تغییرات خصوصیات فیزیکی و شیمیایی خاک تحت تأثیر شدت چرای دام در مراتع مغان

نوع مقاله : مقالات پژوهشی

نویسندگان

دانشگاه محقق اردبیلی

چکیده

خاک از مهمترین اجزای تشکیل‌دهنده اکوسیستم‌های مرتعی و تخریب آن، کاهش توان تولید مرتع را در پی خواهد داشت. این تحقیق با هدف بررسی تأثیر شدت چرا بر خصوصیات خاک در مراتع مغان با استفاده از چارچوب گرادیان چرایی انجام شد. سه روستای تولکلو، کلش و پنجالو بعنوان نماینده مراتع علف - بوته‌زار مغان انتخاب شد. نمونه‌برداری، از سه شدت چرا و در سه فاصله از هر سه روستا انجام شد. در هر فاصله از روستا، سه نمونه خاک، از عمق 0 تا 30 سانتی‌متری (27 نمونه) برداشت شد. پارامترهای خاک شامل اسیدیته، هدایت الکتریکی، رطوبت وزنی اشباع، سدیم، پتاسیم، کلسیم و منیزیم محلول، پتاسیم تبادلی، فسفر قابل جذب، درصد مواد خنثی‌شونده، کربن آلی، کربن آلی ذره‌ای، رس قابل انتشار، نیتروژن کل، میانگین وزنی قطر خاکدانه‌ها و بافت خاک اندازه‌گیری شد. برای مشخص کردن روند تغییر پارامتر‌ها در شدت چراهای مختلف، از شدت چراهای سنگین، متوسط و سبک هر سه روستا میانگین گرفته شد. تجزیه و تحلیل داده‌ها با روش تجزیه واریانس دو طرفه و با استفاده از آزمون دانکن انجام شد. نتایج نشان داد، میزان پتاسیم محلول و آهک خاک با افزایش شدت چرا، افزایش (05/0>P) ولی میزان سدیم محلول و درصد سیلت خاک به صورت معنی‌داری کاهش (05/0>P) می‌یابند ولی در پارامترهای دیگر اختلاف معنی‌داری مشاهده نشد. نتایج همچنین نشان داد که شدت چرا اثر منفی بر برخی خصوصیات فیزیکوشیمیایی خاک از جمله آهک، سدیم محلول و درصد سیلت خاک دارد. بنابراین، در مدیریت مراتع و انجام برنامه‌های اصلاحی و احیایی، باید به خصوصیات فیزیک وشیمیایی خاک توجه شود.

کلیدواژه‌ها


عنوان مقاله [English]

The Effects of Livestock Grazing Intensity on Soil Physicochemical Properties in Moghan Rangelands

نویسندگان [English]

  • S. Jafari
  • Ardavan Ghorbani
  • K. Hashemimajd
  • S. Ghafari
University of Mohaghegh Ardabili
چکیده [English]

Introduction: Soil is one of the important components of rangeland ecosystems. Soil is the natural and dynamic layer of the earth that act as an important component of rangeland ecosystems for the human food security and plants mechanical support which is the background for growth of them. Soil degradation decreases the potential of rangeland production; because soil is the primary factor for forage production in any rangelands with any kind of weather. Different grazing intensities change the chemical and physical properties of soil and plant composition of rangelands. It is important to know soil properties for the proper management of rangeland ecosystems. Therefore, this study was carried out with the objective of investigating the effects of grazing intensity on soil physical and chemical properties in Moghan rangelands using grazing gradient framework.
Materials and Methods: Three villages of Tolklo, Kolash and Panjalo were selected as the representatives of grass-shrubland in Moghan rangelands, in Parsabad county, Ardabil province, northwest of Iran. Samples were collected from three grazing intensities and three distances from the center of villages, as the critical center. Three soil samples were taken at each distance of village (three replications) from 0 to 30 cm (main root activity areas) depth (27 samples). Soil parameters including pH, electrical conductivity, saturated water content, dissolved sodium, potassium, calcium, magnesium, exchangeable potassium, available phosphorus, calcium carbonate equivalent, organic carbon, particulate organic carbon, dispersible clay, total nitrogen, aggregate mean weight diameter and soil texture were measured. To identify the trend of changing soil parameters in different grazing intensities including light, moderate and heavy, weighted average was taken for each three samples, which were collected from the three-grazing intensity at each village. Data statistically analyzed by using the Two-way analysis of variance and using Duncan’s multiple range test.
Results and Discussion: The results of the soil data analysis showed that except dissolved sodium and potassium, lime and soil silt percentage, there was no significant statistical difference between measured values of soil properties in different grazing intensities in Moghan rangelands. The result of the mean comparison for soluble sodium and potassium, lime and soil silt percentage showed that with increase of grazing intensity, the values of soluble sodium decreased. In addition, at the nearby of critical center and with the increase of grazing intensity, the values of soluble potassium increased. However, its highest and lowest amount was observed at the heavy grazing intensity and moderate grazing intensity, respectively. The highest and lowest amount of lime were also observed at the heavy and light grazing intensity, respectively. In other words, in nearby to critical center and with the increase of grazing intensity the value of these parameters increased. The results of the data analysis for soil texture showed that in both areas with the light and moderate grazing intensity, soil texture class was silty clay loam, but in the areas with heavy grazing intensity, soil texture class had gradually changed from silty clay loam to loamy texture. In other words, the soils had progressed to sandy soils, which is due to the change in their silty particles. With approaching to the critical center and with increase of grazing intensity the value of silt percentage decreased. The highest amounts of silt percentage were related to the light and moderate grazing intensities and its lowest amount was recorded in heavy grazing intensity. Results showed that the effects of heavy grazing on soil properties in the grazing gradient framework is detectable, and this framework can be sued for rangeland monitoring to detect the rangeland condition.
Conclusion: Heavy grazing and overall utilization of rangelands have caused soil degradation in most rangelands of Iran. This study revealed that heavy grazing jeopardized the sustainability of the rangeland ecosystem by creating unfavorable changes in soil and avalable minerals. Therefore, it recommended that soil parameters must be included in rangeland inventory and monitoring to use soil information for sustainable range management and, particularly in rangeland restoration and to select sustainable strategies for better and suitable management of these rangelands.

کلیدواژه‌ها [English]

  • Critical center
  • Grazing gradient
  • Rangeland ecosystem
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