تأثیر اندازه‏های مختلف روشنه‏های طبیعی بر تنوع و ترکیب گیاهان در توده‏های آمیختة اسالم

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری علوم جنگل، دانشکدﮤ منابع طبیعی، دانشگاه علوم کشاورزی و منابع طبیعی ساری، ساری، ایران

2 دانشیار، دانشکدﮤ منابع طبیعی، دانشگاه علوم کشاورزی و منابع طبیعی ساری، ساری، ایران

3 دانشیار پژوهش، مؤسسة تحقیقات جنگل‏ها و مراتع کشور، تهران، ایران

چکیده

به‌ منظور بررسی تأثیر اندازة سطح روشنه در تنوع گونههای گیاهی و ترکیب و میزان زادآوری در تودههای آمیخته، قطعة شاهد واقع در سری 3 ناو اسالم انتخاب شد. روشنههای موجود در سطح قطعة مورد بررسی شناسایی و مختصات مکانی آن‌ها ثبت شد. روشنههای موجود در اندازه‌هایی با وسعت کم (کمتر از 2 آر)، متوسط (2 تا 5 آر)، بزرگ (5 تا 10 آر)، و بسیار بزرگ (بیش از 10 آر) طبقهبندی و در هر طبقه تعدادی روشنه با مشخصات نسبتاً همگن از نظر جهت و شیب انتخاب شد. طول دو قطر عمود بر هم (قطر کوچک و بزرگ) هر روشنه اندازهگیری و سطح آن به کمک معادلة بیضی محاسبه شد. گونههای چوبی و علفی زیر قطعه‌نمونه‌های 4 متر مربعی (2×2) در چهار گوشه، محل تقاطع دو قطر کوچک و بزرگ، و همچنین در ربع قطر بزرگ هر روشنه برداشت و شاخصهای تنوع و یکنواختی و غنا محاسبه و تفاوت آن‌ها در طبقات مختلف، با آزمون یک‌طرفه و آزمون ناپارامتری کروسکال والیس ارزیابی شد. نتایج نشان داد متوسط سطح روشنهها 6/442 متر مربع است و از نظر شاخصهای تنوع گونههای چوبی و علفی اختلاف معنادار بین طبقات مختلف روشنه مشاهده نمیشود؛ اما از نظر ترکیب زادآوری بین روشنهها اختلاف معنادار مشاهده شد. مناسبترین اندازة سطح روشنه برای حفظ تنوع گونههای چوبی، در تودههای آمیخته، روشنههایی با ابعاد متوسط (200 تا 500 متر مربع) بود.

کلیدواژه‌ها


عنوان مقاله [English]

Impact of Canopy Gap Size on Plant Species Diversity and Composition in Mixed Stands, case study: Reserve Area, District No.3 Asalem Forests

نویسندگان [English]

  • Beitollah Amanzadeh 1
  • Mohammad Reza Pourmajidian 2
  • Khosro Sagheb-Talebi 3
  • Seyed Mohammad Hojjati 2
1 Ph.D Student, Faculty of Natural Resources, Sari Agricultural Sciences and Natural Resources University, Sari, I. R. Iran
2 Associate Professor, Faculty of Natural Resources, Sari Agricultural Sciences and Natural Resources University, Sari, I. R. Iran
3 Associate Professor, Research Institute of Forests and Rangelands, Tehran, I. R. Iran
چکیده [English]

In order to study the effect of canopy gap size on species diversity and composition in mixed stands, a reserved area which located in Asalem forests was selected. All of gaps in this area identified and were divided into four categories: Small gaps (<200 m2), Medium gaps (200-500 m2) large gaps (500-1000 m2) and Extra large gaps (>1000 m2). In each category, 21 of gaps with a relatively homogeneous in terms of an aspect and slope were selected. The major and minor diameter of the gaps were measured and the area of the gaps was calculated based on an ellipse. Then, 2 m×2 m sampling micro-plots were systematically taken along two diameters of each gap. The number of individuals of tree seedlings and saplings and shrubs were counted and coverage percent of herbaceous species were estimated in each sampling plot based on Braun-Blanquet criterion. Number of species were counted and the Simpson (1-D), Shannon-Wiener (H') indices, species richness, Camagaro and Smith- Wilson’s evenness indices were calculated in different vegetation layers. The Kolomogrov-Smirnov test was used to study the normality of diversity, richness and evenness data in different gaps, then One-Way and Kruskal- Wallis tests were performed using SAS software. The results showed that mean expanded gap sizes were 442.6 m2. Also, the results revealed that there was not significant differences among different size gap categories in terms of diversity, but the composition of regeneration was significant among different gaps. Therefore, based on the results of this study, the medium gaps which area 200- 500 m2 in these mixed-species forests are recommended the species diversity.

کلیدواژه‌ها [English]

  • Biodiversity
  • canopy gap
  • mixed stands
  • Regeneration
 

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