Fine root biomass distribution and productivity patterns under open and closed canopies of tropical forest ecosystems at Kodayar in Western Ghats, South India

Abstract

Standing crop, rates of production and distribution of very fine (≤ 1 mm), fine (> 1 − ≤ 3 mm) and coarse (> 3 mm) roots were estimated for one year (August 1993–August 1994) under open and closed canopies of Tropical forest ecosystems at Kodayar in the Western Ghats of India. In the moist deciduous forest very fine root biomass was significantly higher under the open canopies (309 g m −2) than in the closed canopies (222 g m −2). While in the semi-evergreen and evergreen forest ecosystems closed canopies (Site II: 318, Site III: 315 and Site IV: 275 g m −2) were comparatively higher in very fine root biomass than the open canopies (264, 278 and 239 g m −2). A similar trend was observed in the fine root productivity also. Under the closed canopies, total fine root standing crop biomass was significantly higher under the evergreen forest (1847–2021 g m −2) compared with others (1081 g m −2 and 1298 g m −2). Root production and standing crop biomass showed a seasonal pattern of maximum during the rainy season and minimum in the dry season. Necromass fraction ranged between 52–132 g m −2 and the maximum was in the dry period. Localized disturbances such as canopy openings contributed towards the reduction of fine root biomass. Due to the annual wild fire and the consequent grass community dominance in the moist deciduous forest (Site I), greater standing crop of very fine root biomass and net primary productivity was observed. Further, the study revealed that the fine root biomass and production increased significantly due to litter accumulation ( P < 0.05) and the soil moisture ( P < 0.01) at the ground level. The above results are discussed in the light of understanding the fragility of tropical forests and their management.