Population dynamics of Eupatorium adenophorum Spreng. during secondary succession after slash and burn agriculture (jhum) in north eastern India |
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Authors: | PS KAMAKRISHNAN B K MISHRA |
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Institution: | Department of Botany, School of Life Sciences, North-Eastern Hill University. Shillong 793014. Intlia |
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Abstract: | Eupatorium adenophorum Spreng. is an important weedy colonizer in early successional communities developing after slash and burn agriculture (jhum) at higher elevations of the north-eastern hill regions of India. The relative performance of this species in terms of fecundity and survivorship in successional plant communities has been worked out. A net population increase occurred through both vegetative and sexual reproduction in early successional fallows up to 6 years old, the increase being greatest in a 6-year fallow. Mortality of seedlings was high in 1- and 3-year fallows, low in a 6-year fallow but reached 100% in older fallows. Seedling mortality was maximal during the monsoon although some seedlings also died during winter as a result of drought and frost. Mortality of vegetative sprouts followed a similar pattern to that of seedlings. The reproductive potential was reduced with increasing age of the successional communities and in a 15-year fallow all individuals were non-reproductive. Since E. adenophorum is able to succeed only in fallows of less than 6 years, repeated short jhum cycles of 4–5 years have had the effect of arresting succession al the weedy stage. |
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