Department of Agronomy, Assam Agricultural University, Jorhat-785 013 (Assam), India.
1 Rain Forests Research Institute, Jorhat-785 001 (Assam), India.
Weed flora of pointed gourd (Trichosanthes dioica Roxb.) fields under shifting cultivation was studied in the greater Silonijan area of Karbi Anglong district of Assam during 1997 and 1998. Out of altogether 29 species of weeds, Asteraceae and Poaceae were largest families with seven and six species, respectively, mostly of chameophytic, therophytic and hemicryptophytic life forms. The life-form spectrum showed a marked deviation from the normal spectrum because of biotic interference and climatic factors. Most of the species showed contagious distribution. Altogether 16 species had ‘A’ class frequency and their individual IVI had ranged from 2.29 to 10.70. ‘E’ class frequency was represented by the Mexican chameophytic weed, Ageratum houstonianum Mill. alone, which had 39.92 absolute density and as much as 66.31 IVI. Grasses had maximum accumulation of biomass in these fields. Majority of weeds were exotic in nature and only nine species had origin in Paleotropics. However, the cultivation of pointed gourd might be a step against shifting cultivation towards permanent agriculture.
