Comparing the variations and controlling factors of soil N2O emissions and NO3–-N leaching on tea and bamboo hillslopes

Abstract

Due to the economic benefits, land use change (e.g. deforest to tea or fruit plantation) has been widely occurred in the south-eastern hilly area of China. This may stimulate serious soil nitrogen (N) losses due to large fertilizer inputs (about 1–2 times of that in regular rice-wheat rotation). Therefore, we investigated the soil N2O fluxes and leachate NO3–-N concentrations and their responses to multiple factors on a tea garden (TG) hillslope and an adjacent bamboo forest (BF) hillslope. Soil N2O fluxes and leachate NO3–-N concentrations on the TG hillslope were 3.28 and 4.24 times of those on the BF hillslope, respectively. Soil N2O fluxes measured in spring were the greatest while those measured in winter were the lowest. However, the measured leachate NO3–-N concentrations were the greatest in winter but the lowest in summer. On both hillslopes, soil temperature (ST) and precipitation during the previous seven days (API7) were positively related to soil N2O fluxes but negatively related to leachate NO3–-N concentrations, while the ground water table depth was opposite. Soil water content (SWC) and the ratio of SWC/field capacity (SWC/FC) negatively influenced leachate NO3–-N concentrations on both hillslopes. Positive influences of SWC and SWC/FC on soil N2O fluxes were observed on the TG hillslope, while quadratic relationships were observed on the BF hillslope. Thresholds of ST and API7 were existed in the controlling the spatial variations of soil N2O fluxes and leachate NO3–-N concentrations on both hillslopes. When ST was > 9.5 °C, spatial variations in soil N2O fluxes were controlled by topography, soil properties and soil hydrological parameters on both hillslopes. Similarly, when API7 were < 58.0 mm, the spatial variations in leachate NO3–-N concentrations were also influenced by these factors on both hillslopes. Finding of this study will supplement the knowledge of soil N2O emissions and NO3–-N leaching from the tea planation and bamboo forest.