangelands of Dehno، Kerman province to study the effects of different harvesting intensities of Artemisia sieberi applying simulation method. The experiment was conducted using split plots in a completely randomized experimental design of ten replications to find the best grazing intensity. Treatments are including no harvest (as a control)، 25، 50 and 75% harvest. In each treatment، 10 similar and average plant species were selected as replications. All dependent variables were evaluated during the study and results were analyzed in SAS software. Results showed Minimum and maximum forage production was obtained at 25% harvest in 2008 and no harvest treatment in 2009، respectively. Regarding to the obtained results and soil condition، the 50% harvesting intensity is recommended in Dehno site to maintain the vigority of Artemisia sieberi that is not dangerous for its survival، healthiness and vigority even in drought conditions.

Investigating downstream changes in bed load shape can be useful to detect watershed hydrological processes and it is very important to design hydraulic structures and to manage capacity of large storage dams، properly. Regarding to doing of enforcement studies، this research was conducted in Qalesar River in upstream of Chahardangeh watershed in Mazandaran Province. After recognition of the study area، 6 sections were selected towards downstream for bed load sampling. Laboratory analysis were done to measure and calculate some bed load shape characteristics including skewness، kurtosis، mean، mode، percent of sand، fine gravel، silt and clay، sediment texture، small، medium and large diameters، nominal diameter، sphericity، rounding، width ratio، shape factor and D10، D50 and D90. Results indicated a decreasing trend in shape factor and sphericity، an increasing trend in mean diameters and roundness، a complex trend in width ratio and a uniform trend in 3 axes. Our finding also indicated that this variations may be affected by physiographic، lithologic and geotechnical characteristics of the study area.

A better understanding of rangeland vegetation cover and its variation in different years based on wetness and droughtiness fluctuations is a great importance. Economical priority setting of rangelands is based on variations in rainfall and drought patterns، because it yields to better characterization of vegetative cover. Yet a comprehensive and continuous monitoring of vegetative cover of rangelands has not been established. To study the influence of droughtiness and wetness on vegetation cover and production forage، 11 sampling areas and 3 reference areas were selected in Herat. Three 100-m transects were located 25-m apart within each sampling area. Production and cover were estimated within 10 located 2- plots along each transect. Data were analyzed using Duncan›s test Design a completely random with a factorial GLM procedure at 99% and 95% confidence levels. Results showed that the vegetation cover and production in wetness were significantly different from those in droughtiness (P<0. 01). The vegetation production and cover increased by 36. 3% and 34% respectively in the wetness compared to the droughtiness. The influence on production and cover was positive and efficient in the wetness with the average rainfall higher than the 30-yr average. Finally، the results of flood spreading increased vegetation cover and production forage in dams.

Natural landscape alternation is a problem that has been under debate for a long time. Land utilization techniques like agriculture، forest and rangelands، residential and urban are among influential criteria affecting erosion severity and sediment yield in a given region. In this respect، land management is a promising option to mitigate it. Thus، acquaintance with quantitative soil erosion owing to land-use changes is of great importance for estimating disadvantages and latent and intangible symptoms of erosion. Strategic planning for sustainable development could be benefited from such knowledge. The current research considered a statistical period from 1970 to 2004. This period was sub-divided into two separate periods from 1970 to 1987 and from 1987 to 2004. During these periods، statistics relating to sedimentation، climatology (precipitation) and hydrology were analyzed. Results revealed that the sediment reduction in these two periods under similar rainfall would be as a result of an increase in abandoned areas.