Response Of CH₄ And N₂O Emisson From Peatlands To Changed Environments In Little Xing’an Mountains, Northeast China

Wetland is one of the most important ecosystems on earth. Large quantities of soil organic carbon are accumulated in wetland ecosystems. Wetlands are atmospheric CO2 sinks and CH4 and N2O sources. Little Xing’an Mountains is one of the major wetland and permafrost distribution regions in China. Permafrost thawing fast and extrem drought and precipitation events and N deposition increased obviously effected by global change in recent years. However, few papers reported the green house gas emission from wetlands under global change conditions. It is unfavourable to precise estimating green house gas emission list or establishing the global climate change model.In this paper, field and soil-plant control systems CH4 and N2O emissions were observed from peatlands in Little Xing’an Mountains. The objectives were to (1) reveal the effects of permafrost thawing, extreme drought and precipitation, and N deposition increasing on peatland CH4 and N2O emissions; (2) identify the factors leading to these differences; (3) discuss the potential feedback of changing CH4 and N2O emissions to global change; (4) provide basic data for precise estimating green house gas emission list and establishing the global climate change model; (5) provide scitific basis for national diplomatic negotiations about corban. The results showed that:(1) Seasonal variation of CH4 emissions from peatlands became more obvious with the aggravation of the permafrost thawing. CH4 emission peaks became larger and CH4 absorption decreased untile no CH4 absorptions were observed with permafrost thawing. Seasonal mean CH4 emissions from permafrost severe thawing, moderate thawing and un-thawing peatlands are 6.58 mgm-2h-1,0.38 mgm-2h-1 and 0.12 mgm-2h-1, respectively. CH4 emission increase was caused by the deepened permafrost active layer and the subsequent changes of increased soil temperature, water table and changed vegetation composition. Increasing CH4 emission may cause positive feedback to global warming.(2) Seasonal variations of N2O emission and the accumulated emissions did not change with permafrost thawing. Thus, there was no positive feedback of N2O emissions to global warming.(3) CH4 emissions from the soil-plant systems increased for a short period after weak drought treatments but decreased with the drought period extend. Peatland changed from atmospheric CH4 source to CH4 sink after severe drought treatment. Sufficient precipitation could promote post-drought CH4 emission recovery quickly. However, insufficient precipitation induced post-drought CH4 emission recovery slowly. Post-drought CH4 emission recovery prolonged with longer drought period. CH4 emisisons from peatlands decreased 7.1% to 49.3% by drought/precipitation treatments. These were induced by the decreasing of water table and soil moisture.(4) N2O emissions from the soil-plant systems increased after weak drought treatments but decreased after severe drought treatments. Moderate precipitation could promote post-drought N2O emission. However, extreme precipitation could depress post-drought N2O emission. N2O emisisons from peatlands increased 21.3% to 68.1% by drought/precipitation treatments. These were induced by water table and also soil moisture and ammonium concentration in soil pore water.(5) Herb aboveground biomass increased with N addition. However, there were no significant changes of CH4 emissions from the peatlands with N addition. This may be caused by the inbibation of increasing ammonium concentration to methanogenesis in soil. Manipulated soil-plant systems with 5 and 10 times N deposition had 8 and 20 times higher seasonal mean N2O emisisons than the control systems, respectively. Increased N2O emissions came from the shot-term (<3 d) high emissions immediately after N addition. Nitrate and ammonium concentration increasing were the reason of N?O emissions increased by N addition.