الگوی مکانی و وضعیت رقابت و اجتماع‌پذیری درختان در توده‌های آمیخته ممرز با استفاده از توابع یک و دو متغیره Kرایپلی (مطالعه موردی: قطعه شاهد سری سه حوضه ناو اسالم)

نوع مقاله : علمی- پژوهشی

نویسندگان

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

2 دانشیار، دانشکده منابع طبیعی، دانشگاه علوم کشاورزی و منابع طبیعی ساری

3 دانشیار پژوهش، موسسه تحقیقات جنگلها و مراتع کشور

4 استادیار، دانشکده منابع طبیعی، دانشگاه علوم کشاورزی و منابع طبیعی ساری

چکیده

به‌منظور بررسی الگوی پراکنش و وضعیت رقابت‌پذیری درختان در توده‌های آمیخته ممرز دو قطعه نمونه یک هکتاری در قطعه شاهد سری ناو اسالم انتخاب شد. اضلاع این قطعات به طول 100 متر در جهت شمالی– جنوبی بودند. برای بررسی رقابت و اجتماع‌پذیری درون‌گونه‌ای (Intra-specific)، درختان از نظر قطر در چهار گروه کم قطر (30> سانتی‌متر)، میان قطر(50-35 سانتی‌متر)، قطور (70-55 سانتی‌متر) و خیلی قطور (بزرگتر از 70 سانتی‌متر) طبقه‌بندی شدند. همچنین برای مطالعه تاثیر حضور گونه‌های مختلف بر هم (اثر بین‌گونه‌ایInter-specific ) علاوه بر قطر، گونه‌های درختی نیز برداشت گردیدند. برای تعیین نوع پراکنش درختان و همچنین اجتماع‌پذیری آنها به ترتیب از روش تابع تک و دو متغیره K رایپلی استفاده شد. نتایج نشان داد که الگوی پراکنش دو توده خوشه‌ای بوده و درختان کم قطر دارای اثر متقابل (Interaction) با درختان با قطر متوسط، قطور و بسیار قطور می‌باشند (0/05P>). گرچه اثر متقابل کلاسه قطری اول با سه کلاسه قطری دیگر از نوع اثر متقابل جذب (Attraction) بوده اما نقطه شروع آنها یکسان نیست به‌طوری‌که دو کلاسه قطور و بسیار قطور اثر مثبت خود را در فاصله کم اعمال نموده‌اند، در حالی‌که در کلاسه متوسط تا حدود 10 متر اول اثر معنی‌داری مشاهده نمی‌شود (0/05(P>. بررسی اثر متقابل بین گونه‌ها نیز نشان داد که حضور راش و ممرز وضعیت بی‌تفاوتی را حداقل در فواصل تا 20 متر به نمایش گذاشته است. بعد از آن نیز اثر متقابل از نوع دفع را می‌توان مشاهده کرد. همچنین نتایج نشان داد که گونه راش شدیداً با گونه توسکا در همان فواصل اولیه، اثر متقابل از نوع دفعی دارد. بنابراین به‌دلیل این‌که توده‌های طبیعی در طول چرخه حیاتی خود نیازهای متفاوتی دارند، اثر متقابل درون و برون گونه‌ای در آنها نیز متفاوت و در نتیجه پاسخ آنها به فرآیندهای طبیعی یکسان نخواهد بود. به همین دلیل شناخت الگوها، راهنمایی مناسب در استفاده از اثرات مطلوب پدیده‌های رقابت و اجتماع‌پذیری در راستای مدیریت نزدیک به طبیعت توده‌های جنگلی هستند.

کلیدواژه‌ها

عنوان مقاله [English]

Spatial Pattern, competition and spatial association of trees in Mixed Hornbeam Stands using univariate and bivariate Ripley’s K-function (case study: Reserve area, district 3 of Asalem forests)

نویسندگان [English]

  • Beitollah Amanzadeh 1
  • Mohammad Reza Pourmajidian 2
  • Khosro Sagheb Talebi 3
  • Seyyed Mohammad Hojjati 4
1 Ph.D Student, Department of Forestry, Sari Agricultural Sciences and Natural urces University, Sari, Iran,
2 Associate Prof., Department of Forestry, Sari Agricultural Sciences and Natural Resources, Sari, Iran
3 Associate Prof,. Research Institute of Forests and Rangelands, Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran
4 Assistant prof., Department of Forestry, Sari Agricultural Sciences and Natural Resources University, Sari, Iran
چکیده [English]

In order to study the competition and spatial association of trees in mixed Hornbeam stands, two 1-ha sample plots (100m×100m) were selected in the reserve area of Asalem forests in Guilan. In each plot, species and diameter at breast height (DBH) of all trees with a diameter > 7.5 cm were recorded and mapped using slope-corrected distance and azimuth from southwest corner of each plot. Distances and azimuths were later transformed to Cartesian coordinates, and all of the measured trees were assigned to one of four diameter size classes: ST (Small Timber, (DBH ≤ 32.5 cm), MT (Medium Timber, 32.5 < DBH ≤ 52.5 cm), LT (Large Timber, 52.5 < DBH ≤ 72.5 cm) and ELT (Extra-Large Timber, DBH > 72.5). Spatial patterns of the entire trees as well as the spatial associations among tree size classes (Intra-specific) and among species (Inter-specific) were analyzed by univariate and bivariate Ripley’s K-function. Results showed that the two stands exhibited a clustered distribution. Furthermore, the interaction between the ST class and other classes was significant (P<0.05). Although we found a positive correlation between the ST and other tree classes, spatial distribution of trees showed different patterns at different spatial scales. The starting point of the attraction in LT and ELT classes was observed at a small scale, whereas it tended towards independent associations in MT class at scale of 10 meter (P>0.05). The inter-specific investigation revealed that Fagus orientalis and Carpinus betulus trees tend towards an independent association at 1-20 meter scales. At higher scales they showed yet a negative correlation. Moreover, F. orientalis was significantly and negatively correlated to Alnus subcordata at small scales. However, their mutual intra-specific and inter-specific effects were different due to the fact that different natural stands have variety of demands during their life cycle. Therefore, it may not necessarily conform to their response to natural processes. This study concludes a founded understanding of spatial pattern of stands to be a helpful indicator for managing forests based on the currently operational close- to- nature silvicultural system.

کلیدواژه‌ها [English]

  • spatial association
  • Asalem
  • Spatial pattern
  • Ripley’s K–function
  • mixed stands
  • Competition

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