کاربرد مدل RothC در شبیه‌سازی اثر تغییرات اقلیمی بر انتشار کربن دی‌اکسید و ذخایر کربن آلی خاک اقلیم نیمه‌خشک خراسان رضوی

آب و خاک

مقاله 6، دوره 36، شماره 5 - شماره پیاپی 85، آذر و دی 1401، صفحه 611-628   

نوع مقاله: مقالات پژوهشی

شناسه دیجیتال (DOI): 10.22067/jsw.2022.78752.1202

نویسندگان

صبا باقریفام¹؛ محمد امیر دلاور^{* 2}؛ پیمان کشاورز³؛ پرویز کرمی⁴

¹دانشجوی دکتری گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه زنجان، زنجان، ایران

²دانشیار گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه زنجان، زنجان، ایران.

³دانشیار بخش تحقیقات خاک و آب، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی خراسان رضوی، مشهد، ایران.

⁴استادیار گروه مهندسی مرتع و آبخیزداری، دانشکده منابع طبیعی، دانشگاه کردستان، سنندج، ایران.

چکیده

خاک با از دست دادن کربن به شکل کربن دی‌اکسید، پتانسیل زیادی برای تشدید گرمایش زیست‌کره دارد. از سوی دیگر امکان ترسیب کربن در خاک، راهکار مناسبی جهت کاهش انتشار کربن دی‌اکسید شناخته می‌شود. خاک‌های مناطق خشک و نیمه‌خشک جهان اگرچه حاوی مقادیر کمی کربن آلی هستند؛ اما به‌واسطه وسعت زیاد، امکان ترسیب مقادیر قابل‌توجهی کربن آلی را دارند. از این‌رو جهت بررسی تغییرات ذخایر کربن آلی خاک اراضی زراعی اقلیم نیمه‌خشک جلگه‌‌رخ واقع در استان خراسان رضوی، مدل رتامستد با استفاده از داده‌های مطالعات پیشین و مقادیر اندازه‌گیری شده در سال 2020 اعتبارسنجی شد. مقایسه بین مقادیر کربن آلی اندازه‌گیری شده و شبیه‌سازی‌شده توسط مدل، نشانگر قابلیت مدل در ارائه پیش‌بینی‌هایی با دقت مناسب بود. به‌طوری‌که مقادیر ضریب تبیین، ریشه میانگین مربعات خطا، میانگین مطلق خطا، تفاوت میانگین و شاخص کارایی مدل به ترتیب معادل 97/0، 78/2، 11/2، 33/2 و 70/0 به‌دست آمدند. سپس تأثیر تغییرات اقلیمی بر انتشار کربن دی‌اکسید و ذخایر کربن آلی خاک منطقه مدل‌سازی شد. بررسی تغییرات اقلیمی منطقه در (دوره آماری 1981 تا 2020) نشانگر کاهش بارندگی و افزایش معنی‌دار دما طی 40 سال گذشته بوده است. مدل‌سازی تغییرات اقلیمی تا پایان قرن جاری با اعمال افزایش دما و کاهش بارندگی انجام شد که نتایج بیانگر کاهش همه ذخایر کربن فعال مدل بود، چنان‌که مخازن مواد گیاهی تجزیه‌پذیر، مواد گیاهی مقاوم، زیست‌توده میکروبی، مواد آلی هوموسی‌شده و کل کربن آلی خاک به‌ترتیب معادل 41/2، 72/2، 51/2، 04/1 و 32/1 درصد نسبت به شرایط عدم وقوع تغییرات اقلیمی کاهش و میزان انتشار تجمعی کربن دی‌اکسید از خاک، 26/1 درصد افزایش نشان داد. افزایش دما باعث افزایش ضریب تصحیح دما (a) به میزان 20/2 درصد شد که منجر به افزایش سرعت تجزیه کربن آلی و تلفات کربن به شکل کربن دی‌اکسید شده است؛ اگرچه باعث افزایش تولید خالص اولیه بوم‌نظام نیز گردید. کاهش بارندگی و افزایش تبخیر و تعرق پتانسیل نیز باعث کاهش ضریب تصحیح رطوبت (b) به میزان 23/0 درصد شد؛ این فرایند از یک سو با کاهش فعالیت ریزجانداران موجب کاهش تجزیه زیستی کربن و انتشار کربن دی‌اکسید از خاک شده است؛ اما از سوی دیگر موجب کاهش درصد پوشش گیاهی و پیرو آن به دام انداختن کربن دی‌اکسید طی فرایند فتوسنتز و انتقال آن به خاک می‌گردد.

کلیدواژه‌ها

تجزیه ماده آلی خاک؛ ترسیب کربن؛ شاخص کارایی؛ گرمایش جهانی؛ مدل رتامستد

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