با همکاری انجمن آبخیزداری ایران

نوع مقاله : مقاله پژوهشی

نویسندگان

1 استادیار، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان خوزستان، اهواز

2 دانشیار، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان فارس

3 دانشیار، دانشکده منابع طبیعی، دانشگاه تربیت مدرس

4 استاد، دانشکده کشاورزی، دانشگاه شهرکرد

چکیده

 این پژوهش با هدف انجام مطالعات مورفومتری، بررسی ارتباطات هندسی بین آن­‌ها، در دو کاربری مرتعی و کشاورزی انجام شده است. در ابتدا، ویژگی‌­های هندسی و توپوگرافی 120 آبکند در بخش نیمه‌خشک استان شامل عرض بالا، عمق، عرض پایین، ارتفاع بالاکند، همچنین، ویژگی­‌های سطح حوزه آبخیز آبکندها شامل میزان پوشش سطحی و خاک لخت به‌وسیله پلات­‌های یک متر مربعی به همراه نمونه‌­های ترکیبی خاک از سطح حوزه آبخیز و دیواره آبکند­ها برداشت شد. بر نمونه‌­های خاک آزمایش‌­های فیزیکی و شیمیایی از قبیل بررسی بافت خاک، مواد آلی، آهک کل و فعال، هدایت الکتریکی، اسیدیته، سدیم، منیزیم و کلسیم در آزمایشگاه انجام شد. نتایج بررسی روابط مورفومتریک آبکندها نشان داد که نسبت عرض بالا به عمق آبکندهای کشاورزی و مرتعی به‌ترتیب برابر با 2.1 و 1.5 بوده، نسبت عرض بالا به طول به‌­ترتیب در کاربری کشاورزی و مرتعی برابر با 0.41 و 0.57 به‌­دست آمد که در نتیجه آبکندهای مرتعی کشیدگی بیشتری داشته­‌اند. رابطه معکوس نمایی بین شاخص‌های فوق با شیب نشان داد که عوامل توپوگرافی بر شکل نهایی آبکندها تاثیرگذار بوده است. شاخص عرض پایین به عرض بالا به‌ترتیب در آبکندهای کشاورزی و مرتعی برابر با 0.33 و 0.30 و شکل مقطع­‌های عرضی به‌ترتیب ذوزنقه و V بوده است. نتایج همچنین نشان داد که عامل شیب 14 درصد از تغییرات مساحت مقطع­های عرضی را تبیین کرده، رشد عرضی آبکندها در کاربری­‌های کشاورزی و مرتعی به‌ترتیب 84 و 73 درصد از تغییرات حجم فرسایش را تبیین کرده است و عوامل با تاثیر مثبت بر تغییر حجم فرسایش آبکندی میزان ماسه در خاک سطحی، کاربری و شیب بودند. آبکندهای مورد مطالعه در هر دو کاربری دارای بعد فراکتال متوسط 1.08 بوده­‌اند و به‌صورت خطی با افزایش طول و به‌صورت توانی با افزایش حجم آبکندها افزایش یافته است. توان مساحت در قاعده هک در آبکندهای کشاورزی و مرتعی به‌ترتیب برابر با 0.50 و 0.54 بوده است.

کلیدواژه‌ها

عنوان مقاله [English]

Morphometric relationships of Ilam Province gullies

نویسندگان [English]

  • Banafshe Yasrebi 1
  • Majid Soufi 2
  • Mir Khalagh Mirnia 3
  • Jahangard Mohammadi 4

1 Assistant Professor at Khuzestan Agricultural and Natural Resources Research and Education Center

2 Associate Professor, Fars Agricultural and Natural Resources Research and Education Center

3 Associate Professor, Department of Watershed Management Science and Engineering, Tarbiat Modaress Univesity

4 Professor, Faculty of Agriculture, Shahrekord University, Iran

چکیده [English]

This research focused on studying the morphometric characteristics, topographic threshold of gullies and their relationships, dominant process of gully initiation and development stages as well, in agricultural and rangeland land uses. Also, morphometric characteristics of 120 gullies including top width, bottom width and headcut height and surface characteristics of gullies contributing area including vegetation, rock fragment and bare soil by 1 m2 plot and soil samples from top soil and gullies wall were collected in semi-arid part of Ilam Province. Results showed that top width–depth ratio of gullies in cropland and rangeland is 2.1 and 1.5, respectively that widening and deepening has more important role in gully growth. Top width-length ratios are 0.41 and 0.57 in croplands and rangelands, respectively that shows rangeland gullies are more elongated. Negative exponential relationship between those ratios and slope shows the effect of topographic factors especially slope on final shape of gullies. Bottom width-top width ratio in croplands and rangelands is about 0.33 and 0.3, respectively and cross section shapes are trapezoidal and V shape. Results showed that slope describes 16 percent of cross sections area variation and lateral growth of gullies in croplands and rangelands and describes 84 and 73 percent of gully volume variation. Effective factors on gully volume are sand content in top soil, land use and slope. Studied gullies in both land uses have mean fractal dimension of 1.08 and has linear growth with length and power growth with volume of gully. Power of Hack law in studied gullies in croplands and rangelands gullies are 0.5 and 0.54, respectively.

کلیدواژه‌ها [English]

  • Agricultural and rangeland land uses
  • Fractal dimension
  • Hack law
  • Iran
  • Morphometric characteristics
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