Effects of harvest intensity and shifting cultivation on soil carbon and nutrients: a case study in Sitapahar forest reserve, Bangladesh

Abstract

Background and aims: Changes in primary forests into agriculture and pasture significantly affect soil carbon (C) and nutrient stocks, but these effects are poorly understood in tropical forests. We i) compared concentrations and stocks of soil C and nutrients among intact, fragmented, and shifting cultivation sites in Sitapahar forest reserve of Bangladesh and ii) investigated whether there exist significant correlations between nutrient stocks with tree species diversity or soil C stock. Methods: We sampled 30 main plots (20 m × 20 m), 10 in each of three sites, and identified and measured the trees in them. The determination of soil physical and chemical properties was done in 4 subplots (1 m × 1 m) in 0–10, 10–20, and 20–30 cm depths. Results: Soil C stock was 50% lower, but soil P stock was 26% higher under the shifting cultivation compared to the intact sites. Under the shifting cultivation, soil N and K stock was 57% and 27% higher, respectively, compared to the other two sites. Soil Mg stock in intact site was up to 155% higher compared to the other two sites. Soil C stock was positively correlated with N stock, but negatively correlated with the P stock in all sites. Tree species diversity was positively correlated with K stock, but negatively correlated to N stock in the shifting cultivation site. Conclusion: Sustainable management of the sites should focus on the understanding of soil-plant interactions and protection of soil C, nutrients, and species diversity.