تأثیر مدیریت چرای مراتع بر اشکال مختلف کربن آلی در دشت پنتی ایذه در استان خوزستان

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری گروه خاکشناسی، دانشکده کشاورزی، دانشگاه شهید چمران اهواز،

2 استاد گروه خاکشناسی دانشگاه شهید چمران اهواز

3 دانشیار گروه خاکشناسی دانشگاه شهید چمران اهواز

چکیده

سابقه و هدف: خاک، یک منبع کلیدی و به‏عنوان کنترل‏کننده چرخه‏های ژئوشیمیایی، آب و موجودات زنده و بزرگترین و اصلی‏ترین مخزن ماده‏ی آلی محسوب می‏شود. اطلاعات کمی در ارتباط با تأثیر مدیریت قرق بر اشکال مختلف کربن در خاک‏های مراتع استان خوزستان وجود دارد؛ لذا این مطالعه با هدف بررسی تأثیر مدیریت قرق بر میزان و اشکال مختلف کربن خاک در برخی خاک‏های مراتع دشت پنتی در استان خوزستان انجام شد.
مواد و روش‏ها: براین اساس، دو مرتع با مدیریت‏های مختلف (قرق شده و تحت چرا) در دشت پنتی ایذه انتخاب و سپس از 15 نقطه به صورت تصادفی و از دو عمق سطحی (0 تا 20 سانتی‏متری) و زیر سطحی (20 تا 40 سانتی‏متری) نمونه‏برداری صورت گرفت. پس از هواخشک کردن نمونه‌های خاک و عبور آن‌ها از الک دو میلی‌متری، خصوصیات فیزیکی، شیمیایی و اشکال مختلف کربن خاک شامل کربن آلی کل، کربن قابل اکسید شدن به‏وسیله پرمنگنات، کربن آلی ذره‏ای ریز و درشت، کربن محلول در آب و کربن زیتوده میکروبی خاک‏ها اندازه‌گیری شد.
یافته‏ها: نتایج نشان داد که مدیریت قرق درخاک‏های سطحی و زیرسطحی باعث افزایش میزان ماده آلی خاک شده است ولی در خاک‏های زیرسطحی علی‏رغم افزایش میزان مواد آلی، مقدار آن از لحاظ آماری معنی‏دار نبوده است. در لایه‏های سطحی مقدار آن معنی‏داری بوده است و باعث افزایش میزان کربن آلی کل (از 33/8 به 53/9 گرم بر کیلوگرم)، کربن آلی محلول (از 46/9 به 86/10 میلی‏گرم بر لیتر)، کربن زیتوده میکروبی (از1/418 به 2/456 میلی‏گرم بر کیلوگرم)، کربن قابل اکسید شدن توسط پرمنگنات (از 25/974 به 3/1035 میلی‏گرم بر کیلوگرم)، کربن آلی ذره‏ای ریز (از 6/430 به 7/450 میلی‏گرم بر کیلوگرم) و کربن آلی ذره‏ای درشت (از10/680 به 4/701 میلی‏گرم بر کیلوگرم) شده است. به نظر می‏رسد برای اینکه اثر تغییرات مدیریت به قسمت‏های پایین‏تر خاک تأثیرگذار شود نیازمند مدیریت با مدت زمان بیشتری هست. مقایسه بیومس در داخل (405 گرم بر متر مربع) و خارج قرق (117 گرم بر متر مربع) حاکی از وضعیت خوب پوشش گیاهی در داخل قرق و مؤثر بودن قرق در احیا مراتع منطقه می باشد.
نتیجه‏گیری: نتایج نشان داد که کربن زیتوده میکروبی، کربن محلول خاک و کربن قابل اکسید شدن توسط پرمنگنات حساسیت بیشتری به مدیریت قرق نسبت به اشکال دیگر کربن داشته و شاخص‏های مناسبتری برای بررسی تأثیر مدیریت قرق بر کیفیت کربن آلی اضافه شده به خاک می‏باشند. همچنین، بر اساس شاخص نسبت طبقه‏بندی کربن نسبت به اشکال مختلف کربن آلی در این مطالعه، مدیریت قرق یکی از اقدامات مدیریتی مناسب و کارآمد بوده و باعث بهبود کیفیت خاک گردیده است؛ از این رو ضروری به نظر می‏رسد که تیمار قرق به‏عنوان یکی از برنامه‏های اصلی در طرح‏های منابع طبیعی تجدید شونده مد نظر قرار گیرد. در کل نتایج این مطالعه حاکی از اثرات نامطلوب چرای مراتع بر کیفیت مواد آلی خاک است که می‏تواند در درازمدت پایداری تولید در اکوسیستم‏های مرتعی را به خطر بیندازد.

کلیدواژه‌ها


عنوان مقاله [English]

Effects of Grazing on Different Forms of Organic Carbon in Peneti Plain of Izeh Area in Khuzestan Province

نویسندگان [English]

  • Alireza Owji 1
  • Saeid Hojati 3
1 Phd student, Dept. of Soil Science, Shahid Chamran Univ. of Ahvaz, Iran
2 Shahid Chamran University of Ahvaz
چکیده [English]

Background and objectives: Soil is a key resource that control the cycles of water, biota and geochemicals and the greatest organic matter reservoir. Little information is available about the effects of grazing on different forms of soil organic carbon in Khuzestan Province pastures. Therefore, this study was conducted to evaluate the effects of grazing management on amount and forms of organic carbon in some pasture soils from Peneti Plain of Izeh Area in Khuzestan Province.

Materials and methods: Accordingly, two adjacent pastures with different management (grazing and grazing exclusion) around the Izeh city were selected and then, random soil samples were taken from the surface (0 to 20 cm) and subsurface (20 to 40 cm) in 15 points. After air drying the soil samples and passing them through a 2 mm sieve, physical, chemical properties and forms of organic carbon including total organic carbon (TOC), permanganate-oxidizable carbon (POXC), fine particulate organic carbon (FPOC) and coarse particulate organic carbon (CPOC), dissolved organic carbon (DOC) and microbial biomass carbon (MBC) of the soils were measured.

Results: The results showed that grazing management has increased soil organic matter of surface and subsurface soils the values were statistically significant in the surface layers, and increased the amounts of TOC (from 8.33 to 9.53 g kg-1), DOC (from 9.46 to 10.86 g L-1), MBC (from 418.1 to 456.2 mg kg-1), POXC (from 974.25 to 1035.3 mg kg-1), FPOC (from 430.6 to 450.7 mg kg-1) and CPOC (from 680.10 to 701.4 mg kg-1), but despite the increase in organic matter contents of subsurface soils the difference was not statistically significant. The effect of management practices, in order to have a significant effect to lower parts of the soil, it requires a longer period management. Comparing the biomass upon non-grazing (405 gm-2) and grazed (117 gm-2) areas, indicates a good condition of vegetation in the non-grazing and the effectiveness of enclosure in rehabilitation of pastures in the study area.

Conclusion: The results showed that MBC, DOC, and POXC are more sensitive than other forms of organic carbon to grazing management. They are more appropriate indicators for grazing management on organic carbon quality being added to the soil. Also, based on carbon stratification ratio index (CSRI), regarding different forms of organic carbon in the study area, non-grazing was one of the most proper and efficient management practices which improved soil quality. Accordingly, it seems that non-grazing practices should be considered as one of the major programs in renewable natural resources plans. On the other hand, the results indicate adverse effects of grazing on the quality of soil organic matter endangering the long-term sustainable production in pastures.

کلیدواژه‌ها [English]

  • Pasture
  • Grazing management
  • Soil carbon
  • Soil quality
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