孔隙结构对水稻土温室气体排放的影响

Effects of Pore Structure on Greenhouse Gas Emission of Paddy Soils

土壤结构影响水分和气体的运动和土壤生物活动,进而影响稻田温室气体排放。为探明土壤结构对水稻生长过程中温室气体排放的影响,选取江苏宜兴的湖白土和江西进贤的红壤性水稻土进行盆栽试验。设置不搅动(NP)、搅动(PD)和搅动后掰土回填(RP)3个处理。应用X射线CT成像技术分析不同处理土壤孔隙结构,通过静态箱法测定水稻生长过程中的温室气体排放。结果显示,PD处理降低了土壤大孔隙度和孔隙连通性,而NP及RP处理的大孔隙较多且连通度高。湖白土PD处理的CH_(4)排放量分别是NP处理的2.5倍和RP处理的14.6倍,相关分析表明湖白土CH_(4)的排放与大孔隙度呈显著负相关,表明大孔隙度升高会降低CH_(4)排放。红壤性水稻土NP处理的CH_(4)排放最高,可能是由于NP处理≤30μm的孔隙度最低,促进了CH_(4)的排放;PD处理提高了N_(2)O排放,相关分析表明N_(2)O排放总量和直径30~1000μm孔隙呈显著负相关。两种土壤RP处理全球增温潜势(GWP)强度以及CH_(4)总排放量均显著低于NP和PD处理。研究结果表明土壤孔隙结构的改变影响稻田温室气体的排放,通过改变耕作方式调节土壤结构可能是稻田CH_(4)和N_(2)O减排的途径之一。

Soil structure affects soil water and gas transport and soil biological activities,thus influence greenhouse gas(GHG)emission from soil.In this study,incubation experiment was conducted in two paddy soils(whitish paddy soil and red paddy soil)to study the effects of pore structures on GHG emissions under different treatments,i.e.non-puddling(NP),puddling(PD),and repacked after puddling(RP).Soil pore structure was determined by using the X-ray computed tomography and image analysis,and GHG emissions during rice growth period were measured by the static box method.The results showed that puddling significantly decreased soil macroporosity and pore connectivity,while NP and RP had more large pores with higher connectivity for both soils.PD promoted CH_(4) emission from whitish paddy soil,which was 2.5 and 14.6 times of NP and RP,respectively.Correlation analysis showed CH_(4) emission negatively correlated with macroporosity,indicating the increase of large porosity will reduce CH_(4) emissions.NP had the highest CH_(4) emission from red paddy soil,possibly due to the lowest porosity of≤30μm pores promoting CH_(4) emission.NP significantly increased N_(2)O emissions from red paddy soil,which was negatively correlated with the 30-1000μm pores.The global warming potential(GWP)of RP for both soils was significantly lower than other treatments.In conclusion,this study confirms that the change in soil pore structure greatly affected GHG emissions and maintaining a porous soil structure can reduce CH_(4) emission and global warming potential.