Land use effects on soil quality in a tropical forest ecosystem of Bangladesh

Human population pressures upon land resources have increased the need to assess impacts of land use change on soil quality. In order to assess effects of land use changes on soil quality properties in a tropical forest ecosystem of Bangladesh, soil samples were collected from adjacent well-stocked Shorea robusta natural forest, land reforested with Acacia, grassland and cultivated land. Land use/land cover changes (degradation of natural forest and subsequent cultivation of soils) resulted in surface compaction and significant decreases in silt and clay contents, porosity and aggregate stability, N, fulvic and labile C, and microbial biomass C. Maintenance respiration rates increased in comparison to the soils under natural forest. Use of soil deterioration index showed that soil quality deteriorated significantly (-44%) under cultivation, while in sites revegetated with fast-growing Acacia or grasses, it improved by 6-16%. Degradation of soil quality may have resulted from increased disruption of macroaggregates, reductions in microbial biomass, and loss of labile organic matter due to fire, deforestation, tillage and accelerated erosion. Improvement in soil quality and enhanced biological activity at reforested and grassland sites demonstrated the inherent resilience of these soils once revegetated with highly adaptable and fast growing Acacia (Acacia sp.) and grass species. (C) 2000 Elsevier Science B.V. All rights reserved.