Both storage and sieving of soil samples are still common practices but may alter rates of gross N mineralization and nitrification. In this study, gross N turnover rates of stored (ambient temperature) and in-situ incubated intact and sieved soil from an African tropical lower montane forest were compared. Our results revealed that sieving increases N mineralization and storage stimulates nitrification. Therefore, we conclude that for tropical soils storage under ambient temperature conditions as well as sieving of soil samples can cause large biases in measured gross N turnover rates and ratios, limiting cross-site comparisons. [ABSTRACT FROM AUTHOR]