Desert Management
Year:2020 | Volume:7 | Issue:14 |Papers Count:12

Haloxylon salicornicum (Moq. ) Bunge ex Boiss and Haloxylon aphyllum Iljin are two important halophytes in desert. Hammada salicornicum and Haloxylon aphyllum Iljin have grown extensively in playa and sand dunes and are essential for supplying of forage for livestock, especially camels. The present study investigated the effects of different soil conditions in two areas (soil saline-sodic of playa and sandy soil in erg), on antioxidant activity, pigments characteristics, total phenolics, glycine and glutamine. The results showed that the highest amounts of chlorophyll a and total chlorophyll were measured 4. 35 and 5. 72 mgg-1fw in H. aphyllum and playa habitats, respectively. The highest amounts of chlorophyll b with 2. 85 mg/g fresh weight were measured in H. salicornicum in playa habitats. The amount of anthocyanin was double in the playa habitats and was more than these two plants. The highest amounts of phenol with 458. 97 mg/g fresh weight was measured in playa habitats and in H. aphyllum with 469. 53 mg/g fresh weight. The amounts of antioxidant activity in playa habitats and H. aphyllum were significantly more than the erg habitat H. Salicornicum. Glutamine was not significantly different between the two habitats. The highest amounts of glycine betaine were measured in sandy habitats in H. Salicornicum. H. Salicornicum and H. aphyllum known as halophytes can be countered salinity by various mechanisms, such as improving their biochemical conditions, and thus improving the quality of forage and increasing the foliage preference value.

Rainfall is one of the most important environmental factors affecting the density and canopy cover percentage of plant species, erosion, and natural hazard status and its measurement is important for achieving appropriate water management. Satellite products have been introduced as an alternative method for ground-based measurements due to inaccessibility of some areas such as arid, semi-arid and mountainous areas and lack of temporal and spatial rainfall data. This study aimed to investigate the efficiency of PERSIANN and PERSIANN-CDR satellite products to measure monthly and annual rainfall in Chaharmahal and Bakhtiari province in time span of 2010 and 2016, using correlation coefficient, root means square error and relative bias. Results showed that PERSIANN-CDR yielded the highest correlation coefficient, lowest RMSE and lowest relative bias in both monthly and annual scales. Estimations of rainfall by both PERSIANN and PERSIANN-CDR products were more accurate in monthly scale compared to annual scale. The correlation coefficient of PERSIANN monthly and annual rainfall respectively were 0. 833 and 0. 465. These correlations for PERSIANN-CDR were 0. 877 and 0. 641, and statistically significant for monthly and annual rainfall data, respectively. Due to limited numbers of rainfall gauges and inappropriate distribution and their importance in watershed runoff studies, drought and vegetation studies, and using satellite rainfall products with high spatial and temporal coverage can be considered as a suitable data source in climate studies, especially in arid and semi-arid regions of Iran.

Quantitative description of valley profiles can be used to identify its geomorphologic and dynamic properties and a useful tool in separating of the valleys created by various processes. In this study, the longitudinal and cross-sections of 15 valleys were investigated in three geological formations of Kahar, Taft and Granite. Fractal properties of valleys along with the mathematical functions and two Vf and Fr indices were used to study valley morphology. The average of Vf index was calculated in Kahar, Taft and Granit formations 5. 56, 3. 52 and 1. 38, respectively. The average of Fr index in three formations were calculated 0. 07, 0. 20, and 0. 17, respectively. Results indicated heterogeneity in the lithology and structural of valleys. According to the results, the shape of the valley, from Kahar to Taft formation, is U profile to V-shaped profile. The results showed that less curvature profiles are fitted with linear functions and profiles with more curvature fitted with polynomial functions. In fact, the polynomial functions, especially, fourth order, have high ability in modeling longitudinal and cross-sections of the valleys. Subsequently, multi-fractal analysis of cross-sectional valley, using the general multi-fractal dimensions (Dq) and the technical spectrum f (α q), showed that these sections are transmitted from mono-fractal to multi-fractal. None of the valley sections in Taft formation has multi-fractal properties. In a number of cross-section valleys of Granite and Kahar formations, the multifractal approach seems to be more appropriate, because of varying of fractal parameters depending on the locations. The results of this study showed that the multi-fractal analysis is a useful tool for assessing the complexity of cross-sections of the valleys and explaining hydrological and geomorphologic properties of valley and watershed.

Zehkalut in Jiroft, is one of the arid lands in the country, has been facing desertification problem in recent years, due to the improper exploitation of natural resources. As desertification has become a serious problem in this region, it seems necessary to use models for rehabilitation and biological restoration of the degraded areas, based on environmental conditions and ecological potential. The main aim of this study is to provide a model to determine an appropriate method of reclamation and rehabilitation of desert (desertification) considering all environmental factors for successful implementation of projects. A model for desert reclamation using Fuzzy Analytical Hierarchy Process (FAHP) model has offered in this research. For this purpose, opinions of experts to determine the effective criteria and their priorities were evaluated by using Delphi method and pairwise comparisons. Then, by developing Fuzzy decision-making matrix and using weighted linear combination method, the coefficient of significance of the criteria was determined. Final land suitability map for land reclamation of the area was produced by applying the coefficient of significance of each criterion to the classified map of the same criterion and integrating the maps using a fuzzy gamma operator. Results showed that reclamation of degraded areas could be done only in margins of the watercourses by planting compatible and native tree species. This area include the lands that are predicted to be used with the utmost caution in biological operations, to justify the costs incurred. The results show the ability of the Fuzzy Analytical Hierarchy Process and GIS in assessing land suitability for reclamation considering a group decision-making approach.

To comparison biomass production, accumulation of some elements and ash content of shoots in five halophytes species including Salicornia bigelovii Torr., S. sinus persica, Atriplex lentiformis Torr., Halocnemum strobilaceum Bieb., and Halostachys caspica Botsch irrigated with seawater, a research was conducted at Salinity Research Station in Bushehr province. The results showed that there was a significant difference between the halophytes species in terms of concentration of Na+, K+, Cl-, Na+/K+ ratio, fresh weight, dry weight, shoot water content and ash. The highest and lowest Na+ concentrations were obtained in S. sinus persica and A. lentiformis species, respectively, whereas the rate of shoot Na+ in S. sinus persica was more than A. lentiformis by 101. 3%. The highest concentration of K+, Cl-and Na+/K+ were obtained in leaves of A. lentiformis and shoots of two species of Salicornia and H. strobilaceum species, respectively. A. lentiformis with the production of 18. 98 and 7. 75 ton ha-1, had the highest fresh and dry biomass, respectively. The lowest fresh and dry biomass were also found in S. bigelovii by 10. 13 and 2. 49 ton ha-1, respectively. The highest and lowest ash content were related to shoots of S. sinus persica equal to 48. 8% and leaves of Atriplex lentiformis equal to 37. 5%, respectively. According to the results, Salicornia species has no mechanism of preventing salt entrance in the plant due to high concentration of Na+ and Cl-ions in their shoots. These species follow the mechanism of salt accumulation in plant tissues with the aim of osmotic regulation for survival in high saline conditions. Atriplex lentiformis also produced the highest amount of biomass, which could attributed to the low shoot water content of this species due to the presence of hard stems in the plant in comparison to the succulent stems and higher shoots water content in the other species. According to the production amount and ash content, it seems that A. lentiformis is a suitable species for forage producing in the regions with limited freshwater. Furthermore, Salicornia species could be also considered as part of a livestock diet in this regions.

Investigation of spatial variability of maximum 24-hour rainfall is very important for assessment of water resources and forecasting of natural disasters. In this research, the most appropriate probability distribution to estimate the maximum daily rainfall in return periods of 2, 5, 25, 50 and 100 years using Easyfit software based on Kolmogorov-Smirnov test is Wakeby distribution. Wakeby distribution was fitted to maximum daily rainfall. Semi-variogram values for mentioned return periods were calculated and plotted using simple kriging method and were fitted to an appropriate model. Then Maps of isohyetal line were drawn for different return periods. Results of semi-variogram showed that fitted model to variogram of the maximum 24-hour rainfall in return periods of 2, 5, and 25 is Gaussian and in return periods of 50 and 100 is spherical distribution. Suitability of variogram model was evaluated with cross validation method and calculating ME and RMSE statistics. RMSE criteria was obtained less than %40 for all of return periods that shows the accuracy of estimatings. Simple kriging method is suitable for zonation of the maximum daily rainfall. Central Iran in all of the produced maps have lowest daily rainfall than other regions. Reason of differences in maps at different return periods is differences of rainfall values in mentioned return periods. In the other hand, homogeneous areas are closer to each other in terms of rainfall amounts in a return period.

In arid and semi-arid regions, trees have a great influence on distribution of soil nutrient elements and biochemical processes. Considering the capabilities of Tamarix ramosissimia Ledeb shrub in affecting soil properties, identification and management of this shrub will be important in deserts of Iran. The aim of this study was to investigate the effect of Tamarix shrub on soil physical and chemical properties and carbon sequestration in Farokhabad desert region of Dehloran. In order to study soil characteristics, soil sampling carried out from topsoil 0-5 cm and subsoil 5-20 cm under canopy cover and open area by using systematic randomized method. In this research, soil chemical parameters including organic matter percentage, carbon sequestration amount, pH, EC, N, P, K, CEC, CaCO3, and CaSO4 and soil physical parameters including texture, BD، BP,، FC, PWP, and SP were measured. Results showed that there was significant difference at 1% probability level among soil properties such as soil carbon sequestration, organic matter, pH, EC, CEC, N concentration and CaSO4 percentage between under canopy and open area and even in different soil depths. The results of stepwise regression showed that pH, silt and K are one of the most important components affecting the amount of carbon sequestration in the soil under the canopy of Tamarix shrub. In general, climate condition of the study area is suitable for Tamarix shrub which has a positive effect on soil properties by increasing organic matter and improvement of soil structure. As well as, Tamarix shrub increased soil fertility by increasing nutrient elements of soil, hence protection and reclamation of this species is essential for Ilam province.

Drought is one of the most important environmental stresses that affects plant morphology and physiology. The present study was carried out to measure some physiological indices of four drought resistance trees at Isfahan University of Technology and aimed at managing desert. Physiological parameters of Ailanthus altissima, Robinia pseudoacacia, Morus alba and Melia azedarach including leaf water potential using pressure bomb, stomatal conductance through hand-held Porometer and chlorophyll content using SPAD were measured before and after irrigation. Data analysis and comparison of means was performed using SPSS 22. 0 software, dependent T-Test. The results that showed that drought stress significantly reduced the leaf water potential by 11. 56, 16. 3, 14. 54 and 13. 54 bar as well as the stomatal conductance by 6. 93, 5. 42, 6. 39 and 9. 98 mmol m-2s-1 after irrigation for Robinia pseudoacacia, Ailanthus altissima, Melia azedarach and Morus alba, respectively. The chlorophyll content was also decreased by 1. 5, 2. 83, 2. 16 and 2. 24 mg g-1 after irrigation for Robinia pseudoacacia, Ailanthus altissima, Melia azedarach and Morus alba, respectively, but this was not statistically significant (P>0. 05). According to the physiological responses of the trees, it can be concluded that Robinia pseudoacacia, Ailanthus altissima, Melia azedarach and Morus alba are drought resistance trees, respectively that are recommended in arid areas.

The purpose of this study was to evaluate soil erosion in the present period and to predict soil erosion potential under the impact of climate change over time horizon of 2030. Daily rainfall data and NCEP data during 1985-2015 were used. The future climate was projected using the second generation earth system model (CanESM2) and downscaled using the SDSM model under RCP2. 6, RCP4. 5, and RCP8. 5 scenarios. Rainfall erosivity (R-factor) was estimated for different scenarios and soil erosion were simulated using RUSLE 3D. Results showed that rainfall increases from 146. 7 to 178. 61 mm in the future and R-factor increases from 28. 7 to 34. 33 MJ mm ha-1 y-1, respectively. However, due to increasing rainfall intensity in all scenarios and stations, the amount of rainfall erosivity in the future is more than the baseline period. The amount of soil erosion is estimated 10. 16 ton ha-1 y-1 at baseline period. Considering the constant assumption of other variables in the RUSLE 3D model and the increase in future rainfall erosivity, the erosion rate under RCP2. 6 scenarios increased to 15%, RCP4. 5 to 10% and RCP8. 5 to 3%, respectively. . Accordingly, the increase of rainfall increases the rainfall erosivity factor and consequently increases the erosion rate. Therefore, assessing the present and predicting future soil erosion in the Minab Esteglal dam watershed, provides useful information for environmental and soil conservation.

The milkweed shrub, in addition to ecological functions, has special industrial and medicinal values. This plant is widely planted for afforestation in arid lands in the south of Iran. Regard to scarcity of fresh water, using of seawater as a vital and alternative source of water for irrigating of halophyte plants was suggested. Thus, the current research was carried out to investigate the efficiency of diluted seawater on seed germination, growth and physiology parameters of milkweed seedling. For this purpose, an experiment was conducted in completely randomized design with three replications in two separate experiments; in vitro and nursery, with different levels of diluted seawater i. e. 0, 12. 5, 25 and 50% using saline meter. The results of seed germination test showed that germination parameters and seed vigor index significantly decreased by increasing seawater concentration to more than 12. 5%. The results of nursery experiment revealed that concentrations of more than 25% of seawater significantly reduced growth performance and gas exchange of seedling. The survival rate 55%, height 19. 9 cm, specific leaf area 190. 7 g/cm2 and root length 22. 54 cm as well as photosynthesis rate 2. 83 μ mol, transpiration rate 0. 42 mmol, chlorophyll 20. 45% and relative water content 43. 95% were observed in 25% seawater treatments. It is recommended that researchers conduct a broader study of the salinity-tolerant physiology of this valuable medicinal plant to obtain more comprehensive information for afforestation programs.

Wetlands are one of the most important natural ecosystems in arid and semi-arid regions that their moisture content has decreased in recent years due to the adverse effects of climate changes and droughts. It is necessary to evaluate the impact of such events on different ecosystems, especially these valuable ecosystems. In this study, the future drought status of Jazmourian wetland under elevated temperature was evaluated using the output of the IPCC Fifth Report Model. For this purpose, the standardized precipitation-evapotranspiration index and reconnaissance drought index, which take into account the impact of rising temperatures due to future climate change on droughts, were used. The effect of increasing of temperature on drought risk was studied by using the return period of drought. Results showed that the standardized precipitation-evapotranspiration index was better able to show the effect of increasing of the evapotranspiration and temperature on drought than the reconnaissance drought index. Therefore, Standardized precipitation-evapotranspiration was used to evaluate the future droughts under RCP scenarios. Based on the drought time series, by increasing temperatures, the future long-term droughts might be more intense and longer period than the historical period. Analysis of drought showed that drought risk would decrease on 3, 6 and 12-monthly time scales, respectively. Under the RCP2. 6, RCP4. 5 and RCP8. 5 scenarios, the risk of drought will increase at all study time scales. In general, these results can be useful for assessing climate change and managing of water resources in arid regions.

Nepeta asterotricha Rech. f. is a medicine plant. The goal of this research is to investigate the effect of some environmental factors on amount of essential oil of Nepeta asterotricha Rech. f at 8 habitats in Yazd province to determine optimal environmental factors for rangeland management and reclamation. Soil samples were collected and measured phosphorus, nitrogen, and potassium and pH, electrical conductivity, and sand, silt, and clay (Hydrometric) at three replications from each habitat. Topographic factors including elevation, slop, and aspect were recorded in habitats. Plant samples in three replications in 8 habitat and essential oils were obtained by hydro distillation for 3 hours. Investigation on the correlation between essential oils and some ecological factors were done by using Redundancy Analysis v. 4. Comparison of means were done using Tukey tests (p≤ 0. 05). Number of identified chemical compounds were 31 that 24 components had different between habitats. Results showed that the active ingredients in Nepeta asterotricha Rech. f including α-Thujene, α-Terpinene, p-Cymene, (Z)-β-Ocimene, γ-Terpinene, terpinen-4-ol, cis-Sabinene hydrate, α-Terpinolene, 4aβ , 7α , 7aα-nepetalactone and 4aα , 7α , 7aβ-nepetalactone had significant differences at 95% level in growing and flowering phases, and 8 habitats. The active substances of 1, 8-Cineole, cis-Sabinene hydrate, trans-Caryophyllene and Limonene had most of amount in the growing phase and the Rose furan epoxide, 4 aβ , 7α , 7aα-nepetalactone, α-Pinene, cis-Linalool oxide, α-Terpinolene in the flowering phase. Eelectrical conductivity, potassium, sand and elevation from sea level among environmental factors, had more effects in flowering phase. Scine, Thghiabad and Dehbala habitats had better situations of environmental factors and the essential oil are recommended to ude from the species of these habitats for reclamation of regions with similar environmental factors. Also these habitats were determined as the optimal habitats for this species in Yazd province.