برآورد تعداد درخت و تعیین ساختار توده‌های جنگلی در دو روش طبقه‌بندی خوشه‌ای و منظم تصادفی

نوع مقاله: علمی- پژوهشی

نویسندگان

1 استادیار پژوهش، بخش تحقیقات منابع طبیعی، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان مازندران

2 دانشجوی دکتری، دانشگاه علوم کشاورزی و منابع طبیعی گرگان

3 دانشیار پژوهش، مؤسسه تحقیقات جنگلها و مراتع کشور

4 کارشناس ارشد تحقیقات، بخش تحقیقات منابع طبیعی، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان مازندران

چکیده

پژوهش پیش ­رو با هدف سنجش میزان دقت دو روش نمونه ­برداری از جنگل انجام شد که معیار قضاوت، نتایج روش آماربرداری صددرصد بود. ابتدا 116 هکتار شامل چهار پارسل آماربرداری صددرصد شد. سپس روش منظم تصادفی با شبکه­ ای به ابعاد 200 × 150 متر با قطعات نمونه 1000 مترمربعی و روش طبقه ­بندی خوشه ­ای با وسعت هر خوشه 7500 مترمربع شامل چهار قطعه‌نمونه هریک با وسعت 1875 مترمربع اجرا شدند. درمجموع، 40239 درخت در دو روش منظم تصادفی با 40 قطعه‌نمونه و طبقه ­بندی خوشه ­ای با 14 خوشه آماری مرکب از 56 قطعه‌نمونه اندازه­ گیری شد. شدت آماربرداری در روش خوشه­ ای 9/7 درصد و در روش منظم تصادفی 44/3 درصد بود. این بررسی با پردازش داده ­ها در چهار نوع گروه ­بندی و دسته­ بندی گونه­ های درختی انجام شد. نتایج نشان داد که روش خوشه‌ای برای برآورد تعداد درخت در هکتار و ساختار در مقیاس کل جنگل و نیز به‌تفکیک گونه برای راش و ممرز نسبت به روش منظم تصادفی به‌روش صددرصد نزدیک­تر می­ باشد. بیشینه قطری درختان در روش صددرصد 165، در روش منظم تصادفی 110 و در روش خوشه‌­ای 125 سانتی ­متر ثبت شد. پیشنهاد می‌شود پیش از آماربرداری هر پارسل، تیپ­ها براساس ساختار و ترکیب گونه تفکیک شوند. همچنین تعداد قطعه‌نمونه متناسب با تنوع تیپ تعیین شود وآرایش قطعه‌نمونه‌ها خوشه ­ای و ابعاد آنها بین 19 تا 20 آر درنظر گرفته شود.

کلیدواژه‌ها


عنوان مقاله [English]

Tree density and stand structure estimation by stratifiedcluster and systematic random sampling methods

نویسندگان [English]

  • Mohammad Amini 1
  • Roja Amini 2
  • Khosro Sagheb Talebi 3
  • Seifollah Khorankeh 4
1 Assistant Prof., Research Division of Natural Resources, Mazandaran Agricultural and Natural Resources Research Center, AREEO
2 Ph.D. Student, Gorgan University
3 Prof., Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO)
4 Senior Research Expert, Research Division of Natural Resources, Mazandaran Agricultural and Natural Resources Research Center, AREEO
چکیده [English]

We assessed the accuracy of two sampling methods by comparing their estimations to Full Calipering (FC). The two methods included 1000-msystematic random (SR) sampling plots designed within a 150 ×200 m grid, and acluster sampling (CS) method with 7500-m2 clusters each embracing 4 plots of 1875 m2 each. Full calipering was performed in 4 parcels of 116 ha each. The inventory resulted in total 40239 trees measured in 40 SR plots (sampling intensity=9.7 %) as well as 56 plots within 14 clusters of in CS approach (sampling intensity=3.44 %). Results from CS method were associated with optimum accuracy for tree density and forest structure. The CS method returned results closer to the FC when estimating the beech- and hornbeam-specific no. of trees per ha and their distribution in diameter classes and in parcels. The Maximum trees diameter of 165, 110 and 125 cm were recorded for FC, SR and CS approaches, respectively. Conclusively, this study suggests a forest type and species-specific stratification to be performed prior to each parcel-based inventory. In addition, sample size should be determined on a forest type-specific basis, ideally distributed within a CS design with 1900 to 2000-m2 plot sizes.

کلیدواژه‌ها [English]

  • Number of trees
  • distribution
  • Forest structure
  • stratified cluster sampling
  • systematic random sampling
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