Effects of nitrogen and phosphorus on the production of carbon dioxide and nitrous oxide in salt-affected soils under different vegetation communities

Nutrient availability greatly regulates ecosystem processes in salt-affected soils. However, few studies have explored the impacts of nitrogen (N), phosphorus (P) and N x P interactions on CO2 and N2O emissions from salt-affected soils in the Yellow River Delta (YRD), which is one of the three biggest deltas in China. An incubation study was conducted to test the effects of N or P addition alone, as well as combined NP application, on CO2 and N2O emissions from the soils taken from four sites: bare land (BL) with no vegetation cover and three adjacent vegetation communities, Tamarix chinensis (TC), Suaeda salsa (SS) and Phragmites auswalis (PA) in the YRD. The results showed that N and its interaction with P showed significant and identical effects on both CO2 and N2O emissions in all soils. Nevertheless, the significant effect of P on CO2 production was found in soils covered with vegetation. N addition tended to augment CO2 and N2O emissions. However, the significant positive correlation between cumulative CO2 emissions and P addition was only found in soils collected from different communities. Compared with soils collected from BL, soils from different vegetation communities emitted more CO2 and more N2O. Moreover, soils of woody communities produced more CO2 than those of herbaceous communities. On the contrary, N2O emissions in soils of herbaceous communities were higher than in woody communities. Therefore, more attention, should be paid to the pulse GHG emissions that result from nutrient addition during the reclamation of saline soils, especially those covered with vegetation.