MICROBIAL-C, MICROBIAL-N AND MICROBIAL-P IN DRY TROPICAL FOREST SOILS - EFFECTS OF ALTERNATE LAND-USES AND NUTRIENT FLUX

The effects of alternate land-uses (savanna, cropfield and mine spoil) on microbial C, N and P in dry tropical forest soil of India were studied. The mean microbial C, N and P, respectively, in the four major systems ranged from 250 to 609-mu-g C g-1, 27 to 65-mu-g N g-1 and 12 to 26-mu-g P g-1. The microbial biomass in these systems was characterized by a mean C:N:P ratio of 23:2:1. The microbial C, N and P were positively related to root biomass and total plant biomass (aboveground + root biomass). The derived ecosystems (savanna, cropland and mine spoil) have changed from the original forest ecosystems in terms of soil features and microbial biomass. The conversion of forest into other land-uses resulted in remarkable decline in the amounts of soil nutrients and microbial C, N and P. The microbial nutrients in this dry tropical environment are sensitive to land-use changes. The calculated flux of N and P through the microbial biomass ranged from 27 to 64 kg N ha-1 yr-1 and 13 to 26 kg P ha-1 yr-1. Thus, in this dry tropical environment the microbial biomass appears to contribute substantially to the N and P requirements of higher plants.