Soil Chemistry and Pollution
Alireza Abdollahpour; Mojtaba Barani Motlagh; Amir Bostani; Farshad Kiani; Farhad Khormali; REZA GHORBANINASRABADI
Abstract
Introduction Soil organic carbon (SOC) is the largest source of terrestrial organic carbon and small changes in its components have many effects on global warming and carbon cycle. Soil organic matter (SOM) is considered as the most complex and least known component of soil, because it consists of plant, ...
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Introduction Soil organic carbon (SOC) is the largest source of terrestrial organic carbon and small changes in its components have many effects on global warming and carbon cycle. Soil organic matter (SOM) is considered as the most complex and least known component of soil, because it consists of plant, microbial and animal masses in various stages of decomposition and is a mixture of heterogeneous organic materials that are closely related with mineral components. Soil organic matter has beneficial effects on the chemical (buffering and changes in pH) and biological (precursor and supply of nutrients for microbes) properties of the soil and thus affects the fertility capacity of the soil. The quality and quantity of soil organic matter is the most important criterion for sustainable soil management. Total organic carbon (TOC) consists of labile and non-labile forms of SOC and have different degrees of sensitivity to different types of land use changes and management operations. The purpose of this research is to investigate the effect of changing land use on the chemical components of soil organic carbon and carbon recalcitrant index in Toshan Watershed, Golestan provinceMaterials and Methods For this research, four major and dominant types of land use were considered in the study area, including forest, cropping land, garden and abandoned lands in the Toshan watershed in the northwest of Gorgan city of Golestan province. The soil organic carbon and total C of soils were measured. Furthermore, the soil carbon fractionation was performed by Young's method (using hydrolysis methods with HCl and Labile fraction). In this research, Acid hydrolysis method was used to separate the recalcitrant SOM pool. For this purpose, one gram of SOM sample was treated with 25 ml of 6 M hydrochloric acid solution at 105°C for 18 hours in a Pyrex tube in a hydrolysis package. After cooling, the remaining non-hydrolyzed materials were separated by centrifugation. Then, they were dried in an oven at a temperature of 60 degrees Celsius and considered as a part of resistant organic matter. The resistant part of the soil organic carbon was determined with the CHNS Analyzer device. The Labile fraction consists of water soluble carbon, microbial biomass carbon and mineralizable carbon are measured using the following methods and the labile part of carbon is calculated from their sum. Water-soluble organic carbon is extracted by adding 20 ml of distilled water to 10 grams of wet soil. The mixture will be shaken and centrifuged, filtered. Then they will be quickly analyzed by TOC Analyzer. Microbial biomass carbon will be determined by the chloroform fumigation-extraction method. Mineralizable carbon determined as follow. The amount of CO2 will be measured by titration of NaOH solutions with 0.1 M HCl in the presence of BaCl2. Cumulative amount of CO2-C emitted in 30 days of incubation is called Mineralizable carbon. The data were analyzed based on the factorial test in the form of a completely randomized design (CRD) with two levels of soil depth and four land uses with five replications. Correlation between traits was also estimated. Statistical analyzes were performed using SAS software. Therefore, it can be concluded that depending on the climatic conditions and the condition of the soil, the forest, in terms of natural cover, the correct management of agricultural lands (using modern methods of no-tillage or low-tillage) can be a potential practice. It is to store carbon in the soil as well as various soil components and increase soil formation, which will subsequently reduce the concentration of carbon dioxide in the atmosphere.Results and Discussion The results showed that the first depth of forest use has the highest amount of total carbon and soil organic carbon (6.12% and 3.5% respectively). Also, the highest amount of resistant organic carbon (HCl hydrolysis), water-soluble organic carbon, microbial biomass carbon, and microbial mineralizable carbon were observed in forest land use. The second depth (10-20 cm) of forest land use had the highest and the second depth (10-20 cm) of garden land use had the lowest organic carbon resistance index (82.1% and 50.17%, respectively). In all land uses, except for the forest, the soil organic carbon resistance index decreased with increasing sampling depth. Due to the fact that the carbon management index can be easily calculated, it can be a suitable index for quick assessment of soil quality.Conclusion The results showed that with the change of land use and cultivation, the soil organisms received more oxygen and the speed and intensity of respiration in the soil increased in the short term, which caused more decomposition of organic matter and with the decrease of organic matter in the long term, the quality of soil decreases after a while.
Alireza Abdollahpour; Mojtaba Baranimotlagh; Amir Bostani; Farshad Kiani; Farhad Khormali; REZA GHORBANINASRABADI
Abstract
Introduction Globally, deforestation is the dominant land use change process and has severe effects on soil biogeochemical properties. Large areas of the north facing slopes of the Alborz mountain range in northern Iran are covered by extensive loess deposits. Loess often contain little clay results ...
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Introduction Globally, deforestation is the dominant land use change process and has severe effects on soil biogeochemical properties. Large areas of the north facing slopes of the Alborz mountain range in northern Iran are covered by extensive loess deposits. Loess often contain little clay results in a loss of SOC under cultivation. Deforestation and cultivation on the loess hillslopes in northern Iran have resulted in a deterioration of soil quality, particularly significant reduction in SOC. Loess lands of Golestan province in northern Iran is densely being cultivated following deforestation. Labile fractions of soil organic matter (SOM), rather than total SOM, have been used as sensitive indicators of soils' quality and response to agricultural management changes. Several physical, chemical, and biological methods have been used to distinguish between labile (or biologically active) and recalcitrant pools of SOM. So, this research aims to investigate the effect of land use change from pristine and undisturbed forest as a reference to other land uses on soil organic carbon components and fractions as an important indicator in the sustainable soil management system and maintaining fertility and controlling soil erosion. Also, the effect of these land use changes on total carbon, soil organic carbon, and finally on the physical and chemical components of soil organic carbon.Materials and Methods The study area is the Toshan watershed, which is located in the northwest of the city of Gorgan (Golestan province) in the north of Iran. Four major and dominant types of land use were considered in the study area, including a) garden (olive), b) agricultural (cotton), c) virgin or untouched forest, d) abandoned (raspberry). Soil carbon fractionation was done by two physical methods (soil aggregate fractionation method) and chemical method (hydrolysis of organic matter with hot water). The selection of soils in different land uses was such that they have similar initial conditions and therefore the change in soil carbon in each use is related to the change in land use. The obtained data were analyzed based on the factorial design in the form of completely randomized design and using SAS software.Results and Discussion The results showed that the highest amount of total carbon and soil organic carbon was observed in the forest treatment and in the first depth (6.02% and 3.5%, respectively), which had a significant difference compared to other land use treatments studied. The results showed that despite the absence of a significant difference between the two depths, the amount of stable organic carbon increased with increasing soil depth in agricultural and abandoned uses. The forest land use had the highest amount of stable organic carbon at the depth of 0-10 cm at the rate of 2.51%, followed by garden treatment at the same depth. The lowest amount of stable organic carbon was recorded in the abandoned land use treatment. The highest amount of organic carbon dissolved in water at both investigated depths was obtained in the forest management treatments and then in the abandoned management. While no significant difference was observed between the two investigated depths in the abandoned land use. A significant decrease in organic carbon fractions that can be extracted with hot water was observed in abandoned and agricultural uses, as well as their increase in forest land uses. After the forest land use, the olive garden land use had the highest amount of total and organic carbon, however, there was no significant difference between the agricultural and abandoned treatments. In forest and garden treatments, the amount of stable carbon at a depth of 0-10 cm is significantly higher than the amount of stable organic carbon at a depth of 10-20 cm. In the garden use treatment, the amount of organic carbon in the soil at a depth of 10-20 cm showed a significant increase of 35% compared to the first depth.Conclusion A significant decrease in organic carbon fractions that can be extracted with hot water was observed in abandoned and agricultural uses, as well as their increase in forest uses. In total, the results showed that the carbon of labile fraction was more responsive to the type of land use than other fractions, and among the different methods of carbon fractionation, physical methods showed a clearer response to land use change.
gholamreza Adim; Elham Malekzadeh; Esmael Dordipour; Farshad Kiani; Hassan Mokhtarpour; seraj Moazzemi
Abstract
Introduction In recent years, ensuring the continuous and sustainable production of healthy food products along with environmental protection and paying attention to agricultural economic and environmental problems is very important. Although the use of chemical fertilizers has a high yield of plants, ...
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Introduction In recent years, ensuring the continuous and sustainable production of healthy food products along with environmental protection and paying attention to agricultural economic and environmental problems is very important. Although the use of chemical fertilizers has a high yield of plants, its destructive effects in the long-term are known on the soil biological, physical and chemical properties and environmental pollution. Therefore, a strategy must be considered that can improve soil health and quality as well as produce a high plant yield. Organic manures increase the growth, yield and quality of plants by improving soil conditions and the balance of essential elements. An integrated plant nutrition management system by reducing the use of chemical fertilizers is known as one of the ways to achieve the expected yield and meanwhile, minimize the adverse environmental effects of chemical fertilizers in the world.Materials and Methods The objective of this study was to evaluate the effect of single and combined use of chemical fertilizer (urea, triple superphosphate, potassium sulfate as NPK) with organic and biological fertilizers on the yield and yield components of transplanted canola (Brassica napus L.). Experiment was conducted in a randomized complete block design with six treatments and three replications (18 experimental units) in the 2019-2020 crop year at the Iraqi Agricultural Research Station in Gorgan, Iran. Treatments included: 1) Control (without fertilizer, T1), 2) Chemical fertilizer (T2), 3) Poultry manure (T3), 4) Compost (T4), 5) 50% Chemical fertilizer+ 50% Poultry manure+ 50% Compost (T5), 6) 50% Chemical fertilizer+ 50% Poultry manure+ 50% Compost+ Biofarm-1 biofertilizer (T6). Chemical fertilizer was applied based on soil test including nitrogen equivalent to 250 kg/ha urea was added in three stages during planting, stem elongation, before flowering; phosphorus equivalent to 150 kg/ha of triple super phosphate; potassium equivalent to 50 kg/ha of potassium sulfate, respectively. Organic fertilizers were calculated based on their total nitrogen contents and the equivalent of pure nitrogen recommended based on the soil test for chemical fertilizer and by assuming 50% mineralization rate of organic fertilizers in the soil. Biofertilizer was applied as seed inoculation plus spraying on the plant base in two stages of 4 to 8 leaves and stem elongation. Chlorophyll index was measured in the middle of the flowering stage by using SPAD. After physiological maturity, yield and yield components including pods per plant, numbers of seeds per pod, pod length, 1000-seed weight, seed yield, protein and oil contents of grain were recorded. Results and Discussion The results showed that the effect of fertilizer treatments was significant on yield and yield components (p <0.01). The highest 1000-seed weight, grain yield, protein content of the seed, number of seeds per pod, pod length and pods per plant were recorded in the treatment of 50% chemical fertilizer+ 50% Poultry manure+ 50% Compost+ Biofertilizer (T6) which increased by 21.9%, 43.7%, 33.8%, 29.2%, 37.2% and 37.6%, respectively, in compared to the control treatment (with the lowest values). The pods per plant, 1000-seed weight and grain yield were not significantly different between the combined treatments of chemical fertilizer+bio-organic fertilizers (T6) and integrated use of chemical and organic (T5) fertilizers (p <0.05). The control treatment (T1) by 2248.37 Kg/ha of grain yield (the minimum amount) decreased by 43.7% and 38.3% compared to T6 and T5 treatments, respectively. The chemical treatment (T2) and integrated application of chemical fertilizer+ bio-organic fertilizers (T6) showed the most positive effect on the chlorophyll index compared to other fertilizer and control treatments (with the lowest index, 43.66). Chlorophyll index in the T2 and T6 treatments increased by 35.6% and 33.7% compared to the control treatment (T1), respectively. The treated plants by alone use of organic fertilizers (T3 and T4) without notable difference produced the highest grain oil (by an average of 45.73%) which increased by 6.6% compared to the chemical fertilizer (T2) and control (T1) treatments by an average of 42.7%.Conclusion Combined use of chemical fertilizer with bio-organic fertilizers had the most positive effect on yield and yield components, and often showed significant difference with the single application of chemical and organic fertilizer treatments (T2, T3 and T4). Therefore, the combination use of chemical and bio-organic fertilizers is a better option to increase the yield and yield components of transplanted canola than the single use of chemical fertilizers. The highest pods per plant, pod length, number of seeds per pod, chlorophyll index, protein content, chlorophyll, 1000-seed weight, and grain yield were related to the integrated application of chemical fertilizer with bio-organic fertilizers (T6 and T5), so it can be inferred that the use of a mixture of organic, biological and chemical fertilizers is an effective approach to reduce the using of chemical fertilizers and their destructive environmental effects, as well as increase the yield of transplanted rapeseed
Micromorphology and Clay mineralogy
Masoumeh Pourmasoumi Parashkouh; Farhad Khormali; Shams Ollah Ayoubi; Farshad Kiani; Martin Kehl; Eva Lehndorff
Abstract
Introduction The loess-paleosol sequences in Northern Iran are important archives that represent several cycles of Quaternary climate change and can be used to complete the information gap on loess between Europe and central Asia. Last interglacial soils derived from loess in northern Iran is represented ...
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Introduction The loess-paleosol sequences in Northern Iran are important archives that represent several cycles of Quaternary climate change and can be used to complete the information gap on loess between Europe and central Asia. Last interglacial soils derived from loess in northern Iran is represented by strongly developed Bt horizons of forest soils. In Golestan and Mazandaran area, soils under the forest are mainly classified as Alfisols or Luvisols. Interestingly, E horizons are generally not found in these soils. In the Caspian Lowlands, a pronounced precipitation gradient is reflected in mean annual precipitation rates decreasing from about 1850 mm at Bandar Anzali in the west to about 435 mm at Gonbad- e Kavoos in the east. The results of the loess climosequence in Northern Iran showed that with increasing precipitation, soil pH and calcium carbonate contents decrease, whereas soil organic carbon, clay content, and cation exchange capacity increase. For years, many efforts to quantify the soil properties led to the provision of indices of soil development. Among these indices are forms and ratios of iron, morphological, and micromorphological indices. Many studies have been carried out on the loess-paleosol sequences and modern loess soils in Northern Iran with focus on micromorphology, mineralogy, and dating but more investigation is needed with an emphasis on the forest soils with well-pronounced clay illuviation as a proxy for paleo-moisture. For this purpose, we used micromorphology and soil color indices to report the effects of precipitation gradient on the variability in the formation of soils under forest vegetation. Materials and Methods The study area is located at the northern slopes of Alborz Mountain Ranges, covered with Caspian or Hyrcanian deciduous forests. Field sampling started in summer 2015. More than ten soil pedons with loess parent material were investigated based on former studies. Finally, six representative modern pedons were selected and dug in an east-west direction on loess deposits. The climate data shows that precipitation varies from 500 mm in Qapan (Pedon 1) to up to 800 mm in Neka. Physiochemical properties of soils were studied using standard methods. Thin section prepared for soil micromorphological studies were studied and interpreted based on Bullock et al. and Stoops guideline using a polarizing microscope. The micromorphological index of soil development (MISECA), suggested by Khormali et al (2003), was calculated. Also, color indices were calculated based on Hurst (1977), Torrent (1983), and Alexander (1985) by using the Munsell color chart. In all color indices, Munsell color hue converts to a single number. Results and Discussion The results showed that the downward decalcification and the subsequent clay illuviation were the main criteria influencing the assessment of soil development in this study. So, all of the soils host argillic and calcic horizons and are classified as Alfisols and Mollisols. Micromorphological studies confirmed the morphology studies in the field and the results of physico-chemical analyses. MISECA index showed pedological changes in different pedons in the studied areas. A significant positive relationship between climate gradient (increasing rainfall) and MISECA index was found. The area and thickness of clay coatings show an increasing trend with rainfall. Occurrence and preservation of clay coatings are more pronounced in more humid regions with illite and vermiculite as the dominant clay minerals. These minerals reduce the shrink/swell potential and increase the number of clay coatings present. In Argillic horizons of all pedons, except Toshan, dominant b-fabric is speckled due to carbonate leaching, while in Toshan, it is striated b-fabric. In calcite horizon, b-fabric is crystallitic. The correlation of various forms of iron with three color indices of Hurst, Torrent, and Alexander showed that Torrent and Alexander indices were better than the other one for the study area. Moreover, there was a good correlation between MISECA and Torrent color index. Conclusion The results showed that the soil evolution in the studied areas is strongly influenced by soil formation factors, especially in a climate which shows a change in the micromorphological characteristics of soils. With increasing the rainfall from the east to the west in this gradient, the amount and thickness of clay coating, as well as secondary calcium carbonate accumulation, change significantly. In addition, the micromorphological and color indices of soil evolution can be used as two indicators for assessing the effects of rainfall gradient on soil formation in northern Iran. On the other hand, knowledge of the development of modern loess-derived soils could help to better understand the paleoenvironment.
Soil Physics, Erosion and Conservation
Motahareh Noorzade Roshan; Reza Ghorbani Nasrabadi
Abstract
Introduction Soil quality has been defined as a “The potential of soil to play a positive relationship with the other parts of ecosystem”. Soil biological indicators provide insight into the living component of the soil. Similar to physical and chemical indicators, biological indicators have ...
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Introduction Soil quality has been defined as a “The potential of soil to play a positive relationship with the other parts of ecosystem”. Soil biological indicators provide insight into the living component of the soil. Similar to physical and chemical indicators, biological indicators have a relationship to soil functions and can evaluate soil functions to assess soil quality. Between biological indicators, an index that can be measured quickly and easily is more useful to show the changes. In many studies an indicator of microbial respiration, microbial population, nitrogen mineralization and enzymes activity can be used. Special ability is required to measure quickly and show the quality of soil microorganisms and reaction to environmental changes. Soil health is defined by chemical and physical parameters such as soil texture, soil pH, electrical conductivity, etc., that are not quantifiable completely. Therefore, conservation practices planting and forestry may directly or indirectly affect a organism’s activities. The results of land-use systems without consideration of the consequences on soil quality have been environmental degradation. Agricultural management systems have been generally adopted without attending to soil conservation and soil quality, and this therefore causes significant decline in agricultural soil health worldwide. Different methods of soil conservation have been proposed to prevent erosion and improve soil quality destructive phenomena. In Golestan province due to topographical and climatic conditions and less soil sensitivity to erosion, more attention should be given to this issue. But it remains unclear how far this conservation practice can take to prevent damage. This study aimed to investigate the role of conservative practices to improve the soil quality indicators.Materials and Methods The watershed of Chehelchai is located between North latitudes 36° 59´ and 37° 13´ and Earth longitudes 55° 23´ and 55° 38´. The history of land use in the region shows that more than about 40 years ago, all the study area was covered by forest. Agricultural land use changes occurred on a large scale. With emphasis on conservation operation, parts of the agricultural land were changed to productive gardens, partly forested, partly pasture with native species. Different land uses were selected in loess formations, and slope of 41 %, with life operations was about 6 to 7 years. Protective Operations Garden species, terraces and forestry were selected and quality of soil was compared with agricultural land, pasture and natural forest. In this regard, 10 soil samples were taken. After preparation of the samples, physical, chemical and biological analysis were measured. Additionally, soil properties (pH, Electrical Conductivity, Calcium carbonate, organic matter, texture, bulk density, aggregate stability, microbial respiration, microbial biomass population count of micro- arthropods, biological soil quality) were analyzed. The data were analyzed using software SAS. Ver 9. and the results were compared in a randomized complete block design. Analysis of variance in the form of randomized complete block design was done using the LSD multiple comparison. Results and Discussion Our results showed that the dominant soil texture class in land uses was silty loam. It seems that soil texture is less affected by the land use changes. The results showed that the changes of forest and pasture to agricultural lands have destroyed the soil quality. Soil quality indicators such as organic matter and aggregate stability have declined by 60 and 70 percent respectively. Like wise, biological indicators such as microbial respiration, microbial biomass carbon and QBS (biological soil quality indicators based on the population of micro- arthropods) and EMI (index dependence of soil to soil organisms) showed a similar trend. In contrast, the Conservation practices improved the indices. Biological indicators in the forestry and gardening showed an increase of 40 percent in EMI Microbial biomass carbon and 80 percent in microbial respiration. Terracing had less improvement than other operations in about 11 to 20 percent in EMI and microbial biomass carbon. Conclusion Conservation operations had fewer effects on indicators such as aggregate stability and organic matter. Under estimation of effects in certain indicators maybe due to short time of conservation practices. It seems that these operations will show better results in the future Received: 19 July, 2016Accepted: 10 April, 2018
Micromorphology and Clay mineralogy
masoomeh najafinia; Fashad Kiani; mojtaba Baranimotlagh
Abstract
Introduction Loess sediments of northern Iran represent several cycles of climate change and evolution of the landform for the mid-to-late Quaternary. Climate change in elevations of Iran and its surrounding areas is very controversial in the mid and late Quaternary, and has been discussed in the past ...
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Introduction Loess sediments of northern Iran represent several cycles of climate change and evolution of the landform for the mid-to-late Quaternary. Climate change in elevations of Iran and its surrounding areas is very controversial in the mid and late Quaternary, and has been discussed in the past according to rainfall and rainfall periods and between rainfall, glacial and inter-glacial. Paleomegnatic results also indicate that these sediments have accumulated between, 1.8 to 2.4 million years ago. However, pedogenic processes and the effects of past climate in these soils still have not been fully investigated. The loess deposits in northern Iran are a valuable archive of regional paleoclimatic and paleoenvironmental information. Extensive sedimentological and chronological studies have been carried out on the middle to upper Pleistocene loess during the past decades, but it is necessary to do a comparative research on the older loess deposits. So, this study aimed to conduct a mineralogical and physicochemical investigation on the early Pleistocene loess and to compare it with modern loess soils in Agh-Band, Yelli-Badrag and Qareh-Agach in loess plateau of eastern Golestan. Materials and Methods The study area is located in a hot and dry climate in loess Plateau east Golestan. According to the previous studies, a total of six profiles were excavated and studied. Then, physicochemical properties such as soil texture, acidity (pH), electrical conductivity (EC), saturation moisture (SP), organic carbon (OM), cationic exchange capacity (CEC) and calcium carbonate equivalent (CCE) were measured in the laboratory. Clay separation was carried out with a specific method to separate the clay as well as identification of clay minerals. After preliminary field observations and determining the horizons for each profile in the region, soil classification was done based on soil taxonomy and WRB. Then, soil samples were prepared from each horizon for physicochemical and mineralogical studies in sufficient quantities. Results and Discussion Comparing the results of physicochemical properties (such as color, lime percentage, the cation exchange capacity and the ratio of iron, etc.) in paleosol and modern loess soils indicates that in paleosol soils, soil forming processes have passed several stages. Clay mineralogy is a good indicator for past climate change studies in loess.The existence of the arglic horizons and the evolved calcic in paleosols and their absence, in comparison with the modern soils in which they are present, indicate the change in soil formation conditions. The change in the color of paleosols also represents the soil moisture and the more suitable conditions of the past climate (temperature, and especially rainfall) in comparison with the present climate of the region, this color change was due to activation of soil formation processes in paleosols. All paleosol samples had a higher clay content than the late modern loess soils of the Pleistocene, suggesting favorable climatic conditions for soil formation processes and the development of more ancient soil than parent materials. Decrease in the amount of annual precipitation in the region, compared to the past, has led to decreased smectit and increased chlorite. Therefore, presence of smectit cannot be attributed to the present situation of the region. The presence of these clay minerals in paleosols can be due to wet weather conditions as well as weathering of clay mineral deposits. On the other hand, the dominance of less weathered clay minerals such as illite and chlorite in the late Pleistocene modern loess soils is correlated with the present dry climatic conditions. Conclusion The simultaneous presence of modern and old loess soils in the studied areas demonstrates the general evolution of geographical and climatic conditions during the Pleistocene period which has altered the properties of these layers and ultimately left out the effects of high clay conditions, which is a combination of climatic evidence and intermittent pedogenic soil formation processes. The presence of early Pleistocene loess soils between late Pleistocene loess sediments in Golestan province and the conditions of the study provided pedological and mineralogical comparisons of modern and paleosols in these areas and the results clarified a part of the climate change in northern Iran. The past climate study allows for prediction of the current and future climate change process. Therefore, a more accurate study of clay minerals as the key to all soil behaviors and past climate change in different parts of the eastern Golestan plateau can be very useful in completing studies of evidence of past climate change in paleosol soils
Micromorphology and Clay mineralogy
masoomeh najafinia; Farhad Khormali; Farshad Kiani; mojtaba Baranimotlagh
Abstract
Introduction Loess sediments of northern Iran represent several cycles of climate change and evolution of the landform for the mid-to-late Quaternary. Climate change in elevations of Iran and its surrounding areas is very controversial in the mid and late Quaternary, and has been discussed in the past ...
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Introduction Loess sediments of northern Iran represent several cycles of climate change and evolution of the landform for the mid-to-late Quaternary. Climate change in elevations of Iran and its surrounding areas is very controversial in the mid and late Quaternary, and has been discussed in the past according to rainfall and rainfall periods and between rainfall, glacial and inter-glacial. Paleomegnatic results also indicate that Early Pliestocene loess (Reddish loess) have accumulated between, 1.8 to 2.4 million years ago. However, pedogenic processes and the effects of past climate in these soils still have not been fully investigated. The loess deposits in northern Iran are a valuable archive of regional paleoclimatic and paleoenvironmental information. Micromorphology is an important technique to identify and interpret the loess- paleosol for paleoclimate studies. Microscopy is a method of studying undisturbed soil samples with the help of microscopic techniques (and sometimes with ultramicroscopic ones), in order to identify their constituents, determine their mutual relations in space and time and interpret their formation conditions. Micromorphology uses these characteristics to make interpretations, generally on the soil formation processes. This study aimed to conduct a micromorphological investigation on the early Pleistocene loess and to compare it with the modern loess derived soils in Agh-Band, Yelli-Badrag and Qareh-Agach in loess plateau of eastern Golestan. Materials and Methods The study area is located in semiarid climate in loess Plateau east Golestan. Six profiles were selected and studied. Physicochemical properties such as soil texture, acidity (pH), electrical conductivity (EC), saturation moisture (SP), organic carbon (OM), cationic exchange capacity (CEC) and calcium carbonate equivalent (CCE) were measured in the laboratory. Then, soil samples were prepared from each horizon for micromorphology studies. For micromorphological studies, thin sections were prepared from undisturbed, oriented and dry clods by standard methods and described under a polarizing optical microscope. Results and Discussion Comparing the results of physicochemical properties (such as color, carbonate percentage, the cation exchange capacity, etc.) in paleosol and modern loess soils indicates that the in paleosols, soil forming processes have passed several stages. The existence of the argillic horizons and the evolved calcic in paleosols and their absence in the modern soils in which they are present, indicates the change in soil formation conditions. The change in the color of paleosols also represents the soil moisture and the more suitable conditions of the past climate (temperature, and especially rainfall) in comparison with the present climate of the region. This color change was due to activation of soil formation processes in paleosols. All paleosol samples had a higher clay content than the late modern loess soils of the Pleistocene, suggesting favorable climatic conditions for soil formation processes and the development of more ancient soil than parent materials. Reducing annual precipitation decrease soil pedogenesis. Conclusion Comparison of the results obtained from paleosols of early Pleistocene with modern soils indicates that the time and climate change caused alterations in the soil micromorphology features (such as the type and amount of pores, soil structure and b-fabric and pedofeatures etc.). One of the most important pedofeatures was clay coating around void, presented only in buried paleosols, which is the evidence for moist climate conditions and subsequently enough leaching for clay translocation. Further, the presence of planar void caused by shrink and swell of clay is evidence for evolution in the paleosols. In argillic horizons of paleosols, dominant b-fabric is speckled due to carbonate leaching while in calcite horizon, it is crystallitic b-fabric. The micromorphological index of soil development calculated, showed that these red-colored deposits are formed under an annual precipitation of about 450- 650mm which represents more humid conditions at the time of their formation than the modern loess soils. In modern soils derived from recent loess, lack of clay coating can be a reason for weakly developed soil formation.
