Soil microbial biomass and activity in response to Eucalyptus plantation and natural regeneration on tropical soil

This study compared soil physico-chemical characteristics, microbial biomass and activity in a tropical dry deciduous natural forest, regenerating forest and Eucalyptus plantation site. Although texturally there was no difference in the soils, porosity was less and bulk density greater in the soil of the plantation than the soils of the natural and regenerating forests. Concentrations of soil organic carbon, total soil nitrogen and the sizes of soil microbial and microfungal biomass were comparatively low under Eucalyptus plantation. Proportion of soil organic carbon and total nitrogen in microbial biomass was also the least in the plantation site. There was a decrease in the fungal dominance in the Eucalyptus plantation soil. Microbial metabolic quotient of the three sites showed poor substrate utilisation efficiency of soil micro-organisms under Eucalyptus plantation. The study indicated that the improvement of soil characteristics of barren degraded soil due to Eucalyptus plantation was less than due to spontaneous regeneration. (C) 2002 Elsevier Science B.V. All rights reserved.