تأثیر روندهای درازمدت بارندگی و روزهای خشک متوالی بر زوال جنگل‌های زاگرس در استان ایلام

نوع مقاله : مقاله پژوهشی

نویسندگان

گروه جنگلداری و اقتصاد جنگل، دانشکدة منابع طبیعی، دانشکدگان کشاورزی و منابع طبیعی، دانشگاه تهران، کرج. ایران.

10.22059/jfwp.2025.392721.1344

چکیده

جنگل‌های استان ایلام با مساحت 0/64 میلیون هکتار، بیش از دو دهه است دچار زوال شده‌اند. شاخص روزهای خشک متوالی (Consecutive Dry Days; CDD) که از نشانه‌های بروز تغییر اقلیم محسوب می‌شود، می‌تواند از عوامل تشدیدکنندة زوال باشد. هدف این پژوهش، بررسی روندهای درازمدت بارندگی و روزهای خشک متوالی و ارتباط آن با زوال جنگل‌های استان ایلام بود. داده‌های روزانة هواشناسی ایستگاه همدیده‌بانی ایلام در بازة زمانی 35 ساله (2022-1988) تجزیه‌و‌تحلیل و از آزمون ناپارامتری من-کندال، برای تعیین روند تغییرات بارندگی و تعداد روزهای خشک متوالی استفاده شد. میانگین بارندگی سالانه در این دوره، 544 میلی‌متر با انحراف معیار 173 میلی‌متر بود و روند آن معنی‌دار نبود (1/46=ZMK). میانگین بارندگی سالانه، پیش (605 میلی‌متر) و پس (497 میلی‌متر) از شروع پدیدة زوال، کاهش معنی‌داری داشت (1/98=t). میانگین تعداد روزهای خشک سال، 313 روز با انحراف معیار 12 روز بود و حدود 70 درصد آن در فصل‌های رشد جنگل یعنی بهار و تابستان ثبت شد. به‌طور میانگین، در طی این دوره، در هر سال، 27 دورة خشک با انحراف معیار 4 دوره رخ داد. 26 دوره، کوتاه‌تر از 30 روز و 2 دوره، بلندتر از 30 روز بود. روند تعداد دوره‌های خشک بلندتر از 30 روز پس از شروع زوال افزایشی معنی‌دار نشان داد (3/12+=ZMK). میانگین بیشترین تعداد روزهای خشک متوالی در سال، 150 روز و حداکثر آن 219 روز (سال 2021) ثبت شد. تغییرات اقلیمی، کاهش بارندگی و افزایش دوره‌های خشک طولانی‌مدت، می‌تواند نقش مهمی در تسریع و تشدید پدیدة زوال جنگل‌های زاگرس در استان ایلام داشته‌ باشد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

The effect of long-term trends of precipitation and consecutive dry days on Zagros forests decline in Ilam Province

نویسندگان [English]

  • Somayeh Mirzaei
  • Pedram Attarod
  • Kimiya Mostafanezhad Nesheli
Department of Forestry and Forest Economics, Faculty of Natural Resources, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran.
چکیده [English]

The Zagros forests in Ilam Province, covering 0.64 million hectares, have been in decline for over two decades, with the index of consecutive dry days (CDD)—a key climate change indicator—identified as a contributing factor. We analyzed 35 years (1988–2022) of daily meteorological data from the Ilam synoptic weather station using the Mann-Kendall non-parametric test to assess trends in precipitation and CDD. The mean annual precipitation was 544 mm (SD = 173 mm) with no significant trend (ZMK = 1.46), though a notable decrease occurred from 605 mm before the onset of decline to 497 mm afterward (t = 1.98). On average, 313 (±12 SD) dry days occurred annually, with about 70% during spring and summer. Each year, 27 (±4 SD) dry spells were recorded, mostly under 30 days, but two typically exceeded that threshold (30 days). A significant rise in dry spells longer than 30 days was observed after the decline began (ZMK = +3.12). The mean maximum annual CDD reached 150 days, peaking at 219 days in 2021. These findings indicate that reduced precipitation and prolonged dry periods linked to climate change play a critical role in the ongoing decline of the Zagros forests in Ilam Province.

کلیدواژه‌ها [English]

  • Climate Change
  • Mann-Kendall test
  • Oak decline
  • Quercus brantii

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نشریه جنگل و فرآورده های چوب
دوره 78، شماره 1
خرداد 1404
صفحه 1-10

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