Effects of fertilization on seasonal variations soil CH₄ uptake fluxes in Chinese chestnut stands

To investigate the effects of inorganic and organic fertilizers on seasonal variation ofCH4 uptake flux in the soil of Chinese chestnut stands and to explore the relationships between theCH4 uptake flux and various environmental factors, a field study including control(CK), inorganic fertilizer(IF), organic fertilizer(OF), and half organic plus half inorganic fertilizer(OIF) treatments was conducted in typical Chinese chestnut stands in Linan, Zhejiang Province. SoilCH4 uptake fluxes were analyzed by static closed chamber/GC technique, and soil temperature, soil water content, WSOC and MBC concentrations were determined as well. Results showed that soilCH4 uptake fluxes exhibited a strong seasonal pattern, with the maximum values in September and the minimum in February or March. Application of inorganic fertilizer significantly inhibited the soilCH4 uptake(P 0.05), and annual accumulation of soilCH4 uptake in IF, OF, and OIF treatments were 7.0%, 1.6%, and 4.4% lower than in CK ［CH4 3.09 kg/(haa)］, respectively. In addition, fertilization significantly increased soil WSOC and MBC concentrations(P 0.05) and partly increased the concentrations of soil available nitrogen, ammonium nitrogen, nitrate nitrogen, total nitrogen, and soil organic matter. The correlation analysis showed that soil CH4 uptake fluxes had a significant positive correlation with soil temperature at 5 cm depth(P 0.05), but had no significant correlation with soil water content and soil MBC concentration in all treatments. SoilCH4 uptake rate was correlated with soil WSOC concentration except in CK(P 0.05). In conclusion, the change of soil physicochemical properties(NH+4-N,NO-3-N, TN and SOC) and WSOC concentration caused by fertilization was probably the main reason for the inhibition of soilCH4 uptake in Chinese chestnut stands induced by fertilization.