با همکاری انجمن آبخیزداری ایران

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشیار، بخش تحقیقات حفاظت خاک و آبخیزداری، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان کرمانشاه، سازمان تحقیقات، آموزش و ترویج کشاورزی، کرمانشاه، ایران

2 دانشیار، پژوهشکده حفاظت خاک و آبخیزداری، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران، ایران

چکیده

تغییر کاربری جنگل‏‌ها دارای پیامدهای متعددی از جمله تشدید وقوع سیل، فرسایش، رسوب و گرد و غبار است. به‌همین منظور، پژوهش حاضر با هدف بررسی تاثیرات تغییر کاربری جنگل‏های زاگرس بر فرسایش‏‌پذیری و رسوب‌‏زایی از طریق کاهش کیفیت خاک در بخشی از جنگل‏‌های استان کرمانشاه انجام شد. در این راستا، ابتدا دو محدوده جنگلی و دیم­زار مجاور آن که طی 10 سال اخیر بر اثر تغییر کاربری جنگل حاصل شده بود، انتخاب و 35 نمونه خاک از لایه سطحی (صفر تا 20 سانتی‌‏متر) از هر دو کاربری برداشت شد. سپس، آزمایش‌های فیزیکی و شیمیایی روی نمونه‌های خاک انجام گرفت. در مرحله بعدی، میزان فرسایش‌‏پذیری خاک محاسبه و میزان تولید رسوب هر دو کاربری با استفاده از باران‌ساز قابل حمل در صحرا اندازه‏‌گیری شد. نتایج این بررسی نشان داد که شش ویژگی مهم و کلیدی خاک، شامل پایداری خاک‌دانه‌‏ها، وزن مخصوص ظاهری، کربن آلی، ازت کل، پتاسیم و ظرفیت تبادل کاتیونی از نوع کاربری زمین، تاثیر معنی‌داری پذیرفته‌اند. البته در همه نمونه‌‏های مورد آزمایش مجموع رس و سیلت حدود 80 درصد بود که موجب تشکیل خاک با بافت سنگین شده است. متعاقبا عامل فرسایش‌‏پذیری خاک (K) و نیز شدت تولید رسوب در دیم‌‏زار نسبت به عرصه جنگلی به‏ لحاظ معنی‏‌داری بیشتر به‌دست آمد. با توجه به نتایج این بررسی و نقش اکوسیستم‏ جنگلی زاگرس در استحصال آب باران، تغذیه آب‌های زیرزمینی و مهار سیل و گرد و غبار، تداوم روند فعلی تغییر کاربری این جنگل‏‌ها به‌‏همراه شخم نامناسب، سوزاندن بقایای محصول و تردد ماشین‏‌آلات در دیم‌‏زارهای حاشیه آن‌ها، موجب تشدید گرمایش زمین، افزایش ضریب رواناب و تبخیر، بحران کم‌‏آبی نسبت به شرایط کنونی خواهد شد.

کلیدواژه‌ها

عنوان مقاله [English]

The effect of land use change from forest to rain-fed farms on soil physico-chemical characteristics, erodibility and sediment yield

نویسندگان [English]

  • Mosayeb Heshmati 1
  • Mohammad Ghaietury 1
  • Mahmood Arabkhedri 2
  • Yahya Parvizi 1

1 Associate Professor, Soil Conservation and Watershed Management Research Department, Kermanshah Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Kermanshah, Iran

2 Associate Professor, Soil Conservation and Watershed Management Research Institute (SCWMRI), Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran

چکیده [English]

Forest and land use change has many negative consequences including increased flooding, erosion, sedimentation and dust storms. The aim of the research was thus to investigate the effects of land use change in Zagros forests on erodibility and sedimentation via soil quality reduction in some forests of Kermanshah Province, Iran. In order to achieve this aim, in the first step, afforest area and its adjacent rain-fed farm (which is developed during recent 10 years a result of forest land change), were selected and 35 soil samples were collected from the surface layer (0-20 cm). Then, the physico-chemical analyses were done on the soil samples. In the next step, soil erodibility factor was calculated and sediment yield was assessed using portable rainfall simulator. The results showed that six key properties of soil including soil aggregate stability, bulk density, organic carbon, total nitrogen, total absorbable potassium and cation exchange capacity were significantly (p<0.05) influenced by land use type. Additionally, in all tested samples, the total clay and silt content was about 80%, which  resulted in the formation of soil with heavy texture. Subsequently soil erodibility factor (K) and sediment yield intensity in rain-fed farm was found significantly (P<0.05) higher than those of forest. According to the results and  the role of  Zagros forest ecosystem on water harvesting, aquifer recharge, flood and dust control, the current trend of changing forest landuse to arable lands accompanying improper tillage practice, crops residue burning and heavy machinery traffic in nearby rain-fed farms, cause accelerating global warming, increasing runoff coefficient and evaporation as well as water scarcity in future.

کلیدواژه‌ها [English]

  • Soil aggregates stability
  • Zagros forests
  • Small-revenue rain-fed farms
  • Organic carbon
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