Farzaneh Bandehelahi; Isa Esfandiarpour-Boroujeni; Alireza Karimi; Mohammad Hady Farpoor; Zohreh Mosleh; Morteza Fattahi
Abstract
Introduction Landscape represents a large portion of land/terrain that is either formed by a repetition of similar or dissimilar relief/molding types or an association of dissimilar relief/molding types (e.g., valley, piedmont, mountain, etc.). It is usually affected by a set of natural (e.g., climate, ...
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Introduction Landscape represents a large portion of land/terrain that is either formed by a repetition of similar or dissimilar relief/molding types or an association of dissimilar relief/molding types (e.g., valley, piedmont, mountain, etc.). It is usually affected by a set of natural (e.g., climate, organisms, parent material, topography, time, erosion, sedimentation, etc.) and/or artificial (e.g., artifacts) factors. Soil is one of the most important components of landscape that is affected by various factors such as water and wind. Aeolian or alluvial sediments (from seasonal rivers) in arid areas cause the formation of different landforms and change the landscapes in these areas. Therefore, the study of geoforms in arid regions can lead to a better understanding of geomorphological processes and soil change in these areas. There are various methods, including soil micromorphology and clay mineralogy, to understand the alteration of landscapes and the soils change on them. The aim of this study was to investigate the physical and chemical properties, clay mineralogy and micromorphology of soils in various geomorphic units of Davaran Region, Rafsanjan.Materials and Methods Seven dominant geomorphic units (geoforms) of the region, including pediment, margin of fan and cultivated clay flat, alluvial fan, desert pavement, margin of pediment and sand sheet, active drainage, margin of fan and uncultivated clay flat were selected using Google Earth images and field studies. Nineteen pedons were excavated and described in the geomorphic units. After selecting a representative pedon in each of the geoforms, their genetic horizons were sampled. Besides, in order to conduct soil micromorphology studies, undisterbed and oriented samples were collected from selected horizons. After transferring the samples to the laboratory, their physical and chemical properties were measured using standard methods. In addition, clay mineralogy studies were performed by X-ray diffraction method and micromorphological studies were done using a petrographic microscope. Finally, soil classification was performed based on both Soil Taxonomy (2014) and WRB (2015) systems.Results and Discussion Results showed that gypsification and calcification are the dominant soil forming processes in the studied region, which have led to the formation of Gypsic and Calcic horizons. This has placed the soils in the Gypsids and Calcids suborders based on the Soil Taxonomy system and the Gypsisols and Calcisols reference soil groups according to WRB system. The representative pedon in the margin of fan and cultivated clay flat (pedon 2) geoform lacks a salic horizon based on the Soil Taxonomy; while it is in the Solonchak reference soil group of the WRB. Also, the presence of argillic horizon in the representative pedon of the margin of fan and uncultivated clay flat geoform (pedon 7) indicates presence of a more humid paleoclimate in the history of the region. The results of clay mineralogy showed that the predominant minerals in the region include chlorite, illite, kaolinite, and smectite. The illite, chlorite, and kaolinite are inherited from papent materials of the soils, and the smectite has a transformation origin (from palygorskite and illite). Addition of this mineral by aeolian or alluvial sediments could not also be neglected. The micromorphological results indicated that the soil pores were mainly chamber. The presence of carbonates and gypsum in the studied soils has caused that the b-fabric in the most horizons to be Calcitic Gypsic Crystallitic. Gypsum was observed in the form of vermicular, lenticular, interlocked gypsum plates and subhedral shapes. Other pedofeatures in the studied soils include calcite nodule and limestone.Conclusion The simultaneous presence of aeolian and alluvial sediments in the different geoforms of Davaran region has caused the formation of stratified soils. Existence of dry climate and lack of significant vegetation in the region from one hand, and the addition of different sedimentary layers at different times (which causes soil rejuvination) on the other hand, has caused that the soils of the region, in general, not to be highly developed. As a result, few differences were observed among soils in different geoforms. Comparing the results of two soil classification systems for the studied soils showed that in general there is a relatively good correlation between them. Totally, the role of climate and parent material in alteration of the studied soils is evident; so that the physical and chemical properties, clay mineralogy and micromorphology of soils in different geoforms have been affected.
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 Genesis and Classification
Maryam Mohammadzadeh Mohammadabad; F. Khormali; Farshad Kiani; mohammad ajami
Abstract
Introduction Soil degradation is a widespread environmental problem that occurs as a result of land use change and destruction of vegetation cover that may lead to changes in soil structure and porosity. Land use change and land management have significant effects on physical and chemical properties ...
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Introduction Soil degradation is a widespread environmental problem that occurs as a result of land use change and destruction of vegetation cover that may lead to changes in soil structure and porosity. Land use change and land management have significant effects on physical and chemical properties and biological capabilities of soil. The investigating of undisturbed and natural soil structure using microscopic and ultramicroscopic techniques provides invaluable information about the physicochemical, mineralogical, morphological properties and soil genesis and calcification. Image analysis is an advanced method for quantifying soil properties and increasing the precision of morphological and micromorphological studies. Materials and Methods In this study, in order to investigate the impact of different land uses on porous and microstructure of surface soil horizons, 9 profiles in different land uses, including natural forests, artificial forest, abandoned land, orchard and cropland were extracted and described. Then one sample was taken from each horizon for physical and chemical analysis as well as a few undisturbed samples for micromorphological studies. Physical and chemical parameters such as texture, bulk density (BD), calcium carbonate equivalent (CCE), organic carbon (OC) and mean weight diameter (MWD) were measured. After preparation of thin sections of soil, micromorphological studies were conducted by polarizing microscope. Then from each thin section, 20 photos were taken randomly in plane polarized light (PPL) and cross polarized light (XPL) and transferred to image tool software. The percentage of total porosity of soil, feret diameter and area pores parameters were studied quantitatively. Three classes of feret diameter in micrometer and five classes of area in square micrometers were considered for pores in the soil thin sections. After importing photos to the software and performing calibration, grayscale and subtracting two images, the range of pores was identified by the software. Then in the classification section of software, the highest level of classes in each part was determined and the percentage of pores in each class was calculated and data obtained were analyzed by SPSS 16.0 software. Results and Discussion Micromorphological observations showed that in natural and artificial forests, a significant amount of organic matter in the soil has resulted in the formation of granular and subangular blocky dominant microstructure. While in cropland land use the type of microstructure is mainly massive and angular blocky, due to deforestation and agricultural practices, which resulted in the degradation of soil microstructure. Appropriate environmental conditions and dense vegetation in natural and artificial forests land use lead to significant biological features in comparison to other land uses that were subjected to deforestation. In natural and artificial forests land uses, the percentage of channel and large vughs pores is more than other land uses mentioned above. Tillage results in degradation of soil structure in cropland land use, the majority of pores observed in thin section are vugh and plane. Also, the results of image analysis showed that in natural forests and orchard land uses, pores with diameters ranging from 2 to greater than 10 micrometer and areas ranging from 500 to greater than 1000 square micrometers had the highest frequency in terms of percentage of soil pores. Hence, these soils are considered as quite porous class, while in cropland land use, tillage results in the degradation of large pores showed that pores with diameters less than 2 to 10 micrometers and areas smaller than 5 to 50 square micrometers comprised and the highest percentage of soil pores. Conclusion Asignificant amount of organic matter and low bulk density, and the highest percentage of total porosity are found in natural forest and orchard land uses, while deforestation and cultivation in cropland land use has led to compression and destruction of soil structure. This fact reflects itself in the increased bulk density and decreased total porosity. Agricultural practice has a significant effect on destruction of surface soil structure. Microstructure and voids of cropland land use are mainly massive and angular blocky and plane and vughs, respectively. With changes of land use from forest to cropland, and consequently incorrect land management causes decrease in organic matter. Shortage of organic matter causes decreasing biological activity in surface soils. The best way to prevent degradation of the soil in this area is to preserve natural forests and change cropland land use to orchard and artificial forest land uses.
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.
Atefeh Esmaili Dastjerdipour; Mohammad Farpoor; Mehdi Sarcheshmehpour
Volume 36, Issue 2 , March 2014, , Pages 17-35
Abstract
Cyanobacteria play an important role in providing biological soil crusts in sandy soil of desert areas. The aims of the present research are to investigate the possibility of crust formation under three cyanobacteria (Nostoc. sp (N), Phormidium.sp (Ph) and combination of two genus (Ph + N), two polymer ...
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Cyanobacteria play an important role in providing biological soil crusts in sandy soil of desert areas. The aims of the present research are to investigate the possibility of crust formation under three cyanobacteria (Nostoc. sp (N), Phormidium.sp (Ph) and combination of two genus (Ph + N), two polymer treatments [blank (S0) and 0.3 g per 250 g soil (S1)] and two moisture levels [FC (M1) and 80% FC (M2)] in three separated parts. Crust thickness, increase in soil organic carbon and resistance to penetration of crusts after complete coating (60 days) were measured in the first part of the experiment. Then the effects of time (15, 30, 45 and 60 days) on crust thickness and micromorphological investigations of crusts were performed in the second and third parts of the experiment respectively. Results of the study showed that simultaneous application of two genus at FC level with polymer creates the thickest (6.83 mm) and the most resistant crusts (0.27 MPa) to penetration. Both cyanobacteria genus with polymer and FC level caused the highest organic carbon contents (1.89% and 1.66% respectively). Also the thickest crust (6.8 mm) was formed by simultaneous application of two genus during 60 days. Micromorphological observation showed decrease in macro pores in treated samples compared to control and this decrease of pore space size with application of both cyanobacteria genus was higher than each of them alone.
