نشریه مدیریت اکوسیستم های طبیعی
پیاپی 1 (زمستان 1400)

Rangeland management method is one of the important aspects of rangeland management activities. In livestock grazing management, according to the grazing system and rangeland management method, it is possible to promote the rangeland condition with low cost and optimal management. Therefore, in this study, for the optimal management of Lar Absar rangeland in Mazandaran province, the grazing system and rangeland management method were considered. In this research, the degree of rangeland condition in each vegetation type using the four-factor method and rangeland trend was also determined by grazing system and rangeland method. The results showed that all vegetation types of Lar Absar rangeland have a moderate and good condition and their tendency is constant and in some types is positive. In vegetation type of (Festuca ovina- Onobrychis cornuta) and (Bromus tomentellus- Hordeum bulbosum). Due to the good condition and positive tendency, range management method of Balanced is suggested and in it, efforts should be made to maintain good rangeland conditions. Premature grazing is prevented by segmenting these two vegetation types and implementing a grazing rotation program and due to the large number of livestock per unit area, forage loss is prevented. As a result, forage grazing will be done uniformly and when the livestock is moved to another plot, the plants in the first plot are given the opportunity to continue growing.In other types of Lar Absar rangeland, the rangeland management method will be natural, so that by improving the plant composition in a natural method, plants will be given the opportunity to regenerate and replacement and while giving sufficient opportunity to the plants, the maximum use of forage is done. Therefore, before any intervention in rangeland ecosystems, the rangeland management method should be selected based on the condition and trend, and as far as possible improved rangeland vegetation naturally and by choosing the appropriate grazing system and avoided other costly methods. It seems that selection of appropriate rangeland management methods and grazing systems in vegetation types can be a useful and effective step for rangelands.

Despite the low rainfall, which is amplified by disordered time distribution, a large amount of rainfall in Hormozgan province is wasted as runoff due to highly intensive and shower rains. On the other hand, an important part of the reserves of surface water resources such as rivers and dam lakes are losing due to high evaporation potential. Determining susceptible areas for construction of underground storages in plains covered by quaternary deposits is a good way to develop water resources in these conditions. Determination of the proper areas for this purpose depends on various ecological and anthropogenic criteria. Based on the research literature, socio-economic factors (water need and access), underground dam axis (depth, length and lithology), underground dam reservoir (permeability, slope and surface of the reservoir) and water (quantity and quality of water) named as the most important effective criteria. In this research, the Analytic Hierarchy Process (AHP) used to weigh the main and sub-criteria affecting the determination of the potential of underground dam construction in the study area. Sub-criteria of water quantity with a weight of 0.833, water demand with a weight of 0.8 and axis depth and reservoir permeability with a weight of 0.637 are the most important indicators of the research. The information layers of each criterion were fuzzy. Then, using satellite data and field control 14 axes (options) were distinguished and selected. Then by compilation of information layers in the ArcGIS environment, indices were calculated and ranked for each axis. The results showed that options 14 in the northwest of the region has requirements and the capability to build an underground dam. The system sensitivity in the rankings was tested by changing the ±5 and ±10 percent in weight of the highest-grade criteria. The selected option has suitable permeability and the depth of its axis is 9-12 meters. In addition, it is located in sub-basin B1 with an average annual rainfall of 207.1 mm and a rainfall volume of 1.9 million cubic meters. These features are among the suitable potentials for the construction of an underground dam in the region. So the results showed that the model has the sufficient stability in the axes prioritization relative to each other.

Environmental gradients and land deformation cause gradual changes in non-living factors that affect the density andEnvironmental gradients and land deformation cause gradual changes in non-living factors that affect the density and distribution of species and are important for the spatial distribution of plant diversity. Understanding the ecological processes associated with altitude gradients leads to potential climatic changes in communities. To study the diversity and species richness in the rangeland, two eastern and western slopes were selected in three altitudes of 2000-2400, 2400-2800 and 2800-3200 meters above sea level. Sampling be performed Systematic random. Thus, in each altitude class, three 100-meter transects were placed perpendicular to the slope at a distance of 100 meters from each other, and on each transect, 10 plots of two square meters and in total 180 plots (2 square meters) were located and measured in the area. Then, important ecological indicators such as richness, diversity and uniformity were calculated using PAST software. Statistical analysis of these indicators showed that the most diversity is related to the altitude class of 2400-2800 and 2800-3200 meters and the least of it is related to the altitude class of 2000-2400 meters. Diversity in the east and west directions was not significantly different. Altitude class 2000-2400 meters with east direction has the highest uniformity and the lowest richness. In relation to richness, in the upper two classes of altitude (2400-2800 and 2800-3200 meters) there was the highest amount of richness and the lowest amount of richness was at lower altitudes. However, richness is larger on the western slope than on the eastern slope. The lowest uniformity was observed in the altitude class of 2400-2800 meters and the eastern and western slopes had the same uniformity. In general, with increasing altitude above sea level, diversity and richness have increased in the western geographical direction. Because more than seventy percent of the frequency of precipitation is in of the western slope and at an altitude above 2800 meters due to the cold weather, the amount of richness has decreased.

The increasing demand for water has led to the development of various methods for water resources management. Some structural methods include the construction of barriers in the path of surface flows and make water reservoirs, which earth-fill dams are in this category. Efficiency and productivity of a dam depend on many factors, most importantly, the suitable areas for the construction of these dams. This research was conducted with the aim of developing a decision support system based on RS and GIS techniques and identifying and prioritizing suitable areas for the construction of earth-fill dams in the Beheshtabad watershed of the North Karun watershed. For this purpose, previous studies in this field were reviewed and effective criteria in locating the earth fill dams were selected. After selecting the set of criteria, a pairwise comparison questionnaire was made and provided to relevant experts. Then, using the Analytic Hierarchy Process (AHP), prioritization and determination of the relative weight of these criteria were performed. Maps of each factor were prepared and standardized; then weights obtained by AHP method was then applied to them. Finally, the map was prepared with three categories of inappropriate, good, and very good for the construction of the earth-fill dam in the region. The results show that geomorphologic and geological criteria with the highest weight are the most important in determining the suitable location for earth-fill dam construction. This criterion composes of four sub-criteria: Karst, Fault, Landslide and Erosion. After this criterion, topography, investment, land use, distance from groundwater sources, distance from road and soil depth were ranked in order of importance. It was also found that more than four kilometers of the hydrological network of this watershed have a very good capability for the construction of short earth-fill dams in order to manage water resources.

Dust release from wind erosion is a widespread phenomenon, which has significant consequences for ecosystems and human health. Addition of active ingredients to degraded soils is a suitablegood method to create and stabilize aggregates that can reduce fine dust production. This study was conducted to investigate the effect of powdery maize residues and maize biochar on soil properties and wind erosion of Shahrekord plain. In this study, in addition to powder obtained from maize plant residues, maize biochar was prepared in a size of less than 2 mm and added to the studied loam soil in a ratio of 5% by weight. During the experimental period, soils were sampled at 5, 20, 45 and 60 days after addition of biochar and powder from maize residues, to evaluate changes in soil properties over time. Simulations were also performed over a 60-day period in a wind tunnel to show how soil remediation can indirectly control wind erosion potential. Experimental results showed that the use of powder of maize cob residues caused a significant increase (probability level< 0.05) in organic matter and aggregate stability compared to maize biochar. The use of powder of maize cob residues increases soil organic matter by 1.17, 1.27, 1.77 and 2.1 times on days 5, 20, 45 and 60, respectively, compared to the control sample. Eroded soil on day 5 and 60 of biochar treatments were 184.24 and 65.15 g / m2, respectively, and on days 5 and 60, for powder of maize cob residues were 171.84 and 49.49 g / m2, respectively. Finally, the use of powder of maize residues caused soil stability, increasing soil stability and ultimately led to a significant reduction in (p <0.05) soil wind erosion.

Barkhan is one of the most common forms of sand dunes and the influx of sands in the form of Barkhan hills is considered as one of the most important environmental hazards in most parts of Iran, which will cause a decrease in the quality and quantity of groundwater, reduce soil fertility and increase the susceptibility of lands to erosion and landslides. Therefore, their comprehensive identification is very important. The aim of this study was to investigate the granulometric characteristics of Ardakan Barkhans in different heights. In 2016 the study area was identified using Satellite Images and Google Earth software, then, with a field visit to Ardakan region, sampling was done from 6 Barkhan at two different heights.In the next step in the laboratory, granulometric operations were performed on the samples. Then, by performing independent t-test, the significance of the difference of each variable was investigated. The results showed that the highest frequency of samples in the windward slope is related to sands with a size of 250 to 500 microns by 54.68% and in the leeward slope with a size of 125 to 250 microns by 51.97%. Also, the variables of mean diameter, skewness and sorting in the range of 0-2 meters of windward and leeward wind have a significant difference at the level of 95% and no significant difference was observed between the two slops in the Kurtosis variable. Also, it was found that in the range of 2-4 m of Barkhan hills, there is no significant difference between the variables of sorting and Kurtosis on both slopes of the windward and leeward. In this range, a significant difference was observed between the two variables of mean diameter and skewness at the level of 5%. The results show that the ratio of homogeneity of sand grain dimensions in the windward and leeward is different.