Storages and leaching losses of soil water dissolved CO2 and N2O on typical land use hillslopes in southeastern hilly area of China

Abstract

The dynamics of soil water dissolved CO2 and N2O are important in determining the fates of soil CO2 and N2O. However, related mechanisms and processes have been rarely revealed. In this study, storages and leaching losses of soil water dissolved CO2 and N2O were investigated on the tea garden (TG) and bamboo forest (BF) hillslopes. Soil water storage and leaching flux were simulated by the HYDRUS-3D model and the soil water dissolved CO2 and N2O concentrations were acquired by field monitoring. Results showed that the storages of soil water dissolved CO2 and N2O ranged from 1.30 to 14.86 kg C ha−1 and 0.24 to 388.99 g N ha−1 on the TG hillslope, respectively, while they ranged from 0.49 to 52.29 kg C ha−1 and 0.50 to 14.22 g N ha−1 on the BF hillslope, respectively. The annual leaching loss of soil water dissolved CO2 and N2O were 26.17 kg C ha−1 and 29.46 g N ha−1, respectively, on the TG hillslope, while they were 49.51 kg C ha−1 and 4.35 g N ha−1 on the BF hillslope, respectively. The dissolved CO2 leaching loss mainly occurred in summer, especially in July on both hillslopes. Peaks of dissolved N2O leaching loss on the TG hillslope were observed after the application of basal fertilizer, accompanying with precipitation events. Instead, peaks of dissolved N2O leaching loss on the BF hillslope were observed in summer. The main influencing factors of dissolved CO2 and N2O storages were temperature, precipitation, and fertilization, with total effects generally >0.30. However, that of the dissolved CO2 and N2O leaching losses was the precipitation, with total effects >0.57. Dissolved CO2/N2O concentration was more important than soil water storage in determining the dissolved CO2/N2O storage, while the leaching flow rate was more crucial than dissolved CO2/N2O concentration in determining the dissolved CO2/N2O leaching loss. These findings expanded our knowledge of sources and sinks of greenhouse gases on the terrestrial ecosystem.