مجله مدیریت بیابان
پیاپی 13 (بهار و تابستان 1398)

Drought assessment and monitoring using traditional methods rely on rainfall data, which are limited in arid lands and often is very difficult to obtain near real time and costly. In contrast, remote sensing technology is a method for monitoring of large-scale drought.In this research, drought condition was analyzed using drought indices such as TVDI and NDVI from MODIS sensor data for the Yazd-Ardakan plain, Iran. First, relationship between the drought indices with climatic elements were detected. Coefficient of correlation between TVDI and SPI_6 and SPI_12 were 0.68 and 0.71, respectively. Correlation between NDVI and SPI_6 and SPI_12 were 0.49 and 0.51, respectively. Point correlation between TVDI and SPI_6 in 2004 (as a normal year), 2007 (dry) and 2012 (wet year), were 0.64, 0.78 and 0.67 and for the SPI_12 in the above-mentioned years were 0.65, 0.79 and 0.69, respectively. In other word, efficiency of the TVDI in 2007 is better than the other two years. Correlation of NDVI and SPI_6 in 2004, 2007 and 2012, were 0.41, 0.50 and 0.56, respectively. The correlation between NDVI and SPI_12 in 2004, 2007 and 2012, were 0.52, 0.57 and 0.59, respectively. TVDI which takes into account thermal and reflective bands, and soil moisture, is more accurate than the NDVI, which considers only amount of vegetation of the study area. Results showed that the relationship between vegetation and temperature is negative, while, the relationship between vegetation and precipitation is positive. Using of TDVI can compensate defects of the NDVI and used for identifying and monitoring drought.

Investigation of wind speed trend and analysis of its effective can be a suitable index to environmental variability related to air movement. Any increase or decrease in wind speed over time can impact on agriculture, soil erosion, wind energy production, construction, mental health, and etc. In this study, wind speed trends and line slope by using Mann-Kendall nonparametric test and Sen’s slope estimator were evaluated using wind speed data from 96 synoptic stations of Iran during their recorded period. Zoning of annual mean wind speed showed that four wind regions could be detected in Iran. Although the wind trend in Iran has no a certain temporal pattern, but in the northern half and mountain regions of the country, the trend is more pronounced. January and October with about 50%of the total station, and July and March with about 38% were observed maximum and minimum of the positive trends in the study area, respectively. Most of the area with negative trend is related to July by 13% and lowest is related to January, February, March and October by 6.25%. Generally, the positive trend is 43% and areas with negative trends is 9.3% of the total area of the country. Wind speed slope investigation shows that 75% of the country has positive slope and 25% of the country is with negative slope that have been expanded in all regions of the country. Most positive and negative slope is related to Gorgan and Chabahar Stations, respectively.

Understanding the effect of climate change on distribution of plant species is essential for sustainable management and conservation of rangelands, especially in arid and semi-arid ecosystems which are vulnerable to desertification, because of their sensitivity and frangibility to climate change. Due to the complexity of natural systems and phenomenon of climate change, species distribution models are used to understand the impact of climate change on potential niche of species. In this study, five modeling algorithms including artificial neural network, generalized boosting method, classification tree analysis, multivariate adaptive regression splines and maximum entropy were used to predict current and future distribution of Artemisia sieberi Besser in Central Iran. First, the ensemble model as the average predicted probability of single models’ occurrence was created. Next, pessimistic (RCP 8.5) and optimistic (RCP 2.6) scenarios of CCSM4 and NorESM1-ME climate models for the years of 2050 and 2070 were evaluated to assess the trend in spatio-temporal variations of distribution. For this purpose, layers of environmental factors including six bioclimatic and two physiographic variables were used as inputs of species distribution models. Among the environmental variables, altitude, annual precipitation, isothermality, and slope had the most impact on the habitat suitability. Modeling evaluation indicated that the generalized boosting model had better predictions of climatic habitats than other models, and ensemble model than single models. Maximum probability of species presence was determined in plains and low slope areas at altitude of 1000-2000 m and annual precipitation of 100-200 mm. Analysis of the climate change scenarios showed that, the species habitat would be decreased in 2070 more than 2050, leading to the expansion of desert areas. The results can be used for planning to combat desertification in the habitat of Artemisia sieberi, as well as its restoration and rehabilitation in the vast regions of Iran.

This study was aimed to investigate the effects of seed biopriming with plant-growth-promoting bacteria (PGPB) on some characteristics of germination and growth of Astragalus ovinus Boissunder drought stress. This study was conducted as a factorial experiment in a completely randomized design, with three replications. Percentage, rate of germination, mean germination time, vigor, chlorophyll a, b, carotenoids, fresh and dry weight of radicle, shoot, embryonic leave, seedling and radicle length, shoot and seedling were determined. Plant-growth-promoting rizobacteria at five levels including Pseudomonas aeruginosa (Schroeter) Migula, Azospirillum lipoferm (Beijerinck) Tarrand, Bacillus cereus Frankland, Azotobacter chroococcum Beijerinck and the control treatment were considered as the first factor. The second factor was applying drought stress at four levels of 0.0, -0.2, -0.4 and -0.8 MPa. Among the four biopriming treatments tested, A. lipoferm and A. chroococcum were eliminated, because the seeds were failed to germinate and identified as agent pathogenic. Results indicate that the use of these two PGPB increase the characteristics of germination (percentage, rate of germination, mean germination time and vigor) and growth (fresh and dry weight, length and photosynthetic pigments) of A. ovinus. It can be concluded that these two bacteria increase effectively the growth of A. ovinus under different levels of drought stress. In general, these two bacteria play a role in reduction of the negative effects of drought stress on A. ovinus.

Measuring of subsidence is often challenging due to the gradual occurrence in large-scale, and advanced measuring techniques are required. The first foresighted consequence of this catastrophic phenomenon is irreversible loss of aquifer reservoir. Subsidence is downward motion of the earth's surface with negligible horizontal vector component. Subsidence is occurring with different rates in many aquifers of the country constantly, because of excessive extraction of groundwater for years which causes lowering of the water table. Increasing the intensity of this phenomenon in recent years requires modern methods of measuring subsidence. InSAR technique can be strongly powerful that can extract vertical component in large extent, especially in areas with insufficient geodetic data. In this study, new Sentinel-1A imagery from 2014 to 2018 were used to examine the subsidence rate in the Kashmar and Khalil Abad plain. According to the high correlation between pair images, basic interferograms was calculated. Then, using SBAS method unnecessary phases were removed. Thereafter, the displacement phase was calculated and converted to the vertical component. Maximum subsidence rate is observed near the southwest suburb of Kashmar city and western part of Khalilabad plain. Results indicate that the Kashmar and Khalilabad plain was encountered maximum of 17 cm downward movement annually. Due to uneven and heterogeneous subsidence, the area has susceptibility for formation of longitudinal cracks. Final map can be used to control and manage water resources and prevent natural hazards and desertification

Lead accumulation in soil is influenced by various factors such as physico-chemical properties of soil, parent materials of rock, soil pollutant resources, organic and chemical fertilizers in agriculture and etc. So, the aim of this study is to evaluate the effect of soil physico-chemical properties on accumulation of lead in soil. The study area is located in 20 kilometers ambitious Aq- qala to Inche boroon road. Soil sampling was carried out in 5 blockswith distance of 3000 m. In each block six soil samples from 0-5 cm depth with a gap of 200 meters from each other were taken, totally 30 soil samples. After measuring the lead content, physical characteristics, texture and Bd and chemical, OM, SAR, CaCO3, EC and pH of soil samples were tested. Effects of soil properties on lead accumulation were analyzed by using linear and multiple regressions.Results showed that soil physical properties have no effect on the accumulation of lead. Among soil chemical properties, CaCO3 and EC had significant negative correlation and pH and OM had significant positive correlation with lead accumulation. Moreover, no significant relationship was observed between SAR and lead contents in the soil.Therefore, in the selected model based on the results of analysis of variance (by linear regression method), variables such as CaCO3, EC, pH and OM were selected as the most important factors that could express the lead concentration in the study area.

In arid and semi-arid ecosystems, woody and perennial plants are considered as a key factor in wind speed reduction and windblown sands sedimentation. The present study aims to evaluate the effect of different levels of soil additives on morphological characteristics of Calligonum bungei Boiss. A greenhouse experiment was conducted in factorial plan in a randomized complete block design RCBD. In design of experiments, applied treatments were natural and municipal waste compost biochars as soil additives, each in four levels of 0, 1, 3 and 5%, mycorrhiza present or absent, and plant type. Results showed that treatment NO. 7 cause increased 34.62% in plant height, 42.38% in collar diameter, 554.02% canopy cover volume, 124.04% root length, 30.92% fresh weight of shoot, 36.23% fresh weight of root in mycorrhizal plants and treatment NO. 23 cause increased 39.24% in plant height, 35.98% collar diameter, 152.1% canopy cover volume, 17.74% root length, 68.53% fresh weight of shoot, and 20.75% fresh weight of root in non-mycorrhizal plant accordance with control treatment. Among the used treatment, those in the absence of mycorrhiza due to poor-quality of mycorrhiza and lack of interconnection between plant and mycorrhizal fungal networks had better growth than those of non-mycorrhizal plants. According to the results, treatment No. 7 due to low cost, greater accessibility, improve of soil fertility, and plant establishment were recommended in desert regions.

The present study investigated some habitat characteristics and ecological of Ochradenus ochradeni Abdallah in Abarkouh Bahman area for possibility of restoration function. Geomorphology, climatic and phenology and biometrical characteristics of the population were investigated. Results showed the habitat had a middle to coarse soil texture with relatively high CaCo3 38.7± 26.07% and low CaSO4 2H2O, 0.19± 0.2% and pH equal of 7.1-8.5. The habitat of this species in some parts in bare pediment with low slope. Vegetation canopy of of the studied plant was low equal to 0.39%. Rainfall in all habitats was low and in Hossein Abad was 61.8 and in Bdaf was 47mm annually. The dry period of 10 months and monthly and annual distribution of rainfall was irregular. The highest number of accompany species equal to 52% belong to Chenopodiaceae. Growth season start at spring until mid-August and seeding stage is at summer until mid-August. Autumn and winter was equal to dormancy of this species. The highest germination percentage observed in KNO3 1% equal to 86.66% and KNO3 2% equal to 76.66% .Highest germination rate happened in KNO31% equal to 5.69 number per day. The lowest germination percentage and germination rate measured in moist chilling (in both 2 and 4 weekends) equal to 0.38%. Results showed this species grows from saline-sodium soils to non-saline-sodium soil. Therefore, it can be useful for rangeland restoration and saline soil improvement. This species are suitable for livestock feed and improving of vegetation through a scientific range management.

The purpose of research is to rezoning the climate zones of the north east of Iran- located between 30° 35' to 38° 41'N and 56° 19' to 61° 16'E- based on the analysis of changes in the aridity index, in combination with other climatic parameters changes. Air temperature and precipitation parameters were provided in the scale of monthly average and annual over period time of 1990-2017. At first, the climate classification of the north east of Iran was revised by studying variations in precipitation, evapotranspiration and temperature and results were compared with the De Martonne and Köppen-Geiger climate classification. For analyzing the aridity status, trend of the above parameters in the form of UNEP index was tested using Mann-Kendall non-parametric method and Sen's slope estimator. Results indicated that applying of the aridity index, as a factor in improvement of the used pattern, caused the zoning of this method to be more precise than the previous methods. Therefore, the study area was classified into seven climatic groups, the zone Ac14 (Arid zone with cold winter and hot summer) with 39% and 9 stations, and Ec14 (Extremely-arid zone with cold winter and hot summer) with one station were the largest and smallest climate zones, respectively. Results of the Mann-Kendall test and trend line slope, for UNEP aridity index showed that the aridity and desertification intensity have increased in different parts of the area during 28 years.

Dust emissions by wind have significant implications for human health and ecosystems. The addition of effective materials in degraded soils is a suitable method for stabilizing soil accumulation, which can lead to reduced dust emission. To investigate the effect of biocharand vegetation on soil improvement against wind erosion, a wind tunnel experiment was conducted. This study was carried out in order to investigate the effect of walnut wooden shell biochar (Juglans regia L.) walnut wooden shell powder and three patterns of vegetation including raw, random and zigzag, on the soil erosion of Shahrekord plain soil which is one of the dust source. Biochar and walnut wooden shell in 5% by weight in separate soils were tested in a 60 - day period in the simulated wind tunnel, along with three artificial vegetation patterns. The results showed that soil modification can indirectly control the wind erosion potential. The amount of soil erosion in day 60 of experiment was 1455 g/m2 for control sample, 1270 g/m2 for raw pattern, 840 g/m2 for random pattern and 397 g/m2 for zigzag pattern, that zigzag pattern caused more reduction in soil erosion in comparison with other patterns. Biochar and walnut wooden shell powder resulted in 46.82% and 24.14% in formation of flocculed soil, respectively, in comparison with control sample, which increased resistance to soil erosion. As a result, biochar and powder along with vegetation are able to stabilize the soil and increase soil stability and lead to a reduction in wind erosion.

The purpose of this study was to assess the effects of agricultural development on increasing the intensity of desertification in Dargaz plain in northern Khorasan Razavi province. The intensity of desertification caused by agricultural development, using important criteria that is mainly related to human activities, such as groundwater, irrigation and drainage, agriculture, soil, industrial-urban development, and socio-economic criteria, in 20 years period from 1996 to 2016, were estimated using IMDPA model. Desertification intensity of Dargaz plain was classified into moderate and severe classes with frequency of 22% and 78%, respectively. Therfore, the irrigation and drainage criterion were the most important human factor in increasing of desertification intensity in this region. Then, soil criteria, agricultural development, urban-industrial development, socio-economic factors, and finally, quantitative and qualitative degradation of groundwater, respectively, had the most effective role in increasing the intensity of desertification in the agricultural land of Dargaz plain. Results showed that the increase of salinity in the eastern and northeastern parts of the region due to irrigation with salt water and the conversion of range and forest into agricultural and residential with an area of more than 7000 hectares over the past 10 years were the most important factors of increasing the intensity of desertification in this region. Therefore, to prevent extending of desertification, sustainable land management and preventing of land use change were suggested.

Total Dissolved Solids (TDS, mg/L) indicates the amount of soluble salts in water or in a solution, and usually calculates by measuring the electrical conductivity (ECdw, μS/cm) and then multiplied by 0.64. This is a general conversion factor (CF) and its amount varies depending on the water-soluble components. In fact, TDS meters determine TDSvalueby measuring of the EC solution and default or user-selected CF. Hence, the precise method is to calculate this coefficient according to the solute type. In this research, to determine precisely the amount of soluble solids along with suspended dust in MDCO sediments traps installed in the northof the Yazd-Ardakan plain. To obtain the TDS calculation coefficient from ECdw resulting from leaching of small amounts of dust, three methods including of an experimental coefficient of 0.64, physical vapor deposition weighing and measuring the concentration of ions affecting chemical salinity were compared. Comparison of mean of the CFs obtained from the three methods showed that the TDS valueof the method of coefficient of 0.64 for determination of TDS from ECdw, was significantly lower than the other two methods. Hence, applying of this method, leads to a low level of solute content with dust in the study area. The average of the TDS conversion factor obtained by the physical and chemical methods without significant differences were 1.03 and 0.90 respectively, compared to 0.64 in the experimental method, that makes it possible to calculate more precisely the TDS from the measured ECdw data that derived from leached dust, and it can be used to adjust the TDS conversion factor in EC and TDS simultaneous measurement devices.