Biomass, litterfall and aboveground net primary productivity of herbaceous communities in varied ecosystems at Kodayar in the western ghats of Tamil Nadu

Influence of herbaceous weed community on the forest ecosystem structure and function are essential to manage or control weeds effectively. Therefore, an attempt was made to study biomass, litter production and aboveground net primary productivity (ANPP) of herbaceous community was studied in natural secondary forest and man-modified ecosystems such as rubber plantation, Albizia plantation and wasteland. Man-modified ecosystems showed significantly greater herb density than the natural ecosystem. This may be due to open habitat in the man-modified ecosystems, which favoured colonisation of exotic weed species resulting in greater herb density. All the landuses studied here showed greater standing crop biomass in the tree layer compared to herbaceous layer. However, herbaceous layer aboveground biomass and net primary production varied among the landuse types considerably. Greater biomass of annual exotic weeds and Lantana camara in these man-modified ecosystem could be attributed to high degree of disturbance and open environment. Greater standing crop biomass and net primary productivity of Chromolaena odorata in rubber plantation may be due to the existing practice of ineffective aboveground mechanical weeding. Lower ANPP and greater biomass accumulation quotient of exotics such as C odorata and L camara in the natural secondary forest may be attributed to less favourable resource conditions for its growth and also possibly lack of occurrence of disturbance. Percentage contribution of exotic plants to the total herbaceous community in terms of litter production and ANPP was higher in the wasteland and lower in the disturbed forest. But, the native plants contribution showed a reverse trend. Percentage contribution of exotic plants to the total herbaceous community in terms of litter production and ANPP was higher in the wasteland and lower in the disturbed forest. But, the native plants contribution showed a reverse trend. Greater herbaceous community litter production and net primary productivity in the man-modified ecosystems might be due to faster turnover of ruderal herbaceous community or modification of the tree layer. (C)) 2002 Elsevier Science B.V All rights reserved.