Knowledge Resource Center for Ecological Environment in Arid Area
| 科尔沁沙地退化植被恢复过程中碳氮化学计量特征及储量变化 | |
| 其他题名 | Changes of Carbon&Nitrogen Stoichiometry and Storage in the Restoration Process of Degraded Vegetation in Horqin Sandy Land |
| 吕朋 | |
| 出版年 | 2016 |
| 学位类型 | 硕士 |
| 导师 | 左小安 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 碳（C）和氮（N）元素是陆地生态系统中植物生长与发育过程中不可缺少的重要元素，在生态系统生产力的形成和固碳潜力的维系以及碳氮循环过程中具有重要作用。C、N化学计量特征对于反映植物对营养元素的需要、土壤养分的供给能力和揭示植物对环境的适应及反馈能力具有重要的意义。由于人类活动和气候变化的影响，土地沙漠化已成为我国半干旱农牧交错带最突出的生态环境问题，然而有关沙漠化地区C、N化学计量特征及储量变化的研究较少。因此，在典型沙漠化地区，开展沙地退化植被恢复过程中C、N化学计量特征和储量变化及其对气候变化响应的研究，对于该区域退化生态系统的恢复和管理具有重要的指导意义。本研究在全球气候变暖和科尔沁沙地沙漠化整体逆转的趋势下，通过沙地退化植被恢复过程中不同生境（流动、半固定、固定沙丘和草地）上3次（2011、2013和2015年）群落特征的调查、植被-土壤系统C与N元素含量的测定，开展模拟增温和增雨对四种生境上植被-土壤系统C、N化学计量特征及储量变化影响的控制实验，揭示了沙地植被-土壤系统C、N化学计量特征及储量的时空动态变化规律，阐明了沙地植被-土壤系统C、N化学计量特征及储量对增温与增雨的响应，确定了沙地生态系统C、N化学计量特征及储量变化的关键影响因素，明确了沙地退化植被恢复过程中植被和土壤碳氮固存的效应及其潜力。主要的研究结果及结论如下：（1）在流动、半固定、固定沙丘和草地这一沙地退化植被恢复梯度上，随着沙地退化植被的恢复，植被盖度、物种丰富度、地上生物量、凋落物量和地下生物量明显增加（P<0.01）。从2011到2015年，沙地四种生境上的平均物种丰富度和地上生物量表现出波动变化趋势，半固定沙丘植被盖度持续增加，生态系统的凋落物逐年增加，而根系生物量年际间变化不大。（2）随着沙地退化植被的恢复，地上植物、凋落物和根系的C含量波动变化，土壤（0-10cm）C和N含量及C/N比显著增加（P<0.05）；四种生境中流动沙丘地上植物的N含量最高、C/N比最低，半固定沙丘凋落物和根系的N含量最低、C/N比最高。从2011到2015年，沙地四种生境上的平均地上植物C含量变化不大，N含量明显增加（P<0.01），C/N比下降（P<0.01）；凋落物C、N含量及C/N比波动变化，根系C、N含量及C/N比年际间变化不显著；土壤C含量和C/N比波动变化，N含量明显增加（P<0.01）。沙地退化植被恢复过程中优势植物演替导致了植被-土壤系统中C、N化学计量特征的变化，而封育时间的增加促进了沙地土壤中N的积累。（3）沙地退化植被恢复过程中地上植物、凋落物、根系、土壤的C和N储量明显增加（P<0.01）。由流动沙丘封育恢复到半固定、固定沙丘和草地，总的生态系统碳氮储量分别增加了1.8、4.5、7 和 1.6、3.6、4.2倍，并且超过80%的碳氮储存于土壤中。从2011到2015年，四种生境平均地上植物的C、N储量波动性变化；凋落物C、N储量明显增加（P<0.05）；根系C、N储量变化不显著（P>0.05）；土壤与总的生态系统的C储量变化不显著（P>0.05），而土壤N储量显著增加（P<0.01）。沙地退化植被恢复过程中土壤具有较大的碳氮固存潜力（4）沙地退化植被恢复过程中地上植物、凋落物、土壤的C/N比与物种丰富度存在正线性关系（P<0.01）；地上植物、凋落物、根系、土壤和总的生态系统的C、N储量均与物种丰富度也表现出正线性关系（P<0.01），表明了沙地退化植被恢复过程中群落组成变化影响着植被-土壤系统的C、N化学计量特征及储量的分配。沙地土壤C、N储量与地上和地下总的生物量存在正线性关系（P<0.01），阐明了沙地退化植被恢复过程中土壤碳氮自然积累的植被驱动作用。（5）在模拟增温与增雨的控制实验条件下，沙地四种生境变化中仅物种丰富度之间存在显著差异（P<0.01）。温度增加显著降低了物种丰富度、地上生物量、凋落物量、根系生物量（P<0.05），而增雨以及增温和增雨的交互作用对沙地植被特征的影响不显著（P>0.05）。在全球气候变暖的背景下，生长季温度的增加会极大地影响科尔沁沙地植物群落组成及其结构。（6）在模拟增温与增雨的条件下，由流动、半固定、固定沙丘到草地的地上植物N含量显著增加（P<0.01）、C/N比下降，地下根系N含量及C/N比波动性变化，但地上植物和根系C、N储量没有显著变化；土壤的C、N含量及其储量显著增加（P<0.01）。增温增加了沙地地上植物与根系的N含量，但降低了凋落物的C含量、植物和凋落物的C/N比、地上植物C储量、根系的C和N储量、植被系统和生态系统的C储量。生境与温度的交互作用也对地上植物的C和N含量、凋落物C储量以及凋落物、根系、土壤、生态系统的N储量具有显著影响（P<0.05）。 综上所述，沙地退化植被恢复过程中优势物种和群落组成变化对植被-土壤系统的C、N化学计量特征具有重要影响，长时间的恢复增加了沙地地上植物和土壤的N含量。沙地退化植被恢复过程中物种丰富度、地上和地下生物量的增加促进了土壤中碳氮储量的自然积累，沙地土壤具有较大的碳氮固存潜力。但生长季短期的温度增加会极大地降低植物物种丰富度和生物量及其植被系统C储量，导致区域土壤碳固存仍然具有较大的不确定性。因此，需要进一步开展野外长期的模拟增温和增雨对沙地生态系统碳氮固存效应的影响研究，深入认识沙地植被-土壤碳氮固存对气候变化响应的协同适应机制，才能准确评估气候变化影响下沙地植被-土壤碳氮储量和固存潜力。 |
| 英文摘要 | Carbon(C) and Nitrogen (N) are the two important elements in the growth and development of vegetation in terrestrial ecosystem, playing an important role in the productivity of ecosystem and carbon sequestration potential and carbon and nitrogen cycles. C and N stoichiometry have the important significance in reflecting the need of vegetation for nutrient element, the supply capacity of soil nutrient and revealing the adaptive and feedback ability of vegetation to the environment. Due to the human activities and global changes, land desertification has become the increasingly urgent environmental problem in semi-arid agro-pasturage transition zone in China. While there were few studies about the changes of C and N stoichiometry and their storage in desertification regions, which were closely related to global change. So, we have carried out the studies about the changes of C and N stoichiometry and storage and the feedback to climatic changes in the restoration process of degraded vegetation. It has the great guiding significance in the restoration and management of degraded ecosystem in typical desertification regions. In the current tendency of desertification reversion in Horqin Sand Land, we investigated the community characteristics in three times (2011,2013,2015) and measured the C and N contents and estimated their storage of vegetation-soil ecosystem in four habitats (mobile dune, semi-fixed dune, fixed dune, grassland) in the restoration process of degraded vegetation. We also carried out the controlled experiment about the effects of simulating elevated temperature and water on the changes of C and N stoichiometry and storage in vegetation-soil ecosystem in four habitats. We revealed the spatiotemporal dynamics change of C and N stoichiometry and storage of vegetation-soil ecosystem in sandy land. We also illuminated the response of C and N stoichiometry and storage of vegetation-soil ecosystem in sandy land to elevated temperature and water. We found the key factors that influenced the changes of C and N stoichiometry and storage in sandy ecosystem. We also determined the potential of C and N sequestration of vegetation and soil in the restoration process of degraded vegetation. The main results and conclusions were as followed:(1) Along the gradient of degraded vegetation restoration, vegetation cover, species richness, aboveground biomass, litter biomass and root biomass significantly increased (P<0.01) with the restoration of degraded vegetation. From 2011 to 2015, species richness and aboveground biomass changed undulate; vegetation cover of semi-fixed dune continuous increased; litter biomass of ecosystem increased year by year, while root biomass did not differ between years.(2) With the restoration of degraded vegetation in sandy land, the C content of aboveground vegetation, litter and root changed undulate. The C and N content and C/N ratio of soil (0-10cm) increased significantly (P<0.05). The N content of aboveground vegetation in mobile dune was the highest and the C/N ratio was the lowest, while the N content of litter and root in semi-fixed dune was the lowest and the C/N ratio was the highest in four habitats. From 2011 to 2015, the average C content of aboveground vegetation had a little change in four habitats, while the N content increased significantly (P<0.01) and the C/N ratio decreased significantly (P<0.01); the C and N content and C/N ratio of litter changed undulate, while the C and N content and C/N ratio of root did not differ between years; the C content and C/N ratio of soil changed undulate, but the N content increased significantly (P<0.01). The succession of dominant vegetation in the restoration process of degraded vegetation leads to the changes of C and N stoichiometry of vegetation-soil ecosystem, and the increase of fencing time promotes the accumulation of soil N in sandy land.(3) The C and N storage of aboveground vegetation, litter, root, soil increased significantly in the restoration process of degraded vegetation (P<0.01). From mobile dune, semi-fixed dune, fixed dune to grassland, the total C and N storage of ecosystem increased 1.8, 4.5, 7 and 1.6, 3.6, 4.2 times respectively. More than 80% of C and N storage were stored in soil. From 2011 to 2015, the average C and N storage of aboveground vegetation in four habitats changed undulate, while the litter’s increased significantly (P<0.05) and root’s didn’t change significantly (P<0.05). The C storage of soil and total ecosystem didn’t change significantly (P>0.05), while the N storage of soil increased significantly (P<0.01). These results indicate that the soil has the considerable potential of C and N sequestration in the restoration process of degraded vegetation in sandy land.(4)The C/N ratio of aboveground vegetation, litter, soil had positive linear relationship with species richness in the restoration process of degraded vegetation (P<0.01). The C and N storage of aboveground vegetation, litter, root, soil and total ecosystem also had positive linear relationship with species richness (P<0.01), which indicates that the changes of community composition influenced the C and N stoichiometry and storage’s allocation. The C and N storage of soil in sandy land had positive linear relationship with the biomass of aboveground vegetation and root (P<0.01). This reveals that vegetation strongly drives the natural accumulation of soil C and N in the restoration process of degraded vegetation.(5) In the controlled experiment of simulating elevated temperature and water, only the species richness had the significant difference among habitats. Elevated temperature declined the species richness, aboveground biomass, litter biomass and root biomass significantly (P<0.05). While elevated water and the interaction between temperature and water had little effect on vegetation characteristics in sandy land (P>0.05). In the background of global warming, the increase of temperature in growing season has great effect on the community composition and structure of vegetation in sandy land system.(6) In the condition of elevated temperature and water, the N content of aboveground vegetation from mobile dune, semi-fixed dune, fixed dune to grassland increased significantly (P<0.01),while C/N ratio decreased; the N content and C/N ratio of root changed undulate, but there was no difference in the C and N storage of aboveground vegetation and root in four habitats; the C and N contents and storage increased significantly (P<0.01). Elevated temperature increased the N content of aboveground vegetation and root; while declined the C content of litter, the C/N ratio of aboveground vegetation and litter, the C storage of aboveground vegetation, the C and N storage of root, the C storage of vegetation ecosystem and the C storage of ecosystem. The interaction between temperature and habitats also had important effect on the C and N contents of aboveground vegetation, the C storage of litter, the N storage of litter and root and soil and ecosystem (P<0.05).In conclusion, the changes of dominant species and community composition have the great effect on C and N stoichiometry of vegetation-soil ecosystem. The N content of aboveground vegetation and soil increases after fencing restoration for a long time. The increase in species richness and above- and belowground biomass promote the natural accumulation of C and N in soil, the restoration of soil in sandy land has the considerable potential of C and N sequestration. But the short-term elevated temperature in growing season decreases the species richness and biomass and C storage of vegetation ecosystem, which leads to the uncertainty of carbon sequestration in regional soil. Thus, we should carry out more long-term studies about the effects of simulating elevated temperature and water on carbon and nitrogen sequestration, in order to in deeply understand the synergetic adaptation mechanism of carbon and nitrogen sequestration in response to climatic change, this will be helpful to support that we can effectively and accurately evaluate the C and N storage of vegetation-soil ecosystem and the sequestration potential in the background of climatic change. |
| 中文关键词 | C ; N化学计量特征及储量 ; 退化植被恢复 ; 增温和增雨 ; 植被特征 ; 科尔沁沙地 |
| 英文关键词 | C&N stoichiometry and storage degraded vegetation restoration elevated temperature and water vegetation characteristic Horqin sandy land |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 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/2XILL650/287710 |
| 推荐引用方式 GB/T 7714 | 吕朋. 科尔沁沙地退化植被恢复过程中碳氮化学计量特征及储量变化[D]. 中国科学院大学,2016. |
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