【作者】 陈静；

【导师】 张建国；

【作者基本信息】 西北农林科技大学 ， 土壤学， 2017， 硕士

【摘要】 由温室气体排放所引起的全球变暖和生态环境变化是当今国际社会关注的焦点。全球变暖主要原因是人类活动影响下温室气体排放的增加,而农田生态系统则是陆地生态系统中受人为活动影响最大的一部分。秸秆还田可以改善土壤物理性状和土壤微生物活性等,必然会对农田温室气体的排放产生影响。生物炭具有提高土壤肥力和田间持水量等作用,故添加生物炭也可能会对农田温室气体排放产生影响。玉米和小麦是陕西关中地区的主要作物,本研究以该区夏玉米-冬小麦轮作农田生态系统为研究对象,设置了试验设常规施肥（N）、常规施肥+4 t·hm^-2秸秆还田（NS）、常规施肥+添加4 t·hm^-2生物炭(NBC_low)、常规施肥+添加8 t·hm^-2生物炭(NBC_high)4个处理,既不施肥也无有机物料添加处理为对照（CK）,通过田间定位监测、取样结合室内分析对冬小麦和夏玉米生长期的温室气体排放进行了动态监测,以阐明秸秆还田和生物炭添加对陕西关中地区典型农田温室气体的排放的影响,同时分析秸秆还田和不同生物质炭添加量条件下温室气体排放的差异和影响因素,并进一步分析农田N₂O、CH₄和CO₂排放引起的净增温潜势和生态系统碳足迹值,以期为关中地区农田固碳减排提供科学依据。经过长期的田间监测和室内分析,本研究得出以下主要结论:（1）在土壤层面上,秸秆还田和生物质炭添加对温室气体排放、作物产量、土壤有机碳含量和净增温潜势均有不同程度的影响。与N处理相比,NS处理对土壤N₂O排放没有显著影响,生物炭添加降低了土壤N₂O排放量,且NBC_high处理土壤N₂O排放总量显著低于NBC_low处理;研究区土壤表现为吸收CH₄,秸秆还田和添加生物炭均降低了CH₄吸收量;秸秆还田可以增加土壤CO₂的排放量,但NBC_high处理显著降低了CO₂排放量,而NBC_low处理对土壤CO₂排放量无显著影响。NS处理、NBC_low处理和NBC_high处理年产量分别比N处理提高了13.73%,20.37%和7.56%,而NBC_high处理比NBC_low处理年产量降低了10.64%。与N处理相比,NS处理没有显著影响有机碳含量,而生物炭添加显著增加了土壤有机碳含量;与常规施肥处理相比,秸秆还田和生物炭添加均降低了净增温潜势和单位产量的净增温潜势,且NBC_high处理显著低于NBC_low处理。（2）在小麦农田生态系统层面上,秸秆还田和生物质炭添加对温室气体排放、冬小麦产量和碳足迹值也会产生不同程度的影响。与N处理相比,秸秆还田和生物质炭添加均降低了小麦农田生态系统的N₂O排放量,且NBC_high处理N₂O排放总量显著低于NBC_low处理;秸秆还田增加了CO₂的排放总量,生物炭的添加对CO₂的排放总量无显著性影响,同时,秸秆还田和添加生物炭均会降低CH₄吸收量。NS处理、NBC_low处理和NBC_high处理小麦产量分别比N处理增加了34.71%、71.91%和37.62%。各处理均表现为碳净吸收,与NS处理相比,秸秆还田增加了生态系统的碳足迹值,但施用生物炭降低了生态系统碳足迹值,其中NBC_low处理碳足迹值在所有秸秆还田和生物质炭添加处理中最低。综合考虑温室气体排放量和作物产量,秸秆还田量为4 t·hm^-2或生物质炭添加量为4t·hm^-2是所有处理中较适宜于关中地区固碳减排的良好管理措施,但研究结果需要进一步的长期监测进一步验证。研究结果对于指导关中地区农田的科学管理具有一定的参考价值和实践意义。更多还原

【Abstract】 The global warming and ecological environment change caused by greenhouse gases emission is one current international focus.The main cause of global warming is the increasingofgreenhouse gases emission influenced by human activities,and thecropland ecosystem is mostly influenced in the terrestrial ecosystems.Straw returningcould change the basical physiochemical properties of soils,inevitably would affect the greenhouse gases emission.Biochar could improve soil fertility and increase field water capacity whichmightaffect greenhouse gases emission.Maize-wheat rotation is one of the major cropping systems in Guanzhong Area,in this study,farmland ecosystem of maize-wheat rotation in this region was taken as the research object,we designed 4 treatments(conventional fertilization（N）,conventional fertilization+4 t·hm^-2straw returning（NS）、conventional fertilization+4 t·hm^-2biochar(NBC_low)、conventional fertilization+8 t·hm^-2biochar(NBC_high)),no fertilization and organic material application as control（CK）.The static chamber and gas chromatography method were used to monitor the seasonal dynamics of greenhouse gases emission for one year during the crop growing seasons.Our objectives are to clarify the effects of different organic materials application on greenhouse gases emission,and analyze the difference and factors of greenhouse gases emission,and further analyze NGWPand carbon footprint values resulted from greenhouse gases emission of cropland.The final goal is to provide scientific basis for cropland carbon sequestration and emission reduction in Guanzhong region.The main conclusions are as follows:（1）In the soil level,straw reurning and biochar application had different degree impacts on greenhouse gases emission,crop yield,soil organic carbon content and NGWP.Compared with N treatment,NS treatment had no significant influence on annualN₂O emission,biochar application reduced annualN₂O emission,and annual N₂O emissionof NBC_hightreatment was significantly lower than NBC_lowtreatment.The soil in the study area showedabsorbingCH₄,straw returning and biochar application both decreased CH₄ absorption.The straw returning couldincrease annual CO₂ emission,but NBC_high treatment significantly decreased annual CO₂ emission,and NBC_low treatment had no significant influence on annual CO₂emission.Compared with N treatment,the yield of maize and wheatincreased13.73%,20.37%and 7.56%,respectively,but annual yield of NBC_high treatment reduced 10.64%compared to NBC_lowtreatment.Compared with N treatment,NS treatment had no significant impacts on soil organic carbon content（SOC）,but biochar application significantly increased SOC.Meanwhile,straw returning and biochar application both decreased the NGWP and NGWP of unit yield,and NBC_hightreatment was significantly lower thanNBC_lowtreatment.（2）In the wheatfarmland ecosystem level,straw reurning and biochar application also had different degree impacts on greenhouse gases emission,winter wheatyield and the value of carbon footprint.Compared with N treatment,straw returning and biochar applictionboth decreased annual N₂O emission,and NBC_high treatmentwassignificantly lower than NBC_low treatment.Straw returning increased annual CO₂ emission,but biochar applicationshad no significant influence.Meanwhile,straw returning and biochar applications coulddecrease annual CH₄absorption.Compared with N treatment,the winter wheat yieldof NS、NBC_low andNBC_highincreasedby 34.71%、71.91%and 37.62%and 8 t·hm^-2,respectively.All the treatments in our study showed carbon net absorption,straw returning increased the value of carbon footprint compared with N treatment,but biochar applicationdecreased the value of carbon footprint,and NBC_low treatmenthadthe lowest value of carbon footprint among all the treatments of straw returning and biochar application.Comprehensive considering greenhouse gases emission and crop yield,fertilization with4 t·hm^-2straw returing and the fertilization with 4 t·hm^-2 biochar application are better management measurements for cropland carbon sequestration and emission reduction in Guanzhong region.However,our study results need further long-term monitoring.Our results have certain reference value and practical significance for scientific management of farmland in Guanzhong region,Shaanxi Province.更多还原