Variations in fine root biomass and net primary productivity due to conversion of tropical forests into forest plantations

The changes in fine root biomass and net primary productivity (NPP) following conversion of tropical forests (evergreen and deciduous) into forestry plantations (Teak, Acacia, Albizia, Rubber) were studied at Kodayar in western ghats, South India. The very fine (<1 nun) and fine (1-3 mm) root biomass and NPP were altered in plantations. The very fine root standing crop biomass was significantly (P<0.01) greater under the natural ecosystems (biomass 245 and 263 g m -2 ) compared to that of the monoculture plantations (172, 132, 125 g m -2 ) except in teak plantation (230 g m -2 ). A similar trend was observed in case of fine roots also. Similarly NPP also greater in natural ecosystems (476 and 527 g m -2 year -1 ) compared the plantations (368, 293, 320 g m -2 year -1 ) except teak plantations (463 g m -2 year -1 ). This could be attributed to tree density and basal area along with greater litter accumulation. The lower biomass and NPP in plantation ecosystems could be attributed to species composition, low organic matter and soil fertility. Recurrence of annual fire could lead to re-occupation of land by grass cover. This may be the reason for greater belowground biomass and NPP in deciduous forest and teak plantation.