برآورد و پهنه‌بندی موجودی یک جنگل مدیریت‌نشده خزری به‌روش زمین‌آمار (پژوهش موردی: بخش چلیر جنگل خیرود نوشهر)

نوع مقاله: علمی- پژوهشی

نویسندگان

1 استادیار موسسه تحقیقات جنگلها و مراتع کشور

2 استادیار دانشگاه آزاد، واحد علوم و تحقیقات تهران

3 استادیار دانشگاه تهران

4 پژوهشگر، موسسه تحقیقات جنگلها و مراتع کشور

5 مربی، موسسه تحقیقات جنگلها و مراتع کشور

چکیده

برآورد و پهنه‌بندی موجودی در مدیریت و برنامه‌ریزی جنگل امری اجتنابناپذیر است. در این تحقیق از شیوه درون‌یابی کریجینگ روش زمین‌آمار به‌منظور برآورد و پهنه‌بندی متغیرهای موجودی در یک جنگل طبیعی و ناهمسال مدیریتنشده (فاقد طرح جنگلداری) استفاده شد. منطقه موردبررسی در بخش چلیر جنگل آموزشی- پژوهشی خیرود نوشهر و در ارتفاع 1100 تا 1450 متر بالاتر از سطح دریا واقع شده است و مساحتی برابر 516 هکتار دارد. آماربرداری زمینی با استفاده از قطعاتنمونه 10 آری دایره‌ای شکل و براساس شبکه‌ای به ‌ابعاد 200×75 متر به‌روش منظم- تصادفی انجام و درمجموع 309 قطعهنمونه اندازه‌گیری شد. سپس واریوگرام‌های تجربی با استفاده از داده‌های زمین‌‌مرجع برداشت شده برای متغیرهای موجودی جنگل شامل تراکم (تعداد در هکتار)، رویه‌زمینی (سطحمقطع برابرسینه) و موجودی حجمی جنگل محاسبه شدند. نتایج واریوگرافی نشان داد که دو متغیر رویه‌زمینی و موجودی حجمی جنگل از هیچ‌گونه ساختار مکانی مناسب به‌منظور استفاده در درون‌یابی کریجینگ برخوردار نیستند، به‌جز زمانیکه براساس طبقههای قطری یا گونه‌های غالب درختی طبقه‌بندی شوند، اما متغیر تراکم جنگل از خود ساختار مکانی متوسط نشان داد که در نتیجه با استفاده از مدل کروی برازش شد. در مرحله بعد برآورد و پهنه‌بندی تراکم جنگل به‌روش کریجینگ معمولی- بلوکی انجام شد که نتایج ارزیابی متقابل نشان داد که برآوردها از صحت لازم برخوردارند. نتیجه این پژوهش نشان داد که زمین‌آمار قادر به تبیین تغییرات مکانی تراکم در این جنگل مدیریتنشده بود و می‌تواند نقشه پهنه‌بندی آن را با صحت مناسب تولید نماید که براساس آن می‌توان متغیرهای رویه‌زمینی و موجودی حجمی جنگل را که مستقیماً به این روش قابلبرآورد نیستند، به‌صورت غیرمستقیم برآورد نمود. 

کلیدواژه‌ها


عنوان مقاله [English]

Geostatistically estimation and mapping of forest stock in a natural unmanaged forest in the Caspian region of Iran (Case study: Keyroud forest, Nowshahr)

نویسندگان [English]

  • Reza Akhavan 1
  • Hadi Kia Daliri 2
  • Vahid Etemad 3
  • Majid Hassani 4
  • Khosro Mirakhorlou 5
1 Assistant Prof., Forest Research Division, Research Institute of Forests and Rangelands, Tehran, I.R. Iran
2 Assistant Prof., Science and Research Branch, Islamic Azad University, Tehran, I.R. Iran.
3 Assistant Prof., Faculty of Natural Resources, University of Tehran, Karadj, I.R. Iran.
4 Research Expert, Forest Research Division, Research Institute of Forests and Rangelands, Tehran, I.R. Iran.
5 Senior Research Expert, Forest Research Division, Research Institute of Forests and Rangelands, Tehran, I.R. Iran.
چکیده [English]

Estimation and mapping of forest resources is a prerequisite for research, management, and planning. In this study, we applied kriging geostatistical interpolation for estimation and mapping of forest stock attributes in a natural, uneven-aged and unmanaged forest in the Caspian region of northern Iran. The elevation across the 516-ha study area ranged from 1100 to 1450 m a.s.l. Field sampling was performed using 1000 m2 circular sample plots in a 75 m × 200 m systematic grid. Total numbers of 309 plots were sampled. Experimental variograms were fitted for stem basal area (BA), volume stock (V) and stem density (N) using geo-referenced plots. The variograms of BA and V exhibited no spatial autocorrelation, except for the stratified data based on diameter classes and tree species. The N showed yet a medium spatial structure which was fitted by a spherical model. The stem density was estimated by ordinary block kriging. The cross-validated results showed high estimation accuracy. The applied geostatistical methods were concluded to be advantageous for accurately capture the spatial variability of stem density which was reflected in the stem density maps. The methods can be applied to similar unmanaged, uneven-aged stands in the north of Iran, and thereby support the estimation of forest growing stock.

کلیدواژه‌ها [English]

  • Geostatistics
  • Mapping
  • forest stock
  • unmanaged forest
  • spatial structure
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