| Hetao Irrigation is an important grain base in northern China, soil salinization area is widening because of man-made interference and other climate changing factors in recent years. Our research for the semi-arid steppe and semi-arid forest soils proved that soils of permeability were important carbon sinks, which had an important impact on China and global climate change, while it was unclear to know reasons of CH4 uptake in the semi-arid and saline-alkaline soils. Author monitored variation dynamic of CH4 uptake in different degrees of salinity field, using of fluorescence quantitative PCR to determinate methanotrophy abundance and specific activity. Author analylized the changing of CH4 uptake from microorganisms, revealing mechanism of salt content which affected on CH4 uptake in saline-alkaline soils by culture experiments. Research was arranged from April,2014 to November,2015 in Wulateqianqi, Hetao Irrigation, Author determined soil salinity and calssfied saline-alkaline soils based on standards, using the principles of proximity and lay outing sample point with "S" type, so as to make use of degrees of saline-alkaline soils and divide into slightly salinity soils ?SA?, intensively salinity soils ?SB?, saline soils ?Sc?, Author collected and analyzed changing of CH4 uptake by static chamber-chromatography, in addition to monitor soil temperature, soil moisture, soil conductivity, methanotrophy abundance and specific activity. By culture experiments, Author controled moisture ?25%? and temperature ?25±1? ? conditions unchangeably and explored two different exogenous CH4 content so as to detect how exogenous salt of three different levels of saline-alkaline soils affected CH4 uptake. Research indicated:?1? CH4 cumulative uptake of three different saline-alkaline soils ?SA, SB, SC? in Hetao Irrigation district showed significant difference?F=1326.8, P<0.01? and values were -148.8±10.1mg·m-2,-116.3±32.1mg·m-2,-92.4±11.8mg·m-2, showing:slightly salinity soils ?SA?> intensively salinity soils ?SB?> saline soils ?SC?, namely:The higher was salinty, the larger was CH4 cumulative uptake.?2? Interannual variation of CH4 absorption flux in Hetao Irrigation was:2014<2015, seasonal variation was:summer was highest, because summer was high soil temperature and high soil moisture content, so as to improve the CH4 absorption flux.?3? Methanotrophy specific activity of three different saline-alkaline soils ?SA, SB, SC? in Hetao Irrigation area were 30.0±1.0 ?g·kg-1·copies-1·h-1,3.9±0.7 ?g·kg-1·copies-1·h-1,2.9±1.8 ?g·kg-1·copies-1·h-1, revealing that 2014<2015. Namely:the higher was methanotrophy specific activity in saline-alkaline soils, the larger was CH4 cumulative uptake.?4? Author controlled laboratory condition of soil temperature and moisture conditions remaining unchanged, culture experiments showed that:with two different exogenous CH4 concentrations in the absence of exogenous salt addition, three different of saline-alkaline soils ?SA1, SB1, SC1? were expressed as salinization increase, CH4 cumulative uptake decreased, namely:cumulative uptake of slightly salinity soil ?SA1? was maximum and followed by intensity salinity soil ?SB1?, saline soil ?SC1? was minimum. Exogenous salt added three levels of salinity soils, soil salinity ranged from 0.1% to 5.1%, CH4 cumulative uptake showed significant difference?F=367.6, P<0.01 and F=913.5, P<0.01?, soil salt content and accumulation of CH4 uptake were significantly negative correlation ?R=-0.8020, P<0.01 and R=-0.8470, P<0.01?.?5? With two different exogenous CH4 concentrations in the absence of exogenous salt addition, three different saline-alkaline soils ?SA1, SB1, SC1? were expressed as salinization increase, methanotrophy specific activity decreased, namely:methanotrophy specific activity of slightly salinity soil ?SA1? was maximum and followed by intensity of soil ?SB1?, saline soil ?SC1? was minimum. Because of exogenous salt added to three kinds of saline-alkaline soils, methanotrophy specific activity showed significant difference?F= 134.8, P<0.01 and F=902.3, P<0.01?, soil salt content and methanotrophy specific activity were a significant negative correlation ?R=-0.6667, P<0.05 and R=-0.8970, P<0.01?. At the same time, methanotrophy specific activity and accumulation of CH4 uptake showed a significant positive correlation ?R=0.6741, P<0.05 and R=0.8532, P<0.01?. Therefore, when soil salinity ranged from 0.1% to 5.1%, methanotrophy specific activity was the reason why soil CH4 uptake potential changed. |
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