نشریه علمی - پژوهشی مرتع و آبخیزداری

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکترای دانشکده منابع طبیعی و علوم زمین دانشگاه کاشان، ایران

2 استادیار دانشکده منابع طبیعی و علوم زمین، دانشگاه کاشان، ایران

3 استاد دانشکده منابع طبیعی، دانشگاه تهران، ایران

4 دانشیار دانشکده منابع طبیعی، دانشگاه تهران، ایران

چکیده

به منظور درک بهتر تأثیر خشکسالی بر روی پوشش گیاهی در منطقه خشک بردخون واقع در جنوب غرب ایران، آنالیز تصاویر ماهواره­ای MODIS با ‌فاصله‌ زمانی‌‌16روزه، طی سال­های 2000 - 2015 با استفاده از شاخص­های پوشش گیاهی ­NDVI، EVI، SAVI­، روش SPI، نمونه­برداری میدانی و سیستم اطلاعات جغرافیایی در طول فصل رشد انجام گردید. در تحقیـق حاضر، نقشه واقعیت زمینی با روش نمونه‌گیری و پیمایش­های میدانی تهیه و سپس اطـلاعـات مربوط به پوشش متعلق به 290 پلات در قالب 29 واحد نمونه برداری جمع­آوری گردید. سپس میزان همبستگی بین شاخص­های گیاهی و داده­های میدانی محاسبه، و برای هر شاخص، مدل پوشش گیاهی بدست آمد. به منظور بررسی اثر خشکسالی بر پوشش گیاهی، خشکسالی با استفاده از روش  SPIاز داده­های ‌بارندگی 14 ایستگاه هواشناسی درون و اطراف منطقه مورد مطالعه، در بازه ‌زمانی‌ مشابه ‌با تصاویر‌ ‌ماهواره­ای استخراج گردید. نتایج تحقیق نشان داد که شاخص NDVI بیشترین همبستگی (R2=0.56) را بین شاخص­ها دارد و جهت تهیه نقشه درصد پوشش گیاهی انتخاب گردید. بررسی بین مقادیر شاخص NDVI با شاخص خشکسالی در بازه­های زمانی مختلف نشان داد که بیشترین همبستگی بین شاخص پوشش گیاهی با  SPIشش ماهه وجود دارد. بر اساس آنالیز شاخص خشکسالی مشخص شد که منطقه مورد مطالعه در سال 2012 شدیدترین خشکسالی و سال 2004 بهترین  وضعیت ترسالی را تجربه کرده است. همین روند تغییرات در پوشش گیاهی بر اساس شاخص NDVI مشاهده شد. مقایسه تصاویر طبقه­بندی شده بین سال­های 2012 و 2004 (با تغییر 42 درصدی پوشش گیاهی ضعیف) نشان­دهنده اثر خشکسالی بر روی پوشش گیاهی در منطقه مورد مطالعه است. نتایج نشان داد، همبستگی بین SPI و شاخص پوشش گیاهی می­تواند برای شناسایی خشکسالی کشاورزی مفید باشد.

کلیدواژه‌ها

عنوان مقاله [English]

Identification of Vegetation-Vulnerable Areas to Drought Using Remote Sensing (Case study: Boushehr Province)

نویسندگان [English]

  • Fatemeh bahreini 1
  • Fatemeh Panahi 2
  • Mohammad Jafari 3
  • Arash Malekian 4

1 university of Tehran

2 Assis. Prof. of Faculty of Natural Resources and Earth Sciences, university of Kashan, Iran

3

4 Faculty of Natural Resources, university of Tehran. Iran

چکیده [English]

The complexity of drought phenomenon hinders our full understanding of its impact. Field sampling, Geographic Information Systems, SPI and NDVI, EVI and SAVI indices derived from 16-day interval MODIS images during 2000-2015 were used to better understand the effects of drought on vegetation In recent study, ground true map was prepared by sampling and field surveys and vegetation cover data was obtained from 32 sampling units in 320 plots over the entire study area. Then, the correlation between field sampling data and vegetation indices was estimated and vegetation cover models were produced for different indices. In this study, precipitation data of 14 stations within and around the study area were used and SPI was calculated at the same time scales with the vegetation indices to study the effect of drought on vegetation. The results showed that NDVI has had the highest correlation coefficient (R2=0.56) amongst the indices so it was selected for vegetation cover percentage mapping. Investigating NDVI rates and drought index in different temporal periods, 9-month SPI was found to have the best correlation with NDVI. On the basis of SPI analysis, it was found that the study area had the most severe drought in 2012 and the best wet condition in 2004. The similar trend was observed in NDVI. The comparison of classified images between 2004 and 2012 (with 42 % changes in poor vegetation) indicates the effect of drought on vegetation in the study area.

کلیدواژه‌ها [English]

  • Bordekhun
  • Drought
  • Vegetation indices
  • Correlation
  • MODIS
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