Abstract: [Objective] Soil CO₂ flux of different bamboo plantations was studied under conditions of the protected dike-pond ecosystem of Xixi National Wetland Park, Hangzhou. Additionally, we aimed to provide a scientific basis for the estimation of greenhouse gas fluxes and C and N cycling in the dike-pond wetland ecosystem.[Method] In Xixi National Wetland Park, the soil CO₂ flux rates of two bamboo plantations:Phyllostachys edulis plantation and P. violascens plantation, were quantified using the static chamber-gas chromatograph technique every other month. In addition, soil samples were collected every other month to measure the soil water soluble carbon and nitrogen (WSOC and WSON) by using the distilled water dipping method with a TOC analyzer, and the soil microbial biomass carbon and nitrogen (MBC and MBN) by using the chloroform fumigation-K₂SO₄ extraction method. Soil temperature and soil water content were also measured. Thereafter, the relationships between soil CO₂ flux and the measured soil chemical, biological, and physical characteristics were assessed.[Result] Soil CO₂ flux significantly different between the two bamboo plantations. The soil CO₂ flux rates of P. edulis plantation ranged from (127.4±24.1) to (537.2±41.1) mg·m^-2h^-1, with an annual cumulative CO₂ emission 3 366.3 g·m^-2a^-1. Soil CO₂ fluxes of the P. violascens plantation ranged from (2.1±0.6) to (112.0±22.9) mg·m^-2h^-1, with an annual cumulative emission of 558.4 g·m^-2a^-1. Thus, the soil CO₂ flux of the P. edulis plantation was 6.0-fold greater than that of the P. violascens plantation. Soil CO₂ fluxes of the two bamboo plantations significantly correlated with soil temperature (10 cm depth) and soil water contents. The WSOC concentrations of P. edulis and P. violascens plantations were the highest in August,(348.0±25.5) and (146.1±9.9) mg·kg^-1, respectively, and the lowest in October and December (202.5±28.4) and (54.9±13.8) mg·kg^-1, respectively. Specific pattern of the WSON concentrations in the two bamboo plantations were not shown, and the WSON annual fluctuation was greater. In both P. edulis and P. violascens plantations, the highest concentrations of MBC, (279.0±17.6) and (313.9±38.6) mg·kg^-1, respectively, were measured in June, while the lowest concentrations (219.7±13.8 and 198.7±12.8, respectively) were measured from February to April. The annual fluctuation of MBN concentrations in P. edulis plantation ranged from (21.4±3.8) to (43.7±4.2) mg·kg^-1, which was lower than the range of (13.9±1.4) to (57.0±10.8) mg·kg^-1 in the P. violascens plantation. In both plantations, the CO₂ flux significantly correlated with WSOC, but not with WSON, MBC, or MBN.[Conclusion] The soil CO₂ flux of the dike-pond ecosystem in Xixi wetland had a temporal heterogeneity, which was largely controlled by the seasonal variations in temperature and moisture and the amount of WSOC, a respiratory substrate. Therefore, enclosure of the dike-pond ecosystem was favoralle to change the original rough model of land reclamation, and to reduce WSOC content and soil CO₂ emissions.

Key words: Phyllostachys edulis, Phyllostachys violascens, greenhouse gas, soil water soluble C and N, soil microbial biomass C and N