Climate changes are the main motivation for destruction of ecosystems; in fact the effects of these changes on biodiversity and ecosystems are considered as the most challenging cases in present century. Therefore, since the lakes are the most important services and functions of ecosystems, the effect of climate change on water level fluctuations of Tashk and Bakhtegan Lakes was analyzed as a natural ecosystem in this essay. For this purpose, the data related to six parameters of temperature, precipitation, evaporation, sunshine hours and snowy days were selected during 25-year statistical period , and Mann-Kendall test was used to determine the trend of changes in each time series. Inflow system of the lake, the volume of evaporation and area of water were simulated and fluctuation of lake was also assessed by using dynamic analysis method and to achieve to lake level and analysis of its fluctuations in period under study, the satellite images of Landsat 7 and ETM 5-1 were used in two high waters of April 1987 and April 2010. Results indicate that the lake level has been dropped 6 meters in 2010 compared to the similar period of 1986; in wet years that the rainfall is more than 618/5 mm, high water level is the lake conditions in all months of the year; unlike in most years when rainfall occurred under average of 365.4 mm, lake is faced with dry condition that is mainly due to the reduce of icemaker area, rainfall reduction, increase in evaporation and temperature. These conditions show the extent to which the lake is fragile and affected by climatic conditions that the most obvious evidence of it is decline of genetic storages such as Tashk and Bakhtegan lakes and subsequently instability of the region and reducing of services and ecosystems' functions.

Relationship between vegetation ...; [Zaitchik BF, et al.; 2007] Climate and vegetation in the ...; Aims & Backgrounds One of the most important environmental challenges facing the west of iran in recent years is the dust phenomenon, that today has become one of the most important problems in arid and semi-arid areas. In this research, dust sources identified by Jalali and Davoudi were used to study the effect of surface features on the creation of effective dust sources in the west of the country. The study area is about 1,200,000 square kilometers located in the east of middle east covering Iraq and parts of Iran, Turkey, Syria, Jordan, Saudi Arabia, and Kuwait. The aim of this research is to evaluate geomorphic characteristics and surface sediments, land cover, and wind erosion potential of dust sources in the study area. Methodology For this purpose, according to the Bullard classification, firstly, the layers of geomorphic classes, soil, and land cover were prepared and classified and according to the relative importance of the classes in the release of dust, they were classified into 3 groups, including low, medium and high. Subsequently, using 40 data stations, wind erosion potential (EW) was calculated and zoned by Kriging method. Findings Sand dunes in the geomorphic classes with a dust emission ratio of 3/35 unit had the greatest effect on the creation of dust sources. There was not much compatibility between different classes of land cover and type of soil with dust sources, but there was compatibility between the wind erosion potential and dust sources and the most dust sources were created in areas with high wind erosion potential. Conclusion Geomorphic characteristics have the most important role among the controllers of dust emissions.

Groundwater monitoring of an aquifer performed by an observation well network plays an important role in the management of groundwater resources in which, if the number of wells is small, the calculation of groundwater level is less accurate, and if the number of observation wells is high, the cost of drilling and maintenance of wells and the cost of measurement will increase. This study aimed to identify observation wells' number and optimal density in an aquifer using classical statistics and geostatistical techniques. The Sarfiroozabad aquifer with 45 observation wells was selected as a case study, in which the effective range of each observation well was determined through examination of the coefficients of water table variations in parallel profiles perpendicular to the longitudinal axis of the aquifer and examining geostatistical items including variograms related to water table variations by specifying the optimal number of observation wells. Classical statistics and geostatistics showed the same effective range for wells in the northern aquifer. According to the observations, to obtain the optimal number and density of observation wells, at least 6 observation wells shall be added to the northern aquifer, while only one well should be added to the southernmost part of the southern aquifer and six wells should be eliminated that reduces the cost of sampling. Also, by adding essential wells, the accuracy of groundwater estimation increases which helps better manage groundwater resources.