Environmental Erosion Research

fa تغییرات تیپ غالب Halocnemum strobilaceum تحت تأثیر عوامل محیطی در مراتع شوره‌زار (مراتع اشتهارد استان البرز) Changes in the dominant type of Halocnemum strobilaceum under the influence of environmental factors in salt rangelands (Eshtehard rangelands, Alborz province) مدیریت و کنترل اثرات فرسایش محیطی پژوهشي Research پوشش گیاهی مراتع در مناطق خشک با ریشه‌های گسترده خود به تثبیت خاک، افزایش پایداری آن و مقاومت در برابر فرسایش کمک می‌کند. این پوشش گیاهی همچنین با افزایش نفوذ آب و مواد آلی، به حفظ رطوبت و سلامت خاک یاری می‌رساند. هدف این مطالعه بررسی تأثیر عوامل محیطی بر پوشش گیاهی مراتع شور اشتهارد و ارزیابی تغییرات اکوتیپ غالب، Halocnemumstrobilaceum، تحت این تأثیرات است تا در نهایت به مدیریت بهینه مراتع شور دست یابد. نمونه‌برداری پوشش گیاهی با استفاده از روش تصادفی-سیستماتیک و با استقرار ۶۰ پلات دو متر مربعی در امتداد چهار ترانسکت ۲۲۵ متری انجام شد. همزمان، نمونه‌های خاک برای اندازه‌گیری ویژگی‌های کلیدی شامل هدایت الکتریکی (EC)، اسیدیته (pH)، کربن آلی، نیتروژن کل، فسفر قابل دسترس، پتاسیم قابل دسترس و بافت خاک جمع‌آوری شد. برای تعیین اهمیت نسبی عوامل محیطی مؤثر بر پوشش گیاهی، از تحلیل مؤلفه‌های اصلی (PCA) با استفاده از نرم‌افزارهای XLSTAT و MINITAB نسخه ۱۶ استفاده گردید. تحلیل همبستگی نشان داد که پوشش گیاهی و تولید در منطقه اشتهارد، بیشترین همبستگی را با بارش سالانه و عوامل خاکی مانند نیتروژن، کربن، پتاسیم، اسیدیته و شوری دارند. نمودار PCA نشان داد که دو مؤلفه اصلی، یعنی ویژگی‌های خاک و بارش، مجموعاً ۷۲.۱۲٪ از تغییرات پوشش گیاهی را تبیین می‌کنند. عوامل پوشش گیاهی و تولید، رابطه‌ای مستقیم و قوی با بارش، پتاسیم، سیلت، کربن و نیتروژن خاک نشان دادند، در حالی که رابطه‌ای معکوس با شوری خاک، دما و اسیدیته داشتند. یافته‌های حاصل از تحلیل مؤلفه‌های اصلی به وضوح نشان می‌دهد که ویژگی‌های خاک و بارش، دو عامل محوری در تعیین نوع و تراکم پوشش گیاهی در مراتع شور اشتهارد هستند. شناخت دقیق و مدیریت مؤثر گونه‌های گیاهی غالب، به‌ویژه Halocnemum strobilaceum، برای ساختار اجتماعی-اقتصادی این مراتع حیاتی بوده و برای پایداری اکوسیستم مراتع شور امری ضروری است.   1- Introduction Rangeland vegetation in arid regions plays a fundamental role in soil stabilization through its extensive root systems, which bind soil particles together. This action significantly enhances soil aggregate stability, thereby increasing resistance to both wind and water erosion. Furthermore, this vegetative cover aids in moisture conservation and erosion control by reducing surface runoff and promoting water infiltration. The presence of rangeland vegetation also contributes to an increase in soil organic matter and microbial activity, both crucial for soil health and stability. These characteristics underscore the essential role of rangelands in mitigating soil degradation in drylands. Saline rangelands, as unique habitats, are vital for maintaining biodiversity and ecological equilibrium. This study aims to investigate the impact of environmental factors on the vegetation cover of the Eshtehard saline rangelands and to evaluate the changes in the dominant ecotype, Halocnemum strobilaceum, under these influences, ultimately striving for optimized saline rangeland management. 2- Methodology In this study, a research methodology was designed to investigate the effects of environmental factors on the vegetation of saline rangelands in the Eshtehard region. To survey the vegetation, four 225-meter transects were established, spaced 100 meters apart. Along each transect, 15 two-square-meter plots were used for sampling at 15-meter intervals. In total, data from 60 plots were collected using a random-systematic sampling method to ensure the samples were a reliable representation of the plant community.Within each plot, the percentage of canopy cover and the production of plant species were determined by measuring the plant's diameter and using the clip-and-weigh method. Concurrently with the vegetation sampling, soil samples were collected from a depth of 0-20 cm. These samples were analyzed in the laboratory to measure key factors such as pH, EC, available nitrogen, phosphorus, and potassium, as well as organic matter and soil texture. To analyze the data and determine the relationship between vegetation and environmental factors, Principal Component Analysis (PCA) was performed using XLSTAT and MINITAB software. This statistical method helped identify the most significant environmental variables influencing differences in vegetation. Analysis of Variance (ANOVA) using a completely randomized design and the GLM test was also employed to compare the means.. 3- Results Based on the findings of this research in the Eshtehard rangeland, the average fodder production was 176.5 kg/ha and the average canopy cover was 10%. The highest values were recorded in the year 1401 (261 kg/ha production and 13.7% cover), and the lowest in the year 1404 (143 kg/ha production and 7.6% cover). The analysis of variance indicated that the mean values for cover, production, and most soil factors (silt, clay, potassium, phosphorus, carbon, nitrogen, salinity, and acidity) were statistically significant at a 1% level. Duncan's test further confirmed that the year 1401 had the highest cover and production, while 1404 had the lowest. Correlation analysis revealed that canopy cover and fodder production showed the strongest correlation with annual rainfall and soil factors such as nitrogen, carbon, potassium, acidity, and salinity. The results of the Principal Component Analysis (PCA) confirmed that two main components—soil characteristics and precipitation—accounted for 72.12% of the variations in vegetation. The first component (explaining 54.29% of the variance) was related to factors like potassium, nitrogen, and carbon, indicating a significant influence of these soil nutrients on the vegetation. The second component (explaining 17.83% of the variance) was primarily associated with temperature, soil salinity, and acidity. The PCA plot showed a strong positive relationship between vegetation cover and production with rainfall, potassium, silt, carbon, and nitrogen, while showing a negative relationship with soil salinity, temperature, and acidity. Overall, these findings highlight the critical role of soil properties and rainfall in determining the diversity and extent of vegetation in the saline rangelands of Eshtehard. 4- Discussion & Conclusions Various factors influence the vegetation cover and production of the salt marsh rangelands in Eshtehard, with the most significant being annual precipitation and soil chemical properties. As a crucial climatic factor, rainfall has a direct and considerable impact on plant growth; we observed a significant increase in vegetation cover and production during years with high rainfall. Additionally, the previous year's rainfall plays a vital role by providing soil moisture for the current year's plant growth. Soil properties also contribute significantly to this process. Nutrient elements such as potassium, nitrogen, and carbon have a direct relationship with plant growth, while factors like salinity, temperature, and acidity (pH) have an inverse effect, leading to a decrease in vegetation cover as they increase. The findings also indicate a strong correlation (with a coefficient of 0.72) between canopy cover percentage and plant production, which makes it possible to estimate production based on vegetation cover. On the other hand, the degradation of vegetation cover, for example due to excessive grazing, leads to a decline in soil's physical and chemical quality. Native plant species like Halocnemum strobilaceum, with their protective function, prevent soil erosion and salt movement. Ultimately, the crisis of declining groundwater levels in the region poses a serious threat to the survival of these plant species, making sustainable management of natural resources more essential than ever to combat desertification and preserve the ecosystem.   تحلیل مؤلفه‌های اصلی, پایش, مراتع شور, عوامل محیطی, اشتهارد. Principal Component Analysis, Monitoring, Saline Rangelands, Environmental Factors, Eshtehard. 194 214 http://magazine.hormozgan.ac.ir/browse.php?a_code=A-10-731-5&slc_lang=fa&sid=1 mina bayat مینا بیات bayat10539.m@gmail.com 10031947532846009953 10031947532846009953 Yes Rangeland Research Division, Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Tehran بخش تحقیقات مرتع، مؤسسه تحقیقات جنگلها و مراتع کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران Morteza Khodagholi مرتضی خداقلی khodagholi@rifr-ac.ir 10031947532846009954 10031947532846009954 No Rangeland Research Division, Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Tehran بخش تحقیقات مرتع، موسسه تحقیقات جنگلها و مراتع کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران Ehsan Zandi Esfahan احسان زندی baya10539.m@gmail.com 10031947532846009955 10031947532846009955 No Rangeland Research Division, Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Tehran بخش تحقیقات مرتع، مؤسسه تحقیقات جنگلها و مراتع کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران Mahshid Souri مهشید سوری souri@rifr-ac.ir 10031947532846009956 10031947532846009956 No Rangeland Research Division, Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Tehran بخش تحقیقات مرتع، مؤسسه تحقیقات جنگلها و مراتع کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران Saeedeh Nateghi سعیده ناطقی saeedehnateghi@yahoo.com 10031947532846009957 10031947532846009957 No Rangeland Research Division, Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Tehran بخش تحقیقات مرتع، مؤسسه تحقیقات جنگلها و مراتع کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران