جستجوی مقالات مرتبط با کلیدواژه "کاربری اراضی" در نشریات گروه "فیزیک"

The process of converting rainfall into runoff in a region is complex and is affected by many different factors. There is a close relation between land use and erosion. Soil erosion involves the separation and transport of soil particles by runoff. Therefore, runoff production is an important process that is related to soil loss and environmental effects of agricultural operations due to its involvement in nutrient loss. As a result, it is necessary to study the amount of runoff produced as one of the main processes of soil erosion.Rainfall simulator allow repeated measurements in different fields to determine the factors affecting runoff and erosion. Despite the challenges, the use of simulators is common worldwide due to its many benefits in various fields of soil erosion and sediment production. In Iran this method was used in many researches with different targets. Kavian et al (2019) simulated the effect of herbaceous residues on runoff production, Golshan et al (2018) using the rainfall simulator compared the SWAT model and Regression model. In other countries other research can be mentioned the researches of Biddoccu et al (2016), Zhang et al (2018a) and Wang et al (2018). For this purpose, in the present study, which was carried out in one of the forest areas in the east of Ardabil province, called Fandoghlu forest area, the amount of runoff and sediment from the rainfall was measured and compared in different land uses using a rainfall simulator machine.  In this study, the relationship between land use and runoff and sediment production was investigated in the Fandoghlu forest with 4378 ha area, using a rainfall simulator machine. The used rainfall simulator has 1 m2 area with the ability to adjust the intensity and duration of rainfall. The rainfall simulator machine was installed at 104 points with 21.867 mm / hr. rainfall intensity during the 15 mints in the three different land use consisting of forest, rang and agriculture. Soil sampling was performed from each land use from a depth of 0-20 cm. 34 samples were taken for forest use and 35 samples of intact and untouched soil were collected for each of the agricultural and rangeland uses, and a total of 104 soil samples were collected. The location of the points was recorded via the Global Positioning System (GPS).Using laboratory soil samples, parameters of initial soil moisture, bulk density, organic carbon, soil particle size distribution, true bulk density, total porosity, saturated hydraulic conductivity, saturated moisture, field capacity, permanent and susceptible wilting point usage and weight average of aggregate diameter were measured. The mean values of soil bulk density in forest, rangeland and agricultural uses were 0.881, 1.067 and 1.355 g / cm3, respectively. In rangeland use, the increase in specific gravity of the soil relative to the forest can be attributed to the kicking of livestock due to uncontrolled grazing (Ferreras et al., 2006). The mean values of true specific gravity and total soil porosity in forest were obtained. The rangeland and agricultural uses are equal to 1.905, 2.018 and 2.162, and 53.60, 46.46, 37.09 respectively. The reason for the reduction of true specific gravity in forest use is because the organic part of the soil inherently has a small true specific gravity. As by increasing the share of soil organic matter, the actual specific gravity decreases (Zhang et al., 2018b). In forest, rangeland and agricultural uses, the amount of runoff was equal to 868.5, 925 and 1425 ml/m2. Also, the amount of sediment concentration in each of the land uses was 1.937, 8.889 and 44.222, respectively. The results showed that vegetation, slope, soil characteristics and land use change have a significant effect on runoff and sediment components in the study area. Field studies and direct statistics of harvesting are very important in watershed management and estimating runoff and sediment production. The rainfall simulator used in this research can be transported to difficult areas that can provide integrated information from the watershed. The distribution of soil particle size on runoff and sediment components showed that there is a significant difference between different amounts of silt, clay and sand in each of the land uses and runoff volume. So that the amount of clay and silt from the forest to the pasture and arable land is reduced and the amount of sand is increased. Silty soils have low permeability due to low adhesion and porosity and as a result, more runoff volume. Therefore, land use management in this area can play a very important role in reducing runoff and fertile soil.

Considering the ever-increasing changes in land uses and the need for managers and experts to know how changes have taken place in policy and options for solving the existing problems. Detection of changes to determine the trend over time seems necessary. On the other hand, modeling future changes is important for understanding the quality of future changes. Therefore, the full recognition of land use, its past changes and the prediction of future changes plays an important role in the sustainable management of resources. Modeling land use processes is an important tool in optimizing land use and land use planning. One of the models used to predict landslide changes is the model of artificial neural networks and Markov chain analysis. The features of the artificial neural network include the ability to learn and generalize and process information in parallel. Considering the goal of urban development during the years 2000 to 2012, satellite imagery of the years 2000 and 2012 in June has been used. After the preparation of satellite imagery and pre-processing of images, the landuse in the study area for the years 2000 and 2012 has been prepared. Then useing the LCM model landuse change patterns of changes were analyzed. Then, based on the Markov chain model, the potential for changing each use to residential use is measured. This means that each pixel was capable of showing change the image from one land use to another. Then, based on the major changes in the region in the survey, three sub-models of shifting change were identified as transforming pastures into habitat areas, converting agricultural production into settlements, and transforming dryland farming into settlements. After calculating the potential for the transfer of any land use to a settlement using descriptive data, a plan for predicting the use of land for 2025 and 2040 was then provided. Given that the purpose of the present study was to assess the development of residential areas, the extent of changes in these areas were assessed during the years 2000 to 2012. The results indicate that the residential areas increased from 8.3 square kilometers in 2000 to 12.6 square kilometers in 2012, according to the land use map, and mostly changes in the urban area of Songhor area have been made. The results of the assessment of changes indicate that the land use change from irrigated agricultural to residential use during the 12 year period was 1.9 km2, which for dryland agriculture it was 0.6 kilometers, Also 1.8 km2 of rangelands has become residential. The results of this study indicate that the irrigated agricultural lands of the city of Sangar, especially the southern regions and pastures near the urban area, have had most changes. Among the changes in other uses, about 11.5 km2 of the rangeland has been converted into rainfed farming, and about 12.3 km2 of land has also become rangelands and also, about 4.7 km2 of irrigated agricultural has become arable land or Bayer land and about 1.5 km2 of rangelands has become irrigated agricultural land. The growing population has led to an increase in the number of habitat areas and, as a result, agricultural lands and pastures have undergone changes. The growing trend of settlement development varies from region to region, and in the urban area of Songhor more are moving toward the southern regions of the urban area. Considering the geomorphologic status of the study area, a large part of the range is covered by rangelands. Irrigated agricultural lands which have a significant share, are located on the outskirts of the city of Songhor, which are undergoing further changes. According to the main objective of the research, based on descriptive data such as distance from communication, distance from urban boundaries, elevation and slope, the amount of development of residential areas for 2025 and 2040 is also projected. The results of the forecast indicate that in the case of the growing trend, the development of the settlements will reach about 18.2 km2 in 2025, and will reach 24.2 km2 in 2040, due to the high potential of the southern regions of the city of Songhor, the highest rate of development of settlements will be towards these areas. The results indicate that the increasing number of settlements in the city of Songhor will lead to the degradation of high-quality agricultural lands and pastures. If the trend is continued, the irrigated agricultural around of the city of Songhor will reach the lowest level by 2040. Also most of the pastures will also be degraded. Hence, it is necessary to identify areas suitable for the development of a settlement before increasing of rate the destruction occur, so that less prone areas for agriculture and pastures can be degraded.

Soil organic carbon (SOC) plays an important role in the global carbon cycle, and study of dynamics concerns the recent development of nuclear industry. Physical fractionation, radiocarbon dating and FTIR spectrometry methods are among the most important methods for determining carbon dynamics and thereby the magnitude of soil carbon response to land uses. In this study, methodologies of carbon dating and FTIR spectrometry were used to characterize impacts of land use on mean residence times and quality (functional groups) of soil organic carbon based on physical fractionation methods in three land uses including deciduous, coniferous forests and rangelands. The FTIR spectra showed that higher aromatic carbon proportion and its lower decay rate of organic matter in coniferous forest have caused more SOC content. Free and intra-aggregates particulate organic matters (POM) have been recognized as criterion indices for deciduous forest use. Compared to the other land uses, the higher aliphatic to aromatic carbon ratios were obtained in litter and intra-aggregates POM of deciduous forest. The highest14C age in both forest land uses (deciduous and coniferous) was measured in the Bhorizon, while in the rangeland occurred at the A horizon. Aromatic functional groups as well as 14C age are suitable parameters for homification processes.