ارزیابی سطح تنوع درختی جنگل‌های هیرکانی با استفاده از شاخص تنوع ساختاری ترکیبی (مطالعه موردی: تیپ راش- ممرز، ناو اسالم گیلان)

نوع مقاله: علمی- پژوهشی

نویسندگان

1 دانشجوی دکتری جنگل‌داری، دانشکده کشاورزی و منابع طبیعی، دانشگاه لرستان، خرم‌آباد، ایران

2 استادیار گروه جنگل‌داری، دانشکده کشاورزی و منابع طبیعی، دانشگاه لرستان، خرم‌آباد، ایران

3 دانشیار، گروه منابع طبیعی و محیط زیست، دانشکده کشاورزی، دانشگاه شیراز، شیراز، ایران

چکیده

ساختار توده و تنوع گونه­‌ای دو ویژگی مفید برای اندازه­‌گیری ترکیبی تنوع زیستی جنگل هستند و اطلاعات مهمی برای تصمیم‌گیری، مدیریت و انتخاب شیوه‌­های مناسب جنگل­‌شناسی فراهم می­‌کنند. برای اجرای پژوهش پیش‌رو، ابتدا در واحدهای اکولوژیک همگن موجود در تیپ­ راش- ممرز ناو اسالم گیلان، پنج قطعه‌نمونه یک هکتاری به‌صورت تصادفی انتخاب شدند. برای تعیین شاخص تنوع ساختاری ترکیبی (SI) تیپ، شاخص‌­های زاویه یکنواخت، آمیختگی و تمایز قطر برابر سینه محاسبه شدند. همچنین، به‌منظور تعیین تراکم درختان در این تیپ از شاخص فاصله تا نزدیک­ترین همسایه­‌ها استفاده شد. با توجه به نتایج، میانگین شاخص فاصله تا نزدیک­ترین همسایه­‌ها برای تیپ مورد بررسی 5/58 متر به‌دست آمد. همچنین، میانگین شاخص زاویه یکنواخت 0/52 محاسبه شد که بیانگر توزیع کپه­‌ای درختان بود. شاخص آمیختگی با میانگین 0/45 نشان­‌دهنده سطح متوسط آمیختگی تیپ بود. شاخص تمایز قطر برابر سینه نیز 0/47 محاسبه شد که بیانگر اختلاف متوسط بین درختان از نظر قطر برابر سینه بود. شاخص تنوع ساختاری ترکیبی که بیانگر سه جنبه مختلف ساختار (تنوع موقعیت مکانی، تنوع گونه­‌ای و تنوع ابعاد قطر برابر سینه) است، با ارزش 0/475 نشان داد که تیپ مورد مطالعه دارای سطح تنوع درختی زیادی است. نتایج این مطالعه اطلاعات کلیدی برای مدیریت و حفظ سطح تنوع درختی در تیپ راش- ممرز را با استفاده از شاخص تنوع ساختاری ترکیبی فراهم می­‌کند. همچنین، با پایش و مدیریت سطح تنوع درختی توده­‌های جنگلی می­توان از اثرات منفی فاکتورهای طبیعی و انسانی کاست.

کلیدواژه‌ها


عنوان مقاله [English]

Evaluation level of tree diversity in the Hyrcanian forests using complex structural diversity index (Case study: beech-hornbeam type, Nav-e Asalem, Gilan)

نویسندگان [English]

  • Peiman Farhadi 1
  • Javad Soosani 2
  • Seyyed Yousef Erfanifard 3
1 Ph.D. Student, Department of Forestry, Faculty of Agriculture and Natural Resources, Lorestan University, Khorram Abad, Iran
2 Assistant Prof., Department of Forestry, Faculty of Agriculture and Natural Resources, Lorestan University, Khorram Abad, Iran
3 Associate Prof., Department of Natural Resources and Environment, Faculty of Agriculture, Shiraz University, Shiraz, Iran
چکیده [English]

Stand structure and species diversity are two useful parameters for complex assessment of forest biodiversity, and provide important information for management and decision making for appropriate silvicultural system. For this purpose, five one ha plots were selected randomly in homogeneous ecological units of beech-hornbeam type in Nav-e Asalem, Gilan province. In order to determine complex structural diversity index (SI) in the studied forest type, uniform angle, mingling and DBH dimensions difference indicators were calculated. Also in order to determine density of trees, the nearest neighbors distance index was used. According to the results, the average value of nearest neighbors distance index was calculated to 5.58 meter. Mean uniform angle index was 0.52, which indicates clumped distribution of trees. Mean mingling index (0.45) indicates moderate mixture of the studied mixed stand. The amount of DBH dimensions difference index was 0.47, indicates moderate difference between trees diameter at breast height. The complex structural diversity index which presents three dimensions of structure, including diversity of spatial pattern, species diversity, and diversity of DBH dimensions) was calculated to 0.475. This value confirms a high level of tree diversity. The results of this study provide key information for management and maintaining of tree diversity in the studied mixed beech-hornbeam stand. Also with monitoring and management of tree diversity level we can reduce the negative impact of natural and human factors.

کلیدواژه‌ها [English]

  • Hyrcanian forests
  • tree density
  • tree diversity
  • uniform angle index
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