Yiyong Wang

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.

Nitrous oxide emissions from black soils under a continuous soybean cropping system in northeast China

A large number of natural wetlands in northeast China have been reclaimed as farmland in the last few decades, and soybean is the main rain-fed crop here. For the depth understanding of nitrous oxide (N2O) emission from reclaimed soybean fields, using static opaque chamber method, we conducted a four-year N2O flux measurement at two adjacent soybean fields cultivated after wetland drainage in 1987 and 1993, respectively, in the Sanjiang Plain of northeast China Using static opaque chamber method,. Both sites had two treatments including soybean cropped and bare soils (i.e., SF87, BS87, SF93 and BS93). The results showed that soil N2O emission from all of the plots was severely inhibited by the low temperature in winter (November to March), while a N2O emission pulse occurred during the spring thaw (April and May). Temporal variation of the N2O fluxes during the growing season varied over all the four years but was mainly affected by soil water-filled pore space (WFPS). Intense rainfall events increased the intensity and duration of N2O pulses during the growing season, and most high fluxes were occurred at WFPS > 45%. The mean annual N2O emission from all treatments over four years was 4.8 ± 1.2 kg N ha-1 (ranges: 1.9-19.8), and one third of the emission originated from the spring-thaw. In addition, soybean growth did not increase N2O emissions during the growing season, which support the cancellation of N2O emission calculations from nitrogen fixed by legumes in the 2006 IPCC Guidelines for National Greenhouse Gas Inventories.