آشکارسازی تأثیر خشکسالی بر پویایی زمانی- مکانی جنگل‌های بلوط زاگرس (نمونه موردی: جنگل‌های بلوط لرستان)

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشجوی دکترای اقلیم‏شناسی، گروه جغرافیا، واحد نجف‏آباد، دانشگاه آزاد اسلامی، نجف‌آباد، ایران

2 نویسنده مسئول، استادیار، گروه جغرافیا، واحد نجف آباد، دانشگاه آزاد اسلامی، نجف‏آباد، ایران

3 دانشیار پژوهش، بخش تحقیقات مرتع، مؤسسه تحقیقات جنگلها و مراتع کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران، ایران

4 استادیار، گروه جغرافیا، واحد نجف‏آباد، دانشگاه آزاد اسلامی، نجف‏ آباد، ایران

چکیده

پوشش جنگلی زاگرس یکی از مهمترین اجزای اکوسیستم زاگرس بوده که نقش مهمی در حفاظت آب و خاک این منطقه ایفا می­کند. خشکسالی به‌عنوان یکی از مخاطرات اقلیم‌شناختی، می­تواند تأثیرات چشم­گیری روی پوشش جنگلی داشته باشد. ازاین‌رو آشکارسازی پویایی مکانی جنگل در پاسخ به خشکسالی بسیار مهم است. هدف اساسی این تحقیق آشکارسازی پویایی مکانی پوشش جنگلی لرستان در پاسخ به تغییرات سالانه خشکسالی است. در این راستا مقادیر شاخص بارزشده پوشش گیاهی (EVI) از تصاویر لندست 5 و 8 برای دوره آماری 2000-2017 استخراج گردید. شاخص بارش استاندارد شده (SPI)، برای دوره آماری مذکور با استفاده از آمار بارش ماهانه 9 ایستگاه سینوپتیک منطقه محاسبه شد. با استفاده از تحلیل همبستگی مکانی ارتباط بین مساحت سالانه پوشش جنگلی و شاحص خشکسالی بررسی شد و در نهایت تابع حساسیت تغییرات مکانی پوشش جنگلی با برازش یک مدل خطی به‌دست آمد. نتایج حاصل از نمونه‏برداری‏های میدانی نشان داد که آستانه EVI > 0.4 را می‏توان به‌عنوان آستانه پوشش جنگلی استان در نظر گرفت. تحلیل همبستگی بیانگر آن بود که سری زمانی 18 ساله پوشش جنگلی، 68/0 با شاخص SPI همبستگی داشته است که این میزان همبستگی در سطح اطمینان 95/0 معنی‏دار بوده است. نتایج حاصل از توسعه تابع حساسیت به تغییرات شاخص SPI بیانگر آن بود که پهنه پوشش جنگلی دارای آستانه سبزینگی تعیین شده، حساسیت قابل توجهی به خشکسالی دارد، به‌نحوی‌که به ازای هر 1/0 واحد تغییر در شاخص SPI میزان مساحت پهنه پوشش جنگلی 14880 هکتار در همان جهت تغییر خواهد کرد.
 
 

کلیدواژه‌ها


عنوان مقاله [English]

Spatiotemporal Dynamics of Oak Forest of Zagros in Responce to Drought Case Study: Oak Forest of Lorestan

نویسندگان [English]

  • Z. Alirezaee 1
  • A. Gandomkar 2
  • M. Khodagholi 3
  • A. R. Abasi 4
چکیده [English]

     The Zagros Woodland is one of the main components of Zagros ecosystem that has significant role in water and soil conservation. Drought, as one of the climatic hazards, can have dramatic effects on forest cover. Therefore, detecting the spatiotemporal dynamics of the forest in response to drought is very important. The main objective of this study was to detect the spatiotemporal relationship of forest cover of Lorestan province in response to annual drought. In this regard, the Enhanced Vegetation Index (EVI) values were extracted from Landsat 5 and 8 images for the period 2017-2017. The Standardized Precipitation Index (SPI) was calculated for the mentioned period using monthly rainfall statistics of 9 synoptic stations in the region. By using spatial correlation analysis, the relationship between annual forest area and drought index was investigated and finally, sensitivity function of spatial variation of forest cover was obtained by fitting a linear model. The results of field sampling showed that EVI threshold> 0.4 can be considered as the province's forest cover threshold. Correlation analysis between forest cover and drought indicated that the 18-year time series of forest cover had a significant correalation of 0.68 with SPI (0.95 confidence level). The results of development of sensitivity function to SPI index indicated that the forest cover had significant sensitivity to drought so that for each 0.1 unit change in the SPI index the forest cover area will change as 14880 ha in the same direction.
 
 

کلیدواژه‌ها [English]

  • drought
  • forest cover
  • oak forest
  • Landsat
  • Lorestan province
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