Knowledge Resource Center for Ecological Environment in Arid Area
| 高寒草地土壤有机质化学组成对土壤氮转化的影响 | |
| 其他题名 | Effects of soil organic chemical compositions on soil nitrogen transformation in alpine grasslands |
| 马书琴 | |
| 出版年 | 2018 |
| 学位类型 | 博士 |
| 导师 | 王小丹 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 土壤有机质（Soil organic matter, SOM）是陆地碳库之一，在碳氮元素的生物地球化学循环中具有重要作用。SOM主要是由微生物、植物和动物等生物质转化而来的一种异质混合物。这种复杂性以及有机-无机矿物的相互作用导致在分子尺度上对其化学组成特征的研究具有一定挑战性。但是，对SOM化学组成的精确描述对于确定其在环境中的作用至关重要。目前，在研究SOM的技术中，热裂解（Pyrolysis coupled with gas chromatography and mass spectrometry, Py-GC/MS）可以相对高效的解析SOM化学分子结构，并较为完整地测定SOM各组分的含量和质量。因此，通过Py-GC/MS技术研究SOM化学组成对土壤碳氮循环具有重要的指导作用。高寒区具有独特的高海拔、低温和干旱等环境特征。高寒草地生态系统广泛地分布于该区域，而且为了适应这种极端气候环境，其内部形成复杂、敏感和特殊的碳氮分配、迁移和转化方式。SOM化学组成被报道可以显著影响土壤中的碳转化、微生物数量和活性、酶动力学等，那么SOM中某些特定化学成分是否是控制高寒草地土壤氮转化的关键因子呢？为解决这一科学问题，在藏北高寒草地选择高寒草甸，高寒草原，高寒草甸草原，高寒荒漠草原和高寒荒漠五种草地类型21个样点进行野外原位调查和采样，利用Py-GC/MS技术获得藏北高寒草地SOM化学组成 “指纹图谱”。同时对土壤样品进行室内恒温培养（25℃, 40% WHC, 210天），分析温室气体排放通量，土壤可溶性有机碳、铵态氮、硝态氮、可溶性总氮等动态特征。本文建立了高寒草地SOM化学组成与土壤温室气体、总硝化和净氮矿化等土壤氮转化过程因子以及土壤微生物和酶活性的关系，以氮素的土壤有机质—微生物矿化和硝化过程为主线展开分析并取得以下研究结果：1. 本文通过Py-GC/MS解析出藏北高寒草地土壤和植物中有机质化学成分“指纹图谱”。获得共九类62种化学分子，包括烷烃和烯烃、木质素、含氮化合物、多糖、芳香烃、脂肪酸、酚类、多杂环芳香烃和萜烯，主要物质有2-甲氧基-4-乙烯基酚、D-丙氨酸、吡啶、吡咯、糠醛、苯、甲苯、酚、萘和角鲨烯等。通过对这些化学成分进行分类和统计分析，将高寒草地植物地上部、地下部和土壤中有机质组成进行比较发现，五种草地植物地上和地下部有机质化学成分数均大于土壤中。另外，植物地上部以多糖类（21~28%）为主，地下部以木质素类（28.7~38.6%）为主，SOM化学组成中包括绝大对数来自微生物的含氮化合物（38.0~67.3%）和少量来源于植物的多糖类（如糠醛）和木质素类（如2-甲氧基-4-乙烯基酚）。2. 高寒草甸植被和土壤中解析出的成分要多于高寒草原、高寒草甸草原、高寒荒漠草原和高寒荒漠。高寒草甸、高寒草原和高寒草甸草原植物地上部有机质以多糖类化合物为主。而高寒荒漠草原和高寒草原植物地上部有机质成分中除多糖外还有一定比例的木质素，分别占有机质化学组成总量的17.4%和14.0%。植物地下部有机质化学组成表现为，高寒草甸植物地下部木质素相对含量低于另外四种草地，而多糖则较高。关于SOM化学成分，含氮化合物表现为高寒草甸草原土壤>高寒荒漠草原土壤>高寒草原土壤>高寒荒漠土壤>高寒草甸土壤；芳香烃、木质素和酚类等主要来源于植物根系的物质在高寒草甸土壤中相对含量高于另外四种草地土壤；萜烯类在高寒荒漠草原土壤中相对含量高于其他草地土壤，而烷烃类和多糖类则表现为高寒草甸土壤>高寒草原土壤>高寒草甸草原土壤>高寒荒漠草原土壤>高寒荒漠土壤。3. 高寒草地SOM降解过程中，木质素相对含量在SOM化学组成中均减少；多糖类化合物则表现为增加；除高寒草甸草原土壤外，其余四种草地SOM化学组成中含氮化合物呈现增加趋势。土壤CO2累积排放量与SOM含量、SOM化学组成中多糖和芳香烃相对含量呈正相关关系，而与含氮化合物呈负相关；土壤N2O累积排放量与土壤DOC含量、SOM化学组成中多糖、芳香烃和木质素相对含量呈显著正相关，与含氮化合物负相关关系但未达到显著水平。土壤培养过程中累积净氮矿化量与SOM含量及其化学组成中烷烃和烯烃类、芳香烃类、木质素和多糖相对含量呈正相关，而与含氮化合物、脂肪类呈负相关关系。4. 土壤CO2累积排放量与土壤中糠醛、酚、甲苯、乙烯苯和吡咯相对含量呈正相关，而与D-丙氨酸呈负相关；土壤N2O累积排放量与土壤中糠醛、2-甲氧基-4-乙烯基酚、苯和甲苯相对含量呈显著相关关系。SOM化学组成中2-甲氧基-4-乙烯基酚、吡咯、酚、糠醛、苯、甲苯等物质的相对含量与土壤中细菌、真菌、放线菌、革兰氏阴性细菌和革兰氏阳性细菌数量均存在显著相关关系，另外2-甲氧基-4-乙烯基酚、糠醛、甲苯和乙烯苯相对含量与蛋白酶活性也显著相关。本文通过分析藏北高寒草地SOM化学组成对土壤温室气体排放、土壤累积氮矿化和硝化量以及微生物数量和活性影响，阐明了SOM对土壤氮转化影响的程度和方式，从SOM化学组成角度揭示了影响高寒草地土壤氮转化的关键因子及其作用机理，并为探索高寒特殊环境中土壤氮转化机理提供新的思路。 |
| 英文摘要 | Soil organic matter (SOM), which is a main component of terrestrial carbon pool, plays a key role in the global carbon and nitrogen biochemical cycle in ecosystems. SOM is a complex, heterogeneous mixture resulting from the transformation of biomass residues of microbes, plant and animals. The complicated structure and the organ-mineral interactions make it is a challenge to study SOM at molecular level. However, it is essential to determine the characterization of SOM compositions in order to predict its dynamics and role in carbon and nitrogen cycle. At present, the pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC/MS) was used as efficient tool to analyze chemical structure and compositions of SOM. Therefore, it is important to study the effects of SOM compositions on soil carbon and nitrogen cycle using Py-GC/MS.The alpine ecosystems are characterized by high altitude, low temperature and arid. Alpine grasslands are widely distributed in this region, and formed sensitive and specific characters of carbon and nitrogen distribution, migration and transformation in order to accustom the extreme environment condition. It has been reported that SOM chemical compositions can significantly influence soil carbon conversion, microorganism quantity and enzyme activity. However, it is still unclear that whether SOM compositions is the key factor of controlling soil nitrogen transformation. In this study, we selected 21 samples from five types grassland ecosystems in Northern Tibet, including alpine meadow, alpine steppe, alpine meadow steppe, alpine desert steppe and alpine desert. We used field investigation and sampling, and incubation experiment (25℃, 40%WHC, 210 d), to build the relationships between SOM compositions and carbon and nitrogen processes, including greenhouse gases, soil nitrification, denitrification and net nitrogen mineralization, soil microbes and enzyme activity. The main research results were obtained as follows:1. The “fingerprint” of SOM chemical compositions in soils and plants was analyzed using Py-GC/MS, and we detected nine categories and 62 kinds of chemical molecules, including alkanes and alkenes, lignin, N-compounds, polysaccharide, aromatics, ployaromatics, fatty acids, phenols and terpenes. The main chemical molecular included 2-methoxy-4-vinylphenol, D-alanine, pyridine, pyrrole, furfural, benzene, toluene, phenol and naphthalene. The results showed that the vegetation biomass, SOM and nitrogen contents, soil microbial biomass and enzyme activity were the highest in alpine meadow, and lowest in alpine desert. The number of organic compositions in plant were higher than the soil in all grasslands. The organic matter of shoot mainly contained polysaccharide compounds (21~28%). The root has a higher component of lignins (28.7~38.6%). In soils, N-compounds (38.0~67.3%), which come from microbial transformation and immobilization, were the dominant composition. SOM compositions also contained a few compounds derived from plants , eg. furfural and 2-methoxy-4-vinylphenols.2. The spatial differences in organic matter chemical compositions of plants and soils in alpine grassland were found in this study. The number of organic chemical compositions from vegetation and soil were higher in alpine meadow than those in alpine steppe, alpine meadow steppe, alpine desert steppe and alpine desert. The chemical compositions in shoot from alpine meadow, alpine steppe and alpine meadow steppe mainly contained polysaccharide compounds. And the chemical compositions in shoot from alpine desert steppe and alpine desert contained both polysaccharides and lignins, and the relative abundance of lignins were 17.4% and 14.0%, respectively. The relative abundance of lignins in root from alpine meadow is lower than that in other grassland types, while the polysaccharide is highest. For SOM chemical compositions, N-compounds showed a pattern of alpine meadow steppe > alpine desert steppe > alpine steppe > alpine desert > alpine meadow; the relative abundance of aromatics, lignins and phenols, which were derived from roots, were higher in alpine meadow than those in other grasslands; the relative abundance of terpenes are higher in the alpine desert steppe than other grasslands; the relative abundance of alkanes and alkenes, polysaccharides showed a pattern of alpine meadow > alpine steppe > alpine meadow steppe > alpine desert steppe > alpine desert.3. There is a similarity tend of SOM chemical components in different grassland ecosystems during the degradation process. The relative abundance of lignins in SOM chemical compositions decreased in all the alpine grassland soils during incubation period, but polysaccharide compounds showed a increasing pattern; except alpine meadow, nitrogen-compound in SOM chemical compositions showed an increasing trend in the other soils. The effects of SOM chemical components on soil nitrogen transformation in alpine grassland soils were found. The SOM content significantly correlated with the cumulative emissions of CO2, net nitrogen mineralization and nitration; and the DOC content significantly correlated with N2O cumulative emission. The cumulative emission of soil CO2 positively correlated with the relative abundance of polysaccharides and aromatics, and negatively correlated with N-compounds in SOM compositions. Soil N2O cumulative emission positively correlated with the relative abundance of polysaccharides, aromatics and lignins in SOM compositions, while its negative relationship with N-compounds with was non significant. The accumulation of net nitrogen mineralization in soil positively correlated with alkanes and alkenes, aromatics, lignins and polysaccharides, and negatively correlated with N-compounds and fatty acids in SOM compositions.4. The effects of different SOM chemical molecules on soil nitrogen transformation in alpine grassland soils were studied. Specifically, the cumulative emissions of CO2 positively correlated with the relative abundance of furfural, phenol, toluene, ethylbenzene and pyrrole, but negatively correlated with d-alanine; the cumulative emissions of N2O significantly correlated with the relative abundance of furfural, 2-methoxyl-4-vinylphenol, benzene and toluene. The relative abundance of 2-methoxy-4-vinylphenol, pyrrole, phenol, furfural, benzene, toluene had significant correlation with soil bacteria, fungi, actinomycetes, gram negative bacteria and gram positive bacteria. The relative abundance of 2-methoxy-4-vinylphenol, furfural, toluene and ethylbenzene significantly correlated with protease activity.This study revealed that SOM chemical compositions are key influencing factors of nitrogen transformation, and provided a new aspect to clarify the mechanism of soil nitrogen transformation in alpine grassland. |
| 中文关键词 | 土壤有机质 ; 高寒草地 ; 木质素 ; 磷脂脂肪酸 ; 温室气体排放 |
| 英文关键词 | Soil Organic Matter Alpine grassland Lignin Phospholipid fatty acids Greenhouse gases emissions |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院成都山地灾害与环境研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/288059 |
| 推荐引用方式 GB/T 7714 | 马书琴. 高寒草地土壤有机质化学组成对土壤氮转化的影响[D]. 中国科学院大学,2018. |
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