جداسازی محیط های بیابانی بر پایه آستانه های اکوژئومورفیک

نوع مقاله : علمی -پژوهشی

نویسندگان

1 دانشجوی کارشناسی ارشد مدیریت مناطق بیابانی، دانشگاه فردوسی مشهد

2 استادیار دانشکده منابع طبیعی و محیط زیست، دانشگاه فردوسی مشهد

چکیده

تفکیک محیط­های بیابانی از غیربیابانی اغلب به­دلیل تنوع بالای الگوهای پوشش گیاهی، خاک و سنگ در مجاورت یکدیگر دشوار است. مطالعه روند تغییرات اکولوژیک و ژئومورفولوژیک یک منطقه می­تواند در تعیین آستانه­های اکوژئومورفیک به­منظور تفکیک محیط­های بیابانی از غیربیابانی بر پایه پتانسیل­های برگشت­پذیری و پتانسیل­های فرسایش­پذیری ملاک عمل قرار گیرد. به­­طوری که بر اساس نسبت پتانسیل­های فوق میزان تاب­آوری و ارتجاعیت اکولوژیک اکوسیستم دچار تغییر می­شود. هدف از این پژوهش جداسازی محیط­های بیابانی در بخشی از استان خراسان رضوی بر پایه مرزهای اکوژئومورفیک می­باشد. لذا در این پژوهش، با استفاده از چهار نقشه لیتولوژی، پوشش گیاهی، رده­بندی خاک و نقشه هم­بارش، تغییرات نسبت پتانسیل­های فرسایش­پذیری و برگشت­پذیری مورد مطالعه قرار گرفته است. در ابتدا با انتخاب منطقه­ای محدود در سطح استان که از لحاظ گرادیان اقلیمی و ارتفاعی بیانگر شیب تغییرات باشد، چهار نقشه فوق تفکیک گردید. از داده­های رقومی TM/ETM و نقشه­های زمین­شناسی و خاک در مقیاس 1:250000 در تولید نقشه­های مذکور استفاده شده است. به منظور ارزیابی صحیح­تر این جداسازی، پیاده­سازی یک طبقه­بندی نظارت نشده بر روی تصویر سنجنده MODIS از منطقه مطالعاتی، به­خوبی روند تغییرات عوامل اکوژئومورفیکی را همگام با تغییرات چهار نقشه فوق نشان می­دهد. بررسی تغییرات اکولوژیک و ژئومورفولوژیک همگی در یک راستا روند تغییر نسبت پتانسیل­های فرسایشی و برگشت­پذیری را در منطقه مطالعاتی تأیید کردند. نتایج پژوهش مشخص­کننده دو آستانه یا گذر اکوژئومورفیک در منطقه مورد بررسی می­باشد، گذر اکوژئومورفیک از منطقه غیربیابانی به نیمه­بیابانی و گذر اکوژئومورفیک نیمه­بیابانی به محیط بیابانی تفکیک شدند.  AbstractAccording to the high diversity of vegetation, soil and bare rock patterns in the desert ecosystem and non-desert districts, distinguishing these areas is difficult. The approach used in this research introduced an ecogeomorphic view based on inverse recovery and erodibility potential to identify desert zones. The recovery/erodibility ratio can change the ecological resilience of ecosystem which shows resistance degree of system to environmental disturbances. The aim of this study was distinguishing desert environment based on eco-geomorphic boundries in Khorasan Razavi province as critical region to desertification process in Iran. In view of this four maps including lithology, vegetation cover, soil and isohyet were provided for analyzing the changes of recovery and erodibility ratio. The TM/ETM+ imagery data, geological map and soil map in scale 1:250'000 were used to prepare layers. An unsupervised classification was applied based on MODIS imagery data which shows eco-geomorphic dynamics along climatic/lithologic gradient.A zone as case study was selected where located in Lut and Sabzevar geological blocks. The climatic and topographic gradients were main reasons for choosing this case study in the KR province. Ecological and geomorphologic changes confirmed the erodibility - recovery oscillations in the study area. Results indicated two ecogeomorphic thresholds delineated based on characteristics of lithological, soil, and vegetation cover, rainfall fluctuations. The transition shows an ecogeomorphic transition between non-desert to semi-desert environments and a transition between semi-desert to desert region. Keywords: Desert Environment, Erodibility, Recovery, Ecogeomorphic Thresholds  

کلیدواژه‌ها

عنوان مقاله [English]

Distinguishing Desert Environments by Ecogeomorphic Thresholds

چکیده [English]

According to the high diversity of vegetation, soil and bare rock patterns in the desert ecosystem and non-desert districts, distinguishing these areas is difficult. The approach used in this research introduced an ecogeomorphic view based on inverse recovery and erodibility potential to identify desert zones. The recovery/erodibility ratio can change the ecological resilience of ecosystem which shows resistance degree of system to environmental disturbances. The aim of this study was distinguishing desert environment based on eco-geomorphic boundries in Khorasan Razavi province as critical region to desertification process in Iran. In view of this four maps including lithology, vegetation cover, soil and isohyet were provided for analyzing the changes of recovery and erodibility ratio. The TM/ETM+ imagery data, geological map and soil map in scale 1:250'000 were used to prepare layers. An unsupervised classification was applied based on MODIS imagery data which shows eco-geomorphic dynamics along climatic/lithologicgradient.A zone as case study was selected where located in Lut and Sabzevar geological blocks. The climatic and topographic gradients were main reasons for choosing this case study in the KR province. Ecological and geomorphologic changes confirmed the erodibility - recovery oscillations in the study area. Results indicated two ecogeomorphic thresholds delineated based on characteristics of lithological, soil, and vegetation cover, rainfall fluctuations. The transition shows an ecogeomorphic transition between non-desert to semi-desert environments and a transition between semi-desert to desert region.

کلیدواژه‌ها [English]

  • Desert Environment
  • Erodibility
  • Recovery
  • Ecogeomorphic Thresholds

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