【作者】 周杰；

【导师】 邹建文；

【作者基本信息】 南京农业大学 ， 环境科学， 2016， 硕士

【摘要】 氧化亚氮(N2O)和一氧化氮(NO)是两种人为排放到大气中的重要氮化物,能够直接或间接的导致全球变暖和大气污染,也是生物地球化学氮循环过程中的重要组成部分。现有研究表明土壤的酸化不仅会影响茶树的生长、茶叶的品质和产量,还会导致大量N2O排放和NO排放。茶园是我国主要的土地利用方式之一,茶树也是我国重要的经济作物之一,且我国茶园土壤酸化现象日益严重,目前我国典型茶区有50%以上的茶园土壤pH低于4.5。但有关中国茶园垄间土壤和树冠下土壤N2O和NO的排放特征及其影响因子却未见报道。本文以常规施肥一年后的茶园垄间土壤和树冠下土壤为研究对象,利用静态暗箱-气相色谱法通过田间原位观测试验,研究N2O和NO排放的季节性变化,以期了解江苏典型茶园的N2O和NO排放特征,解释其排放规律及其影响因素,并判断茶园生态系统中N2O和NO的主要排放源并估算其年累计排放量。主要研究结果如下:1.茶园垄间和树冠下土壤N2O呈现明显的季节性变化,春夏季高,秋冬季低。春夏季垄间和树冠下土壤N2O排放占全年总排放量的70%左右;2.在整个观测期,茶园垄间和树冠下土壤中N20排放通量的变化范围为11.40-408.65μg m-2 h-1;垄间土壤和树冠下土壤N2O的年累计排放量分别为8.459、3.026kg N ha-1;垄间土壤N2O的排放量占整个试验小区的65%,树冠下土壤中N2O排放占35%。垄间土壤是茶园N2O的主要排放位点;3.垄间土壤和树冠下土壤中N2O排放均与土壤温度、WFPS呈显著正相关关系,与pH呈显著负相关关性;同时与土壤中NH4+-N、NO3--N呈显著负相关关系;4.茶园树冠下土壤中NO排放呈现明显的季节性变化,春夏季高,秋冬季低。春夏季树冠下土壤NO排放占全年总排放量的74%;垄间土壤NO排放无明显季节性变化;5.在整个观测期,茶园生态系统中NO排放通量的变化范围为-10.73-377.83μgm-2h-1;垄间土壤和树冠下土壤NO的年累计排放量分别为0.92、2.137kgN ha-1;树冠下土壤NO排放占整个试验小区的78%,垄间土壤NO排放只占试验小区的22%。树冠下土壤是茶园NO的主要排放位点;6.垄间土壤NO排放与温度呈极其显著正相关,与WFPS呈显著负相关关系;树冠下土壤NO排放与WFPS、pH呈显著负相关关系;不论垄间土壤还是树冠下土壤,在整个观测期内NO排放与NH4+-N和NO3--N无显著相关性,但是在茶树生长季(即3-9月),垄间土壤和树冠下土壤中NO排放与NH4+-N呈显著正相关关系,却与NO3--N呈显著负相关关系。更多还原

【Abstract】 Nitrous oxide(N2O)and nitric oxide(NO)are two of the most important anthropogenic nitrogen compounds emitted to the atmosphere,which are directly or indirectly involved in global warming and atmospheric chemistry,as well as an important part of nitrogen biogeochemical cycle.It has been reported that the soil acidification could not only affect the habitat of tea trees,the quality and yield of tea,but also result in a large number of N2O and NO emissions.China is the largest tea plantation country in the world,and tea is one of the main economic crops.In fact,the soil acidification is increasingly serious in China,there was more than 50%of the tea soil pH less than 4.5 in Chinese typical tea plantation.So far,however,no study is available for N2O and NO fluxes from tea plantation soil between rows and soil under canopy,which hinders the development of a sound N2O and NO emission inventory.To characterize and quantify annual N2O and NO fluxes and to clarify the underlying mechanisms,as well as to assess the contribution of N2O and NO emissions from soil between rows and soil under canopy of tea plants to the total N2O and NO emissions from tea fields and to determine the factors responsible for changes in N2O and NO emissions,we performed in situ measurements of N2O and NO for a 380 days from a Chinese subtropical tea plantation under different soils(i.e.,soil between rows,soil under canopy),using a closed Chamber-Gas Chromatography method.Through this study,the results were as follows:1.N2O fluxes from soil between rows and soil under canopy showed a seasonal variation,with the highest in spring and summer,accounting for approximately 70%of annual cumulative N2O emissions from the soil between rows and soil under canopy;2.Across the annual tea plantation,soil N2O flux ranged from 11.40-408.65μg m-2 h-1 under two types of tea soils.And the cumulative N2O emissions were about 8.459、3.026kg N ha-1 for the soil between rows and soil under canopy,respectively.Meanwhile,total N2O emissions were approximately 65%and 35%of total N2O emissions from the entire tea field in soil between rows and soil under canopy,respectively.So the soil between rows is the main emission source of N2O flux in tea plantation;3.In the soil between rows and soil under canopy,there was a significant correlation between N2O flux and soil temperature,moisture and pH;however,there was a significant negative correlation between N2O flux and ammonium and nitrate content;4.NO fluxes from soil under canopy showed a seasonal variation,with the highest in spring and summer,accounting for approximately 74%of annual cumulative NO emissions from the soil soil under canopy;and there was no significant seasonal variation about NO fluxes from soil between rows;5.Across the annual tea plantation,soil NO flux ranged from-10.73-377.83μg m-2 h-1 under two types of tea soils.And the cumulative NO emissions were about 0.92.2.137kg N ha-1 kg N ha-1 for the soil under canopy and soil between rows,respectively.Meanwhile,total NO emissions were approximately 22%and 78%of total NO emissions from the entire tea field in soil between rows and soil under canopy,respectively.So the soil under canopy is the main emission source of NO flux in tea plantation;6.There was a positive correlation between NO flux and soil temperature,a negative correlation between NO flux and moisture in the soil between rows;there was a significant negative correlation between NO flux and moisture and pH in the soil under canopy;Meanwhile,no matter from soil between rows and soil under canopy,there were no significant correlation between NO flux and ammonium,nitrate content throughout the overall experiment.During the tea-growing period from March to September(i.e.,in the spring and summer seasons),however,in the soil between rows and in the soil under canopy,there was a significant positive correlation between NO flux and ammonium content and a significant negative correlation between NO flux and nitrate content.更多还原