جستجوی مقالات مرتبط با کلیدواژه « soil evolution » در نشریات گروه « جغرافیا »

Soil characteristics and development are influenced by environmental factors such as land use. Investigating the agricultural use effect on soil development and evolution can be useful in maintaining and improving the quality of land resources and preventing soil erosion and degradation. Soil development and evolution are the result of changes in its physical, chemical, biological, morphological, micromorphological and mineralogical characteristics, so the study of soil evolution indices indicates the impact of soil on environmental factors. Various morphological, physicochemical, and micromorphological indices of soil evolution due to their special nature show different aspects of soil impact from environmental factors. Therefore, the study of soil evolution as a result of environmental conditions of its formation and development can provide a suitable perspective for the continuation or the need to change the current management to maintain or improve land quality. This research study intends to examine the various indices of soil evolution that consider each aspect of soil development and evolution in relation to land management to be a fundamental step for the sustainable management of agricultural land.

The study area is the cultivated lands of alfalfa, corn, onion and wheat, and the adjacent barren lands in the Shurgol section of Bonab city of East Azerbaijan province, which is the site of selected control soil profiles under constant and uniform management over an average period of 15 years. After selection, the soil profiles were dug and described, and disturbed and undisturbed samples were taken from genetic horizons for physicochemical and micromorphological analyses and were transferred to the laboratory. Soils were identified and classified according to field studies and the results of laboratory analysis based on 12th edition of the Keys to Soil Taxonomy. Micromorphological studies of thin sections prepared from undisturbed soil samples were performed using a polarizing microscope based on a standard terminology system. In this study, a set of soil evolution indices, including harden, clay accumulation, appearance cation exchange capacity, MISODI, MISECA, and revised MISECA were used. Harden index is obtained by comparing the characteristics of texture class, plasticity, adhesion, type and degree of structure development, dry and wet stability of aggregates, clay coatings, darkening, lightening color and acidity of soil solum with C horizon. Clay aggregation and the apparent cation exchange capacity indices have been calculated based on the differences between the amount of soil clay in horizons B and C and the ratio of soil CEC to the percentage of clay, respectively.
To calculate the MISODI, MISECA and revised MISECA indices, the studied pedofeatures during micromorphological analyses, including microstructure, b- fabric, coating, nodule and degree of weathering and evolution of mineral particles were used. For this purpose, each of the mentioned characteristics, in terms of quality and quantity, was assigned a weight based on the relevant scoring tables, and the final evolution index was calculated from all of them.

The results showed that the soils of the region are non-saline and pH neutral; their texture is clay loam to clay and different amounts of organic carbon with irregular depth distribution are observed in soils under each type of productivity. Based on a complete study of the characteristics, different families of Inceptisols were identified with cambic and calcic horizons characteristic as well as Vertic properties in the soils of the region. Micromorphological studies revealed that the voids are simple and compound packing and include channels with granular and blocky microstructure in the surface horizons as well as chamber and sometimes vugh with massive microstructure in the lower horizons, while in the middle horizons angular blocky and subangular blocky microstructure were observed. According to the boundary between fine and coarse particles with 20 microns dimensions, the c/f particles in all soils have increased from surface to depth and the coarse part includes a variety of minerals. The b-fabric and related distribution pattern between the predominant coarse particles are of the crystalline and porphyric types, which in some cases are observed in speckled and monic forms, respectively. Pedofeatures observed in the soils of the region include intact, semi-decomposed and fully-decomposed organic residues, partial clay coatings and continuous and incomplete lime coatings and infillings in the channel. Soils under alfalfa productivity type with values ​​of 26.98, 1345.83, 13, 15 and 16 were identified as the most complete soils for harden, clay accumulation, MISODI, MISECA and revised MISECA soil evolution indices, respectively, while barren soils with 15.52, 419.75, 7,8 and 8 were identified as the least developed soils for the mentioned indices and the evolutionary order between these two groups is based on the mentioned indices for the productivity types of corn, onion and wheat. The values for the appearance cation exchange capacity index were 0.7 for wheat and barren soils, 0.68 for corn and onion and 0.67 for alfalfa.

As for soil classification, although differences exist at different categories or levels, but in this study, even at the family category or level, it is not possible to express the differences between soils under the productivity types of corn, onion, wheat and barren lands. In such cases, it can be useful to consider the soil evolution indices that quantitatively examine soil properties and determine their differences. Soil properties and, consequently, their evolution are affected by the productivity type in agricultural uses, and among these properties, the ones related to soil fabric are affected more than the others. Observing the evolutionary order of the majority of soils based on the studied indices for the productivity types of alfalfa, corn, onion, wheat and barren lands indicates that optimal agricultural operations and sustainable land use lead to accelerated evolution. Based on the quantitative values obtained for different indices in different types of productivity, it can be stated that the effectiveness of soils from the cultivated crop depends on the morphological and physiological characteristics of the plant and their planting, holding, and harvesting operations. Therefore, in arid and semi-arid areas, such as the studied area, where the soils are young and at the beginning of their evolution, the existence of more complete soils will be in line with increasing their quality and will prevent land degradation.

Climate, terrain condition, vegetation coverage, parent materials, and time are among the factors that affect the soil formation and contribute to such soil properties as porosity, apparent and actual specific gravities, and clay and carbonate contents. The forest soils have been consistently regarded for their high content of organic matter and suitable structure. In the meantime, changes in the management scheme, land use, and soil treatment procedures can significantly alter the organic matter content and other physical and chemical properties of the soil (Hagedorn et al., 2001; Stoate et al., 2001; Dawson and Smith, 2007). The organic matter greatly contributes to improved crop yield by directly affecting the physical and chemical properties of the soil. Considering the importance of the soil and its properties for many managerial programs, the present research aims at investigating the reasons behind the formation of various soil types within the Kasilian Area, Mazandaran Province, Iran. Similar areas can be observed in other places across the so-called Hyrcanian Forests by Quick review of the satellite images. Accordingly, the findings of the present research are important for similar forest areas and forest settlements.

The watershed area range was delineated based on satellite images and topographic maps. The area was then surveyed by selecting and studying a number of soil sections where the soil variations were relatively large across an acceptably large extent. The extents of different formations were identified and the land components were determined by using geological maps. By considering the available geological and geomorphological data and interpretation of the satellite images combined with terrestrial observations and profile descriptions of the profiles and the land component sections, different land components were distinguished. The land components were considered as relatively homogeneous work units, and the pedological studies were focused on these units. The units were relatively identical in terms of the soil, physiography, climate, and the parent materials, with an attempt made to take into consideration about the relation between the transacts and the soil evolution. Seven soil profiles were selected by the studied profiles and sections, as to control for which the experimental results and classification outcomes were presented.

The climatic condition was almost the same across the entire study area, so that its impact on the soil was similar in different parts of the area. The more important factor that mitigated the impact on the climatic condition and contributed to the formation of various soil types across the region was the versatility of the geological formations and the terrain over the study area. So the present-day variations in the soil classification can be greatly linked to the changes in the Mollic horizon thickness. In this research, the maximum organic carbon content was observed in the samples taken from the forest lands, with its value significantly dropped in the deforested areas, especially the farmed lands. Variations of the organic carbon content of the soil is an important indicator of the soil quality for investigating the effects of managerial operations in the farmed and forest lands. The soils formed on top of the Lar (L1J), Delichay (jd), and Shemshak Formations (TR3.JS) were found to be residual soils. Although the Lar and Delichay formations are dominantly composed of lime, their evolution has been interrupted in the region due to the very high slopes to which the formation has been exposed, making the corresponding soils classified as Inceptisol. This is while the Shemshak Formation has been exposed to a relatively slower slope, so that the forest vegetation coverage and more limited horizontal displacement of the soil have provided enough time to form the Mollic horizon and the Mollisols. In the sediments located within the valleys between the quaternary hills and mounts, which were previously covered by forests and now are turned into low-slope pastures, the Mollic horizon has been appropriately preserved, with the lime content of the parent materials transported to underlying horizons to form a calcite horizon. This part of the land is covered by Mollisols that were generally classified as calciudolls considering the moisture regime of the soil. In the sloping lands, as a result of the erosion of the surface soil, the Mollic horizon was degraded, which made the soil classified under Entisols and the great class of Udorthents. On such lands, upon erosion of the overlying soil, the underlying rocks along the soil profile are exposed.

A Comparison of soils in Bare lands with forest lands showed a dramatic declining trend in the soil properties. In this respect, the farmlands were dominantly covered by Entisols while the pastures were most often covered by Inceptisols and the forests were dominated by Mollisols; these showed the soil variations under similar natural conditions as a result of changes in the land use. It is recommended to set the scene not only to limit the deforestation process, but also to suit the pastures for natural forestation in an attempt to prevent further erosion of the invaluable soil and preserve the even more valuable natural resources.

Soil is one of the most important elements of the universe, substrate production; food security and self-sufficiency are directly related to soil conditions. Soils are formed on geomorphologic surfaces. These surfaces have certain age, aspects and slopes and also specific position. Time dependent soil formation generally occurs in regions with certain age land­­forms such as river terraces debris fans or slide masses and mud flows. This may leads to soil diversity in different geomorphological environments. Therefore geomorphological studies, due to different physical and human factors, could have an important role in identification of agricultural prone areas and planning for soil conservation and preventing from soil losses. This research uses a comprehensive procedure and soil lithological and geomorphological data in order to assess the effects of geomorphology on rate of soil forming process in Joghatay County.
In this study, after preparing the required maps of physical characteristics, layers were incorporated and then locations of sampling were determined. These points were located in different elevation, different slopes, certain plan and profile curvature and lithological features. Partial Least Square Regression method was used to analysis and determining the important factors in soil forming process in studied area. PLS path modeling is primarily used to develop theories in exploratory research. It does this by focusing on explaining the variance in the dependent variables when examin­ing the model.
Using 9-unit model of catena, 7 units were identified in studied area and from these units soil samples were prepared.
Most of samples in unit 4 have large to medium grain size. Except in sample 5, 6 (because of convex slops). In unit 5 amount of sand in comparison with silt and clay is higher. Also, soil depth in this unit is low and minimum soil depth is l0 cm. Gravel size in this unit is medium. In the middle of this unit formation of some geomorphic factures such as alluvial fans is common. Hydrometric analysis of this unit samples (3, 4, 8, 12, 14) show that in sample 3 that is located in upper part of the fan, amount of sand is more than silt and clay. Results from sieve analysis show that the percent of coarse grain size in sample 3 is more than sample 2 and 4. The reason is that in an alluvial fan from higher elevation to flatter areas, coarser grain sizes changed to finer grain sizes. Sample 4 is located between 2 alluvial fans. In this area the percent of sand is more than two others. Samples 12, 8, 14 have large amount of sands since they are located in upper part of alluvial fan. In location of sample 14, the slope has a special from. The plan curvature in this point is convex and profile curvature is concave therefore there is a high convergence in this location, therefore gravels are not enable to persist here. In units 6, 7 that are concave parts of slope and receive large amounts of sediments and solutions in overland or underground flows and deposited in foot slope. In sample 2 that is located in lower part of alluvial fan, sand has the first rank in soil components (84%) but the amount of silt and clay is less than sample 3. Sample 1 that is located in flattest part of the area has a fine grain soil and the least amount of sand and gravels are in minimum ranges. Also, locating of sample 1 in the end part of alluvial fan and near the Jovein river, resulted in increasing soil depth.
Part 2 of investigation, begins with preparing of a model to investigate the role of each soil forming factor on soil formation and development in study area. This model as mentioned before is in the form of structural equations and PLS procedure. In this case, latent variables are divided in 2 forms reflective and formative variables. Fitting of this model was performed in 3 parts. 1- Fit of measurement model 2- Fit of structural model 3- Fit of general model. In designed model, four models related to hydrological, topographical and geomorphological, geological and soil formation variables were created. The results are shown in table 1. The results show that all of models have proper design and are suitable for our study.
Each unit of catena in slope extent is affected by special process and drainage condition and show different soil properties, therefore, slopes are the best areas for soil geomorphological studies. In unstable areas such as slope shoulder, weathered materials transfer to down slope and deposit in more stable area. In studied area slope gradient and aspect are of important factors in soil formation. Especially southward slopes have an important effect on soils. Elevation is another factor that shows direct effects on soil formation that leads to very thick soil layers in flat areas and very thin layer in high gradient slopes and slope shoulders. Also hydrological factors such as soil moisture and order of river are effective factors on soil genesis and development. Results from PLS analysis show that among all investigated factors, slope is the most important one that has critical effect on soil formation. Regarding these results it is clear that geomorphology could have an important role in soil conservation planning because in each unit of slope concerning its influence on soil formation we can present suitable strategies for soil conservation and maintenance.