جستجوی مقالات مرتبط با کلیدواژه "پوشش اراضی" در نشریات گروه "آبخیزداری، بیابان، محیط زیست، مرتع"

Carbon storage in terrestrial ecosystems is an important part of global carbon storage and plays a vital role in mitigating climate change. The purpose of this research is to investigate the effects of different types of land uses/land covers (dense rangelands, semi-dense rangelands, low density rangelands, barren lands and agricultural lands) on the amount of soil carbon and plant biomass sequestration as an important ecosystem service in Sefiddasht watershed in in Chaharmahal va Bakhtiari province. Sampling of soil and vegetation was done randomly and systematically. For this purpose, 60 plots of 4 square meters were used for collecting soil, plant material and litter. Plant biomass was sampled by direct measurement method. Soil samples were also collected from the depth of 0-30 cm and 20 samples in each area. The results showed that there is a significant difference between the investigated regions in terms of total carbon storage. The total carbon storage from the highest to the lowest in order includes dense rangelands (46.42 tons/ha), semi-dense rangelands (38.49 tons/ha), agricultural lands (31.62 tons/ha), low-density rangelands (26.12 tons) per hectare) and barren lands (17.21 tons per hectare). The economic value of the total carbon storage per hectare of the examined uses, including dense rangelands, semi-dense rangelands, agricultural lands, low-dense rangelands, and barren lands, was determined to be $5446, $4516, $3710, $3065, and $2019, respectively. Therefore, it can be concluded that the implementation of appropriate policies to prevent or minimize the conversion of land uses with a higher carbon storage capacity to land uses with a lower carbon storage capacity is of particular importance.

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.

One of the ecological crises is the degradation of Nebka's ecosystems that threatens environmental stability and causes many regional and trans-regional impacts, such as increasing the risk of wind erosion. The aim of this study was to investigate the trend of spatial and temporal changes in future land cover with Nebka and accumulated erosive sediments around the phanerophyte species Salvadora persica L. and Alhaji camelorum L. in the Persian Gulf and Oman sea. Thus, Markov chain and satellite images were used to simulate the existing land uses, and trend of temporal and spatial changes. Land cover maps were prepared for the years 2001, 2011, and 2021, using Landsat satellite data and applying maximum likelihood supervised classification method.  After model evaluation procedures, the land cover maps for 2030 and 2040 were predicted using both Markov chain and automatic cell model. Results of land cover changes in 2001, 2011 and 2021 showed that the areas of Nebka have decreased by 1047.9 ha. Predictive maps for 2031 and 2041 with an overall accuracy of 91.4% and kappa coefficient of 0.88%, have high accuracy. The sediment levels of nebka will decrease from 8.67% in 2021 to 4.26% in 2031 and 2.09% in 2041, respectively. The decrease in the area of nebka in the past and predicting the downward trend of changes in nebka land in the future showed that the natural barriers to the movement of suspended sediment were destroyed and reduced.

Sabzkouh protected area, with the variety of natural ecosystems and landscapes, is very rich from the point of diversity in climate, topography, habitats and wildlife that is located in central Zagros. Evidences show that its ecosystems such as other Iranian semiarid natural ecosystems, undergone changes in their vegetation structure over the past years. Obtaining multi-spectral and multi-temporal data via Satellite Remote Sensing (RS) with Geographical Information System (GIS) would be able to identify type, quantity and location of land use/land cover changes. The aim of present study is to detect land cover changes in recent three decades by RS in Sabzkouh region. Therefore, the images of Landsat MSS (1975) and Landsat ETM (2003), Digital Elevation Model (DEM) and Transformed Soil Adjusted Vegetation Index (TSAVI1) were used as ancillary data to obtain land cover maps. These maps were produced by applying supervised maximum likelihood classifier and included five classes namely: agriculture, herbaceous rangeland, shrub and brush rangeland, barren land and forest. To detect changes, Post Classification Comparison approach was used. The net change calculations indicated that were added to shrub and brush rangelands and forest. On the other hand, herbaceous rangeland and barren land have been converted to the other classes.

Natural resource management is requires update and accurate information. Thus, monitor changes would have help to optimal management of natural resources and accurate recognition of resource changes. In this study, using digital data MSS (1977), TM (1988), ETM (2002) and OLI (2014) studied hamoun wetlands and land cover Its surrounding changes over a period of 38 years (2014-1977) using the comparative after classification method (post classification) and was predicted land cover map for 2025. Land cover mapping was conducted after pre-processing and processing satellite images, creation of training samples and assessing maps accurate was done by coefficient kappa and overall accuracy. Results of wetland changes and its surrounding land cover showed that wetland changes Has been negative in the first and second periods but, changes has been positive and wetland moved forward to revive in the third period. Generally, during the whole period the trend of wetland changes has been destruction. Land cover changes, canebrake, Barren lands classes and Saline Soils reduced and only will increase vegetation class. This study also can be used as a pattern for other studies to predict ecosystem changes in arid regions should be used.

Sabzkouh protected area is located in central Zagros. This area, with a variety of natural ecosystems and landscapes, is very rich from the point of diversity of climate, topography, habitats and wildlife. Its ecosystems, like other semi-arid ecosystems of Iran, have undergone changes in their structure in recent years. Nowadays, Markov chain models are widely used in ecological studies to predict these changes quantitatively. For this purpose, satellite images and geographic information system were used to predict the future condition of the region using CA-Markov model. Finally, the land cover map of the region for the next fifteen years (2003-2018) was predicted by CA-Markov model. According to the prediction map, an increase in the area of agricultural lands, shrub/brush rangelands and forests of the region was observed, while the area of forbs rangelands and bare lands decreased. The results of these predictions provide a valuable tool to the managers and policy makers of natural resources and environment.

During the time، land cover and as a result land use patterns go through fundamental changes and human factors can have the most important role in this process. Knowing these changes could be of great help to the future management of this region. According to this، the main purpose of this study is to monitor the land use-cover changes in the Hamedan province area during the three recent decades. Therefore، in order to discover the changes created in the study area، images of TM satellite sensor (1989)، ETM satellite sensor (2000) and LISS3 detector of IRS (2008) were processed. Then after performing needed preprocesses، the enhancements were performed and then by using supervised classification with Maximum likelihood method، land-use cover objective maps were prepared. These maps were compared with the Post classification comparison method in form of a couple in the first period between1989-2000 and the second period between 2008-2009. The results shows that the area of the land use-cover classes، rangelands and plain lands were decreased during the three decades and on the other hand water area، arid and residential-industrial area were increasing during this period. Woodland areas decreased during the first period and increased in the second period. However، farmlands’ area increased during the first period and decreased during the second one.