不同水分条件下氨基酸添加对温带暗棕壤碳氮含量和甲烷排放的影响

Effects of amino acid addition on carbon and nitrogen content and CH_(4) emission in temperate dark brown soil under different water conditions

【目的】解析土壤pH值与土壤氮以及CH_(4)排放速率与土壤碳氮含量间的相互关系,为明确碳氮转化及温室气体排放规律、优化温带森林暗棕壤的水分管理提供依据。【方法】以温带森林暗棕壤为研究对象,采用室内培养法,设置水分条件为土壤饱和持水量(WHC)的40%、60%、90%,通过向温带暗棕壤中添加两种不同性质的氨基酸,探讨其对土壤碳氮含量及CH_(4)排放的潜在影响,运用Pearson相关分析法分析土壤碳氮含量、pH值及CH_(4)排放速率间的相关性。【结果】(1)氨基酸处理显著增加了土壤可溶性有机碳(DOC)含量、铵态氮(NH_(4)^(+)-N)含量及CH_(4)排放速率。亮氨酸处理使DOC、NH_(4)^(+)-N含量分别升高21.39%、45.10%,CH_(4)排放速率较CK升高3.20倍,甲硫氨基酸使DOC、NH_(4)^(+)-N含量分别升高21.39%、72.71%,CH_(4)排放速率较CK升高7.00倍;(2)不同氨基酸对土壤硝态氮(NO_(3)^(-)-N)含量的影响存在差异。亮氨酸处理使土壤NO_(3)^(-)-N含量升高了8.41%,但其对于土壤硝化作用的影响可能存在滞后性,而甲硫氨基酸能够显著抑制土壤硝化作用,NO_(3)^(-)-N含量显著降低了37.90%;(3)土壤不同水分条件对土壤DOC、NH_(4)^(+)-N、NO_(3)^(-)-N含量及CH_(4)排放速率均存在显著影响。90%WHC使DOC含量升高11.95%~19.91%,使NH_(4)^(+)-N升高19.83%~35.46%,使NO_(3)^(-)-N降低10.05%~23.79%,使CH_(4)排放速率升高至另外两种水分条件的1.48~2.06倍。60%WHC条件使NH_(4)^(+)-N升高13.05%,使NO_(3)^(-)-N含量升高24.62%。60%WHC可能是温带暗棕壤硝化作用的最适含水量,90%WHC条件有利于DOC积累,同时对NO_(3)^(-)-N的产生存在明显抑制作用;(4)土壤pH与N H4+-N含量呈极显著正相关,与NO_(3)^(-)-N含量呈正相关。CH_(4)排放速率与NO_(3)^(-)-N含量呈极显著负相关,与NH_(4)^(+)-N含量呈负相关,与DOC含量呈极显著正相关。【结论】不同性质氨基酸添加在温带森林暗棕壤碳氮含量及CH_(4)排放中发挥的作用不尽相同。一定范围内,土壤水分含量的升高有利于土壤NH_(4)^(+)-N、NO_(3)^(-)-N、DOC的积累及CH_(4)的排放,但土壤高含水量条件对NO_(3)^(-)-N的产生具有抑制作用。因此,在研究温带森林暗棕壤碳含量、CH_(4)排放及氮转化机制时,建议关注不同氨基酸的差异性作用,同时考虑水分的变化。

[Objective] To clarify the response of carbon and nitrogen content and CH_(4) emission to different soil moisture conditions and the additions of amino acid in the dark brown soil of temperate forests,this study analyzed the relationship between soil pH and nitrogen,CH_(4) emission rate and soil carbon and nitrogen content,to assist related research on water management,carbon and nitrogen transformation,and greenhouse gas emission in temperate forest dark brown soil.[Method] In this study,an indoor soil incubation was conducted with 40%,60%,and 90% of the soil water holding capacity (WHC).Additionally,the potential effects of adding two amino acids on soil carbon and nitrogen content and CH_(4) emissions were explored.The Pearson correlation analysis was used to analyze the correlation between soil carbon and nitrogen content,pH and methane emission rate.[Result] (1) Amino acid addition increased soil dissolved organic carbon (DOC) content,and meanwhile significantly increasedNH_(4)^(+)-N content and CH_(4) emission rate.Leucine treatment increased the contents of DOC and NH_(4)^(+)-N by 21.39%-45.10%,respectively,and the CH_(4) emission rate was 3.20 times higher than that of CK,methionine treatment increased the contents of DOC and NH_(4)^(+)-N by 21.39%-72.71%,respectively.and the CH_(4) emission rate was 7.00 times higher than that of CK.(2) The influence of different amino acids on soilNO_(3)^(-)-N content was different.Leucine treatment increased NO_(3)^(-)-N content in soil by 8.41%,but its effect on nitrification in soil may have a lag,while methionine can significantly inhibit nitrification in soil,and NO_(3)^(-)-N content was significantly reduced by 37.90%.(3) Different soil moisture conditions had significant effects on soil DOC,NH_(4)^(+)-N,NO_(3)^(-)-N and CH_(4) emission rates.90%WHC increased DOC content by 11.95%-19.91%,NH_(4)^(+)-N by 19.83%-35.46%,NO_(3)^(-)-N by 10.05%-23.79%,and CH_(4) emission rate increased to 1.48-2.06 times of the other two water conditions.Under 60%WHC condition,NH_(4)^(+)-N increased by 13.05%,NO_(3)^(-)-N content increased by 24.62%.60%WHC may be the optimum water content for nitrification in temperate dark brown soil.The 90%WHC condition was conducive to the accumulation of DOC,and had an obvious inhibitory effect onNO3--N production.(4) Soil pH was significantly positively correlated withNH_(4)^(+)-N content,positively correlated with NO_(3)^(-)-N content.The CH_(4) emission rate was significantly negatively correlated with NO_(3)^(-)-N content and NH_(4)^(+)-N content,and significantly positively correlated with DOC content.[Conclusion] Addition of different types of amino acids plays different roles on the carbon and nitrogen content and CH_(4) emissions of dark brown soil in temperate forests.Within a certain range,the increase of soil moisture content is beneficial to soilNH_(4)^(+)-N,NO_(3)^(-)-N,DOC accumulation and CH_(4) emission,but high soil moisture content inhibits the production of NO_(3)^(-)-N.Therefore,the role of amino acids and changes in moisture should be considered when studying carbon content,CH_(4) emissions and nitrogen transformation mechanisms in temperate forest dark brown soils.