اثرات خشکسالی بر تغییرات پوشش مرتعی با تاکید بر شاخص‌های دورسنجی (مطالعة موردی: حوزه آبخیز سلفچگان- نیزار)

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانش‌آموخته کارشناسی ارشد بیابان‌زدایی، دانشکده منابع طبیعی و علوم زمین، دانشگاه کاشان، ایران

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

3 استادیار، گروه مهندسی منابع طبیعی، دانشکده کشاورزی و منابع طبیعی، دانشگاه هرمزگان، ایران

چکیده

پوشش مرتعی به‌عنوان یکی از مهم­ترین اجزای اکوسیستم مناطق خشک به­شمار می‌رود و تعیین تغییرات پوشش گیاهی مرتعی تحت تاثیر خشکسالی و ترسالی امری ضروری به­نظر می‌رسد. تحقیق پیش‌رو با هدف بررسی ارتباط میان شاخص‌های ماهواره‌ای و شاخص SPI در مراتع قم صورت گرفت. بدین منظور ابتدا شاخص SPI در میانگین‌های متحرک یک، سه، 5 و 7 ساله مورد محاسبه قرار گرفت. در مرحله بعد با استفاده از تصاویر سنجنده لندست و پس از انجام اصلاحات مورد نیاز این نوع از سنجنده بر روی تصاویر، از سه شاخص NDVI، MSAVI و EVI، نقشه پوشش گیاهی تهیه گردید. در نهایت به‌منظور بررسی ارتباط میان شاخص‌های تصاویر ماهواره‌ای با شاخص SPI از ضرایب همبستگی استفاده گردید. نتایج نشان دهنده همبستگی متوسط و خوب میان شاخص‌های ماهواره‌ای MSAVI با شاخص SPI در ماه‌های اوج رشد پوشش گیاهی با میانگین متحرک یک ماهه شاخص SPI بیشتر بود. نتایج این پژوهش نشان دهنده این است که جهت برآورد خشکسالی کشاورزی از طریق سنجش‌از دور، شاخص MSAVI روش بسیار مناسبی بوده و در مناطقی که ایستگاه­های هواشناسی به­صورت پراکنده بوده (و یا اصلا وجود ندارد) می­توان از این مدل برای برآورد خشکسالی استفاده کرد. زیرا تعداد نقاط نمونه برداری در تصاویر ماهواره‌ای بسیار بیشتر از تعداد ایستگاه­های هواشناسی است.

کلیدواژه‌ها


عنوان مقاله [English]

Drought Impacts on vegetation cover an emphasis on Remote Sensing (Case Study: Salafchegan – Neizar Watershed)

نویسندگان [English]

  • Vahid Veisi 1
  • Mansoureh Ghavam 2
  • Omolbanin bazrafshan 3
1 Former M.Sc. Student in Combat Desertification, University of Kashan, Iran
2 Assistant Professor, Department of Range and Watershed Management, Faculty of Natural Resources and Earth Sciences, University of Kashan, Iran.
3 Assistant Professor, Department of Natural Resources Engineering , Faculty of Agriculture and Natural Resources, University of Hormozgan, Iran
چکیده [English]

     Rangeland vegetation is one of the most important components of arid ecosystems and it is necessary to determine changes in rangeland vegetation under drought and wet years. The present study aimed to investigate the relationship between satellite indices and SPI index in Qom rangelands. For this purpose, the SPI index was calculated in moving averages of 1, 3, 5 and 7 years. In the next step, using Landsat images and after making the necessary adjustments to the images, the vegetation map was prepared using NDVI, MSAVI and EVI indices. Finally, correlation coefficients were used to investigate the relationship between satellite image indices and SPI index. The results showed a moderate and good correlation between MSAVI satellite indices and SPI index at peak vegetation growth months with a one month moving average of SPI index. The results of this study show that to estimate agricultural drought through remote sensing, the MSAVI index is a very suitable method and can be used for estimating drought in areas where meteorological stations are scattered (or nonexistent). Because the number of sampling points in satellite images is far greater than the number of meteorological stations.

کلیدواژه‌ها [English]

  • Drought monitoring
  • satellite images
  • vegetation index
  • Landsat images
  • Rangland

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