Temporal Dynamics of Greenhouse Gas Flux of Warm Temperate Deciduous Broad-Leaved Forest Ecosystem Soil in North China

Abstract Background: According to the WMO's (World Meteorological Organization) Greenhouse Gas Bulletin (2019), the fastest increase atmospheric concentrations of the three main greenhouse gases has been detected in the past 20 years. Researchers have paid more and more attention to the problem of greenhouse gas (GHG) emission. Among the studies, people focus much more on grassland ecosystem than that of forest ecosystem，which has a more important effect on the emission and absorption of greenhouse gases. Estimating the impact of forest ecosystem on greenhouse effect in China is of great significance. Methods: 6 deciduous broad-leaved forest communities with similar elevation, slope orientations and slope gradient in Wuling Mountain National Natural Reserve are employed to conduct the GHG flux study. Five 50cm×50cm square stainless-steel bases are set in the study site by mechanical spot arrangement method to sample the GHG. The environmental temperature and soil moisture content is measured every sampling time. Static chamber-gas chromatograph method is adopted to examine the greenhouse gas fluxes of CO 2 , CH 4 and N 2 O. Results and conclusions: The GHG flux of CO 2 , N 2 O and CH 4 in the Warm Temperate Deciduous Broad-Leaved Forest Ecosystem has great relationship with environmental temperature and soil water content. GHG flux varies with seasons. Among them, the CH 4 flux shows the character of source or sink in different seasons. The other 2 are always the source of GHG flux during the study period. The peak value of CO 2 is in summer and that of N 2 O in March. The flux of CH 4 shows the feature of source in April and sink in other seasons. The peak value of sink comes in late July. The flux of CO 2 has the greatest relationship with the soil temperature 5cm below the ground surface and the flux of N 2 O has the greatest relationship with the soil water content. The relationship between CH 4 flux and the environmental temperature or the soil water content is complex.