بررسی ترکیب و تنوع گیاهان علفی پس از آتش‌سوزی در جنگل‌های بلوط ایرانی، زاگرس جنوبی

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانش آموخته کارشناسی ارشد جنگلداری/دانشگاه یاسوج

2 استادیار گروه جنگلداری/دانشگاه یاسوج

3 دانشجوی دکتری مرتعداری/دانشگاه مازندران

چکیده

سابقه و هدف: جنگل‌های زاگرس که عمدتا جزو جنگل‌های نیمه‌خشک و شاخه‌زاد هستند از خطر آتش‌سوزی در امان نبوده و آتش بطور مداوم این جنگل‌ها را تحت تأثیر قرار می‌دهد. مطالعه تغییر در ترکیب و مقدار پوشش گیاهی در عرصه‌های دچار آتش‌سوزی می‌تواند علاوه بر تعیین شدت تخریب، میزان توانایی بازسازی منطقه را مشخص سازد. هدف از انجام این تحقیق بررسی ترکیب، تنوع و پاسخ گیاهان علفی پس از آتش‌سوزی در جنگل‌های شاخه‌زاد بلوط ایرانی در منطقه تولگهی در استان کهگیلویه و بویراحمد است.
مواد و روش‌ها: آتش‌سوزی در تابستان 1389 صورت گرفت و ویژگی‌های پوشش گیاهی علفی شامل ترکیب و تنوع گیاهان علفی پس از گذشت 4 سال از آتش‌سوزی اندازه‌گیری شد. برای برداشت پوشش علفی در داخل هر قطعه نمونه اصلی 1000 متر مربعی (که به صورت تصادفی منظم در یک شبکه آماربرداری 100×50 متر جهت اندازه‌گیری خصوصیات جنگلشناسی طراحی شده بود)، 5 ریز قطعه ‌نمونه یک متر مربعی در مرکز و چهارگوشه‌ی قطعه نمونه اصلی برداشت و نوع گونه و درصد پوشش آن تخمین زده شد. در مجموع در دو منطقه آتش‌سوزی شده و شاهد تعداد 200 ریز قطعه ‌نمونه (در هر منطقه 100 ریز قطعه‌ نمونه) مورد اندازه گیری قرار گرفت. برای محاسبه شاخص‌های تنوع از نرم افزار PAST و جهت بررسی پاسخ گروهی کل گونه‌های گیاهی به آتش‌سوزی از آنالیز افزونگی (RDA) در نرم افزار Canoco 4.5 استفاده شد.
یافته‌ها: نتایج نشان داد از 72 گونه علفی شناسایی شده، 22 گونه فقط در منطقه آتش‌سوزی و 9 گونه نیز تنها در منطقه شاهد حضور داشته و 41 گونه بین دو منطقه مشترک بودند. نتایج مقایسه میانگین‌ها نشان داد که از بین گونه‌های گیاهی مختلف ، 17 گونه از لحاظ درصد تاج پوشش پاسخ معنی‌داری نسبت به آتش‌سوزی داشتند. آتش‏سوزی موجب شد تا درصد تاج‌پوشش تیره‌های Gramineae و Rubiaceae به طور معنی‌داری نسبت به شاهد افزایش یابد. نتایج بررسی شاخص‌های تنوع گونه‌ای نشان داد که بین دو منطقه شاهد و آتش‌سوزی شده از لحاظ این شاخص‌ها هیچ اختلاف معنی‌داری وجود ندارد. نتایج آنالیز چند متغیره تحلیل افزونگی (RDA) نیز نشان داد که گونه‌های علفی پاسخ‌های متفاوتی نسبت به آتش‌سوزی داشتند، به طوری‌که درصد تاج‌‌پوشش گونه‌های Onobrychis sativa، Orobanche sp.، Hordeum glaucum، Pimpinella sp.، Bellevalia sp. Bromus danthoniae، Bromus tectorum و Chardinia orientalis در منطقه آتش‌سوزی بیشتر بود.
نتیجه‌گیری: نتایج تحقیق پیش‌رو نشان داد که آتش‌سوزی عامل مهم و تأثیر‌گذاری است که پس از گذشت 4 سال از وقوع آن؛ موجب افزایش معنی‌دار گندمیان و پهن‌برگان یک‌ساله و در مقابل کاهش معنی‌دار گندمیان و پهن‌برگان چندساله در پوشش علفی زیر اشکوب جنگل‌های بلوط ایرانی شده است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Survey of composition and diversity of herbaceous plants after a fire in Persian Oak forests of Southern Zagros

چکیده [English]

Abstrcat
Background and Objectives: The Zagros forests, mostly located in semi-arid regions, are not safe from fire hazards, and fire affects these coppice forests continuously. Studying the change in the composition and quantity of vegetation in the areas exposed to fire can determine the extent of damage, and the potential of the region for reclamation. The aim of this study was to investigate the composition, diversity, and response of understory herbaceous plants to fire in the Persian oak forests in the Tulgahi region of Kohgilouyeh and Boyer-Ahmad province.
Materials and Methods: The fire took place in the summer of 2010. Four years after the fire, the characteristics of herbaceous vegetation, including composition and biodiversity of plants, were measured. Sampling of herbaceous plants was carried out within each main plot of 1000 square meters (designed to measure the forest parameters with systematic random sampling in a 50 by 100 meter grid), five subplots of one square meter were sampled in the center and four angles of main plots and the species type and cover percentage were recorded. In total, 200 subplots were measured in the fire and control regions (100 subplots at each region). The diversity indices were calculated in the PAST software, and plant species response to fire was determined with redundancy analysis (RDA) using Canoco 4.5.
Results: The results showed that out of 72 herbaceous species identified, 22 species were exclusively found in the fire region, 9 species exclusively in the control region, and 41 species were shared between the two regions. The results of mean comparisons showed that among the study species, 17 species had a significant response to the fire in terms of canopy cover percentage. The fire caused the canopy cover percentage of Rubiaceae and Gramineae to increase significantly compared to control. The results of biodiversity indices revealed that no significant difference was found between the two regions in terms of biodiversity indices. The redundancy analysis (RDA) results showed that herbaceous species had different responses to fire, so that canopy cover species of Onobrychis sativa, Orobanche sp., Hordeum glaucum, Pimpinella sp., Bellevalia sp., Bromus donthoniae, Bromus tectorum and Chardinia orientalis were increased in the regions where fire occurred.
Conclusion: The results of this research showed that fire was an important and effective factor, causing to increase of grasses and annual forbs significantly after four years of its occurrence. In contrast, the presence of perennial grasses and forbs was decreased significantly by fire in the understory of Persian oak forests.

کلیدواژه‌ها [English]

  • Forest fire
  • Redundancy analysis
  • diversity indices
  • Zagros forests
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