نوع مقاله : مقاله پژوهشی

نویسندگان

1 استادیار گروه مرتع و آبخیزداری، دانشکدة منابع طبیعی، دانشگاه زابل

2 دانشجوی دکتری آبخیزداری، دانشکدة جنگل‌داری، دانشگاه پوترا، مالزی

3 دانشیار دانشکدة مطالعات محیط زیست، دانشگاه پوترا، مالزی

چکیده

هدف این مطالعه کمّی‌سازی واکنش ریشة گونة Brachiaria decumbens به چرای گاو در چراگاه استوایی در کشور مالزی بود. تیمارها عبارت بود از: چرای تناوبی با شدت متوسط (7/2 واحد دامی در هکتار) در بلندمدت (33 سال) و عدم چرا. نمونه‌های ریشه همراه با خاک تا عمق 30 سانتی‌متر برداشت شد. خصوصیات مورفولوژیک ریشه‌ـ یعنی طول، قطر، سطح، و حجم آن‌‌ـ با استفاده از دستگاه WinRhizo Root Scanner اندازه‌گیری شد. چگونگی توزیع ریشه در واحد حجم خاک با استفاده از روابط مربوطه محاسبه شد. داده‌ها با روش تجزیة واریانس، اندازه‌گیری‌های مکرر، و آزمون t تجزیه و تحلیل شد. اثر چرا در طول ریشه و توزیع آن در خاک و متوسط قطر ریشه معنی‌دار نبود) 05/0(P >. قطر ریشه در عمق میانی (10-20) و زیرین (20-30 سانتی‌متر) خاک در منطقة چراشده به‌ترتیب 50 درصد و 72 درصد بیش از مقادیر آن در سایت چرانشده بود )05/0(P <. حجم و مساحت سطح ریشه و چگونگی توزیع آن‌ها در واحد حجم خاک در هر دو منطقة چرا و عدم چرا یکسان بود) 05/0(P >. چرا، عمق خاک، و اثر متقابل آن‌ها تأثیر معنی‌داری در وزن ریشه و تراکم وزن ریشه در واحد حجم خاک داشت )05/0(P <. در هر سه عمق خاک، وزن ریشه در سایت چراشده بیش از مقدار آن در سایت چرانشده بود )05/0(P <. چرای تناوبی با شدت متوسط در بلندمدت تأثیر منفی در خصوصیات مورفولوژیک ریشة Brachiaria decumbens و نحوة توزیع آن‌ها در واحد حجم خاک نداشته است.

کلیدواژه‌ها

عنوان مقاله [English]

Effect of long-term cattle grazing on root distribution and morphological characteristics of Brachiaria decumbens (Case study: tropical pasture, Malaysia)

نویسندگان [English]

  • Majid Ajorlo 1
  • Mahboubeh Ebrahimian 2
  • Ramdzani Abdullah 3

1 Assistant Professor, Faculty of Natural Resources, University of Zabol, Iran

2 PhD Candidate, Faculty of Forestry, University Putra, Malaysia

3 Associate Professor, Faculty of Environmental Studies, University Putra, Malaysia

چکیده [English]

Root morphological and distribution responses of signal grass (Brachiaria decumbens) to long-term cattle grazing were examined in a tropical pasture in Malaysia. The treatments were no grazing by cattle and grazing at a moderate stocking density (2.7 animal unit/ha) under rotational grazing for 33 years. The method consists of taking soil core using a soil corer to a depth of 30 cm and extracting roots from cores by hand-washing and subsequent measuring of root morphological characteristics including length, surface area, average diameter and volume using WinRhizo Root Scanner. Root length density, mass density, surface area density, and volume density were calculated as indicators of root distribution pattern in the soil volume. Data were analyzed using repeated measure analysis of variance and independent t-test. Root diameter, length and length density were affected neither by grazing treatment nor the interaction between them (P > 0.05). Root diameters in the middle (10–20 cm) and lower (20–30 cm) soil layers of grazed site were 50% and 72% greater than that in the ungrazed site. Root volume, surface area and their densities were not affected (P > 0.05) by grazing and the interaction between grazing and soil depth. Mean root mass and mass density were affected (P < 0.05) by moderate grazing and soil depth, and the interaction between them. Mean root mass in all soil depths in grazed site was greater than that in the ungrazed site. Long-term rotational moderate grazing has no negative impact on root variables of signal grass in tropical pasture.

کلیدواژه‌ها [English]

  • root diameter
  • Root length
  • root mass
  • root surface area
  • root volume
  • tropical pasture
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