جستجوی مقالات مرتبط با کلیدواژه « r software » در نشریات گروه « اکولوژی »

Identifying environmental factors affecting the habitat preference of medicinal species is a fundamental and valuable action for cultivation and domestication and reducing the pressure on natural resources is a fundamental and valuable action. This study was performed with the purpose of investigate the most important ecological factors affecting the habitat of Stachys lavandulifolia Vahl in eastern Alamut rangelands located in Qazvin province. For this purpose, the maximum entropy in MaxEnt software was used. Species presence points were recorded in field operations. Also, in the habitats of this species, soil samples were collected by random-systematic method (4 transects and 72 soil samples). soil variables were measured in the laboratory. Geostatistical methods were used to make maps of soil variables. Finally, 19 environmental variables maps were entered into MAXENT software including soil, climatic and physiographic. Based on the results, the accuracy of the habitat suitability map was 95%, Also, the most influential environmental factors on the habitat suitability of this species are soil magnesium (0.3-1.3 mM), organic matter, average annual rainfall (more than 400 mm), average annual temperature, altitude (up to about 3100 m). The optimal habitat of this species has been in soils with heavy texture, low electrical conductivity and neutral acidity (7.5) in this region. Also, increasing soil potassium has a positive effect, and increasing the soil sand and lime have a negative effect on the establishment of this species. The results showed that the favorable areas for the growth of the studied species is 5599.67 hectares, which covers 7.93% of the total study area.

Most of the water needs in arid and semi-arid regions is supplied through groundwater, so it is important to study the quantitative and qualitative changes of these waters and the factors affecting them. Land use changes can cause changes in groundwater quality. Here, land use changes in the period 2003 to 2020 in Damghan watershed were studied using Landsat 8, 7 and 5 satellite images, eCognition software and GIS. 1760 wells data in Semnan province were used for intermediation and accurate preparation of groundwater quality maps and extraction of geostatistical maps. Also, the information of 58 deep wells inside the watershed was used to analyze and study the groundwater quality changes. The results showed that the area of rangelands, forests and agricultural lands decreased and the area of gardens, urban areas, barren lands and surface water resources (due to the construction of the dam) increased. During this period, groundwater quality changes included Cl increased by 1.01 mEq, SO₄-2, decreased by 0.34 mEq, HCO3- increased by 0.46 mEq, Mg increased by 0.32 mEq, Ca decreased by 2.25 mEq, Na increased 3.58 mEq, electrical conductivity increased  by 44.81 μmohs / cm, Total dissolved solids increased by103.88 mg / l and pH increased by 0.09. These changes were evaluated with R software and the results showed that changes in groundwater quality are related to land use changes.

Astracantha gossypina (Fisch.) is one of the most important rangeland plants in the northeastern region of Iran and has a great role in soil conservation and the economy of ranchers. unreasonable uses and management of desire plant species usually led to species loss and the replacement of endemic and specialist species by invasive endemic or exotic species. This study was conducted to determine the potential habitat of As. gossypina species in the rangelands of Khorasan Razavi and North Khorasan provinces using MaxEnt model. In this purpose, 757 species presence points in 17 different areas recorded by GPSMap 60CSx in field sampling. Environmental variables including 19 bioclimatic layers, 3 layers of slope, direction and altitude, geology and soil data layers (texture, soil potential, hydrological groups) as predictor variables analyzed for correlation and corelated variables were removed. Analysis of prediction layers and presence points performed using Maxent 3.3 software. According to the results the area under the curve index (AUC = 0.98) showed, the maximum entropy model had good accuracy and efficiency in detecting the factors affecting the geographical distribution of the species. Based on the jackknife test results, environmental factors included DEM, SOILLAND, BIO1, geology, BIO17, BIO19 and BIO15 respectively had the most role in determining the habitat suitability of the species. Finally, the study area was divided into four suitability classes and more than 218 thousand hectares, equivalent to 1.52% had moderate to good potential for the growth and harvesting of the species.

Forecasting river flow in flood conditions is an essential part of river engineering studies that, if accurately estimated, can greatly contribute to the effectiveness of management programs and reduce financial and human losses. Using appropriate models and increasing the accuracy of these models will lead to improvements in the accuracy of prediction results. One of the available solutions to increase the accuracy of existing and valid rainfall-runoff models is to build a combined model with the help of preferably intelligent methods link to these models. In the present study, the combination of WEAP 21 hydrological model with black box models based on ANN and GMDH methods is used to increase the accuracy of WEAP model and then the created model was used to simulate the flood of part of Halilrud river in Kerman province. Precipitation, flow, humidity, wind and temperature data were entered into the WEAP model for the existing record minus the last two years. After calibrating and validating the model, the last two years were forecasted. The results showed that the WEAP-ANN (R2 = 0.78) model was able to estimate the runoff with higher accuracy compared to the WEAP-GMDH (R2 = 0.59) and WEAP (R2 = 0.14) models in the basin.

Adequate knowledge about suitable habitats for wildlife is essential to prevent habitat destruction and extinction of species and for their conservation and management. The Eurasian lynx is one of the mostly distributed cats in Asia. In this study, we applied an ensemble habitat suitability modeling approach, using ten predictor variables to model Eurasian Lynx’s habitat suitability in Saveh Zarandieh Kharaghan Area, Markazi Province. Due to the high value of the area under the curve index (AUC > 0.9) for Maximum Entropy, Random Forest, Boosted Regression Tree, and Generalized Linear Model, these models were used to produce the final distribution model of the target species. Based on the ensemble model, 53.22% of Saveh Zarandieh Kharaghan Area were identified as suitable for this species. According to the results, distance to residential areas, distance to river and availability of prey were identified as the most important variables, affecting the distribution of Eurasian Lynx. This study indicated that the Eurasian Lynx habitats need more protection.

The distribution pattern of plants is an important characteristic of plant communities, being of critical importance in ecological studies and sampling plans. This study was designed to investigate the efficiency of different shapes and sizes of quadrants to delineate the spatial patterns of Astragalus verus Olivier by using dispersion indices. At Mayan Rangeland (Khorasan Razavi), a digital camera and R software were used to locate the coordinates of individual plants and to demarcate the boundary of the study area. We used plots of different shapes, square, wide rectangular and long rectangular, with the areas of 1, 2, 4, and 8 m2, for a total of 12 combinations of shapes and sizes. The distribution indices used included Green, Lioyd, Morisita, and the Standardized Index of Morisita. The results of the study showed that the standard Morisita's index and Morisita’s index had the same distribution patterns in all shapes and sizes of plots. These two indices were not affected by plot size and shape in displaying the distribution pattern. The current study alsoshowed that Morisita’s and standard Morisita’s indices were more precise in comporison with Green and Lioyd indeces.

The estimation of water demand is one of the most important factors in managing water resources and the necessities of any irrigation and drainage plan. Estimation of the potential of the reference plant (ET) should be estimated to meet the water requirement. The level of utilization of surface water and underground resources in each region is directly related to the water needed to irrigate agricultural products in that area. In this study, which was conducted in the watershed of Yazd-Ardakan plain, OPTIWAT software was used to calculate the need for water. Irrigation and horticultural products of Yazd-Ardakan plain are about 54,000 ha. The water required for irrigation of these three products is 917.6 × 106 m3, which accounts for approximately 70 % of the water needed for irrigation of the total crops in the study area. The amount of water need for irrigation of crops and orchards of Yazd-Ardakan plain was achieved with current crop and current yield (45%) equal to 831.7 × 106 m3. The amount of water required for these products for drip irrigation and efficiency of 60, 75 and 90 percent were calculated 594 × 106 m3, 464.7 × 106 m3, and 382 × 106 m3, respectively. Therefore, it can be concluded that by changing the pattern of cultivation and increasing the irrigation rate, the use of the aquifer in the plain can be reduced and added to the amount of underground storage.

Water is a scarce resource in the Middle East region and climate change is expected to exacerbate this situation. Developing countries are vulnerable to these changes, primarily due to their limited adaptive capacities in dealing with extreme events. Therefore, investigation of this phenomenon will be very crucial in such areas. In the past decades, water shortage in Yazd province which is located in arid regions of Iran has resulted in transferring the water from Isfahan. But recently, due to increasing in water demand, inadequacy of this project clearly has felt. Evapotranspiration and agricultural water requirements are two crucial issues of this area which affected by climate change. Thus, considering climate change projections and future agricultural water requirements is necessary to determine water stress risks in the study area, Hence, this study aims to answer the following research questions:
Currently, how much irrigation water do we need in the Yazd-Ardakan region?
How does future climate change impact future irrigation requirements?
How does future climate change influence sustainability of the agricultural water consumption? The data used in this analysis represented into two time periods, including (i) present (values for the period 1971–2005), and (ii) future, called year 2070 (values for the period 2021–2070). To evaluate future climate changes, daily climate data from Yazd Synoptic station for 1971-2005 period have been used. Data, including precipitation, maximum and minimum temperatures and sunshine hours. To investigate the climate changes of Yazd-Ardakan plain in the future period of 2021-2070, RCP 4.5 scenario has been used through SDSM 4.2.9 software. The effect of climate change on reference evapotranspiration and agricultural water needs were estimated. Crop evapotranspiration and irrigation requirements for two periods, were estimated following the standard procedure described in the FAO Irrigation and Drainage Paper 56 (UN-FAO, 2007) and CROPWAT software. Two indices considered to evaluate the sustainability of the agricultural water consumption in the study area. These indices including the ratio of evapotranspiration to the precipitation (EPR) and the ratio of maximum agricultural water deficit to the amount of agricultural water need as deficit index (MD). These indices estimated under present and future climatic conditions. To evaluate the amount of water used for main agricultural products, questionnaires were completed in the area. The results of statistical validation of the predicted values, showed no significant differences between historical and predicted values of precipitation, maximum and minimum temperatures and sunshine. Therefore, suitability of LARS-WG model to simulate climatic data of the study area is confirmed. Investigation of the precipitation in the Yazd station showed that in spring season, precipitation will be declining and in autumn will be increasing. In other words, the distribution of precipitation in the future will have significant changes and as winter precipitation decreases the spring precipitation will have increasing trend. Results showed that monthly minimum and maximum temperature will increase in almost all months. Results of estimating agricultural water requirements showed that due to higher temperature, reference evapotranspiration, crop evapotranspiration and irrigation requirements will be increased up to 4% under climate change conditions. The EPR and MD indexes will increase by 24% and 13% respectively. The results revealed the imbalance between agricultural water use and the precipitation in the study area. In the other hand, results of the questionnaires showed that, the water used in irrigated agricultural areas is not in accordance with the requirements of products and therefore leads to water stress and, consequently, yield reduction of products. Therefore, in these conditions, appropriate management strategies and planning should be implemented to ensure the sustainability of water resources inthe Yazd-Ardakan plain. This work focused on the climate change impact on cultivated area in the Yazd-Ardakan plain considering the possible alterations of crop evapotranspiration and irrigation requirements. According to this study by increasing in maximum temperature in the future, water needs of agricultural section will grow significantly. Therefore, planners and authorities should consider this fact for the future water resources allocation and strategies.