نشریه مرتع و آبخیزداری
سال هفتاد و چهارم شماره 4 (زمستان 1400)

Meteorological drought affects the water resources of the basin with a time delay, which leads to the occurrence of hydrological drought. Assessment of rainfall variability and drought is necessary to determine the existing water crisis and water resources management. This study was done in 42 watersheds of Khorasan Razavi province during 1975 to 2015 years to determine the temporal relationship between meteorological and hydrological drought. The hydrological drought severity was calculated with SDI index and meteorological drought was calculated with SPI index. The trend of precipitation and discharge was investigated with Mann-Kendall test. The temporal relationship between the mentioned indices was studied with Pearson correlation coefficient as simultaneously and with a time delay from one to 12 months. The results of Mann- Kendall test were indicative the negative trend of discharge in all watersheds and the most negative slop (-0.052) occurs in PolKhaton watershed. A combination of positive and negative trends in precipitation changes was observed in the study areas. However, the calculated positive trends were not significant at the 95% level in any of the watersheds. In 36.5% of the studied watersheds, no significant correlation coefficients were obtained at 95% level between SDI and SPI. In 60% of the studied watersheds, the highest correlation coefficient between precipitation and discharge with one-month delay, in 25% of watersheds without time delay, in 12.5% of watersheds with 2 months’ time delay and in 2.5% of watersheds with a time delay of 12 months were obtained.

Soil organic carbon (OC) is one of the most important soil properties, especially from an environmental point of view. For this reason, OC modeling and estimating has been highly considered. In modeling, application of pedotransfer functions to estimate soil properties from the other ones have an important place in soil science. Unfortunately, not much attention has been paid to the valuable data that are obtained with the least cost and time in the soil profile description. The aim of this study was to determine the importance of data that obtained from soil profile description to estimate the soil organic carbon in Dehgolan region in Kordestan Province. For this purpose, 30 pedons were excavated and described. Soil samples were collected from different horizons and soil properties such as texture, pH, EC, CCE and gypsum were determined. Modeling was performed in three scenario including laboratory data, data of soil profile description and application of laboratory and soil profile description data simultaneously. The results showed that based on laboratory data, soil organic carbon has a significant relationship with silt and CCE properties with a coefficient of determination about 25% (R2 = 0.25); While, the two soil profile description data of soil color (chroma) and genetic horizon with coefficients of determination about 65% (R2 = 0.65). With compilation of laboratory and soil profile description data the coefficient of determination was also obtained 65%. This level of accuracy clearly shows the value and importance of data related to the soil profile description data.

Nowadays, the destructive factors of the environment and natural resources are so widespread that the alarm of destruction of these natural wonders is sounded all over the world. Due to the importance of this topic, the study was conducted to estimate the willingness to pay of local communities to conserve and restore desert areas of Gosht plain in Saravan in order to attract people's participation to finance projects for the preservation and rehabilitation of desert areas. The sampling process was conducted using Cochran's formula with 303 samples by simple random sampling method. Conditional valuation method and Logit model were used to estimate the people’s willingness to pay. The results showed that gender, education, participation in rural government institutions, employment of trusted executives, the history of participation in educational-developmental classes, being native, income and directly being beneficiaries from the environment of the region has a positive and significant effect on the willingness of people to pay for Gosht plain protection. The variable of age and suggested amount had a negative and significant effect on willingness to pay, but the size of household had no significant effect on willingness to pay. Moreover, the variables of existence of a management organization for participation, acquaintance with the environment, having environmental literacy, and government financial support of the projects had a positive and significant effect on the willingness to pay for the Gosht plain protection. The average of peoples’ willingness to pay monthly in 1398, was obtained 113890 Rials per each person.

In order to investigate the preference value of plants, this study was conducted in Sirik rangeland in Hormozgan province. To determine the preferred value in this region, two methods of timing and production and consumption of plant species were used. The results of analysis of variance of the preferred value in both timing methods (using a video camera) and the operating percentage yielded the same results. Because in both methods, there was no statistically significant difference at the level of 5% between the years and months of the study and only a significant difference between species. In the chronological method, Sphaerocoma aucheri with statistically assigned the highest mean (29.8%) along with annuals with an average (28.9%) were placed in a class statistically, followed by Moltkiopsis ciliata and Cenchrus pennisetoformis 9.3 and 7.8, respectively. In the method of exploitation percentage, the highest exploitation percentage was Cenchrus pennisetoformis with 52.9%, although with Heliotropium bacciferum with 49.6%, Moltkiopsis ciliata with 45.8%, Sphaerocoma aucheri with 44.6% and Cyprus conglomeratus with 44.5% were in a group. In the Sirik region, Sphaerocoma aucheri was one of the high density and high consumption species and Cenchrus pennisetoformis was the low density and high consumption species. Sphaerocoma aucheri was in the first place in terms of preference value, but it should be noted that livestock tends to graze more than annuals at the beginning of the growing season and at the end of the growing season with drying or seeding of grasses, annuals are received less attention.

In this study, 18 variables affecting avalanches have been studied. These variables are related to the conditions: geomorphological and topographic, climatic, snow and also Some activities are related to human factors. In this study, the avalanche risk map was prepared and analyzed using the risk model (HEV) and the variables affecting the occurrence of avalanches. Avalanche hazard map was prepared using three models: AHP, Garp and MaxEent. Based on three risk factors for avalanches, obstacles in the avalanche route and also sensitivity to avalanches, a risk map was prepared. Comparison of the results with field visits and avalanche occurrence areas and past statistics and information indicate the accuracy of the hazard map with 93.85% accuracy by the AHP method. One of the most important variables in avalanche occurrence in this area is the slope. Then, using two maps of avalanche risk elements and avalanche susceptibility map and avalanche hazard map, snow avalanche risk map has been prepared. The results showed that the avalanche hazard map has a very inherent difference with the avalanche risk map. Areas in the low-hazard category on the avalanche risk map became more important in the avalanche risk map. The most important reason is the existence of endangered elements and the development of residential lands in this area over the past few decades

Erosion and sedimentation phenomena are two inevitable phenomena of watersheds that are subject to complex factors. Identifying these factors and recognizing their effect on erosion and sediment will help in better planning to reduce the damage caused by erosion and sediment in a basin. In this study, to determine the factors affecting sedimentation, the Urmia Lake watershed was selected as the study basin. After identifying 30 characteristics affecting the sedimentation of sub-basins of the study area, including hydrological, physiographic, geomorphological, geological and soil characteristics, climate, land use and vegetation as independent variables, the amount of sediment produced in each sub-basin. Was identified as a dependent variable. Using factor analysis, principal component analysis (PCA), cluster analysis and stepwise multivariate regression between selected independent variables and dependent variable using SPSS software Statistical relationship was obtained between sedimentation of sub-basins and watershed characteristics. According to the selected regression model, it is determined that the amount of sediment in the watershed of Lake Urmia to five factors of agricultural land area (rainfed, irrigated and orchards), the area of sub-basins, the total area of erosion and Quaternary structures, average discharge The annual and basin form factor depends on the fact that these five factors control 89% of the sediment production changes in the selected sub-basins, which is significant at the 5% confidence level. In general, the factors affecting erosion and sedimentation of the Urmia Lake watershed can be divided into three groups: human factors and land use change, geology and physiography.

We investigated the trend analysis of rainfall characteristics in the Hyrcanian region of northern Iran in a 33-years period (1987 to 2019). Annual, seasonal, and three 11- years periods (1987-1997; 1997-2008; 2008-2019) were analyzed using data recorded at eight synoptic weather stations of Astara, Rasht, Anzali, Ramsar, Noshar, Babolsar, Ghaemshahr, and Gorgan. The Mann–Kendall (MK) non-parametric test was used to determine the rainfall trends. The mean annual rainfall was 1143 mm with the highest and lowest amounts recorded in Anzali (1694 mm) and Gorgan (529 mm), respectively. The MK test demonstrated no significant trends for annual rainfall in each station and the whole region (MK value: 0.32). Rainfall of 11-year periods showed slight differences (1140, 1145, and 1146 mm for the three consecutive periods). Rainfall and the number of annual events per year illustrated positive significant correlations in all weather stations (mean r = 0.58). The mean annual number of rainfall events was 118 with a mean rainfall event of 9.5 mm increased by approximately 0.5 mm (5%) during the recent period. In the Hyrcanian zone, 21% and 31% of the annual rainfall were less than 10 mm and larger than 40 mm, respectively. 34% of yearly rainfall (383 mm) was recorded in the first half of the year and the largest amount of seasonal rainfall was in autumn (43% of total annual rainfall). Plant communities, forest ecosystems, and agricultural activities in the Hyrcanian region will definitely be affected by any change in precipitation.

Ecological processes at different scales led to heterogeneity in the landscape by changing the pattern of the landscape structure. These would result in fragmentation and disintegration of landscape structures and filtering biodiversity characteristics such as species functional diversity. We performed this study to quantify the patches and classes characteristics of the landscape (metrics) and their impact on indicators of species and functional diversity. Sampling was performed in a semi-steppe rangelands of Chaharmahal and Bakhtiari, where the natural structure of the landscape creates various patches such that classified in seven different classes of plant communities. In each class, different patches were randomly selected and within them 5 to 10 macroplots of 30 * 30 m were randomly-systematically established. Afterwards, 3 plots of 2 * 2 m2 installed in macroplots in order to sample canopy cover and number of species. Taxonomic, functional diversity and functional beta diversity indices were measured using "Vegan", "FD" and "betapart" statistical packages in R software, respectively. The landscape metrics were also measured using Fragstats software. Finally, the relationships between diversity indices and landscape metrics were analyzed using linear regression. The results at the patch level showed a significant negative relationship between the shape and functional diversity indices such as leaf nitrogen weight average and leaf specific surface area weight average. The results at the class level indicate the positive effect of the functional evenness index on the edge density metric as well as the functional beta diversity of the patch richness metric.

Social participation is an important factor in the social, economic and cultural development of human societies. Engagement in natural resources management also plays an important role towards sustainable development and is an important approach to achieve goals and to success in natural resource plans. In this regard, this research aims to investigate factors affecting people's participation in the implemented natural resource plans by conducting a questionnaire survey in the counties of Sarakhs (the villages of Bazangan, Zalughal, and Kalateh Awaz), Torbat Jam (the villages of Musa Abad, Tamink Olya, Tamink Sofla, and Kalate Ghazi), and Kashmar (the villages of Jardavi, Baharieh, and Ghochpalang), Khorasan Razavi Province, Iran. For sampling, out of 3077 households of these ten villages, 807 households were randomly selected and surveyed by cluster systematic method. The collected data were analyzed by SPSS and Amos software. Structural equations were modeled for visual and graphic design. The main indices and fitting coefficients of the model were identified. The results of the statistical tests showed that people had willingness to participate in the plans and some factors had a significant impact on public participation in the region, such as economic profitability of the plans, education, employment, social conflicts, and environmental attractions (sig <0.05). As a result, these factors should be strengthened and given more consideration for the future successful implementation of natural resource plans. Finally, identifying these factors in each region will be an important step in the success of any plan.

Nowadays, using satellite imagery is one of the fastest and lowest-cost methods in rangeland assessment. Also, remote sensing-based vegetation indices are among the most widely used tools to assess and monitor vegetation changes, especially in the post-fire period, and to map the burned regions in rangelands. The present study was conducted considering the importance and extent of rangelands and the recently increased prevalence of fires in the semi-steppe rangelands of Iran, especially in Chaharmahal and Bakhtiari Province. The main objective of this study was to distinguish and identify the burned areas during 1-3 year and 3-5 year periods to adopt an appropriate post-fire management program in these areas using spectral indices. After calculating the spectral indices, the M statistical parameter was determined to designate the separation capability of the burned areas from the adjacent ones. According to the findings, using NBRT, NBR, and CSI indices is recommended to identify and distinguish the burned areas 1-3 years after the fire from the adjacent areas in semi-steppe rangeland regions of Iran. Overall, these indices are of high efficiency in separating these ranges. Moreover, T.C. Brightness and NBRT indices can efficiently identify and separate the burned areas 3-5 years after the fire. Among the studied indices for both periods of fire in the studied semi-steppe rangelands, the NBRT index showed a high potential for identifying the burned area from the adjacent areas.

In recent years, extensive practices have been done on flood control, erosion and sediment in the fields of research and implementation of watershed management. Therefore, the purpose of this study was to assess the effects of watershed management practices on the characteristics of runoff and suspended sediment load in two subwatersheds in Ghaleh Gol watershed in Lorestan province, Iran. In this research, for comparing the effect of watershed management practices (WMP) on discharge and suspended sediment load (SSL) from both subwatersheds, the flow velocity was measured and the SSL was sampled directly from the beginning of the rainfall events until the end of them. Results showed that in all measurements, the discharge and suspended sediment load of the southern subwatershed with watershed management practices was higher than the northern subwatershed without such practices. According to the results of ANOVA test, it was found that the difference between discharge peak (P=0.691) and suspended sediment load peak (P=0.840) was not significant in two subwatersheds. Also, according to the results, the difference between specific discharge and specific SSL was not significant (P>0.05). Based on these results, it was found that the implementation of WMP in the study area apparently has no the required performance to reduce the discharge and SSL, and the WMP have lost their performance before the end of their useful life. Therefore, in order to increase the performance of mechanical watershed management practices (MWMP), the biological and biomechanical practices has to be performed simultaneously.

This study examines spatial and temporal changes in water resources; including blue and green water resources components, taking into account their changes in four main land use in the Zayandeh-rud basin. The spatial and temporal changes were studied using the semi-distributed hydrological model SWAT (Soil and Water Assessment Tool) by applying the most complete data set developed for the watershed over 20 years and for four different 5-year intervals. Due to the high ability and efficiency of the SWAT model to simulate climatic parameters and surface runoff, the minimum 5-year average of blue water, green water flow, and green water storage at the basin level occurred; in the fourth period 2010-2014 (approx. 15 mm), the second period 2000-2004 (26 mm) and the first period 1995-1999 (30 mm), respectively. On the other hand, the mean values of the blue water component, the green water flow and the green water storage components were estimated to be higher in the western parts of the basin than in the eastern parts. Other findings from this study are the changes of blue water and green water regarding precipitation and land use. For example, the maximum amount of blue water was observed in forests and irrigated agricultural lands, the highest amount of change in green water flow in irrigated agricultural and dry farming lands, and the minimum amount of green water flow in grasslands. Acknowledgment of available water resources, water potentials of an area and critical areas enables comprehensive management of water resources and long-term planning.

Today, the use of surface water to meet various human requirements such as drinking, agriculture and industry has endangered the health of this river ecosystem and its role in the natural system. The minimum environmental flow in the river provides a safe level of protection for the water-dependent environment. In the present study, the environmental flow requirement of three stations of Cheshmeh Langan River located in Isfahan province were calculated by two hydraulic methods slope and maximum curvature of wetted perimeter. The results showed that both slope and curvature methods estimate the same minimum environmental flow requirement. So that the difference between the two methods in S1 station was about 0.07m3/s. According to the discharge measured at station S1, minimum environmental flow requirement is provided in all months except December. While the measured discharge at S2 and S4 stations cannot provide the minimum environmental flow requirement due to the impact of the dam and water transfer in any of the months. The flow of 0.39 m3/s for the first station (S1) and 1.44 an 1.68 m3/s for the second and third stations, respectively has been proposed as the minimum environmental flow requirement of Cheshmeh Langan River. The results of this study showed that the environmental flow requirement can be estimated using hydraulic method in data scarce.

Cloud seeding is a new and efficient approach to deal with water scarcity and mitigate the effects of drought. Cloud seeding is one of the most flexible and cost effective ways for water resources management that can cause 10 – 30 percent increase of yearly precipitation. The Beheshtabad watershed is located in the uplands of Karoon river, can be one of the areas in Chaharmahal-va-Bakhtiari Province, that prone to cloud seeding. So we investigated the potential of cloud seeding in this region using physiography and meteorological data. The results show that 25.4 percent of study area (in the southwest) has the potential of cloud seeding. The runoff of Beheshtabad watershed was modeled in IHACRES. Two scenarios of a 10% increase in precipitation of February and a 10% increase in precipitation of the six months (in an average year) were tested. The results showed that a 10 percent increase in precipitation in February added 3.6 percent and a 10 percent increase in precipitation in the six months added 13.7 percent to the annual flow of Beheshtabad River. Also, a 10% increase in precipitation in a dry and humid year was compared, and the results show that the effect of cloud seeding is greater in drought.

Snow is one of the effective fators on vegetation rate and function in mountainous areas. The aim of this study was to investigate the impact of snow cover area index and snow cover duration index on two declining and dominant plant species including Astragalus adscendens and Quercus brantii in Chaharmal and Bakhtiari Province from 2003 to 2016. For this purpose, Normalized Difference Snow Index (NDSI) and Normalized Difference Vegetation Index (NDVI) were extracted from MODIS satellite images and compared using Pearson analysis in forest decline regions (Barz, Seveh, Helen and control area) and in rangeland decline regions including Astragalus adscendens decline and control areas. Results showed that about 32% of the snow cover in the study area has been reduced, although a constant trend was not observed. The studied snow indices showed the highest relationships with rangeland and forest vegetation cover in March. The decline region of Astragalus adscendens had the maximum relationship with the snow cover area (R>0.70) and snow cover duration (R>0.71) in March. According to the findings, snow precipitation in late winter season and its duration is more effective on the rangeland Astragalus adscendens species than forest vegetation cover and this pecies can be more sensitive to decline in case of snow reduction.