جستجوی مقالات مرتبط با کلیدواژه « تغییر کاربری » در نشریات گروه « آب و خاک »

Limited fresh water resources and access to these resources as well as providing food security for the growing world population have led researchers to make extensive efforts in the field of optimal management of water consumption and determining the cultivation pattern in different regions. Therefore, identifying cultivated crops in a region and determining their area can be very effective in land management and water allocation in these regions. With the growth and advancement of technology in the field of satellite and remote sensing in recent decades, the use of satellite images in order to identify types of land use and types of cultivated products has expanded greatly. Sentinel-1 (radar) and Sentinel-2 (multi-spectral) satellites have been very popular in agriculture due to their improved spatial resolution (10 meters) and appropriate time resolution (5 days for Sentinel 2 and 12 days for Sentinel 1).

The studied area is located downstream of the Fariman dam in an area of 22.51 square kilometers (5122 hectares) and the central coordinates are 35 degrees 41 minutes and 59 seconds north latitude and 59 degrees 50 minutes and 49 seconds east longitude. In order to classify satellite images and produce crop maps, ground observation data is needed to train the classification model and also evaluate the accuracy of the results. For this purpose, sample points were taken from different land uses in the region, using GPS. Since it was not possible to take enough samples for all land uses and crops in the determined border, a larger sampling area was selected. Then, all collected data were sorted and for each class, 70% of the data was randomly used to train the classification model and 30% was used to validate the obtained classification results. In the present study, Sentinel 2 satellite images for the first 6 months (crop season) of 2021 and 2022 and digital elevation image (DEM) of the study area were considered. According to the surveys conducted and the reports of the agricultural jihad of Fariman city, the main crops cultivated in the region include maize, tomato, sugar beet, wheat and barley. Therefore, according to the phenological stages of these products in the region, the appropriate time series of images was selected. The accuracy of the classified map was evaluated using the Kappa coefficient and overall accuracy.

In order to identify and separate the land use in the study area according to the major cultivated crops, first the agricultural calendar of the crops was determined. Then, satellite images were selected based on crop cultivation period. Based on the evaluation indexes of commission error, omission error, overall accuracy as well as the Kappa coefficient, it was observed that the identification of classes and land use was done well and with high accuracy, so that the overall accuracy for the classification map of 2022 is equal to 0.97 and the kappa coefficient value was 0.94. In order to compare land use changes during the two years 2022 and 2021, classification was also done for the images of the crop year 2021. Since the training samples of agricultural crops were not available separately and in sufficient numbers in the crop year of 2021, the classification map of this year was produced only based on the type of land use, and all crops in one class entered the classification model training process. The values of overall accuracy and kappa coefficient in 2021 were obtained as 0.97 and 0.95 respectively. According to the obtained results, the area of the orchard class has increased since 2021 compared to 2022. After repeated field visits to the study area and investigation of some land uses that had been changed and turned into orchard use, it was found that in some areas in 2022 there was the growth of villa gardens and in some areas the farmers have converted cropland to orchard (construction of an orchard). Even in some cases, the old orchard in the region was destroyed by the farmers and the land was fallow for 2 to 3 years (2021, fallow). In 2022, the farmer built a new orchard. It is also necessary to mention that fallow lands are included in the soil class depending on whether they are newly plowed or have no vegetation, and if weeds have grown on these lands, they are included in the rangeland class. 

The effective management of water resources from dams for agricultural purposes necessitates the identification of land use downstream of the dams, along with determining the types of crops and their respective areas. In this study, Sentinel 2 satellite images were employed to classify and delineate land use associated with agricultural cultivation downstream of the Fariman dam in Razavi Khorasan Province, spanning the crop years of 2021 and 2022. The results indicate that the Sentinel 2 satellite demonstrates a high capacity to differentiate between various types of land use and crops. The generated map depicting changes in land use and crop cultivation areas can be instrumental in water use planning and the allocation of water resources.

Soil resources are important components of the ecosystem, and therefore, their quality should be considered. One of the important factors affecting the quality of soils is land use change. The present study was conducted to investigate the effects of land use change and deforestation on some soil fertility and biological characteristics in the forest area of the Yasouj region. In this area, four land uses of dense forest, sparse forest, deforested (degraded) lands, and rainfed agriculture were randomly sampled from two slope classes. In each land use 10 soil surface samples were taken. Fifteen soil fertility and biological characteristics were measured using routine methods. The results showed that dense forest and deforested (degraded) lands had the best and worst conditions, respectively, in terms of the measured parameters. Among the measured characteristics, the values of alkaline phosphate, exhaled respiration, nitrogen, basal respiration, acid phosphatase, manganese, and zinc showed the greatest decrease respectively, and the values of phosphorus and potassium exhibited the least decrease, as a result of land use change from dense forest to degraded lands. The findings showed that the conversion of ecosystems such as forests to agricultural lands or deforestation has led to a severe decrease in the fertility and biological indicators of soil quality. Therefore, the protection programs of these areas should be more considered.

Changing land use may have a major influence on physical, chemical, and biological soil properties with a consequence for soil functioning and productivity. Abandonment of agricultural lands is actually a kind of restoration of these lands to their original natural conditions, which is often done through human intervention. Soil restoration after land abandonment is a complex phenomenon. The pastures of our country are typically cultivated in rainfed methods, and the use of agricultural inputs such as animal manure, poisons, and chemical fertilizers is not very common. Therefore the continuous cultivation of a product and the lack of use of agricultural inputs causes a gradual decrease in fertility and increase erosion. Hence, after years of cultivation, the production potential decreases, and the land is abandoned.
This study was conducted to determine the effects of land abandonment on some physical, chemical, and biological soil properties in the 0-20 and 20-40 cm depth at three different sites including Lal Abad, Qaleh Kohneh and Chalab-e Pain, using 2×2 factorial layout arranged in a completely randomized design (CRD) with three replications. The physical, chemical, and biological characteristics of the soil were measured by conventional laboratory methods. Electrical conductivity of saturated paste extract (ECe) with electrical conductivity meter device in saturated paste extract, pH of saturated paste with pH meter device, and bulk density by cylinder method were determined in the samples. The amount of dispersible clay (DC) was determined by the method of Gee and Bauder and the Mean Weight Diameter (MWD) was determined by the method of the wet sieve. The amount of absorbable phosphorus by extraction method and total soil nitrogen by Keldahl method were measured in the samples. The amount of soil organic carbon (OC) in the samples was determined by the method of Walkley and Black. Mineralization of organic carbon (soil respiration) (Cmin) and metabolic quotient (qCO2) were obtained by validated and conventional methods.
 The results showed that the abandonment of agricultural lands significantly increased the MWD and reduced the amount of dispersible clay. Bulk density also decreased due to the abandonment of agricultural land in all areas except the Qaleh Kohneh area. The results of the analysis of the chemical characteristics of the soil indicated a decrease in soil pH in all areas and depths, except in the Qaleh Kohneh area. The biological results also showed that the abandonment of agricultural lands caused the change in biological characteristics. Abandonment of agricultural lands in all three regions led to an increase in microbial biomass carbon and soil microbial respiration. High microbial respiration in abandoned lands is probably related to more organic carbon in these soils. Loss of soil organic matter due to cultivation and improper soil management is often the main reason for reducing soil respiration in agricultural lands compared to abandoned lands.
Changing land use from agriculture to abandonment improved the physical, chemical, and biological indicators of soil quality, especially the surface layer of the soil, which ultimately led to the improvement of soil quality in all the studied areas. It can be concluded that the release of agricultural lands has increased soil health by increasing the carbon input into the soil, improving the soil aggregates, and improving the microbial activity of the soil.

Management practices such as land use change is one of the main components of global change that affects the process, structure and function of ecosystems by changing microbial communities (due to their role in the decomposition of organic matter and food mineralization(.Changes in soil biological characteristics due to land use change and management practices may lead to significant changes in soil organic carbon dynamics, soil microbial respiration and affect nutrient cycle and plant growth. Therefore, to better understand human management on carbon cycle, it seems necessary to understand the correlation between soil microbial properties during land use change.

The aim of this study was to investigate the temporal dynamics of soil microbial characteristics during land use change in rangelands around Kiasar Chahardangeh city of Mazandaran. For this purpose, in this basin, the studied habitats were including Erost village with pastures turned into agricultural lands (barley) and orchards (apples and walnuts) with an age of more than 30 years, with a control pasture, Vavsar village with pastures turned into lands. Agriculture (barley) and orchard (apple and walnut) with an age of more than 20 years and also rangelands converted to garden use (apple and walnut) less than 10 years, with a control rangeland and Ara village with rangelands converted into agricultural land (Barley) less than 10 years old with a pasture. Soil sampling in each land use was done systematically randomly from two depths of 0-15 and 15-30 cm.In total, nine soil samples from landuses were transferred to the laboratory for analysis of soil physico-chemical characteristics including texture, bulk density, moisture content, organic carbon, total nitrogen, pH and microbial characteristics including Basal respiration, Substrate induced respiration, Microbial biomass carbon, Microbial biomass nitrogen and Microbial biomass phosphorus, qCO2, microbial ratio and carbon capability index.

The results showed that the highest amount of physicochemical characteristics (except sand and silt percentage and bulk density, pH and C/N) and soil microbial characteristics (qCO2, microbial ratio and carbon capability index and MBC/MBN) at both depths and mean depths belonged to orchard land uses older than 20 and 30 years. Principal Component Analysis (PCA) indicates that over time, higher values of microbial activity and soil fertility in the orchard uses are older than 20 and 30 years with a completely different location on the axis. In general, the results of this study showed that the variability of organic carbon, total nitrogen, acidity and soil moisture content in the long run caused an increase in microbial respiration rate (Basal respiration and Substrate induced respiration), While the qCO2 in the orchard less than 10 years old and control rangeland for lands older than 20 years, also the microbial ratio in the control rangeland for lands less than ten years old had the highest value, while the carbon capability index showed no significant difference between users of different ages.

In general, the results of this study showed that soil characteristics in orchard uses with older ages were in a better condition. Also, variability in soil physicochemical properties changed the microbial characteristics of the soil over time. Therefore, it is suggested that long-term studies and management strategies to reduce uncertainty and estimate the rate of organic carbon pool of ecosystems, which are not unrelated to soil microbial characteristics, are considered necessary during land use change.

Human activities such as deforestation, conversion of natural ecosystems to farming, biomass burning, tillage and cultivation, grazing, fertilizer use have a significant and negative impact on soil organic carbon pool. In particular, the conversion of natural ecosystems to agriculture reduces soil organic carbon pools. Understanding the spatial distribution of organic carbon in soil is particularly important for understanding the role of soil in the global carbon system. Therefore, the purpose of the present study was to investigate the changes of total carbon and its components in different sizes of aggregates of a forest soil after conversion to paddy.

For this study, Poplar Research Station in Guilan province was selected. Soil samples were collected from two uses of forest and adjacent paddy fields at two depths (0-20 and 20-40 cm). In the soil samples, aggregates of different sizes were separated and the amount of organic carbon in these aggregates was measured. Organic carbon was then fractionated into different sizes of these aggregates in both land use.

Investigation of organic carbon distribution in relation to aggregate size in two land uses showed that with increasing aggregate size, organic carbon content increased so that organic carbon content in Populus natural forest and rice fields were 4.5 and 3.3 times higher in aggregates larger than 2 mm (larger aggregates) than smaller aggregates 0.053 mm, respectively. The amount of organic carbon in the aggregates decreased with the change from natural forest to paddy fields. However, the decrease was greater in aggregates larger than 2 mm and lowest in aggregates (0.25–0.053 mm). Results of soil organic carbon fractionation showed that percentage of soil weight in fractions increased with increasing density in two land use. This situation was visible in two depths and in all the aggregate sizes. By increasing the density of fractions, the concentration of organic carbon in the fractions decreased. The organic carbon content of the fractions as a percentage of organic carbon content of whole soil, in all the aggregate sizes, and in the fractions with density < 2 g cm-3 was smaller than those of fractions with density > 2 g cm-3. In all of the aggregates, with increasing depth, organic carbon content of the fractions with density < 2 g cm-3 as a percentage of organic carbon content of whole soil decreased while those of the fractions with density of > 2 g cm-3 increased. By increasing the density of fractions, the C/N ratio of the fractions decreased. In all of the aggregate, due to the change of land use from natural forests to rice field, organic carbon content of the fractions as a percentage of organic carbon content of whole soil, decreased in the fractions with density < 2 g cm-3 and increased in the fractions with density > 2 g cm-3 and this was more pronounced in aggregates of larger size. The most sensitive and resistant fractions to land use change were fraction 2g/cm3 respectively. The ratio of carbon to nitrogen decreased as a result of land use change from natural forest to the rice field.

The change of land use and long-term cultivation in virgin forests and its transformation in rice field has changed organic carbon content of the fractions. The amount of free and occluded particulate organic matter in the aggregate (light fraction), which plays a very important role in the nutrition of the crop, was greatly reduced. This reduces the soil's health and the potential for carbon sequestration in the soil.

Forest fires and land use change have become a major global concern due to their significant role in environmental degradation and climate change. Meanwhile, the soil of forests and pastures has always been considered due to its relatively high organic matter and suitable structure. But fires and changes in the management of these ecosystems and the application of tillage have had detrimental effects on soil structure and loss of organic matter of the natural ecosystems. Therefore, this study investigates the effect of wildfires and land use change to vineyard on soil organic carbon (SOC) content and its soil organic carbon decomposition rate (SDR) in aggregate size fraction in an Oak Forest in Northern Zagros.

For this purpose, topsoil (0-5 cm depth) was sampled in a natural oak forest from both inside (FI) and outside (FO) sprout clumps, a portion of the forest burned three years earlier from areas undergone high (BHI), moderate (BMI), or low (BLO) severity, and a vineyard planted thirty years earlier in place of the forest from both under the foliage of vines (VI) and outside it (VO). All soil samples were air-dried and sieved to obtain four aggregate size fractions (8–2, 2–1, 1–0.25, and

The results of this study showed that cultivation and fire, especially its severe type, cause significant damage to large aggregates and increase the fine aggregates. So that, the highest and lowest amounts of coarse aggregates (2–8 mm) were obtained in FI (61.6%) and VI (11.1%) treatments, respectively. Whereas, the highest and lowest amounts of fine aggregates (< 0.25 mm) were obtained in VI (12.4%) and FI (5.7%) treatments, respectively. The results also showed that in all the studied treatments, the amount of SOC increased with decreasing of the soil aggregates size. Furthermore, in compared to the virgin forest, cultivation in the vineyard resulted in a significant reduction in SOC, while no changes in this parameter were observed in the fire treatments. The results also showed that in all the studied treatments, the amount of SDR index increased with decreasing of the soil aggregates size and this index followed the trend: FI (7.2) > BHI (5.4) > FO (5.2) > BMI (4.7) > BLO (2.9) > VI (1.4) > VO (0.4).

Overall, thirty years of farming were more impacting on soil aggregates degradation than a single fire, although severe; nevertheless, severe fire appears to have been much more impacting on soil aggregates degradation than every single yearly plowing. The results also showed that the SDR in soils that are rich in organic matter (FI and BHI) could be more sensitive to warming and intensify global warming more strongly than arable lands (VI and VO).

In this study, the effects of land use change (conversion of natural forest to paddy fields) and regeneration of deforested land on some qualitative and enzymatic properties of the soil were investigated. For this study, Populus Research Station in Guilan province, Astana Ashrafieh city was selected. Soil samples were collected from 5 land uses (natural forest, populus, Alnus and Taxodium and paddy forests) and two depths (0-20 and 20-40 cm). The data were analyzed as a factorial experiment in a completely randomized design with three replications. The factors included land use type at five levels and soil depth at two levels that were studied in three replications. Therefore, the number of treatments were 5 * 2 = 10, totally 30 units accounting replications. In total, there were 30 samples of disturbed soil and 30 samples of undisturbed soil that constituted the statistical data of the experiment. Some physical, chemical and biological properties of the samples were measured. The results showed that the mean weight diameter (75%), saturated hydraulic conductivity (95%), water repellency (53%), organic carbon (52%), total nitrogen (52%) and microbial biomass carbon (53%) in the natural forest were higher than the ones in the paddy field. Also, the activity of urease and arylsulfatase in the paddy soil was significantly lower than the one in the natural forest soil. However, the activity of dehydrogenase in the paddy soil was higher than the one in natural forest soil, indicating oxygen availability and moisture affect the activity of dehydrogenase and its activity increases as the soil moisture increases. Reclamation of some deforested lands by hand planted forest showed that Populus vegetation was more effective than the other vegetation covers in increasing aggregate stability, hydraulic conductivity, and microbial biomass carbon. While Taxodium cover increased the activities of urease, arylsulfatase and acid phosphatase more than the ones in other vegetation covers. The specific activity of enzymes (enzyme activity per unit of organic carbon), in dehydrogenase was significantly higher in the paddy soil than in the soil under natural forest. This indicates that the activity of this enzyme is independent of soil organic carbon changes and is dependent on soil moisture. Overall, it can be concluded that, in comparison with the qualitative and enzymatic activity, Taxodium coating improved these properties better than populus and Alnus coating.

Agricultural activity, especially cultivating rice, is one of the main reason of the destruction of natural forests in the north of Iran. This study was performed to investigate the effects of changing natural forest to Paddy Field on some physical and chemical properties of the soil and to determine the most sensitive indices to the disturbance of an ecosystem. Moreover, in this study, the Principal Component Analysis (PCA) method was used to create a minimum set of data from measured physical and chemical parameters. Accordingly, two land uses (natural forest and paddy field) were selected in Gilan province and soil samples were collected from five different depths (0-20, 20-40, 40-60, 60-80, and 80-100) three times. Soil texture, density, field capacity, dispersible clay, mean weight diameter (MWD), pH, electrical conductivity, calcium carbonate, organic carbon, total nitrogen, cation exchange capacity, extractable carbohydrates with acid and extractable carbohydrates with hot water at each depth were measured and the results were analyzed as factorial in a completely randomized design. The results indicated that by changing the land use from forest to paddy field, the average apparent density of the soil profile (15%) and dispersible clay (33%) were increased. However, the MWD (76%), organic carbon content (57%), total nitrogen (53%), and cation exchange capacity (31%) were reduced. The sensitivity index (SI) showed that among the physical and chemical parameters, MWD and organic carbon content were respectively more sensitive than the other parameters to land use change. The results of PCA revealed that the four factors could almost justify more than 90% of the variance in MWD, organic Carbone, density, moisture content in field capacity, extractable carbohydrates with acid, and extractable carbohydrates with hot water. These parameters showed the highest commonality and the clay percentage had the minimum relative importance among the estimation of commonality values.

The evaluation of biologic parameters of soil quality plays an important role in assessing the land management and sustainability of agricultural systems. For this purpose, the biological properties of soil quality, which are sensitive to farming are measured and investigated. The aim of the present study is to evaluate the biological changes forest soil quality after converting to the paddy field and determining the most sensitive properties to disturbance of an ecosystem and the creating a minimum set of data from these parameters using the factor analysis method.

The present study was performed in Poplar research station in Gilan Province. The soil sample collection was done in both natural forest and closest paddy field from five different depth (0-20, 20-40, 40-60, 60-80, and 80-100 cm). The data were analyzed as a factorial test in a completely randomized design with three replications. The factors including the type of land use in two levels and soil depth in five levels were studies in three replications. Therefore, the statistic population of the present study was 10 treatments (5 × 2 =10) with three replications (totally 30 test units). In the study, the microbial respiration, the mineralization percentage of carbon, the microbial biomass carbon, microbial fraction, and the metabolic coefficient of the samples were measured and the sensitivity index to each feature was calculated. The data were analyzed using SAS software. Mean comparison of parameters of Duncan’s test and factor analysis using principal component analysis method were performed.

The results of the study showed that any land use changes from forest to paddy field led to increasing the mineralization percentage of carbon and the metabolic coefficient by 28 and 21% respectively. However, microbial biomass C (61%), microbial respiration (31%), and basal respiration (49%) were reduced. Sensitivity index (SI) indicated that microbial biomass is more sensitive than other parameters to land use. The use of principal component analysis (PCA) showed that two factors could explain more than 70% of the variance in microbial biomass and carbon mineralization percentage and more than 60% of the variance in the amount of carbon mineralization, basal respiration, and a metabolic fraction (quotient). These parameters represent the maximum communality estimation, and the microbial fraction showed the minimum relative importance among the estimates of the total communality values.

The change in land use from forests to the paddy fields had an adverse effect on the biological parameters of soil quality, which led to reducing the soil health and carbon sequestration potential in soil. Therefore, cultivation in these lands exacerbates soil degradation and stopping the process results in longer recovery and resilience time.

World population growth, human need of food, his interference in natural ecosystems and changing soil intrinsic properties by degradation, increases the need of evaluating land use changes impacts, on soil quality. This study was carried out to evaluate the effects of land use change on some of soil quality indicators in land use changed forest of Northern Zagros.
in this study about 96 soil samples were taken from North Zagros forests as well as adjacent areas with land use changed. Some soil properties including basal respiration (BR), substrate induced respiration (SIR), microbial biomass carbon (MBC), pH, electrical conductivity, total nitrogen, available phosphorus, dissolved and exchangeable potassium, cation exchange capacity (CEC), soil organic matter (SOM), sodium adsorbtion ratio (SAR) and exchangeble sodium percent (ESP) were measured. Soil quality index (SQI) was determined using principal component analysis (PCA).
The results showed that changing forest to other land uses significantly reduced microbial biomass carbon, basal respiration, substrate induced respiration, the amount of dissolved calcium and potassium, exchangeable calcium, magnesium and sodium, organic matter, CEC, SAR and potassium. Soil organic matter amount in pasture, garden and agriculture decreased 16, 47 and 57.5 percent compared to forest, respectively. As a result of changing forest to pasture, gardens and agriculture MBC amount decreased 28.34, 48.66 and 58.28, respectively. The amount of total nitrogen, potassium and CEC in forest were 2.5, 1.39 and 1.4 times more than agriculture, respectively. Also, in different land uses, depth effect on all measured parameters was significant. As the results showed, the highest amount of potassium, nitrogen, cation exchange capacity, basal respiration, microbial biomass carbon and substrate induced respiration was seen in forest surface soils. Principal component analysis showed that between 16 properties assessed soil quality as total data set (TDS), organic matter, carbon availability, microbial carbon proportion to organic carbon, available phosphorus, pH and SAR, as the most important or the least effective properties on soil quality (minimum data set or MDS), had the greatest impact on the quality of studied soils. According to the cumulative soil quality index (SQI), soil quality for forest (0.756) and pasture (0.73) was II (lowly restricted) and for agriculture (0.646) and garden (0.626) was III (with limitation for plant growth).
Therefore, any management and land use change that increases soil disturbance, will reduce soil quality and increase land susceptibility to soil erosion. So, in order to maintain soil quality, appropriate management practices should be done.

This research was conducted to study the effect of land use change on some physical fractionation component of organic matter and some of its quality factors. Therefore, two uncultivated and cultivated (such as rotational cropping and sugarcane) were selected in Khuzestan province. Disturbed and undisturbed soils were sampled from 0-30 and 30-60 cm depths. Total N, OC, dispersible clay (DC), aggregate stability and organic matter differentiation were comprised as factorial in Randomized blocks. The results showed that total carbon content was increased from 3.57 g kg-1 for uncultivated to 10.5 and 10.65% for sugarcane and rotation cropping system, respectively. Maximum aggregate stability was belonging to sugarcane and minimum was for uncultivated land use. Due to land use changes, dispersible clay content was reduced from 44 in uncultivated land to 33 and 38% under sugarcane and rotation cropping system, respectively. Organic carbon content and total N was increased with land use change from uncultivated to cultivate but sand component was more sensitive to the land use change as comparison to other component and reacted rapidly. Also, organic carbon and nitrogen was more reach in sand particle of organic matter in surface layer. While, the change of land use increased clay fraction of organic matter at first level, this was for sand fraction in second level and third level was belong to silt. This is related to aromatic structure and resistance of this fractionation of organic matter. It was concluded that for soils do not have good quality, best management practices (BMP) and increase organic matter can improve the soil quality and aggregate stability due to make good situation for cultivation.

Land-use and land-cover are considered as determining factors in studies of water resources, erosion, and sediment yield watershed (32). Computerized simulation of land-use change effects on the watershed processes have been studied in the last decade (2,13,16,24,25). Modeling the effects of land-use change on flood has been numerously investigated in the last decades (2). Bahremand (2006) has conducted a research on the effect of afforestation on the flood hydrograph features in one of the watersheds in Slovakia. The results revealed that 51 percent increase in jungles led to 12 percent reduction of Debi peak and also causes nine-hour increase up to the hydrograph peak using WetSpa distribution model (2). Banasik and Fam (2010) have investigated the effects of land-use change on flood hydrograph in a watershed in Netherlands using Curve Number method and Nash model. The results indicated that land-use change in 2007-2009 increased Debi peak from 1.1 cubic meters to 8.92 cubic meters (3). Therefore, regarding the significance and the role of land-use change and also considering the fact that flood hydrograph is the hydrological respond of the watershed to land-use change, in this study, land-use change effects have been studied on flood hydrograph in Jafarabad watershed in Golestan province using GFHM (21) distribution model.
In this study, land-use change effects have been studied on flood hydrograph in Ja’farabad watershed using GFHM (21) distribution model. GFHM (21) model is a hydrological temporal and place distribution model. DEM maps, land-use, soil type, and also precipitation data of the watershed are the main data required by this model. In order to calculate surplus precipitation amount, this model applies Kinematic- wave method using curve number method of Natural resources reservation organization (NRCS) and the kinematic-wave method for routing. Based on the conditions of the watershed, four management scenarios were developed with an approach of the effects of destruction and land-use reclamation on flood hydrograph.
The results indicated that 4.2 percent jungle growth (scenario 4), reduces flood Debi peak to 0.55 percent and decreases the flood volume to 2.6 percent. Changing 3.9 percent jungle lands to arid lands (scenario 2) increases flood Debi peak to 0.85 percent and also adds 1.83 percent to flood volume. Also changing 17.8 percent semi-dense lands to water-fed lands (scenario1) can raise flood Debi peak to 7.8 percent and increase flood volume to6.08 percent. The results also depicted that land-use change affects cloudbursts with low Debi, and has more effects on peak Debi and flood volume.
The results revealed that flood Debi and volume can be reduced through non-structural land management in order to lower and manage the floods. Hence, land-use reform plan of watersheds with a jungle reclamation pattern and also changing agricultural land-use into agro-forestry lands especially olive orchards (most similar areas are conducted in Golestan Province) significantly increase early casualties and land capture.

P in soils exists in many complex chemical forms, which differ markedly in their behavior, mobility and resistance to bioavailability in the soils. The total P content of a soil provides little information regarding the behavior of P in the environment. The various forms of P present to a large degree, determine the fate and transport of P in soils. Fractionation schemes using different chemical sequential extractions have been used in order to describe the many different forms in which P can be found in the soil. The reason for fractionating and studying P forms in the soil is usually to allow a more precise description of the potentials for P release from the soil. The forms and dynamics of soil P can be greatly affected by agricultural management practices. Since inorganic P is the preferred source for plant uptake, knowledge of the inorganic form within soils is fundamental to understanding bioavailability of P and sustainability of agricultural practice. The aim of this study was to investigate the effect of land use change on the form and distribution of inorganic P using a sequential extraction procedure. In order to study the impact of land-use change from forestland to cultivated land, composite samples in four replicates from the upper 10 cm of the different land use systems (natural forest, pasture, bower olive, farmland) were collected. We collected five subsamples from each land use in a radial sampling scheme. The five subsamples were then bulked into one sample. The spacing between the subsamples on the radii ranged from 5 to 10 m. The soil samples were transferred to polyethylene bags and transported to the laboratory where they were slightly crushed, passed through a 2 mm sieve prior to fractionation and chemical analysis. Soil texture, cation exchange capacity, organic carbon (OC), electrical conductivity, pH and calcium carbonate equivalent (CCE) were measured with standard methods. Total P and total inorganic P (Pi) contents were measured by the ignition method, for which P in the ignited (550 °C) and unignited soil samples were extracted by 0.5 M H2SO4. A modified version of the sequential extraction of Olsen and Sommers (1982) was used to fractionate inorganic P. Phosphorus was measured in the extracted supernatants by the molybdate–ascorbic acid method. The results showed that clear-cutting of the indigenous forests and their conversion into agricultural fields significantly decreased total P and total organic P levels. Land-use changes from natural forest to farmland decreased the total P by 23% (from 644 to 495 mg per kg). Clearing and subsequent cultivation of the native woodland resulted in a marked depletion of total organic P. In addition, the land-use conversion from the natural forestland to an agroecosystem (cultivated land) led to increases in total inorganic P and inorganic P forms levels (labile P, P non-occluded, occluded in oxides of iron and aluminum, soluble calcium phosphate and sparingly soluble calcium phosphate). Labile inorganic P (NaHCO-Pi) showed the greatest changes, such as labile inorganic P in the amount of change from 1.75 in the forest land to 13.01 mg per kg of cultivated land, which represent an increase of approximately 8-fold compared to control (natural forest). The results also revealed that the refractory inorganic P fractions (HCl-Pi) were the major inorganic P pool, comprising 50-70% of the total inorganic P pool, indicating CaCO3 control over phosphorus availability in the studied soils. This study indicated that forestland degradation and cultivation caused chemical changes of P dynamics. Large-scale conversion of indigenous forests to cultivated land, driven by long-term agricultural development in the Toshan region, has greatly impacted the forms and content of P in the soils. Generally, the conversion of natural ecosystem to agroecosystems, decreased the proportion of organic P (Po) in the top-soils at depth of 0 to 10 cm. The depletion in organic P from the cropped fields could be attributed to the enhanced mineralization of soil organic P caused by cultivation and removal of P in the crops. However, the conversion of natural forest to farmland led to increases in inorganic P (Pi). About 50% to 70% of the TP was bound to CaCO3, and thus this solid phase is critical to P fate in the soils and ecosystem of the Toshan Region, Golestan province.

To study the effects of land use change and climate on micromorphological properties and clay minerals distribution in loess derived soils of Golestan Province, 12 soil profiles in summit geomorphic position consisting of aridic, xeric and udic moisture regimes with cultivated, pasture and forest land uses were studied. The results showed that in aridic moisture regimes weakly developed Entisols, in the xeric soils moisture regime, Inceptisols, Mollisols were dominant, and in udic moisture regime, the most developed Hapludalfs were formed. Micromorphological studies revealed that there was a good positive correlation between soil development and climate index (evapotranspiration ratio). Environmental conditions such as land use and climate consequently affected micromorphological properties such as voids, microstructure, b- fabric, and pedofeatures. In the udic moisture regime, thick clay coatings were observed in speckled b- fabric matrix. However, in the soil with aridic moisture regimes, massive microstructure, and crystallitic b- fabric can be seen. Microscopic observations showed granular microstructure in forest surface horizons has been transformed to massive microstructure in cultivated land use. Results obtained from mineralogical studies showed that there were differences in type and distribution of clay minerals in different climate. Illite was found as the main clay mineral of loess parent materials and soils of the three land uses. The origin of illite, kaolinite and chlorite clay minerals are mainly inheritance while smectite and vermiculite are pedogenic. With increasing precipitation and weathering intensity from xeric zones toward udic zone, illite and chlorite have transformed to smectite and vermiculite. Amount of smectite and vermiculite are mainly affected by climate. It can be concluded that conversion of natural land resources into croplands causes serious soil degradation in loess derived soils in Golestan province.

Organic carbon pools and carbon lability directly affect soil biological، physical and chemical characteristics. Besides، capacity of self-organization of soil is related to the organic carbon pools. Sand size fraction (> 50 µm) organic matter is more labile than silt+clay size fraction organic matter. Assessment of this organic carbon variation can be a suitable index to determine soil quality. The aim of present study was to evaluate the impact of land use change on particle size fractions of organic carbon and carbon pool index. In September 2010، soil samples were collected from the three major land use types including wetlands around the lake، wetlands converted to wheat، and alfalfa cultivations. Soil samples were collected from the 0-30، 30-60 and 60-90-cm depths in each of land use. According to the results of particle size fractionation of organic carbon in 0-30-cm layer، the highest and lowest amounts of sand size fraction organic carbon were obtained in wetland (67. 01 g. C. kg-1soil) and wheat land use (24. 57 g. C. kg-1soil)، respectively. Land use change from wetland to alfalfa and wheat caused a decrease of silt+clay size fraction organic carbon in 0-30-cm by 48. 39 and 45. 14 t. C. h-1، respectively. In the 30-60-cm layer of cultivated land، soil organic carbon storage in silt+clay size particle was more than sand size fraction organic carbon. Results showed that carbon pool index in alfalfa، and wheat land was decreased by 50 and 60% compared to wetland، respectively. And carbon management index in alfalfa and wheat was declined by 44. 90% and 66. 70%، respectively.

The quantity and variability of soil organic carbon (SOC) is one of the most important indices to determine the effect of land use changes on the soil quality. Regarding long-term changes from rangeland to dry farming in the Roin area of North Khorasan, the objectives of this study were to investigate the effect of long-term land use changes on the SOC in different slope faces and use SOC as an index to make a proper decision about the future of land use in this area. 140 soil samples were taken from 0-15 cm soil depth of back slope position of north-, south-, west- and east-facing slopes of rangeland, dry farming, alfalfa dry farming and garden in 7 points. 14 soil samples were taken from irrigated farming, too. The results showed that garden and irrigation farming with averages of 2.03 and 0.78% have the maximum and minimum SOC content. The average of SOC content in rangeland was 1.40% that decreased by land use change to 1.04 and 1.27% in dry farming and alfalfa dry farming, respectively. SOC content in southern slope aspects showed a significant difference compared to other slope aspects. The most SOC content occurred in east aspects. It seems that after long-term land use changes, the SOC content have equilibrated to environmental and land use conditions. The average SOC content in different slope aspects except south one changed from 1.4% in rangeland to 1.11% in dry farming and 1.32% in alfalfa dry farming, which are a suitable value for semiarid regions. In conclusion, to protect land from degradation and considering this fact that dry farming is the main income of the people in the study area, it is recommended to stop dry farming on south aspects and continue on east, north and west aspects with conservation practices.

Paddy soils provide the staple diet for nearly half of the world's population. The formation of the Anthrosols is induced by tilling the wet soil (puddling), flooding and drainage regimes associated with the development of a plow pan and specific redoximorphic features. The aim of this study was to evaluate the effects of long-term rice cultivation on physico-chemical properties and clay mineralogy of soils of three rice farms and compare the results with adjacent virgin lands in Yasouj region. Paddy soils exhibited larger contents of clay, organic carbon, saturation percentage, cation exchangeable capacity, cation exchange activity classes, electrical conductivity and lower content of calcium carbonate equivalent compared to non-paddy soils. This land use showed higher proportions of Feo, Fet and lower content of Fed. No such differences were noticed with the type of clay minerals in both land uses. Paddy soils contained greater amount of smectite, particularly in the surface horizons. Smectite in paddy soils exhibited lower layer charge and higher degree of crystallinity compared to non-paddy soils. Transformation of illite and chlorite to expandable minerals is a possible mechanism for lower amounts of these minerals in paddy soils.

The aim of this study was to assess the effects land use change on soil aggregate stability in marginal lands of Zrebar Lake. Soil samples were collected from the five major land use types including wetland, wetland converted to alfalfa and wheat cultivations, forest and forest converted to vineyard, from the 0-30 and 30-60 cm depth in each land use. Soil aggregate stability was measured on soil samples. The amount of large water stable aggregates in 0-30 cm depth of wetland and forest soils was significantly more than cultivated and vineyard soils. The highest amount of mean weight diameter (MWD) was observed in wetland and forest. Conversion of forest to vineyard caused to 20% decrease in soil large macro aggregates, whereas the of soil microaggregate increased by 11%. Wetland soils converted to alfalfa resulted in 31% decrease of aggregates larger than 2 mm and 15% enrichment of microaggregate in depth of 0-30 cm. Land use change from wetland to wheat cultivation caused a reducation of large macroaggregate by 23% and 16% increase of microaggregates.

Study of soil quality indicators were considered as a useful method in the land use management. Population growth tends to high pressure to nature resource and change of the forest to other land uses and building in Golestan Province. Therefore this study to evaluate the effects of land use change and Villa building on some selected indicators of soil quality in the four land uses forest, pasture, cultivated and the urban, in two North and West geography aspect. Soil samples were taken of 0 to 30 cm depth and analysis of data taken by the method of completely randomized split-plot design with six replications. Soil quality indicators were containing physical, chemical and biological important parameters. Analysis data showed that the amount of organic carbon in both urban and cultivated land uses decreased 70 and 52 percent with respect to forest land use, and also bulk density from 13 to 35%; mean weight diameter from57 to 87%; total nitrogen from 39 to 60%; and microbial respiration 22 to 26% respectively in the urban and pasture land uses. The amount of carbonates increased in both urban and cultivated land uses 80 to 88%; electrical conductivity 42 to 84% with respect to forest and soil reaction in cultivated and pasture13 to 17 with respect to forest. Water infiltration of soil in the forest showed that decrease of soil and water quality because the high pollution in this resourced in the Gorgan the main city province. If this changing will be continued, the health of the ecosystem and especially human life in the cities will be changed.

In this study the effects of land use changes from pasturelands to croplands on soil microbiological and biochemical properties were studied in Kangaver, Dehno and Soltanye regions. Composite soil samples from 0-20 and 20-40 cm depths of pasture and cultivated lands were taken from Kangaver, Dehno and Soltanye regions, and soil microbial respiration, microbial biomass C and N, and urease, alkaline phosphatase, saccharase and arylsulfatase activities were determined. Results showed that land use changes from pasture to arable lands resulted in a significant reduction of microbial respiration in Kangaver (36-64%), Dehno (45-60%) and Soltanye (34%) regions. Similarly, substrate-induced respiration (SIR) decreased between 13 to 37% due to land use changes in all the three regions studied. The microbial biomass C (30-60%), N (18-56%) and C/N ratios (9-17%) in the two soil depths of cultivated sites were lower than those of forest sites in the three regions while metabolic quotient (36-95%), the portion of carbon (4-60%) and nitrogen (3-76%) of microbial biomass in total soil and percentage mineralized C (36-95%) in all the three regions increased due to land use changes. The assay of enzyme activities showed that alkaline phosphatase in both soil depths did not change substantially for each region. In Soltanye region, urease activity decreased (18%) only in the 0-20 cm depth and land use effects were not significant for the other enzymes. Conversion of pastures to agricultural lands in Kangaver region resulted significant decreases in urease (20%), saccharase (33%) and arylsulfatase (11%) activities in the surface layer, but not in the 20-40 cm depth. In Dehno, increased urease and arylsulfatase activities in both soil depths due to land use changes from pastures to cultivated lands were significant, but increased saccharase activity was significant only in the 0-20 cm depth. Overall, it is concluded that a change in land use from pastures to croplands with widespread agricultural practices, specifically long-term intensive tillage activities, may lead to enhanced availability of oxygen and substrate to microorganisms, which could result in increased microbial activity including soil respiration.