麦秸与毛叶苕子共同调控青海高原土壤温室气体排放的作用机制

Mechanism of co-incorporating wheat straw and hairy vetch in controlling greenhouse gas emissions in Qinghai Plateau of China

【目的】研究青海高原麦秸和豆科绿肥混合添加下土壤温室气体排放规律及其碳氮转化机制,为该地区农田系统秸秆和绿肥科学利用提供依据。【方法】采用室内模拟试验,设无添加对照(CK)、单独添加毛叶苕子(VS)、单独添加麦秸(WS)、麦秸与毛叶苕子混合添加(VWS),共4个处理。测定了温室气体排放速率、土壤活性碳氮组分、土壤酶活性、细菌、古菌、真菌、amoA、nirK和narG基因丰度。【结果】VWS处理与VS处理相比,CO_(2)和N_(2)O的累积排放量分别减少24.8%和74.6%,CH_(4)累积吸收量增加9.1%,综合增温潜势(global warming potential,GWP)显著降低76.1%(P<0.05);与WS处理相比,CO_(2)累积排放量增加33.7%,CH_(4)累积吸收量与N_(2)O累积排放量分别降低12.0%和43.1%,GWP降低49.4%。有机物料添加可调节土壤pH,增加土壤碳氮含量。VWS处理的土壤pH显著高于CK和VS处理;土壤水溶性有机碳(DOC)和微生物量碳(SMBC)含量较VS处理分别增加了21.6%和4.9%,无机氮(Nmin)、土壤水溶性有机氮(DON)和微生物量氮(SMBN)含量分别降低了77.3%、59.5%和6.3%;土壤Nmin、DOC、DON、SMBC和SMBN含量较WS处理分别增加64.0%、22.5%、56.5%、23.2%和27.8%。VWS处理较其他处理,α-葡萄糖苷酶(AG)和β-葡萄糖苷酶(BG)活性显著提高,亚硝酸还原酶(NIR)活性显著降低。VWS处理的真菌和古菌群落丰度较WS处理分别提高83.8%和69.8%,较VS处理分别降低62.6%和20.3%;VWS处理细菌群落丰度较VS处理降低33.4%。VWS处理下,AOB amoA、nirK和narG基因丰度较VS处理分别降低56.6%、41.4%和16.3%,较WS处理分别降低30.3%、25.9%和12.0%。相关分析结果表明,CO_(2)和CH_(4)排放与土壤有机碳、全氮、DOC、SMBC和SMBN含量,AG、NAG和NR活性,真菌、细菌、nirK和narG基因丰度呈显著正相关;N_(2)O排放与土壤全氮、DON、SMBC和SMBN含量、真菌、AOB amoA和nirK基因丰度呈显著正相关,与土壤pH和BG活性呈显著负相关。偏最小二乘路径模型分析(PLS-PM)表明,AOB amoA是调控土壤N_(2)O排放的主要功能菌群。【结论】麦秸、毛叶苕子单独添加以及二者混合添加均可促进土壤CO_(2)排放,减少CH_(4)吸收。相较于二者单独添加,混合添加可通过降低土壤AOB群落丰度等途径,实现N_(2)O减排和综合增温潜势下降,可作为青海高原旱地土壤温室气体减排的一项有效措施。

【Objectives】This study explored soil greenhouse gas emissions and mechanism of carbon and nitrogen transformation under the co-incorporation of wheat straw and leguminous green manure residues in Qinghai Plateau of China,which can provide a theoretical basis for the scientific utilization of straw and green manure in dryland agricultural ecosystems.【Methods】An incubation experiment was carried out using wheat straw and hairy vetch(Vicia villosa Roth L.).There were four treatments:no straw addition control(CK),hairy vetch alone(VS),wheat straw alone(WS),and wheat straw and hairy vetch together(VWS).Greenhouse gas emissions,soil active carbon(C)and nitrogen(N)components,soil enzyme activities and the abundances of bacteria,archaea,fungi,amoA,nirK and narG were determined.【Results】Compared with VS,VWS treatment decreased of cumulative emissions of CO_(2) and N_(2)O by 24.8%and 74.6%,increased cumulative absorption of CH_(4) by 9.1%,and significantly reduced global warming potential(GWP)by 76.1%(P<0.05).Compared with WS treatment,VWS increased cumulative CO_(2) emissions by 33.7%,but decreased cumulative CH_(4) absorption by 12.0%,and the cumulative N_(2)O emissions by 43.1%,GWP by 49.4%.VWS treatment significantly increased soil pH compared with CK and VS.Compared with VS treatment,VWS increased the contents of the dissolved organic C(DOC)and microbial biomass C(SMBC)by 21.6%and 4.9%,but decreased the mineral N(Nmin),dissolved organic N(DON)and microbial biomass N(SMBN)by 77.3%,59.5%,and 6.3%.Compared with WS treatment,VWS increased Nmin,DOC,DON,SMBC and SMBN by 64.0%,22.5%,56.5%,23.2%,and 27.8%,respectively.Plant residues significantly increased enzyme activities,and VWS treatment recorded higherα-glucosidase(AG)andβ-glucosidase(BG)activities,and lower nitrite reductase(NIR)activity than the other treatments.The abundances of fungi and archaea in VWS treatment were 83.8%and 69.8%higher than those in WS treatment,but 62.6%and 20.3%lower than those in VS treatment,respectively.The bacterial abundance of VWS treatment was 33.4%lower than that of VS treatment.In VWS,the abundances of AOB amoA,nirK and narG genes were decreased by 56.6%,41.4%,and 16.3%,than those in VS treatment,and by 30.3%,25.9%,and 12.0%compared with WS treatment,respectively.The results of correlation analysis showed that CO_(2) and CH_(4) emissions were positively correlated with soil organic C,total N,DOC,SMBC,and SMBN,AG,NAG and NR activities,and the abundances fungi,bacteria,nirK and narG.N_(2)O emission was positively correlated with soil total N,DON,SMBC and SMBN,the AOB amoA and nirK abundances,and was negatively correlated with soil pH and BG activity.Partial Least Squares Path Model analysis(PLS-PM)showed that AOB amoA was the main functional bacteria regulating soil N_(2)O emission.【Conclusions】Both the single and co-application of wheat straw and hairy vetch increases soil CO_(2) emissions and reduces CH_(4) absorption.Co-incorporating of wheat straw and hairy vetch is more effective in reducing N_(2)O emission and GWP through the reduced abundance of AOB,so is an effective measure for greenhouse gas emission reduction in dryland soil of Qinghai Plateau in China.