مدل‏سازی تاثیر تبدیل پوشش گیاهی و تغییر اقلیم بر دینامیک ذخیره کربن آلی خاک در یک اکوسیستم پیچیده

نوع مقاله : مقاله کامل علمی پژوهشی

نویسندگان

1 کارشناس ارشد مدیریت مناطق بیابانی، بخش مهندسی منابع طبیعی و محیط زیست، دانشگاه شیراز،

2 استادیار بخش مهندسی منابع طبیعی و محیط زیست، دانشگاه شیراز

چکیده

سابقه و هدف: تبدیل پوشش گیاهی طبیعی به سایر پوشش‏های گیاهی و تغییر اقلیم اثرات زیادی بر تجزیه کربن آلی خاک و در نهایت میزان انتشار دی‏اکسیدکربن (CO2) از خاک به اتمسفر گذاشته‏اند. اما تاکنون در ایران تحقیقات انگشت شماری به بررسی اثر تبدیل پوشش گیاهی و تغییر اقلیم بر میزان ذخیره کربن آلی به عنوان یک مؤلفه کلیدی در کاهش اثرات تغییر اقلیم و گرمایش جهانی پرداخته‏اند. جهت فائق آمدن بر محدودیت مطالعات میدانی، مدل‏های ماده ‏آلی خاک، ارائه دهنده بهترین درک علمی از دینامیک ماده‏آلی خاک هستند. مدل کربن روتامستد (RothC ) از پرکاربردترین مدل‏ها در مطالعات مربوط به ترسیب کربن خاک می‏باشد که در مطالعات فراوانی برای بررسی اثر تغییر اقلیم بر ذخیره کربن خاک به‌ کارگرفته شده است. هدف تحقیق حاضر بررسی اثر تبدیل پوشش گیاهی بومی (مرتع) به چهار پوشش گیاهی جدید (مراتع زیر اشکوب سرو، مراتع زیراشکوب بادام کوهی، درختان بادام کوهی و درختان سرو) و همچنین شبیه سازی اثر دو سناریو اقلیمی (عدم وقوع تغییر اقلیم و وقوع تغییر اقلیم) بر دینامیک ذخیره کربن آلی خاک (SOC ) با استفاده از مدل کربن روتامستد (RothC) درپنج پوشش گیاهی منطقه باجگاه شهرستان شیراز برای 36 سال (2014-2050) می‏باشد.
مواد و روش‏ها: در این مطالعه 210 نمونه خاک برای تعیین کربن آلی خاک و بافت خاک و همچنین 420 نمونه به منظور تعیین وزن مخصوص ظاهری خاک جمع آوری شده است. پس از اندازه‏ گیری پارامترهای ذکر شده، ذخیره کربن آلی خاک در عمق 20-0 سانتی‏متری در هر تیمار پوشش گیاهی محاسبه شد. در نهایت اثر تبدیل پوشش گیاهی و دو سناریو اقلیمی بر میزان ذخیره کربن آلی خاک با استفاده از مدل روتامستد در پنج پوشش گیاهی منطقه باجگاه شیراز بررسی شد.
یافته‏ ها: نتایج نشان داد که افزایش ذخیره کربن آلی خاک در اثر کاشت درختان سرو بعد از 15 سال بیشتر از میزان افزایش ذخیره کربن آلی خاک در اثر کاشت درختان بادام کوهی بعد از 30 سال در منطقه باجگاه بوده است. نتایج شبیه‏ سازی مدل روتامستد نیز نشان داد ذخیره کربن آلی خاک در سال 2050 در تیمارهای مرتع، مراتع زیر اشکوب درخت بادام، مراتع زیر اشکوب درخت سرو، درختان سرو و درختان بادام در اثر تغییر اقلیم نسبت به سال 2014 به ترتیب 19/12، 14/12، 11/12، 37/10 و 49/10 درصد کاهش خواهد یافت. میزان ذخیره کربن آلی خاک در هر کدام از تیمارها، قبل و بعد از تغییر اقلیم در سطح 5 درصد (p <0.05) باهم تفاوت معنی ‏دار داشتند.

کلیدواژه‌ها


عنوان مقاله [English]

Modeling the effect of vegetation conversion and climate change on the dynamics of soil organic carbon stock in a complex ecosystem

نویسندگان [English]

  • Bijan Azad 1
  • Sayed Fakhreddin Afzali 2
  • gholamabbas ghanbarian 2
1 Shiraz University
چکیده [English]

Background and Objectives: The conversion of natural vegetation to other vegetation covers and climate change has had a major impact on the decomposition of soil organic carbon and eventually the emission of carbon dioxide (CO2) from the soil into the atmosphere. But so far in Iran, little researches have looked at the effect of the conversion of vegetation and climate change on the amount of soil organic carbon (SOC) stock as a key component in reducing the effects of climate change and global warming. To overcome the limitations of field studies, SOM models provide the best scientific understanding of the dynamics of SOM. RothC Carbon model is one of the most widely used models in soil carbon sequestration studies that has been used in many studies to study the effect of climate change on soil carbon stock. The purpose of present study, investigate the effect of converting native vegetation (rangeland) into four new vegetation (rangelands of cypress under-story, rangelands of almond under-story, cypress trees and almond trees), as well as the simulation of the effect of two climate scenarios (non-occurrence of climate change and the occurrence of climate change) on the dynamics of SOC stock in the five vegetation covers of the Shiraz Bajgah region for 36 years (2014-2050).
Materials and Methods: In this study, 210 soil samples were collected to determine the soil organic carbon and soil texture as well as 420 samples for determining the soil bulk density. After measuring the parameters, SOC stock at 0-20 cm depth was calculated for each vegetation cover treatment. Finally, the effect of vegetation conversion and two climate scenarios on the amount of SOC stock using the RothC model was investigated in the five vegetation covers of Shiraz Bajgah region.
Results: The results showed that the increase of SOC stock due to planting of cypress trees after 15 years was higher than the amount increase of SOC stock due to the planting of almond trees after 30 years in Bajgah region. The simulation results of the RothC model also indicated that in comparison with 2014, the SOC stock in the 2050 in the rangeland, rangelands of almond under-story, rangelands of cypress under-story, cypress trees and almond trees treatments will be decreased by 12.19%, 12.14%, 12.11%, 10.37% and 10.49%, respectively due to climate change; and the amount of SOC stock in each of the treatments before and after climate change at 5% level (P <0.05) had significant difference.

کلیدواژه‌ها [English]

  • Keywords: Vegetation conversion
  • Soil organic carbon (SOC) stock
  • Rothamsted carbon model (RothC)
  • Bajgah region
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