Changchun Song

Fluxes of carbon dioxide and methane from swamp and impact factors in Sanjiang Plain, China

The fluxes of CO2 and CH4 emission of the two types of primary swamp were measured in Sanjiang Plain using the opaque chamber and gas chromatogram technique. The mean value of ecosystem respiration flux in continuously inundated swamp ecosystem is 548.04 mg · m−2 · h−1, lower than that of the seasonal inundated swamp (713.08 mg · m−2 · h−1). The peaks concentrated on July and August which are the growing period of the vegetation. CH4 emission was different from the respiration flux of ecosystem. The CH4 flux of continuously inundated swamp was 12.80 mg · m−2 · h−1, larger than that of the seasonal inundated swamp (8.56 mg · m−2 · h−1), and they were varied at different periods, the continuously inundated swamp emitted CH4 mainly from July to September, whereas from last August to middle September in the seasonal inundated swamp. The ecosystem respiration flux of the swamp has the significantly positive correlation with the soil temperature (0–10 cm depth) and the water temperature, but CH4 emission was associated with the soil temperature in a certain degree. The CH4 emission from swamp depends on the integral function of water table and soil temperature.

Effects of soil moisture, temperature, and nitrogen fertilization on soil respiration and nitrous oxide emission during maize growth period in northeast China

Abstract To evaluate the response of soil respiration and nitrous oxide (N2O) emission to soil moisture, temperature and nitrogen fertilization, and to estimate the contribution of soil and rhizosphere to total soil carbon dioxide (CO2) and N2O emissions, a field experiment was conducted in the Sanjiang Mire Wetland Experimental Station, Chinese Academy of Sciences, in the northeast of China. The experiment included four treatments: bare soil fertilized with 150 kg N ha−1 yr−1 (CK), and maize-cropped soils amended with 0 (N0), 150 (N150), and 250 (N250) kg N ha−1 yr−1. The cumulative soil CO2 emission in the CK, N0, N150, and N250 treatments was estimated to be 698, 863, 962, and 854 g CO 2 C m−2, respectively. The seasonal soil CO2 fluxes were significantly affected by soil temperature, with a Q 10 value between 1.99 and 2.47. Analysis of the stepwise regression indicated that the CO2 flux can be quantitatively described by a linear combination of soil moisture content and soil temperature 5 cm below ground. Approximately 70, 58, 60, and 44% of the variability in CO2 flux can be explained by these two parameters, in CK, N0, N150, and N250, respectively. Nitrogen fertilization with 150 kg N ha−1 yr−1 increased CO2 fluxes by 14.5% compared with soils fertilized with 0 kg N ha−1 yr−1. However, in the soil fertilized with 250 kg N ha−1 yr−1, high N fertilization suppressed soil respiration. There was an exponential relationship between soil temperature 5 cm below ground and N2O flux, with a Q 10 value of 1.30–2.91. Mean cumulative soil N2O emissions during the maize-growing season in the CK, N0, N150, and N250 treatments were estimated to be 86, 44, 200, and 484 mg N2O-N m−2, respectively. In contrast to the maize planting, soil fertilized with 150 kg N ha−1 yr−1 and with 250 kg N ha−1 yr−1 increased N2O fluxes by 354 and 1000%, compared with soils fertilized with 0 kg N ha−1 yr−1, respectively. Soil respiration and N2O fluxes measurement using the root-exclusion technique indicated that the rhizosphere of the maize could be the dominant habitat of soil respiration and N2O formation.