نشریه علمی - پژوهشی مرتع و آبخیزداری

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشیار دانشکدة علوم زمین دانشگاه شهید بهشتی

2 دانشجوی دکتری ژئومورفولوژی‌- مدیریت محیطی، دانشگاه شهید بهشتی

3 دانشیار دانشکدة منابع طبیعی دانشگاه تهران

4 استاد دانشکدة علوم زمین دانشگاه شهید بهشتی

چکیده

پدیدة فرسایش خاک از مخرب‏ترین پدیده‏هایی است که موجب خسارت‏های فراوان در بسیاری از مناطق می‌شود. از طرفی، کارایی هرچه بیشتر پروژه‏های حفاظتِ خاک مستلزم آگاه‌بودن از اطلاعاتِ تغییرات زمانی و مکانی رسوبات تولیدی در یک آبخیز است. با توجه به اینکه بخش اعظم رسوب‌های خروجی از یک حوضه طی وقایع زمانی سیلابی انجام می‌شود، تمرکز بر منشأیابی رسوبات حمل‌شده به هنگامِ سیلاب، اعم از بار معلق یا کف، در طراحی نوع عملیات حفاظت خاک بسیار مؤثر است. در این بررسی با تفکیک منابع رسوب در قالب کاربری‏های مختلف اراضی و واحد‏های سنگ‌شناسی و با بهره‌گیری از روش منشأیابی رسوب سهم هر یک از منابع رسوب در تولید رسوب حوضة آبخیز طالقانی تعیین شد. بدین منظور، در این مطالعه، 39 نمونه خاک از منابع مختلف در سطح حوضه و 19 نمونه از رسوب تولیدی حوضه (شامل 11 نمونه از رسوبات کف بستر و 8 نمونه از رواناب خروجی حوضه) برداشت شد. یازده عنصر (Fe، Mn، Mg، Zn، Cu،  K، Na، P، N، C و Ca) ردیاب‏های اولیه در نظر گرفته شد. پس از اندازه‏گیری غلظت ردیاب‏ها، با استفاده از آنالیز آماری و تجزیة تابع تشخیص، ردیاب‏هایِ Zn، C، Mg وCa  به عنوان ترکیب بهینه برای منشأیابی و تفکیک کاربری‌های اراضی انتخاب شدند؛ در حالی که هیچ ردیابی برای تفکیک واحد‌های سنگ‌شناسی از یکدیگر شناسایی نشد. ناتوانی در تفکیک واحدهای سنگ‌شناسی از یک سو به دلیل فقدانِ تنوع (سه سازند) و از سوی دیگر آهکی‌بودن سازند تله‌زنگ و تأثیر بیشتر آن در تولید بار محلول است. نتایج مطالعه نشان داد با استفاده از مدل‏های چندمتغیرة ترکیبی، سهم منابع مختلف در تولید رسوب به دست آمد: کشاورزی، مرتع و جنگل به‌ترتیب برابر با 4/53، 4/30 و 2/16 درصد. همچنین، ردیاب‏های واردشده در مدل ترکیبی مبیّن تأثیر مدیریت کاربری و تفاوت بارز کاربری‌های مختلف در تغییر ترکیب شیمیایی خاک است.

کلیدواژه‌ها

عنوان مقاله [English]

Determining of landuse effects on sediment yield of watershed through sediment fingerprinting technique of suspendedload and bed materials in Taleghani catchment, Khorram Abad

نویسندگان [English]

  • Kazem Nosrati 1
  • Frouzan Ahmadi 2
  • Ali Akbar Nazari Samani 3
  • Mohammad Reza Servati 4

1 Department of Physical Geography, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran

2 Department of Physical Geography, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran

3 Faculty of Natural Resources, University of Tehran, Tehran, Iran

4 Department of Physical Geography, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran

چکیده [English]

Soil erosion is one of the most destructive phenomena which cause significant ecological changes in many areas. Soil conservation and erosion control is essential because of the irreparable damage caused by soil erosion. Soil conservation programs will not achieve until to find adequate methods of combating land degradation and ways to reduce the sediment. Therefore, we need to have enough knowledge of the sediment sources and identify places to be at high risk to soil erosion. In this study we used fingerprinting technique in the Taleghani catchment, Khorram Abad city, Lorestan Province to determine the contributions of sediment sources including agricultural, rangeland, and forest in sediment yield. In view of this, 39 soil were collected from different sources: agriculture, rangeland, forest and channel bank and 19 sediment samples including 11 samples from bed sediment and 8 samples from suspended runoff, respectively. 11 tracers including C, N, P, Na, K, Cu, Zn, Mg, Mn, Fe and Ca were selected as the primary tracers. The results showed that discriminant function analysis were selected Mg, C, Zn and Ca as the optimum set of tracers that can discriminate 3 sediment sources. Mixing model results showed that the contribution of each sediment source is 53.37, 30.37, and 16.26 percent for agriculture, rangeland, and forest, respectively. These results were consistent with the evaluation results of nitrogen and organic carbon stocks. The results of this study can be used in selecting most appropriate erosion control method the study area and generalized to similar areas.

کلیدواژه‌ها [English]

  • Talaqani catchment
  • Sediment sources
  • Soil Erosion
  • Sediment fingerprinting
  • Geochemical tracers
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