فصلنامه تحقیقات مرتع و بیابان ایران
سال سی‌ام شماره 4 (پیاپی 93، زمستان 1402)

According to the studies, environmental factors can affect the secondary metabolites in plants, including the essential oil and its chemical composition. therefore, it is essential to understand the effect of these factors and which of the environmental factors have a more effective role on the quantity and quality of secondary compounds extracted from plants. the purpose of this study is to investigate and compare the effect of physical and chemical properties of soil and climate factors including temperature and rainfall on the chemical composition of the essential oil of the medicinal species of Stachys lavandulifolia in the northern and southern aspects of Bagh tilak rangeland of Sari.

The present research was conducted in Baghtilak rangeland, which is one of the summer pastures of Mazandaran province. in order to take samples, plant samples were taken according to the patchy distribution of the plant in the region, the aerial branches of the plant were randomly collected in three selected spots with three repetitions from the northern and southern aspects in late June.then the soil samples were also collected at the base of the plant from a depth of 0-30 cm. after the samples were transferred to the laboratory, the essential oils of the plants were extracted by clevenger and their composition was determined by GC and GC/MS.  Soil samples were also measured and evaluated based on existing guidelines. also, the required meteorological information was obtained from the Kiyasar meteorological station. in order to analyze the quantitative and qualitative data of soil and essential oil, the normality of the data was first checked using the Kolmograph-Smirnov test. after confirming the normality of the data, using the independent T-student test, the comparison of plant chemical compositions and soil quality indicators in the two northern and southern spects was performed by SPSS version 22 software, and the relationship between the plant chemical composition data was analyzed. It was done with soil quality indicators and climatic data by PCA principal component analysis method in PC ord5 space.

The results showed that the yield of essential oil in the southern aspect is significantly higher (P≤0.05) than the northern aspect. Also, among the compounds obtained from the essential oil, the compounds α-Pinene, α-Fenchene, p-cymene, Sabinene, Thymol, α-Thujene, Limonene, GermacreneD, bicyclogermacrene, cis-sabinene hydrate with the highest amount have a significant difference from they showed themselves in two aspects. the data obtained from principal component analysis into main components in relation to soil and climatic factors with essential oil compounds indicate that soil chemical factors including EC, OM, Mg, MWD, bulk density, sand and silt have a stronger relationship compared to other factors. also, in this analysis, soil factors such as apparent specific gravity, pH, Ca, sand, and the climatic factor of temperature have a positive and direct relationship with Sabinene, β-Pinene, Myrcene, α-phellandrene, p-cymene, Limonene, cis-sabinene hydrate compounds, thymol, Germacrene D, bicyclogermacrene and Phytol. also, soil factors such as EC, OM, bulk density, silt, Cao, P, Na, SAR and precipitation climatic factor have a negative and inverse relationship with Cyclofenchene, 1-8-Cineole, cis-ocimene, α- Terpineol, Terpinene-4-acetate, Bicyclo, Caryophyllene and Hexadecanoic acid were established.

Conclusion :

The result of this research shows that the quantitative and qualitative performance of medicinal plants is affected by factors such as the type of species, climatic characteristics, soil characteristics and topographical conditions, and the effect of environmental factors on the components of secondary metabolites can be due to the different effects of these factors on The biosynthetic pathways of these compounds in the plant. also, the present study showed that the yield of essential oil obtained from the Stachys lavandulifolia plant in the southern aspect of Baghtilak rangeland is significantly higher than the northern aspect, so it is recommended to consider more for the exploitation of this aspect.

Changing the use of natural ecosystems, including dam construction and also the conversion of pasture land to agricultural land, can cause irreparable damage to different parts of the ecosystem. Based on the research results the most destructive of them is the reduction of vegetation, the increase of erosion and also the reduction of biodiversity. In the management of natural ecosystems, monitoring vegetation changes is very important. The present research was carried out with the aim of investigating the changes in the vegetation cover indices and species diversity in the plowed and abandoned agricultural lands and the natural cover of the pastures around the Yan Chashmeh underground dam located in Ben city of Chaharmahal and Bakhtiari province.

To carry out this research, four sites including natural pastures around the dam, lands upstream of the dam (rain fields under cultivation), lands where the dam reservoir is being built (plowed and abandoned for less than 7 years) and lands downstream of cedars have been planted for more than 15 years) were selected and in each of the sites, three transects with a length of 50 meters parallel to each other and perpendicular to the slope of the area were established at a distance of 50 meters from each other. 15 plots of 2 x 2 square meters were placed on the transects with a distance of ten meters from each other. And then, in each plot, the percentage of canopy cover, biomass, percentage density of leaf litter and bare soil were recorded. The theoretical estimation method was used to determine the level of plant canopy in the plots. The biomass of the species was determined using the cutting and weighing method. In order to check species diversity, Simpson and Shannon-Wiener indices and to compare species richness, Margalf and Menhinik indices were calculated in Past software. Determining the condition of the pasture was done using two modified four-factor and six-factor methods.

 The results showed that plowing and changing the use of pasture land to agricultural land has caused a significant reduction in the crown cover and, as a result, a decrease in the amount of biomass density, and also a decrease in diversity and species richness in the plowed and abandoned lands compared to the sloping pastures of the region. The results showed that in addition to reducing the cover, plowing has caused a change in the species composition and an increase in annual and invasive species and a decrease in shrub species. According to the results of the change of pasture use, the surrounding pastures decreased from average to weak and very weak condition in plowed and cultivated pastures (upstream) with a negative trend.

The measures taken to build the dam and then the expansion of agriculture have caused plowing and soil manipulation in the region. Besides, it is possible that in the long term, abandoning agriculture due to the drop in the water level of the underground dam will cause more soil erosion. Therefore, it is necessary to continuously monitor the vegetation changes in the are

Wind erosion and dust phenomenon are considered as one of the important processes of land degradation and a serious challenge in Iran. This phenomenon occurs due to the interaction between weather and terrestrial processes. The purpose of this research is to investigate and analyze the trend of temporal and spatial changes in the number of dusty days in Iran and to investigate the role of climate in its spread.

In this research, after receiving hourly and daily statistics of dust events (through 148 synoptic and climatology stations) and parameters of precipitation, evaporation, temperature as key climatic elements (from 171 stations) in 22 provinces located in arid and semi-arid regions of Iran, The spread of dust was investigated and the correlation between climate and dust was determined. After calculating the number of dust days in Iran, the information was called in the GIS environment and a map of the spatial changes of the parameter of the number of dust days in the three decades of 1987-1996, 1997-2006, 2007-2016 was prepared. In the following, the spatial analysis of this parameter and its expansion over three decades were investigated. Next, the climate parameter that had the highest correlation with the number of dusty days was selected and after preparing a map of its spatial changes in the GIS software environment, the spatial compatibility of the desired parameter with the expansion of the number of dusty days was investigated. In the next step, after performing the homogeneity test on the dust occurrences, the partial square regression model was used to determine the contribution of the three mentioned climatic elements as independent variables and the number of dust days as a dependent variable.

The results showed that the number of dusty days and the area of its occurrence have increased in Iran, so that in the last decade under study (2007-2016) compared to the previous two decades, the dustiest event occurred in Iran. This increase has been more intense especially in the western and southwestern regions of the country, which were also affected by extra-local dust events. These dust events have spread to the central regions of the country with greater frequency. The homogeneity test in many provinces showed a common change point (year 2007-2008) in the number of dusty days, which could be related to the beginning of severe droughts and climate changes from this year in Iran. The study of climatic parameters (temperature, precipitation and evaporation) on changes in the number of dust days in Iran showed that during recent years, temperature had the highest significant correlation level (0.58) with the occurrence of dust. The temperature gradient map in the last decade (2007-2016) compared to the previous decade (1997-2006) also showed the increasing trend of temperature, especially in the western and southwestern regions as well as the southeastern regions of Iran. Modeling the effect of climatic parameters of temperature, precipitation and evaporation on the parameter of the number of dusty days showed that the contribution of the studied climatic parameters to the occurrence of dusty days is about 33% and other effects can be related to things such as human factors or soil characteristics, type of vegetation, solar radiation, etc.

In general, the results of examining the trend of changes in the number of dust days and climatic indicators for nearly 3 decades indicate a significant increase in the number of dust days in most parts of Iran and the conditions for this increase have been provided and if the trend of changing these indicators in the coming years is according to the current trend, the risk of environmental problems in the country can be expected to increase.

Due to the increase in the consumption of fossil fuels and chemical fertilizers, especially nitrogen-containing fertilizers, the entry of nitrogen into the cycle of ecosystems has been more than normal.Nitrogen deposition as a consequence of increasing nitrogen input to the atmosphere, can be a threat to ecosystems. It can affect soil properties, soil microorganisms and their activities, vegetation and animals. The aim of the present study is to investigate the effects of deposition of different rates of atmospheric nitrogen on the biochemical properties of a summer rangeland's soil.

For this purpose, the seeds of Medicago sativa were planted in 36 pots containing rangeland soil in a completely randomized block design.  Two months after seed germination in pots, six Nitrogen treatments included control,30, 60,90,120 and 150 kg ammonium nitrate/ha which dissolved in water were applied in 6 replications during a period of 75 days. At the end of experiment, some soil biochemical properties (acidity, electrical conductivity, absorbable phosphorus, total nitrogen, organic carbon and exchangeable potassium along with biomass and microbial respiration) and Root weight and depth factors were measured.  Data analysis was done using analysis of variance method and mean comparison was done using Duncan's test.

The results demonstrated that increasing the level of ammonium nitrate deposition to 60 and 90 kg per hectare per year, despite the significant increase (p < 0.05) of organic carbon and total soil nitrogen, causes a significant decrease in other measured biochemical properties of the soil (p < 0.05). An increase in nitrogen deposition in the early stages may be partially responsible for root growth, but with nitrogen saturation in the soil and the occurrence of nitrate leaching, as well as the loss of soil fertility, unfavorable conditions for root growth are provided. With the increase of nitrogen deposition in the soil, up to the level of 60 kg /ha, the average respiration and microbial biomass increased, But at higher levels of  nitrogen deposition, respiration and microbial biomass decreased.

In case of an increase in mineral nitrogen deposition in the studied area, it is recommended to use the Medicago sativa in the improvement of vegetation restoration projects of summer rangelands to absorb the deposed mineral nitrogen in excess of the soil holding capacity, its alleviate negative consequences and creating a suitable root zone for the the  activity of soil microbial.

Soil is considered one of the most valuable natural resources and the existence of life on the surface of the earth depends on the existence of soil in addition to water and air. Soil stability is an important factor in the health of the soil system and it is a prerequisite to perform processes such as the cycle of elements in the soil. Soil erosion is a serious problem and threat in different regions of the world, and therefore protecting and preventing soil erosion as a non-renewable natural resource is of high priority. To prevent soil erosion, there are various physical, mechanical, and chemical methods.  Due to their high cost and harmful effects on the environment, today much attention is paid to biological methods that are friendly to the environment. This study aimed to investigate the potential of urease producing bacteria on biological stabilization and prevention of soil erosion.

Soil samples were collected from the Bazoft area in Chaharmahal va Bakhtiari provinces and transported to the laboratory. The enrichment and selective method was used to screen urease producing bacteria in the urea agar base culture medium. The activity of the urease was investigated by the electrical conductivity method and three strains with the highest urease activity were selected and used in further steps. The selected strains were identified by molecular methods, colony PCR by using 14f and 1492r universal primers, and sequencing. The compressive and shear strength was estimated in inoculated soils after 14 days.  The wind erosion threshold velocity was measured in the wind tunnel. The soil loss was estimated at different wind speeds (17.3, 22.09, and 27/20 m/s) in the inoculated soils.

The urease-producing bacteria were identified by changing the color of the culture medium from yellow to pink. The results showed that the soils of this area have a high potential for urease producing bacteria. Three species were selected based on their urease activity and identified as Bacillus thuringiensis (RIFR-U3), Bacillus sp. (RIFR-U7), and Exiguobacterium sp. (RIFR-U10). The compressive and shear strength increased in soil inoculated with the selected bacteria compared to the control.  The highest compressive (1.56± 0.241 kg/cm2) and shear strength (2.066±0.18 kg/cm2) were detected in the soils inoculated with Bacillus sp. (RIFR-U7) and Exiguobacterium sp. (RIFR-U10) strains, respectively. The wind erosion threshold velocity was 12.19 m/s. The soil loss was less in the inoculated soils with bacteria compared to control and Bacillus sp. (RIFR-U7) had the highest efficiency in preventing soil loss.

The increased compressive and shear strength showed that these selected strains are moderate to good stabilizers for increasing compressive strength and very good for increasing shear strength. The wind tunnel results showed that Bacillus sp. (RIFR-U7) inoculated soil was more resistant to wind erosion compared to the other two strains and controls. In conclusion, it seems that different strains or a combination of them can be used based on what characteristic of the soil is to be improved or the purpose of resistance against which erosion.

Failure to meet needs, climate change and resulting social and economic conflicts have faced many challenges in the life of nomadic communities. So that they are forced to leave animal husbandry temporarily or permanently. In this regard, the present research has identified and analyzed the reasons for the abandonment of livestock by nomadic in the summery rangeland of northeastern Iran.

The current research purpose is applied and descriptive information was collected by survey method and using a mixed approach. The statistical population is consists of 175 Kurdish nomadic households of Kurmanj, North Khorasan, from four traditional communities in the rangelands of Ajisu area in Marve-tape city, Golestan province. According to Yamane's (1967) formula, 122 beneficiaries were selected as a sample using a stratified random method with proportional assignment within the studied customary systems. The measurement tool was a researcher-made questionnaire, the items and components of which were finalized based on 15 interviews with experts who were identified based on the snowball technique. So that the questionnaire was prepared based on 46 items in the form of 11 components. Each of the items through a five-point Likert scale including very little (with a numerical value of 1), little (with a numerical value of 2), to some extent (with a numerical value of 3), a lot (with a numerical value of 4) and A lot (with a numerical value of 5) were measured. The content and face validity of the questionnaire was confirmed through experts' opinions and based on the convergent validity criterion (AVE), which has a minimum value of 0.5. To determine the reliability of the measurement tool, two criteria, Cronbach's alpha coefficient and composite reliability (CR) were calculated, for which a value greater than 0.7 is acceptable. After collecting data, statistical calculations in this research were done based on SPSS25 and Smart PLS3 software in two descriptive and inferential sections.

The results obtained from the average rank comparison showed that the five components of "livestock and rangeland management challenges", "climate changes and the resulting threats", "incompatibility of the market with the new needs of grazing", "lack of economic The presence of animal husbandry and the reduction of saving power" and "life experiences outside of animal husbandry and changes in local customs" respectively, with the highest mean values of 10.09, 9.87, 8.27, 8.14 and 7.93 are the highest. It has had a degree of importance and influence in the abandonment of livestock by nomadic in the studied area. The results obtained from the relationships between the components of the model of the reasons for the abandonment of livestock by nomadic showed that all the relationships were positive and significant at the 95% confidence level. So that the strongest relationships are assigned to "life experience outside ranching → conflict" and "reduction in family ability → life experience outside ranching" with path coefficients of 0.687 and 0.547. The weakest of them also belong to the two relations "weakness of government services → reduction of savings" and "weakness of government services → market mismatch". As the results showed, climate change and its consequences on the two factors of production reduction and poor access to financial resources (ρ=0.010, β=0.363 and t=2.585) and the weakness of government services and lack of Infrastructures (ρ=0.000, β=0.301 and t=4.364) had a positive and significant effect at the 99% confidence level.

According to the obtained results, the development of livelihood support of the government, including educational facilities and health and medical infrastructures, providing facilities and cheap bank loans for the development of businesses with the aim of reducing the dependence of users on rangeland, development of veterinary services free in the affairs of the nomads of the province, increasing government subsidies in the distribution of supplementary animal feed, flour and fuel, laying the groundwork for providing drinking water for animals and families, creating job opportunities through the holding of professional and skill training courses Businesses such as handicrafts and the production of targeted dairy products, the creation of livestock markets and the sale of live livestock are suggested in order to prevent nomadic communities from abandoning traditional animal husbandry.