نشریه مرتع و آبخیزداری
سال شصت و چهارم شماره 4 (زمستان 1390)

Forage quality is one of the most important affecting factors on the livestock performance which is affected itself by different parameters. In this research، four dominant and palatable range species were collected from Gorab Feraidonshar of Isfahan province in three phenological stages (vegetative، flowering and maturity) over two years (2007 and 2008). The plant species consist of Ferula ovina، Bromus tomentellus، Astragalus macruorus and Prangos uloptera. The samples were ground، and then nitrogen (N) and acid detergent fiber (ADF) were measured and the crude protein (CP)، dry mater digestibility (DMD) and metabolizable energy (ME) was estimated. Split plot design was used to analyze the data. Overall amount of crud protein، dry mater digestibly and metabolizable energy had significant differences in two years so that amount of these indices in 2007 (wet year with 725. 1 mm annual precipitation) was higher than those of 2008 (dry year with 284. 1 mm annual precipitation) in vegetative and flowering stages. However، amount of acid detergent fiber in 2007 was lower than that of 2008، but was not significance. In the maturity stage، significant differences were not found among the total indicators.

Desertification is a global phenomenon that may occur anywhere and lead to substantial damages and losses. Hence research on desertification mitigation and prevention of its development is essential. In order to study desertification severity، after investigating current condition of the region، three criteria including water، soil and vegetation as the most effective factors on desertification in the study area were evaluated and several indices for each criterion were considered based on the local conditions. Scores of indices related to each criterion were determined by using desertification model of IMDPA. By IMDPA model، work unit was considered as the basic unit of desertification evaluation and for each index، a map was prepared by noting the conducted weighting. So that، qualitative map of the criterion obtained through employing the geometric mean of indices related to each criterion. Then، by the combination of the layers produced from each criterion، determination of their geometrical means، and classification of resultant the map، the map of desertification potential status was created for the study area. By noticing the assessment made، it can be revealed that the soil criterion with a weighted average of 2. 66، water criterion with the weighted average of 2. 37 and vegetation criterion with weighted average are classified in intensive class، moderate class، and moderate class، respectively. Between the studied parameters، soil depth index with the weighted average of 3. 52 is the most effective factor while chlorine and sodium adsorption ratio، with weighted averages of 1. 18 and 1. 18، respectively، are the least effective in the desertification of the region. The results indicated that study area is located in a position that has the potential occurrence of severe desertification as 20. 07% of the area is classified in severe class، 70. 53% in moderate class while 9. 36% in low class of desertification.

Contineous data with appropriate length is very important in flood studies. However، data inadequacy and gaps in the existing data series is a common problem in many watersheds of arid and semi-arid regions. Therefore، several methods have been proposed for reconstruction of missing data series. In this research it has been tried to evaluate the efficiency of some new methods in reconstruction of instantaneous peak flow data in arid and semi-arid regions of Iran. For this purpose، flow data of 29 gauging stations in central part of Iran for the time period of 1965 to 2007 was collected، and after quality and homogeneity control، it was tried to reconstruct instantaneous peak flow data series using maximum daily data and by using four methods including regression method (REG)، artificial neural networks (ANN)، genetic algorithm (GA) and adaptive neuro-fuzzy inference systems (ANFIS). The results of this research showed that in all studied stations، ANFIS appraoch presented results with higher accuracy in comparison to other methods.

Realizing the chemical components of plant species possessing multi-purpose significance can specify the planning priorities for utilization and wise management of rangeland species. Camphorosma monspeliaca and Echinophora platyloba are two of the endemic species in Chaharmahal & Bakhtiary rangelands that because of their grazing importance، it is necessary to study the nutritional elements for better range management. To study the mineral elements of the species in Doto-tangsayad habitat، the collection of species was carried out in three stages of growing، flowering، and seeding in spring، summer and autumn. Mineral elements of sodium، potassium، magnesium، calcium، zinc and copper were measured. First، the data of mineral elements were examined by SPSS software for normality then، these indices were comparing at three stages of growing، flowering، and seeding for these species with critical level livestock by applying one way ANOVA and T-test. The results showed there isn’t a meaningful difference concerning the amount of mineral elements between two of the species at phonological stages (growing، flowering، and seeding) except in copper. The amount of mineral elements in two plants has been decreased from growing to seeding during the time. There is also a meaningful difference in the mineral elements of Echinophora platyloba except zinc. There is no difference on growing stages of mineral elements of Camphorosma monspeliaca except Magnesium. Generally، mineral elements of two species are provided all elements livestock needs، except zinc and sodium.

Land degradation in arid and semi-arid regions makes it more susceptible to desertification accelerated by climate change and unwise human activities. Aim of this research was to investigate the role of water، soil and vegetation cover indices in desertification assessment in Jarghooyeh، Esfahan in order to prepare desertification map. IMDPA methodology was used in this case study and three criteria including water، soil and vegetation cover were considered. Some indicators were considered for each of the criterion and the final map of desertification intensity of the region was prepared by overlaying and geometric average the indices layers. The results showed that soil and water criteria with geometric average of 2. 25 (classified in medium class of degradation) and 1. 14 (classified under low class of desertification) are the most and least effective factors on desertification، respectively. It is also concluded that severity of desertification intensity for total area is 1. 72 which is classified under low class of degradation.

In rangeland management، appropriate grazing and utilization period is determined based on plant life stages. Accordingly، phenology of Artemisia sieberi was studied in three research sites namely Roudshor، Hasaan Abad and Khojir over three years. Totally، 20 samples of the mentioned species were selected and monitored regularly starting from early March 2005. Phenologic stages of plant life were the vegetative stage، flowering، seeding and winter dormancy. The collected data were then interpreted using with climatic data (temperature and rainfall) and for each stage، the necessary heat or total cumulative growth degree days (GDD) was calculated. The results showed that the beginning and end of growth was different over the studied years and these changes are subject to climatic conditions، especially temperature and soil moisture. Ar. si had a longer phenological period in cool years than warm and dry years. But the cumulative temperatures required in all stages of phenology were calculated similarity in different years. The results showed that plant growth is subject to growth degree - day (GDD) and cumulative rainfall during the growing season. ANOVA results also showed that plant height in the studied sites and different years was statistically significant (P <0. 05).

The degradation of rangeland vegetation due to overgrazing can be reflected in soil seed bank composition and size as well. In this study both of the standing vegetation and soil seed bank were studied under different grazing intensities in rangelands of Mahoor Mamasani in Fars province. Grazing intensities were as long-term exclosure، moderate grazing and heavy grazing. Vegetation and soil seed bank were sampled along transects and in 1 m2 quadrates. Seed bank size and composition was identified through glasshouse germination. The result of this study showed that in exclosure there were 104 and 52 species in vegetation and seed bank، respectively. These were 96 and 39 species for moderate grazing and 46 and 18 species for heavy grazing. We found 36، 26، and 11 species which were common in both vegetation and seed bank in exclosure، moderate and heavy grazing، respectively. The dominant families in both vegetation and seed bank were Papilionaceae، Compositae and Gramineae. Less palatable and desirable species were detected in vegetation and seed bank as grazing intensities increased. Standing vegetation significantly showed greater species richness and diversity than that in soil seed bank. We also found that not only the differences between vegetation and seed bank according to species composition in different grazing intensities but also the correlation between vegetation and seed bank varied under grazing intensities. Here، only in heavy grazing there was not significant correlation.

Diversity conservation is a main objective in rangeland management. Diversity is a suitable index for showing the changes of vegetation in rangelands and has a high correlation with ecosystem parameters. Therefore، using this index it is possible to find the changes and manage the ecosystem correctly. The current research was performed to determine the species diversity in Fashandak rangelands of Taleghan. To do this، 110 plots each one with an area of 1 m2 were established based on randomized-systematic method and density of the species within each plot was recorded. Species properties including the related genus and family in addition to life form، growth form and biological type were determined. Shannon، Simpson and McIntosh diversity indices were used. Results showed that diversity of Fashandak rangelands could be considered as moderate. The highest distribution frequency was related to the species of Bromus tomentellus، Hypericum perforatum and Thymus kotschyanus.

In the present study، Analytic Hierarchy Process method was used for weighting different assessed criteria for land suitability of irrigated wheat and the results obtained from fuzzy methods compared with those from conventional methods. Comparison of fuzzy and parametric land indices showed that fuzzy approach has increased the land indices in all of land units. The correlation coefficient between land index and observed yield in the study area for fuzzy approach based on AHP method and parametric approach were 0. 91 and 0. 87، respectively. Although، the fuzzy set approach offers the higher accuracy for land suitability assessment، the most critical issue in its application to land suitability assessment remains the choice of membership functions، cross-over points and weight values for different land characteristics.

Nowadays، avalanche and its related damages to human lives and infrastructure are considered as a major natural disaster. Advancement of science and technology and application of spatial analysis in the field of natural resources has made possible understanding، predicting and controlling of avalanche with acceptable probability. In this study، by using the effective factors in the occurrence of avalanche in five parameters including slope percentage and direction، elevation، geomorphological facies and vegetation cover، the map of hazard zonation occurrence was prepared based on Analytic Hierarchy Process (AHP) in Semirom region، Iran. Each of the mentioned parameters was divided into sub-classes and then were weighted and compared according to AHP. The weighted parameters were overlaid in GIS in order to obtain avalanche hazard zonation map. According to the weighted parameters، slope due to its effect on the gravity of snow layer، elevation for its influence on the type of precipitation and slope direction for the absorption of solar energy and melting of snow layer are mostly involved factors in avalanche occurrence. Vegetation cover and geomorphological facies are considered in the next orders because of their effect on soil surface roughness and form of topographic features. It is noted that effect of some factors such as slope direction and elevation are related to climatic condition. For example slope direction fairly accounts for wind direction. To evaluate the results of model، field visits and Google Earth images were considered and the prepared zonation map was compared with the avalanche occurred areas. The results indicate 90% of total passage ways of the avalanche were located in the high risk class which clearly proves suitability of avalanche hazard zonation method.

Drought and salinity are considered as the most important factors limiting plant growth and due to water and soil limitations، they have attracted more attention of plant physiologist. This study investigated the effects of drought and salinity stresses on seed germination behavior of Halocnemum strobilaceum in four drought levels (0، -0. 2، -0. 4and -0. 6 MPa) and six levels of salinity (0، 50، 100، 150، 200 and 250 mM). In order to study the effect of drought stress on seed germination، a solution of polyethylene glycol 6000 (PEG) and different levels of NaCl as salt stress were used. SAS statistical software in a completely randomized design and LSD test were used for comparison. The results showed that among all levels of drought treatment، except plumule there is a significant difference at 1% and 5%. Also there is significant difference at 1% among all salinity levels except germination percentage and rate. Maximum germination in salinity was also observed at 100 mM and up to 200 mM the germination rate increased. Considering the radicle، plumule، seed vigor index and allometric ratio there was difference between levels of salinity of control and other treatments، but differences between the levels of 50 to 250 mM were not statistically different. The highest amount of germination characteristics in -0. 2 MPa is observed and with increasing drought level to more than -0. 2 MPa germination rate decreased. Results of this study concluded that H. strobilaceum is more resistant to salinity than drought and resists on salinity levels up to 250 mM.