Knowledge Resource Center for Ecological Environment in Arid Area
| 氮素添加对科尔沁沙质草地生态系统碳交换的影响 | |
| 其他题名 | Effects of nitrogen addition on Horqin sandy grassland ecosystem carbon exchange |
| 孙殿超 | |
| 出版年 | 2015 |
| 学位类型 | 硕士 |
| 导师 | 崔建恒 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 氮素是陆地生态系统中关键的限制性资源，直接影响陆地生态系统植被分布格局、初级生产力、凋落物分解等重要过程，也是影响陆地生态系统碳循环的重要因素之一。在以氮素为限制性因素的沙质草地生态系统中，研究氮素输入对生态系统碳交换的影响，这对于深入认识沙质草地生态系统碳交换的特征，预测未来全球变化背景下沙质草地生态系统的生物地球化学循环的响应过程具有重要科学意义。本研究以位于我国北方半干旱区的科尔沁沙质草地为研究区域，通过不同水平的氮素添加试验，动态观测植物生长季沙质草地碳交换过程中的土壤呼吸、微生物呼吸、根呼吸、生态系统呼吸、生态系统净碳交换量，分析了沙质草地生态系统碳循环关键过程对氮素添加的响应过程。主要研究结果及结论如下： （1） 添加氮素降低了土壤的pH值，提高了土壤的含碳量和植被的地上、凋落物生物量。相对高水平的氮素添加（N20）显著（p <0.05）降低了土壤的pH值，显著（p <0.05）提高了土壤的碳含量和植被的地上、凋落物生物量，而相对中（N10）、低（N5）水平氮素添加的这种影响不显著（p >0.05）。 （2） 在植物生长季，氮素添加可以提高土壤呼吸、微生物呼吸、根呼吸的速率，但这种提高并不是随着施氮添加水平的提高呈正的相关关系。N20显著（p <0.05）提高了土壤呼吸及其根呼吸的速率；N5显著（p <0.05）提高了土壤呼吸及其根呼吸的速率；而相对中等水平（N10）的氮素添加与对照相比只显著（p <0.05）提高了根呼吸的速率，其对土壤呼吸和微生物呼吸速率的提高较对照区不显著（p >0.05）。 （3） N20、N10显著（p <0.05）提高了沙质草地的总生态系统光合作用和生态系统呼吸。与对照相比，N5、N10、N20处理的GEP分别提高了1.05、1.29、1.26倍，ER分别提高了1.35、1.22、1.06倍。在观测期间，4个处理均表现为碳汇功能，N0、N5、N10、N20分别净固定的碳为131.27 g CO2·m–2，125.03 g CO2·m–2，233.68 g CO2·m–2，76.64 g CO2·m–2，N10净固定的碳最多，而N20净固定的碳最少。从净碳固定的角度来看，10 N m–2·a–1水平的氮素添加最有利于净碳的固定，而20 N m–2·a–1水平的氮素添加在极大的促进碳固定的同时，也更大的促进了生态系统碳的释放。 （4） 沙质草地土壤呼吸、根呼吸、微生物呼吸及其总生态系统光合作用与土壤温度均无显著（p > 0.05）的指数关系；土壤呼吸、根呼吸、微生物呼吸、生态系统呼吸与土壤水分有极显著（p <0.01）的线性关系。而总生态系统光合作用与土壤水分不存在线性关系。指数拟合可以很好的揭示生态系统呼吸与土壤温度的关系。 因此，相对低水平（N5）和高水平（N20）的氮素添加均会促进沙质草地土壤碳的释放。相对中等水平（N10）的氮素添加最有利于沙质草地净碳的固定，而相对高水平（N20)的氮素添加最不利于净碳的固定。持续增加的氮沉降可能会使沙质草地从弱的碳汇变成碳源。这对进一步认识氮沉降背景下，沙质草地生态系统的生产力和碳循环关键过程以及碳的源汇有重要意义。 |
| 英文摘要 | Nitrogen is a key restrictive resource in terrestrial ecosystems. It has a direct impact on vegetation distribution pattern, the primary productivity of terrestrial ecosystem, litter decomposition and other important process. It is also one of the important factors that affect the terrestrial ecosystem carbon cycle. It has a important scientific significance in study the effect of nitrogen input on ecosystem carbon exchange of sandy grassland, which is restricted by nitrogen, in having a in-depth understanding of sandy grassland ecosystem carbon exchange characteristics, in predicting the biogeochemical cycle under the background of future global change. This study was conducted in Horqin sandy grassland in half arid areas in north China. Different levels of nitrogen was added, then we monitored the dynamic processes of sandy grassland carbon exchange of soil respiration, microorganism respiration, roots respiration, ecosystem respiration (ER), net ecosystem carbon exchange (NEE) in plant growing season, and analyzed the key process of sandy grassland ecosystem carbon cycle response to nitrogen addition. The main research results and conclusions are as follows: (1) Adding nitrogen reduced the soil pH value, improved the soil carbon content , above-ground and litter biomass. Relatively high levels of nitrogen addition (N20) significantly (p < 0.05) reduced the soil pH, significantly (p < 0.05) improved the soil carbon content, above-ground and litter biomass. However, this effect of relatively middle (N10) and low level (N5) of nitrogen addition was not significant (p > 0.05). (2) In plant growing season, nitrogen addition can increased the soil respiration, microorganism respiration, roots respiration rates, but this increase is not in proportion with the increase of nitrogen addition. N20 significantly (p < 0.05) increased the soil respiration and roots respiration rates; N5 significantly (p < 0.05) increased the soil respiration and roots respiration rates as well; and relatively moderate (N10) nitrogen addition only significantly (p < 0.05) increased the roots respiration rates, while this effect on soil respiration and microorganism respiration rates is not significant than control area (p > 0.05). (3) N20, N10 significantly (p < 0.05) increased the gross ecosystem photosynthesis (GEP) and ecosystem respiration (ER) of sandy grassland. GEP of N5, N10, N20 treatments compared with the GEP of N0 increased 1.05, 1.29, 1.26 times respectively; while the ER increased 1.35, 1.22, 1.06 times respectively. During the period of observation, four treatments all showed carbon sequestration function, and N0, N5, N10, N20 treatment sequestrated carbon 131.27 g CO2·m–2, 125.03 g CO2·m–2，233.68 g CO2·m–2，76.64 g CO2·m–2 respectively. The most net sequestrated carbon is N10, and the least net sequestrated carbon is N20. From the view of net carbon sequestration, the 10 N m–2·a–1 level is most conducive to the net carbon sequestration. 20 N m–2·a–1 level greatly promoted the carbon sequestration, but at the same time, it also greatly promoted the release of ecosystem carbon. (4) There are no significant index relationships between the soil respiration, roots respiration, microorganism respiration, gross ecosystem photosynthesis and the soil temperature (p > 0.05). And there are significant relationships between soil respiration, roots respiration, microorganism respiration, ecosystem respiration and soil moisture (p < 0.01). However, there is no linear relationship between the gross ecosystem photosynthesis and soil moisture; Index fitting could reveal the relationship between ecosystem respiration and soil temperature well. In conclusion, the relatively low level (N5) and high level (N20) nitrogen addition could promote the soil carbon release of sandy grassland; Relatively moderate (N10) nitrogen addition most conducive to sandy grassland net carbon sequestration, and relatively high level (N20) of nitrogen addition is most unfavorable to net carbon sequestration. Increasing nitrogen deposition thus may lead to sandy grassland from weak carbon sink to carbon source. It exerted an important significance to understand sandy grassland ecosystem productivity and the carbon cycle key process as well as the carbon sources or sinks under the background of the further nitrogen deposition. |
| 中文关键词 | 土壤呼吸 ; 总生态系统光合作用 ; 生态系统呼吸 ; 生态系统净碳交换量 ; 氮沉降 |
| 英文关键词 | soil respiration gross ecosystem photosynthesis ecosystem respiration net ecosystem carbon exchange nitrogen deposition |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生物工程 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287550 |
| 推荐引用方式 GB/T 7714 | 孙殿超. 氮素添加对科尔沁沙质草地生态系统碳交换的影响[D]. 中国科学院大学,2015. |
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