تاثیر تغییر کاربری اراضی بر ذخیره کربن آلی و برخی ویژگی‌های بیولوژیکی خاک در بخشی از حوزه‌ی آبخیز رکعت در استان خوزستان

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشجوی کارشناسی ارشد گروه خاکشناسی، دانشکده کشاورزی، دانشگاه شهید چمران، اهواز، ایران

2 دانشیار گروه خاکشناسی، دانشکده کشاورزی، دانشگاه شهید چمران اهواز، خوزستان ایران

3 استادیار گروه خاکشناسی، دانشکده کشاورزی، دانشگاه شهید چمران، اهواز، ایران

4 کارشناس ارشد، اداره کل منابع طبیعی و آبخیزداری استان خوزستان، اهواز، ایران

چکیده

خاک اصلی‌ترین منبع کربن در اکوسیستم‌های خشکی است، اما فعالیت‌های انسان در سراسر جهان از جمله تغییر کاربری اراضی منجر به کاهش قابل توجه کربن خاک گردیده است. به نظر می‌رسد که در طول قرن گذشته تغییر گسترده کاربری اراضی موجب هدر رفت بخش عظیمی از کربن آلی خاک‌ها شده است. از اینرو این مطالعه به منظور بررسی تاثیر تغییر کاربری اراضی از مرتع به زراعت بر ذخیره کربن آلی (C Stock) و برخی شاخص‌های بیولوژیکی خاک شامل  (کربن آلی کل (SOC)، تنفس پایه خاک (BSR)، کربن زیست توده میکروبی (MBC)، نسبت میکروبی (MQ) و ضریب فعالیت متابولیکی (qCO2)) در شرق استان خوزستان (حوزه آبخیز رکعت) مورد بررسی قرار گرفت. برای این منظور نمونه‌های خاک در هشت تکرار از لایه‌های 15-0 و 30-15 سانتیمتری در هر دو کاربری تهیه شدنددر این آزمایش مقادیر qCO2 ، میزان SOC، MBC و  MQدر کاربری کشاورزی نسبت به مرتع طبیعیتفاوت معنی داری نداشتند ولی  مقدار ذخیره کربن آلی خاک نیز در کاربری کشاورزی در لایه‌های 15-0 و 30-15 سانتیمتری با مقادیر 5/19، 3/8 تن بر هکتار نسبت به مرتع طبیعی (7/29، 9/15 تن بر هکتار) به ترتیب 34 و 47 درصد کاهش یافت. مقدار SOC در کاربری کشاورزی در لایه‌های سطحی و زیرسطحی خاک (47/8، 28/5 گرم برکیلوگرم خاک) نسبت به مرتع طبیعی (29/13، 55/6 گرم برکیلوگرم خاک) 36 و 19درصد کاهش داشت. همچنینMBC  در لایه­های 15-0 و 30-15 سانتیمتری خاک در کاربری کشاورزی نسبت به مرتع طبیعی به میزان 60 و 71 درصد کاهش، MQ به میزان 37 و 65 درصد کاهش و qCO2 به میزان 4-3 برابر افزایش نشان دادند.بطور کلی تغییر کاربری اراضی موجب هدر رفت قابل توجه کربن آلی کل و تقریباً نیمی از ذخیره کربن آلی در سطح خاک شده است. کم شدن مقدار کربن آلی در کاربری کشاورزی موجب کاهش قابل توجهی در کربن زیست توده میکروبی نسبت به سایر صفات گردیده است که می‌توان آن را یک شاخص کلیدی در ارزیابی تغییرات کربن آلی خاک به حساب آورد.

کلیدواژه‌ها


عنوان مقاله [English]

Effect of land use change on C stock and some biological characteristics of soils in parts of Rakaat watershed, east of Khuzestan province

نویسندگان [English]

  • parisa heydari 1
  • Saeid Hojati 2
  • naieme enayati 3
  • amir raiat pishe 4
2 Associate Professor of Soil Science, Shahid Chamran University of Ahvaz, Khuzestan, Iran
چکیده [English]

Soil is a major reservoir of terrestrial carbon, but human activities around the world including land use change lead to a significant emission of carbon from the soil. It seems that soil organic carbon has been significantly decreased due to the land use changes over the last century in Iran. Therefore, the objective of this study was to investigate the effect of land use change (rangeland to agriculture) on organic carbon stock and some biological indices of soil quality (soil organic carbon (SOC), basal soil respiration (BSR), microbial biomass carbon (MBC), microbial quotient (MQ), and metabolic coefficient (qCO2) in east of Khuzestan province. Soil samples were collected in eight replicates and two depths (0-15 and 15-30 cm) in both land uses. Results showed that except qCO2, the amount of TOC, MBC, and MQ in agricultural use decreased significantly as compared to rangeland. According to the results, C stock of agricultural lands in 0-15 and 15-30 cm layers was 19.5 and 8.3 Mgha-1, showing 34 and 47 percent decrease when compared to natural rangeland with 29.7 and15.9 Mgha-1 C stock. The SOC content in 0-10 cm soil layers of agricultural use and natural rangeland was (8.47 and 5.28 gKg-1) and (13.29, 6.55 gKg-1), respectively, demonstrating 60 and 71 percent reduction in agricultural lands. In addition, in 0-15 and 15-30 cm layers of agricultural lands, MBC (60 and 71 percent), MQ (37 and 65 percent) showed reduction and qCO2 increased 3-4 times when compared to natural rangeland. Results show that agricultural activities lead to considerable loss in total organic carbon and half of organic carbon stock in the soil. Limitation of organic carbon in agricultural land use makes noticeable reduction in MBC than other properties. Thus, it can be used as a suitable indicator for monitoring changes of organic carbon in the soil.

کلیدواژه‌ها [English]

  • carbon stock
  • land use
  • Microbial biomass
  • rangeland
  • respiration

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