معصومه شهابی

Dust storms affect different regions of the globe countries and Iran. The dust storm events were considered as one of the climatic components in arid and semi-arid regions and it is called one of the most important environmental problems of these regions. Therefore, in this research, the activity class of sand dunes were investigated based on the Lancaster index in Iranshahr city in Sistan and Baluchistan province. The aim of this study is to investigate the climatic different conditions on the mobility of sand dunes in Iranshahr city. Meteorological data for synoptic station of Iranshahr were collected from the Iranian Meteorological Organization for 15 years (2003 to 2018). After examining the wind speed velocity in Iranshahr, and extracting the seasonal and annual Wind rose diagrams, Dust Storm Index (DSI) was calculated.  Finally, the effects of possible changes in climatic elements on the mobility of sand dunes were predicted. The results showed a significant correlation between the Lancaster index and the amount of annual rainfall, wind and drought index. The results of the sensitivity analysis also showed that if the frequency of erosive winds and potential evaporation and transpiration increases to 30%, the activity of sand dunes in Iranshahr station increases by 25 and 23%, respectively, on the other hand, with a 30% increase in rainfall, the activity of sand dunes decreases by 30%.

Drought is a long-term natural phenomenon when the average precipitation rate is less than that of the normal periods. As a natural phenomenon, drought has turned into a  natural disaster occurring throughout Iran in recent decades with all its associated consequences. On the other hand, although rainfall is considered as the main indicator of water availability, the temperature is also an important factor in this regard, as it controls the evapotranspiration rate. Therefore, parameters such as precipitation and temperature can be used as indicators for analyzing the drought. Moreover, identifying drought trends based on previously recorded data, noting their occurrence in different times and places, and studying their variation over time play a significant role in managing water resources. It should be noted that the purpose of trend analysis is to determine the decreasing or increasing nature of trends in a series of observations performed for a random variable over time.

The Standardized Precipitation Evapotranspiration Index (SPEI) is a meteorological drought index that considers the variability of both precipitation and temperature in predicting drought conditions in a region. Enjoying a multi-scale ability to monitor and analyze drought in different scientific disciplines, the index fulfills the requirements of a drought index, being recently used in a variety of drought analyses. This study measured SPEI using precipitation and temperature data from eleven meteorological stations in Sistan and Baluchestan Province, Iran, during the study period.  The Drought events were then identified via the Standardized Precipitation Evapotranspiration Index over both 3 and 12-month timescales. The total geographical area of Sistan and Baluchestan Province is approximately 187,000 km2, located at 25° 03 N to 31° 28 N (latitudes), and 58° 47 E to 63° 19 E (longitudes). The province has an arid and semiarid climate with a mean annual rainfall of about 100 mm. The monthly precipitation and temperature data recorded at the stations were obtained from the Sistan and Baluchestan's Meteorological Organization. One of the commonly used tools for detecting changes in climatic and hydrologic time series is trend analysis. Mann-Kendall is a non-parametric trend test commonly used to assess the significance of trends in time series. This study used both nonparametric trend tests (Mann-Kendall) and graphical Mann-Kendall model trend analysis (statistical significance at 95% confidence level) to explore the drought trends in each station. The purpose of trend analysis is to determine whether the time series of a random variable's observations generally increases or decreases over time. While parametric trend tests are more powerful, it is non-parametric trend tests are widely used, as they can accommodate outliers in the data and require independent data.

The study's results indicated no negative trend in precipitation but revealed a significant trend in temperature. The SPEI values measured for the short-term time scale (SPEI 3) showed a statistically significant downward trend for all stations, which corroborates the occurrence of more critical drought periods in recent years. Moreover, the study of the frequency of drought occurrence in the stations during 10-year periods suggested an increasing trend in the occurrence of drought in recent years. As for the maximum drought index, it could be said that the index's value has typically increased in recent years, that is, more severe droughts have occurred. According to the results, the most severe drought belonged to the Khash station, and the wettest period was found in the Chabahar station.

This study sought to identify possible drought trends in Sistan and Baluchestan province using the Mann-Kendall test, considering the fact that detecting such changes offer valuable information for future water resources management. Accordingly, the analysis of previous drought events showed that more severe droughts are expected to occur in the years to come. Although this study did not seek to find possible causes of decreasing trends, the results presented herein could be used as a benchmark for further analysis of the consequences of climate change. It could be argued that low precipitation and high potential evapotranspiration (PET), especially the PET caused by rising temperature, are the main factors that could influence drought in the future. Therefore, the influence of the PET should not be ignored in drought analysis, and it is suggested that more comparative studies of different drought indices be conducted on analyzing future climate change-induced droughts.

Studying the phenology of range species is an important factor in management actions for optimal utilization of these species. On the other hand, drought and stresses arising from it cause to the changes in plant growth stages, affecting forage yield. Bromus kopetdaghensis ¡ Festuca arundinacea ¡ Stipa arabica and Poa bulbosa are the main elements of semi-steppe areas to dry forests of Khorasan rangelands as relatively palatable species, grazed by livestock. In the current research, phenology of the mentioned species was studied during 2007-2010. Moisture conditions and drought classes were also studied by Standardize Precipitation Index (SPI) in rangelands of Binalood, Khorasan Razavi province in a twenty-year period. Effects of different drought periods were investigated on emergence of plant organs and the period length of vegetative and reproductive stages. Results showed that reproductive growth was shorter during drought period. Under drought conditions of 2008, vegetative growth was started earlier compared to other years and the change from vegetative to reproductive stage occurred in a shorter period. Results of growth degree-day showed that the range was from 2814.12 in 2010 to 2406.95 centigrade degree in 2008. Consequently, GDD model could be used with relatively high accuracy in determining the appropriate time for livestock entry and exit.

Drought means scarcity of water, which various sectors of human society, agriculture, water supply, industry and environment can adversely affect due to its occurrence. Drought is best characterized by multiple climatological parameters as a natural hazard. An understanding of the spatio-temporal dependence relationships between effective variables on drought is necessary to its description and analysis. The main purpose of this study is investigation of climatological drought in synoptic station of the Kurdistan Province, Iran, by using Triple Diagram Model (TDM). The data consists of monthly average temperature, precipitation, and also relative humidity from seven synoptic stations. The standardized precipitation index (SPI) was calculated for each station. The semivariogram of different used models have been analysed and were been chosen using the cross validation method. According to coefficient of determination and residual sum of squares indices appropriate method was selected for drawing triple diagram models. The triple diagram models have been prepared based on geostatistic principles by SPI, Temperature, and relative humidity variables. The results indicate that SPI classification is characterized by the scattering in two input variables can provide the analysis framework of the characteristics and variations of climatological factors. The spatial relationship between stations/regions can be carried out by comparison of the humidity conditions. Application of the triple diagram models can be recommended for drought analysis in other climatological stations. The triple diagram plots help to make interpretations in spite of extreme scatter points facilitate the explanations of the influencing trend among variables.

In order to investigate the effect of root pruning in morphological and physiological characteristics of Juniperus excelsa seedlings an experiment was carried out on transplanted one year-old seedlings. Treatments included root pruning intensities (1-slight pruning (2-moderate pruning and 3- control (no root pruning)). Experiment design was completely randomized design. Each treatment included three replicates and each replicate included 20 seedlings (in total 180 seedlings). The results showed that root pruning improved the quality and growth of root and seedlings survival. Results indicated that root pruning enhanced seedling quality index of J. excelsa seedlings and had a good capability for pruning. Root length, root diameter, root biomass, shoot biomass and total biomass were significantly correlated with habitat quality index which increasing these factors improves plant quality. The ratio of root to shoot biomass and total biomass was significantly correlated with plant survival. Survival was improved by increasing these factors. Also, according to high correlation between quality index and root collar diameter and on the other hand, another characteristics such as root length, root biomass is so hard to identification, root collar diameter is suitable index for qualitative classification Juniperus excelsa seedlings in nurseries.

Ecological studies are principal methods for scientific maintenance and utilization of natural resources and environment. In this research the study of range plant species autecology has been performed in Khorasan Razavi province. Ecological factor such as topography, soil characteristic and climate were studied. Associated species, the presence of species in vegetation, root system and phenology were studied. The results showed that B. kopetdaghensis was distributed in 1300-2600 m range of altitude and 20-75% of slope. The average of precipitation varies from 325.8 mm in Shamkhal station to 351.3 mm in Zoshk station and the average of annual temperature was about 8.6 ˚C. Soil analysis showed that Bromus kopetdaghensis appears in sandy-loam, loamy and silty-loam soil with pH of 6.5-7.8. The amount of crude protein at vegetative stage was 72% more than reproductive stage. Phonological studies showed that vegetative growth was started from late March and continued until May. Flowering stage was beginning from Late May until June. Seedling and seed ripening was continued until the mid-July. Seed weight varied between 7.8-3.4 gr and optimum temperature for germination was 20 ˚C and germination power reach to 95%. Seeds could preserve their germination vigor and they can germinate under suitable condition. The studies of phytomass showed that root to shoot ratio was higher and it would increase in arid years. General and absolute recognition of ecological characteristic for main range lands species or autecology in order to accurate range lands management, planning improvement and utilization would be necessary.