Effects of Fertilization on Soil CO_(2) Efflux in Chinese Hickory(Carya cathayensis)Stands

Chinese hickory(Carya cathayensis Sarg.)is a popular nut tree in China,but there is little information about the influences of fertilization on soil CO_(2) efflux and soil microbial biomass.This study evaluated the short-term effects of different fertilizer applications on soil CO_(2) efflux and soil microbial biomass in Chinese hickory stands.Four fertilizer treatments were established:control(CK,no fertilizer),inorganic fertilizer(IF),organic fertilizer(OF),and equal parts organic and inorganic N fertilizers(OIF).A field experiment was conducted to measure soil CO_(2) effluxes using closed chamber and gas chromatography techniques.Regardless of the fertilization practices,soil CO_(2) effluxes of all the treatments showed a similar temporal pattern,with the highest value in summer and the lowest in winter.The mean annual soil CO_(2) efflux in the IF treatment was significantly higher than that in the CK,OIF,and OF treatments.There was no significant difference in soil CO_(2) efflux between the OIF,OF,and CK treatments.Soil CO_(2) effluxes were significantly affected by soil temperature.Soil dissolved organic carbon(DOC)was positively correlated with soil CO_(2) efflux only in the CK treatment.Regression analysis,including soil temperature,moisture,and DOC,showed that soil temperature was the primary factor influencing soil CO_(2) effluxes.Both OF and OIF treatments increased concentrations of soil microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN),but decreased the ratio of MBC:MBN.These results reveal that applying organic fertilizer,either alone or combined with inorganic fertilizer,may be the optimal strategy for mitigating soil CO_(2) emission and improving soil quality in Chinese hickory stands.