Effects of Meteorological Factors and Water-Nitrogen Management Techniques on Carbon Dioxide Fluxes in Wheat Fields in a Dry Semi-Humid Area

Abstract

Studying carbon dioxide fluxes in wheat fields is becoming increasingly important. The dry semi-humid area in China is an important wheat production area, but the variations in carbon dioxide fluxes in wheat fields and the mechanisms associated with the carbon dioxide flux response to meteorological factors and water-nitrogen management have rarely been studied systematically in this area. Thus, we conducted a monitoring experiment in order to clarify the responses of CO2-C fluxes to meteorological factors and water-nitrogen management in wheat fields in this dry semi-humid area, and modeled the relationships between CO2-C fluxes and meteorological factors under different water-nitrogen managements. Four water-nitrogen treatments were tested in wheat fields: rain-fed (no water and nitrogen added), irrigation (150 mm water added), rain-fed plus nitrogen application (225 kg ha−1 nitrogen added), and irrigation plus nitrogen application (150 mm water and 225 kg ha−1 nitrogen added). The CO2-C fluxes and meteorological indicators were monitored and analyzed, before fitting the relationships between them. The direct and total effects of precipitation, air temperature, and water vapor pressure on CO2-C fluxes in wheat fields were all positive, and their total effect coefficients were more than 0.7 and significant. Irrigation and nitrogen application increased the CO2-C fluxes in wheat fields by 6.82–14.52% and 51.59–55.94%, respectively. The fitting results showed that partial least squares regression models of the relationships between meteorological factors and CO2-C fluxes in wheat fields under different treatments were all effective, with R2Y (cum) and Q2 (cum) values around 0.7. Overall, these results suggest that precipitation, air temperature, water vapor pressure, and water and nitrogen addition have positive effects on CO2-C fluxes from wheat fields in dry semi-humid areas. The partial least squares regression method is also suitable for modeling the relationships between meteorological factors and CO2-C fluxes. These results may provide a scientific basis for predicting and regulating CO2-C fluxes in wheat fields in dry semi-humid areas, and provide a methodological reference for ecosystem carbon dioxide flux simulation studies.