Effects of grazing on the emission of CH4 flux in the Zoige Plateau wetland
Wetland ecosystems,as the main source of atmospheric methane (CH4),could seriously affect the concentration of atmospheric CH4 and further climate change.Presently,wetland ecosystems have been severely affected by human actives (i.e.,drainage,grazing,and harvesting).However,the effects of grazing on the CH4 emission of wetland ecosystems have not been well investigated.Therefore,to evaluate the effects of grazing on the emission of CH4 fluX,we performed the field experiments in the Zoige Plateau wetland,southwestern China,from June to October 2013.We also performed field experiments to investigate the effects of simulated increased in sheep or yak grazing by the clipping on CH4 emission in the same studied sites from May to October 2014.CH4 emission was measured using a dark static chamber and the fast greenhouse gas analyzer (FGGA) during the two growing season.We observed an obvious seasonal variation in CH4 emission at the studied sites.The CH4 emission varied from-0.42 to 18.06 mg m-2 h-1 and its maximum value occurring in summer and/or autumn.These results showed that the CH4 emission in the grazing and fencing plot was (31.32±19.57) g/m2 and (30.31±23.46) g/m2,respectively,during the growing season,and there were no significant differences in CH4 emission between grazing and fencing plots (P＞ 0.05).However,the CH4 emission in the grazing plot was (21.01 ± 12.35) g/m2 during heavy grazing periods (from July to September 2013),which was 54.3％ higher than that in the fencing plot (ungrazed plot).Moreover,the results revealed that the CH4 emission in the two clipping plots with 8 cm and 4 cm of vegetation height after clipping were (5.01±5.37) g/m2 and (4.69±5.99) g/m2,respectively,during the growing season,which were significantly higher in the 8 cm vegetation height in the clipping plot (335.9％) than that in the non-clipping plot (1.15±1.89) g/m2(P＜0.05),and 308.0％ higher in the 4 cm vegetation height in the clipping plot than that in the non-clipping plot.Furthermore,we also measured the aboveground biomass in both the grazing and clipping plots.The results indicated that grazing decreased the aboveground biomass,which was 37.5％ lower than the control plot ((525.88±103.47) g/m2 vs.(886.09 ± 124.46) g/m2) (P ＜ 0.05).We also found a significantly negative correlation between aboveground biomass and CH4 emission in August (P＜0.05),which may imply that CH4 flux emissions decrease due to the reduced height of herbaceous vegetation.In summary,the results of the present study suggested that the sheep or yak grazing and clipping disturbance increased CH4 emission in plateau wetland,via the reduction of the transporting distance from soil to the atmosphere due to significantly decreased aboveground biomass.This result provides the basic date for habitat protection and management in the plateau wetland in China.
国家科技期刊平台
NSTL
万方数据
维普
