تأثیر گلازنی بر ویژگی‌های زیست‌فنی و مقدار مسلح‌سازی ریشه وی‌ول (Quercus libani)

نوع مقاله : علمی- پژوهشی

نویسندگان

1 دانشجوی کارشناسی ارشد مهندسی جنگل، دانشکده منابع طبیعی، دانشگاه تهران، کرج، ایران

2 دانشیار، گروه جنگل‌داری، دانشکده منابع طبیعی، دانشگاه تهران، کرج، ایران

3 استاد، گروه جنگل‌داری، دانشکده منابع طبیعی، دانشگاه تهران، کرج، ایران

چکیده

پوشش ‌گیاهی اثرات مهمی در افزایش پایداری و کاهش نرخ فرسایش دارد که یکی از مهم‌ترین آن‌ها مسلح‌‌‌سازی خاک توسط ریشه‌‌‌ها است. میزان مسلح‌‌‌سازی یک‌گونه به ویژگی‌‌‌های زیست‌فنی ریشه بستگی دارد. این پژوهش سعی دارد تأثیر سرشاخه‌زنی (گلازنی) درازمدت درختان وی‌ول (Quercus libani Oliv.) را بر ویژگی‌های زیست‌فنی و میزان مسلح‌سازی خاک بررسی ‌‌‌کند. به‌منظور برآورد نسبت سطح ریشه به خاک (شاخص تراکم ریشه) از روش نمونه‌گیری با سیلندر از هسته‌های خاک استفاده شد. در اطراف هر درخت، نمونه‌گیری هسته خاک در سه عمق مختلف، در چهار سمت درخت و در فاصله یک متری از تنه انجام شد. در هر هسته، تعداد ریشه و مجموع طول ریشه برای هر طبقه قطری تعیین شد. برای اندازه‌‌‌گیری مقاومت ‌کششی، نمونه‌‌‌های ریشه از سمت بالا و پایین شیب (بیشترین و کمترین تنش قابل ‌انتظار سربار) جمع‌‌آوری و مقاومت‌‌‌ آن‌ها با دستگاه اینسترون استاندارد اندازه‌‌گیری شد. نتایج نشان‌‌‌ داد که پراکنش ریشه‌ها در رابطه با عمق دارای واریانس زیادی بود. گلازنی اثر منفی معنی‌داری بر مقدار نسبت سطح ریشه به سطح خاک ریشه‌های نازک و مقاومت‌ کششی ریشه‌ها داشت. درصد نسبت سطح ریشه به سطح خاک ریشه‌های نازک در درختان شاهد 0/47 و در درختان گلازنی‌شده 0/28، میانگین مقاومت ‌کششی ریشه در درختان شاهد 40/31 و در درختان گلازنی‌شده 19/94 مگاپاسکال و میانگین مقدار مسلح‌سازی ریشه‌‌‌های نازک در درختان شاهد 2/29 و در درختان گلازنی‌شده 1/12 کیلوپاسکال به‌‌‌دست آمد. نتایج این پژوهش تأیید کرد که گلازنی درختان وی‌ول با کاهش تراکم ریشه‌‌های نازک و کاهش مقاومت ‌کششی ریشه‌‌‌‌ها، تأثیر مثبت این گونه را در مسلح‌‌‌سازی خاک کاهش می‌دهد.

کلیدواژه‌ها

عنوان مقاله [English]

Effect of pollarding on biotechnical characteristics and reinforcement amount of Lebanon oak (Quercus libani Oliv.) roots

نویسندگان [English]

  • Mahabad Salimi Zand 1
  • Ehsan Abdi 2
  • Baris Majnunian 3
  • Seyyed Ataollah Hosseini 2
1 M.Sc. Student Forest Engeeniring, Faculty of Natural Resources, University of Tehran, Karaj, Iran
2 Associate Prof., Department of Forestry, Faculty of Natural Resources, University of Tehran, Karaj, Iran
3 Prof., Department of Forestry, Faculty of Natural Resources, University of Tehran, Karaj, Iran
چکیده [English]

Among positive effects of vegetation in erosion control, reinforcement of soil by roots is very important. The quantity of reinforcement depends on root biotechnical characteristics such as root density and tensile strength. The aim of current study is to assess the effect of traditional pollarding on root biotechnical characteristics, soil reinforcement and slope stability. To estimate the Root Area Ratio (RAR/Root density index) core sampling with cylinder cores was used. For this purpose, core samples were taken from four sides around each tree in three different soil depths. In each core, number of roots and total root length was determined for each diameter class. Root samples were collected from both up and down slope and their strength was measured with a standard Instron. The results showed that root distribution in relation to depth had a wide variation. The results of ANOVA revealed that pollarding had a significant negative effect on RAR. Also the results of Wald chi square showed that pollarding had a significant negative effect on tensile strength of roots. Mean RAR values of fine roots in control and pollarding samples were 47.0 and 28.0%. Mean tensile resistance in control and pollarding samples were 40.31 and 19.94 MPa, respectively. The average reinforcement of fine roots in control and pollarding samples were 2.29 kPa and 1.12 kPa. The results of this study confirmed that traditional pollarding not only have negative effect on aboveground biomass of oak trees but also significantly reduce the positive effect of vegetation on soil reinforcement.

کلیدواژه‌ها [English]

  • Bioengineering
  • Root Area Ratio
  • root tensile strength

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