نشریه خشک بوم
سال یازدهم شماره 2 (پاییز و زمستان 1400)

The stability of the soil structure shows the ability of the soil to resist erosive forces and rebuild after destruction. Considering that the soil is one of the important components of the rangland ecosystem, it is important to maintain its stability. The purpose of this study was to investigate the effect of range restoration activities on soil stability was using seven-factor, scoring and Emerson indices in ranglands of the Yazd province, evaluate these indices, and provide a suitable and compatible method for rangland. For this purpose, first among the biological and biomechanical projects implemented in the ranglands of the province, the Crescent water catchment, Furrow and Contour Trenching, were selected in three traditional systems. Sampling of soil and vegetation was done using systematic-random method with the establishment of transect and plot. In order to compare the effects of different reclamation methods on soil stability indicators by entering the data into the SAS environment, nested variance analysis was used. Then, by using Statgraphics software, the relationship between soil factors and vegetation was investigated and the classification of soil stability for the studied ranglands was done. The results showed that all soil parameters, except organic matter and lime, have significant differences in the studied areas. The most important soil parameters affected by remediation include SAR, ESP, pH, sodium, calcium and magnesium content with special values ​​of 0.30036, 0.30035, 0.2928, 0.2907, 0.2898 and 0.2894, respectively. Considering that the soil of the studied areas was mostly sandy, sandy-loamy and loamy-sandy, it did not agree with the textures mentioned in the classes of the seven-factor soil stability index. So this index was not suitable for determining soil stability. On the other hand, the algebraic sum index of four soil factors and Emerson's method can not show the changes of soil stability within each region (control, intra-operation and inter-operation) well. Finally, the classification method of soil stability in arid ranglands was proposed based on the results of this research.

Fire is an integral part of many terrestrial biomes and one of the main causes of destruction in nature. This study investigates the cause and characteristics of wildfires in the middle Zagros ecosystem for two consecutive years. There have been recorded to conduct this research, whole fire events that occurred in the natural areas of Gilan-e Gharb in 2019 and 2020 during the fire season from late May to early December. The gathered data in this study include the region name, type of affected area by the fire (forest, non-wooden rangeland, wooden rangeland, and mixed forest-rangeland), the cause of the fire, date, duration, area, and its location. The results showed that the fire rate includes 11% in the forest, 47.8% in non-wooden pastures, 26.5% in wooden pastures, and 14.7% in mixed forests and pastures in 2019. The fire frequency was 50% in the forest, 38% in non-wooden pastures, 2% in wooden pastures, and 10% in mixed forest and pasture in 2020. The lowest and highest amount of burnt area in 2019 contains the forest (9.4%) and non-wooden pasture (53%), respectively. Furthermore, the lowest and highest portion of burned area in 2020 includes forest (7%) and mixed forest and pasture (42.6%). According to the available evidence, nearly 72% and 50% of the human causes of fire in 2019 and 2020, respectively. There are recreational factors, disputes, and conflicts. Duration of less than one hour for extinguishing fires has the highest frequency, the amount of which is about 36% and 14% in 2019 and 2020, respectively. The highest frequency with 12 and 11 events includes the Cheleh in 2019 and 2020, respectively, among the common burned areas. In addition, among the factors compared in the study years, human factors of fire under the influence of different conditions have significant differences from each other (p=0.05). Therefore, it is essential to consider the structural causes and motivations of fire-causing factors that affect fire to reduce and avoid fire as much as possible.

Land degradation due to its impact on agricultural production, environment, security and quality of life in the 21st century has been raised as a global issue. It provides evidence such as biodiversity loss and climate pollution. The purpose of this study is to investigate the effects of socio-human factors on land degradation in the coasts of Bushehr, Hormozgan and Sistan and Baluchestan provinces. For this purpose, during the period 1988-2019, Landsat satellite data including OLI, ETM+ and TM sensors and population census information were used. To prepare the land use map, first geometric and radiometric corrections were made. Then, the supervised classification method and the maximum probability algorithm were used. In order to determine the role of effective variables, multivariate regression analysis method was used. SAVI and SI1 were considered as dependent variables, use of man-made areas and population density were also considered as independent variables. Based on the results of the change detection, the land use class of man-made areas and the population variable are associated with an increase of 2.7 and 2.3 times, respectively. Population density in the study period has increased from 96 to 194 people per square kilometer. According to the results of regression analysis, the use of man-made areas was selected as a more influential variable on the SAVI and SI1 indices. On the other hand, indicates the impact of socio-human factors on the process of land degradation by 37%, that the socio-human variables are an important factor and part of the process of land degradation. Therefore, the findings of this study will enable the adoption of fundamental decisions in the formulation of management policies for planners and managers in the field of natural resources and the environment for the sustainability and evaluation of coastal areas.

Tamarix ramosissima, due to its high potential for settling in arid and semi-arid lands, considered as one of the valuable plants for creating vegetation in these areas. The use of the plant in the east of Isfahan can be reproduced and expanded for desertification purposes; however, information on its habitat and ecological requirements is limited. The aim of this study was to identify the factors affecting the distribution of this species and to model the potential habitats for the growth of this species in Isfahan province. The distribution points of the plant were determined according to the flora of Iran and by referring to the region, sampling was performed and its geographical and ecological characteristics were recorded. A total of 55 distribution locations were registered in 14 cities. Using the maximum entropy model, 19 bioclimatic and three topographic variables were used to model the distribution of the species and the importance of each of them in the modeling process was evaluated by Jack Knife test. The results showed the area under the receiving operator curve was equal to 0.967 by using Maxent model. The produced model had an acceptable accuracy as its Kappa coefficient index was 0.80. .Environmental factors related to topography including slope percentage and climatic factors precipitation of coldest quarter, annual precipitation, temperature annual range and mean temperature of coldest quarter had the greatest impact on species distribution, respectively. According to the prediction of the presence of the species based on habitat potential, about 19% of the area of ​​Isfahan province, provided the absence of limiting factors, has the desired potential for the presence of this species.

Persian Wild Ass, the only representative of the order Perissodactyla, is the largest wild herbivore in Iran and inhabits the plains and hills of desert and steppe habitats. Study the status, population growth, and evaluation of management measures taken for this species in nature, reproduction, and rewilding areas are the main purposes of this study. According to the census data in 2021, there were a total of 1315 individuals, including 1231 individuals in the nature of Iran in the two protected complexes of Bahram-e-Gur and Turan and 84 individuals in the rewilding centers. In 2021, the minimum population was 170 individuals and the average of the last 14 years (2021-2008) was 160 individuals in the Turan complex, which decreased sharply compared to the population of 471 individuals in 1997 and 800 individuals in 1976. Changes in the population of the wild Ass in Bahram-e-Gur complex indicate that the population increases from 93 individuals in 1997 to 1061 individuals in 2021. The most important factors of population decline have been habitat loss, hunting, and droughts, and the most important factors in increasing the population of this species have been the intensification of conservation, forage supply, and water resources. Captive breeding programs and reintroduction have been prioritized for nearly two decades and have been successful to a large extent. Although this species is still in the group of endangered species, one of the most successful conservation programs executed in Iran is its management due to the population growth positively and the improvement of the conservation status.

Plants producing nectar and pollen, producing abundant nectar and pollen strengthen the pollinator population and increses biodiversity and honeybee products. Teucrium and Thymus kotschyanus are among the most important species to produce vegetable nectar in Iran. These plants play a major role in producing honey and pollen in rangelands. In the present study, the potential distribution for T. kotschyanus and T. polium was assessed by using the MaxEnt model.  Firstly, 19 bioclimatic variables were extracted from chelsa data collection for evaluating the current weather condition and was modeled by max software. According to the results, the organic carbon content in the soil profile (orc) is the most important variable affecting the distribution of both species. In. T. kotschyanus not only the soil organic carbon but also the amount of sunlight (solar), deriest month (BIO14) and aspect are the most influential variable. In addition to the amount of aspect, annual rainfall (Boio12) and the weight percentage of sand particle are also considered to be the most important environmental factors in the distribution of T. polium and Thymus kotschyanus species. The results of this study can provide valuable information to identify the priority of areas and possible future shelters for the protection of T. kotschyanus.  T. polium. Species.

The impact of dust storms on the Sistan and Baluchistan region is one of the most important current issues in this region. The current research is an attempt to investigate the effects of climate change on the trend of changes in dust storms in Sistan and Baluchistan province in the future perspective (until the end of 2100) compared to the base climate period (2010-2020). The study method consists of two parts, namely, analyzing the trend of dust storm events changes from the past to the present and projection the future situation. In the first step, using the multiple linear regression method, the correlation and relationship between the variable of days with dust with other climatic parameters (temperature, rainfall, relative humidity, and wind speed (during the statistical period of 2010-2020 was obtained. Then, the modeled data of the CMIP6 global model in three scenarios and 8 decades from 2020 to 2100 were used as inputs of significant regression relationships during the period 2010 to 2100 to investigate the future status of dust storms. Analysis of the results showed that, the trend of dust event change based on three scenarios of optimistic, moderate, and pessimistic in Sistan and Baluchestan provinces is increasing. As expected, the least dusty days are seen based on the optimistic scenario (SSP1-2.6). The dust trends based on the middle (SSP3-7.0) and pessimistic (SSP5-8.5) scenarios have almost the same trend and are increasing. Therefore, we can expect to have more frequent dust events in the future as climate change continues. As a result, the necessary investments for adaptation measures and mitigation against the harmful effects of dust need to be put on the agenda from now on.

Proper designing of green space in educational centers increases vitality and ensures the safety of users and reduces costs. The purpose of this study was to estimate the lack of root and canopy growth space of the most important green space trees of Yazd University. At first 124 pine and 102 elm trees were randomly selected in different parts of the University and their morphological characteristics were measured. The height/diameter coefficient was used to determine the susceptibility to wind-throw. To determine the shortage of canopy growth space, the canopy area of ​​5% of the largest trees and to calculate the shortage of root growth space, the British standard were used. Then, classification of frequencies was done. Results showed that the mean height coefficient of pine and elm were 56.85 and 51.21 respectively. About 87.1% of the pines and 42.2% of the elms were in a stable condition. About 96% of the elm trees and 94.4% of the pine trees had insufficient planting distance and therefore, do not have enough space to reach the maximum dimensions of the crown. According to the results, 77% of pines and 54% of elm trees lacked root growth space. Tomographic examination via ultrasonic technology showed decay only in some broken trees. Based on the results, it is recommended to assign enough space for the growth of canopies and roots in order to reduce the possibility of uprooting, before designing the planting areas and building curbs and sidewalks.

Wind erosion, causes air and environment pollution by transferring microscopic particles into the atmosphere. Occurrence of this phenomenon in the source areas causes soil erosion and in other places proportional to the strength and speed of the wind causes the accumulation or deposition of particles. Knowing the areas for combat to desertification operations is one of the necessities for the success of corrective actions. The type of planning and control methods for wind erosion are different in each of the stages of deflation, transportation and sedimentation. The most principled and successful areas in this regard are deflation areas. In this study, using field studies, satellite imagery and visual interpretation, erosion areas including transportation, sediment and deflation were identified. Selecting two areas in the points of deflation and transportation, the durability and longevity of pebble mulch for three years was studied to show that spending time in finding the best place to implement combat to desertification projects is the most important step in reducing human and financial costs and dust control. Estimation of wind erosion rate in deflation points was done by measuring wooden indices. The results obtained from the collected data of wooden indices in Segzi plain indicate an average of 1.9 kg/m² y-1 from the soil surface, and in Fesaran plain indicate an average of 1.2 kg/m² y-1 from the soil surface, Which shows that the project site in Segzi plain is located in the source area and the amount of wind is higher than the project site in Fesaran plain, which is a transport and sediment area, is faced with less wind erosion. Also, by soil science studies, the reason for failure of Haloxilon ammodendron species planting projects in some parts of Segzi plain can be understood, which indicates the incorrect choice of the location of biological projects.

One of the fields in vegetation ecology is understanding the relationships between plant species and environmental factors and analyzing species reactions along the slope of environmental factors. Considering the importance of Salsola arbusculiformis Drob in soil conservation and forage production, the reaction of this species to environmental factors was investigated using the Generalized Additive Model in Shoghan region of North Khorasan province. For this purpose, a systematic random-method was used to measure plant parameters and environmental factors. Canonical Correspondence Analysis was used to examine the relationship between vegetation and environmental factors. The results showed that environmental factors such as percentage of sand, sulfate ions and soil bicarbonate, annual rainfall and altitude, respectively, expressed 5.8, 11.4, 5.7, 9.1 and 7% of the existing variance and have an important role in vegetation changes in the studied habitat. The study of the reaction of this species to environmental factors showed that out of 25 environmental variables studied, 14 variables had a significant effect on plant yield (p <0.01). The response pattern of the studied species along the slope of factors such as acidity, percentage of sand and clay, altitude and finally the percentage of slope was unimodal. The optimal growth limit for each of the above factors was 8.4, 66%, 28%, 1452 meters and 5%, respectively. The response of this species to the amount of sulfate and percentage of soil lime followed a decreasing model, so that with increasing the values of these factors, its yield decreased. The response pattern of the desired species was in two modes, along the slope of factors such as chlorine, sodium, organic carbon, nitrogen, soil salinity and average annual temperature. This model indicates a competitive constraint startsrecalong the peripheral slope. The results also showed that this species has the highest yield in the northern slopes. Studying the reaction of the desired species along the slope of topographic and soil factors provided valuable information for determining the ecological needs of this species, which can be considered in rangeland improvement operations in similar areas.

In recent years, the dust events frequency and the drought severity have increased in many arid regions of Iran, so it is very important to discover the relationship between these two phenomena in these regions. In the present study, the drought situation of Kerman province using the standardized precipitation-evaporation index (SPEI) and the frequency of dust events using codes 07, 08, 09, 35-30 and 98 recorded in synoptic stations during 1990-2018 has been investigated. In addition, Palmer Drought Severity Index (PDSI) and Aerosol Optical Depth (AOD) were also used to confirm the results obtained from meteorological data. The trends of changes in drought indices, dust occurrences and AOD were analyzed using the Mann-Kendall test and their correlation with each other was analyzed using the Pearson correlation coefficient. The results showed that Kerman faced the most severe drought events in the period from 1998 to 2010, and the longest drought with a duration of 21 years and an intensity of 11.84 occurred in the northwest of the province. The temporal analysis of dust events showed that intensification of their activity in the spring and winter seasons, especially in the months of March, April and May. The results of the analysis of SPEI changes showed that the drought in Kerman had an increasing and significant trend, while the trend of changes in the frequency of dust occurrences had a decreasing and insignificant trend. Analysis of changes using satellite data also proved the significant increasing trend of PDSI and non-significant decreasing trend of AOD, especially in hot seasons. Correlation analysis between SPEI and dust events showed that the intensification of dry conditions in November had a significant effect on the intensification of dust events in Kerman province (r = -0.46; P-value<0.05), while in other months, it has no significant effect on the dust events frequency. The results of PDSI and AOD confirmed the weak correlation between these two phenomena in Kerman province. The results also showed that the effect of drought time delays on the dust phenomenon in this province was weak and insignificant.

Identifying suitable plant species to create green belts around cities in arid and desert areas, in order to reduce air pollution is very important. Air pollution tolerance index is one of the known indicators to determine the tolerance of plant species to air pollution. The aim of this study was to investigate the effect of dust on the physiological and biochemical characteristics of two halophyte species of Haloxylon aphyllum and Nitraria schoberi and to determine the appropriate species for green belt. The experiment was done in a factorial experiment in a completely randomized design, with two treatments (no dust and dust) in three replications for 5 months in greenhouse conditions. In order to investigate the effect of dust, dusting was performed on the samples with a time interval of one week (1.5 g/m2/month) using a dust simulator. Finally, the parameters of ascorbic acid, total chlorophyll, relative water content and pH of leaf extract and finally the air pollution tolerance index of the two species were measured. The results showed that the total chlorophyll parameter of H. aphyllum and N. schoberi decreased by 8 and 19%, respectively, compared to the control, while relative water content increased by 3 and 8%, respectively. The pH of N. schoberi leaf extract increased by 29% compared to the control. The highest APTI value of 8.15 was related to H. aphyllum and the lowest APTI value of 7.41 was related to N. schoberi species. According to the obtained results, despite the small differences between the air pollution tolerance index of the two species, H. aphyllum species can be a suitable option for planting a green belt to reduce air pollution due to its higher tolerance index and plant height than N. schoberi.