جستجوی مقالات مرتبط با کلیدواژه « land cover » در نشریات گروه « آبخیزداری، بیابان، محیط زیست، مرتع »

Urbanization which has been considered the main contributor to climatic problems in cities, not only changed the physical environment in cities, but also has affect the characteristics of local climate zone. This study aims to investigate the relationship between surface properties of Local Climate Zones (LCZ) extracted from satellite resolution images and Land Surface Temperatures (LST) in a semi-arid region. By employing the LCZ approach, the study seeks to understand how LCZs influence LSTs in this specific environmental context. This study consisted of four main steps: Image preprocessing, LST retrieval, LCZ map preparation and spatial analysis. In this way, the LCZ scheme was used to classify the study area based on two sets of built-up types and land-cover types. Google Earth was used to specify training areas under study and to define different LCZ types. The Split Window Algorithm (SWA) was used to retrieve LST from Landsat-8 TIRS. The results showed that the built type and the land-cover type behave like two independent sets of patterns in the study area. The build type set fluctuated in a higher LST range than the cover land set (forest, farmlands and bushes). By shedding light on the relationship between the surface properties of LCZs and LSTs, the study provides valuable insights into the factors influencing thermal dynamics in semi-arid environments. Armed with this knowledge, urban planners can develop more informed strategies and interventions aimed at mitigating heat-related challenges and improving overall urban livability.

The aim of this study was to evaluate the impact of forest on erosion and runoff variables and compare it with rangeland and agricultural in part of Mereg watershed located in Kermanshah province. At first, three forest mass were identified and divided into three density categories (low, medium and Many), then Soil and hydrological parameters were measured in each forest density area and also in both agricultural and rangeland using a rainfall simulator. Rainfall was run at a rate of 83 mm / h for 24 minutes with 18 repetitions. The hydrological results in forest mass showed that the mass 2 (with medium density) produced 32.6 percent more runoff than the first stand and 33.5 percent more than the third Mass, which could be due to the soil repellency in forest, but no statistically significant difference was observed in other variables. Also, the comparison of the hydrological variables in three land uses (forest, rangeland and agriculture) showed that although the runoff from forest was 61.5 percent more than rangeland and 54.2 percent more than agricultural, however, the amount of sediment output from these plots was 62 percent less than rangeland and 91percent less than agricultural. This decrease in rangeland compared to agriculture was 76.26 percent.

Desertification is a serious ecological, environmental, and socio-economic threat to the world, and there is a pressing need to develop a reasonable and reproducible method to assess it at different scales. Therefore, in the present paper, changes in cover and desertification of Kashan, Aran and Bidgol regions in the north of Isfahan were developed using Landsat ETM and OLI data. According to this research, NDVI (Normalized Difference Vegetation Index), TGSI (Topsoil Grain Size Index), and land surface albedo were selected as indicators for representing land surface conditions from vegetation biomass, landscape pattern, and reflection. A Decision Tree (DT) approach was used to assess the land cover change and desertification of the study area from 1995-2020. Temporal changes indicated an increase in NDVI, TGSI, and albedo trends during this period. The spatial distribution of NDVI showed that values greater than 0.5 were observed only in a small part of the west and southwest, while high values of TGSI and albedo occupied a large area of the study area. There was also a correlation between the above three indicators at 95% (R = 0.99). The results also showed that desertification is increasing in the study area, so that the intensity of desertification from 1995 to 2020 in classes without desertification was low, medium, and severe. The high desertification class decreased by 1420.75 square kilometers (13.54%), while severe desertification increased by approximately 1388.8 square kilometers (13.23%). The highest NDVI values were found in the non-desert area and the low desertification class, while the highest TGSI and albedo values were found in the high and severe desertification classes.

Soil erosion is one of the major environmental problems worldwide. Morphometric and landcover  analysis provides a platform for quick and efficient watershed management In the present study, morphometric parameters have been coupled with land cover classes to assess soil erosion susceptibility of sub-watersheds of  lavasanat watershed. The data used in this study included Advanced Space borne Thermal Emission and Reflection Radiometer (ASTER) data, with 30 m spatial resolution for drainage generation; and Landsat8  (OLI/TIRS) data with 30 m spatial resolution (band 1 to 11 expect band 3) to generate land cover information of the study area. we estimated 15 morphometric parameters using ASTER DEM  with Arc Hydro package. At first, for proper determination of flow direction and flow accumulation, DEM sinks identified and filled. We used a critical threshold 100 for defining streams. Strahler’s scheme for stream ordering has been used.The sub-watershed erosion prioritization by using morphometric parameters and COPRAS method showed that sub-watersheds 12, 2 and 1 have the highest sensitivity to erosion with the lowest scores (0.098, 0.095, 0.088). In order to prioritize sub-watersheds based on surface coverage, the percentage of each surface coverage class in each sub-watershed was calculated. Based on the results of sub-watershed prioritization based on surface coverage, sub-watersheds3, 2 and 1 with the lowest scores (0.234, 0.221, and 0.164) have the most sensitivity to soil erosion and must be taken up for implementation of soil and water conservation measures.