Knowledge Resource Center for Ecological Environment in Arid Area
| 科尔沁草地生态系统结构和功能对不同管理措施的响应 | |
| 其他题名 | The response of ecosystem structure and function of Horqin grassland to different management |
| 张婧 | |
| 出版年 | 2017 |
| 学位类型 | 博士 |
| 导师 | 左小安 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 人类活动和气候变化作用下的草地退化已成为干旱、半干旱区最为突出的生态环境问题之一。深入认识半干旱风沙区草地生态系统结构和功能对不同土地利用和管理措施的响应，能够为我国沙漠化地区退化草地生态系统的恢复和持续管理提供科学依据。在半干旱风沙区和北方农牧交错带的典型代表区域科尔沁草地针对区域草地生态系统结构、功能及其相互关系如何响应土地利用和管理方式变化这一科学问题，基于长期放牧和围封下的草甸、针茅草原、疏林草地和沙质草地植被特征与土壤特性的调查测定及结果分析，开展了围封、氮添加、增水和多年生植物种子添加四因素的不同管理措施对一年生植物为主的沙质草地结构和功能影响的控制实验，阐明了不同草地植被结构和功能以及植被-土壤系统碳氮储量对长期放牧响应的异同，明确了沙质草地植被特征和土壤特性对不同管理方式的协同响应，揭示了不同管理措施影响下沙质草地植被结构和功能变化的土壤驱动机制。本文主要结论如下： （1）通过长期围封和放牧下的四种草地植被特征与土壤特性变化的对比分析，草地植被特征与土壤特性对放牧的响应有所差异。围封草地中优势植物为多年生禾本科植物，放牧草地中一年生植物优势明显。与围封相比，长期放牧降低了四种草地的植被盖度、地上/地下生物量、凋落物量，而地上生物量的降低主要是由放牧导致多年生草本植物生物量下降所引起。就不同草地土壤特性而言，长期放牧显著降低了四种草地土壤中极细砂含量，也降低了针茅草原和疏林草地土壤碳氮含量，沙质草地土壤pH和电导率。不同草地植被结构和功能对长期放牧的响应较为敏感，而不同草地土壤特性对放牧响应存在明显的差异性。因此，长期放牧的退化草地需要禁牧或者围封管理，以缓解草地植被组成及其群落功能的退化。（2）在围封草地中，物种丰富度、多年生植物丰富度与土壤水分、电导率和pH显著正相关，土壤碳氮含量与地上生物量、粘粉粒含量显著正相关，与土壤容重存在负相关关系。在放牧草地中，土壤碳氮含量与地上生物量和凋落物量显著正相关，地上/地下生物量、多年生植物丰富度与土壤水分之间存在显著正相关关系。这些结果表明，科尔沁草地土壤水分变化决定着多年生植物的丰富度，土壤肥力对地上生物量具有重要影响，而长期放牧消除了草地中物种丰富度与土壤特性之间的关联性。（3）长期放牧对草地植被和土壤碳含量没有显著影响，但增加了四种草地地上植物氮含量以及针茅草原、疏林草地和沙质草地凋落物氮含量，针茅草原根系氮含量。围封的不同草地植被系统碳氮储量均显著高于放牧草地，分别增加了1.55和0.75倍，而不同草地土壤碳储量相对稳定。草地植被-土壤系统碳氮储量分别是5654.07g m-2和601.09 g m-2，超过90%的碳氮储存于土壤中，表明了科尔沁草地土壤具有较大的碳氮固存潜力。围封和放牧下土壤碳储量与生物量碳储量之间均存在显著正相关关系，草地植被及其碳储量变化对土壤碳积累具有重要的影响。（4）通过围封、氮添加、增水和多年生植物种子添加四因素管理措施对沙质草地植被与土壤特性影响的模拟控制实验表明，多年生植物种子添加对沙质草地植被特征和土壤特性没有显著影响。围封增加了沙质草地的生物量；氮添加降低了物种丰富度，增加了其生物量；增水提高了物种丰富度和生物量。氮添加降低了沙质草地一年生和多年生植物的丰富度，增加了一年生植物生物量；围封增加了多年生植物的生物量。氮添加极显著降低表层土壤pH，围封和氮添加显著提高土壤无机氮含量，增水显著降低其含量。一年生植物为主的沙质草地植物群落物种丰富度和生物量及其土壤的可利用氮和pH对水氮变化响应较为敏感。（5）通过不同管理措施下的植被特征与土壤特性的相关分析表明，土壤pH与物种丰富度、多年生植物生物量、地下生物量显著正相关，与一年生植物生物量极显著负相关。土壤无机氮含量与地上生物量、凋落物量、一年生植物生物量显著正相关，而与物种丰富度、多年生植物丰富度、多年生植物生物量显著负相关。土壤水分含量与物种丰富度、一年生植物丰富度、多年生植物生物量、地下生物量显著正相关。围封、水、氮添加通过影响沙质草地土壤pH、可利用性氮和水分含量来影响着群落的组成及生物量。（6）围封和氮添加能够极大地影响沙质草地植被-土壤碳氮含量及储量变化。氮添加显著降低了沙质草地地上植物和凋落物碳含量，极显著增加其氮含量；围封显著增加地上植物和凋落物的碳含量。氮添加提高了草地表层土壤碳含量，对土壤氮含量无显著影响；3年后土壤碳含量增加明显。氮添加显著提高地上植被和凋落物碳氮储量，围封显著提高凋落物碳储量和氮储量。短期实验后，表层土壤碳储量显著提高，氮储量无显著变化。这些结果表明，一年生植物为主的沙质草地短期快速的土壤碳积累效应，为退化沙质草地的恢复和碳的管理提供了理论依据。综上所述，本研究阐明了科尔沁草地植被与土壤系统及其碳氮分配对不同管理措施的响应和适应，明确了沙质草地植被的组成及功能与土壤特性对水氮变化的响应较为敏感，确定了围封、水、氮添加通过影响沙质草地土壤pH、可利用性氮和水分含量来影响群落的组成及功能，阐明了沙质草地具有短期快速的土壤碳积累效应，揭示了沙质草地植物群落组成及功能变化的土壤驱动机制。因此，在科尔沁草地实施围封、水、氮的管理以及建立人工草地是退化沙质草地的恢复和可持续发展的有效途径。 |
| 英文摘要 | Under the background of human activities and global climate change, grassland degradation is one of the most important ecological environment problems in arid and semi-arid areas. Doing research on ecosystem structure and function’ response to different land-use and management has instructive significance on the restoration and management of degraded ecosystem in desertification areas. Horqin grassland is a typical representative of the semi-arid sandy region and the agro-pastoral transition zone of northern China. Under the scientific problem of the response of grassland ecosystem structure, function and their interactions to different land-use and management, we firstly investigated and analyzed the vegetation characteristic and soil properties of meadow, Stipa steppe, scattered tree grassland, and sandy grassland at long-term grazing and fencing. Secondly, we carried out a control experiment that contained fencing, water, nitrogen, perennial seed addition and their interactions on the sandy grassland. We further illustrated the different response of vegetation structure and function and plant-soil system carbon and nitrogen storage to grazing, indicated the cooperative response of vegetation characteristic and soil properties to different management, revealed the soil mechanism on vegetation structure and function of sandy grassland at different management. In this paper, main conclusions are as follows: (1) Through the comparative analysis of vegetation characteristic and soil properties at long-term fencing and grazing, there had a different response of vegetation characteristic and soil properties to grazing. The dominant species are perennial grasses in fenced grassland, whereas annuals in grazed grassland. Compared to fencing, long-term grazing significantly decreased vegetation cover, above- and belowground biomass and litter mass. The reason of the decline of aboveground biomass was the decline of perennial plant biomass by grazing. Grazing decreased the very fine sand content of four grasslands, soil carbon and nitrogen of Stipa steppe, soil pH and electrical conductivity of sandy grassland. The response of vegetation structure and function of different grassland to the long-term grazing were particularly sensitive, whereas soil properties to grazing were different at grassland types. Therefore, the degraded grassland caused by grazing need enclosure and grazing prohibition to cope with the degradation of vegetation composition and community features in grassland ecosystem. (2) In fenced grassland, species richness and perennial plant richness were significantly positive correlated with soil moisture、electric conductivity and pH. There are positive correlation between soil carbon and nitrogen and aboveground biomass, clay and silt, conversing correlation between soil carbon and nitrogen and soil bulk density. In grazed grassland, soil carbon and nitrogen were significantly positive correlated with aboveground biomass and litter mass. Soil moisture was significantly positive correlated with above- and belowground biomass, perennial plant richness. It was indicated that the change of soil moisture determined perennial plant richness and soil fertility played an important role in affecting species richness and biomass of Horqin grassland. Grazing may eliminate the association of species richness with soil properties in semi-arid grasslands. (3) Long-term grazing had no significant effect on vegetation and soil carbon, while significantly increased aboveground biomass nitrogen of four type’s grassland, litter mass nitrogen of Stipa steppe, scattered tree grassland, and sandy grassland, root biomass nitrogen of Stipa steppe. The plant system carbon and nitrogen storage in fenced grassland were higher than these in grazed grassland, increasing by 1.55, 0.75 times, respectively, while soil carbon and nitrogen storage had no significant response to grazing. The carbon and nitrogen storage of plant-soil system were 5654.07g m-2 and 601.09 g m-2, respectively, which more than 90% of the carbon and nitrogen storage stored in soil. Therefore, grassland soil has a greater potential for carbon sequestration. There were significantly positive correlation between soil carbon storage and biomass carbon storage at fencing and grazing. The change of grassland vegetation and its carbon storage had an important influence on the soil carbon sequestration. (4) Through the effect of the management composed by fencing, nitrogen addition, water addition and perennial seed addition on the vegetation and soil properties at sandy grassland, it indicated that perennial seed addition had no significant effect on sandy grassland vegetation characteristic and soil properties. Fencing significantly increased aboveground biomass, perennial plant biomass and soil inorganic nitrogen. Nitrogen addition reduced species richness, annual and perennial plant richness and soil pH, but increased biomass, annual plant biomass and soil inorganic nitrogen. Water addition significantly increased species richness and aboveground biomass, while decreased soil inorganic nitrogen. The above- and belowground biomass and litter mass of 2016 were significantly increased. The responses of species richness and biomass, soil available nitrogen and pH of annuals dominated sandy grassland, to the water and nitrogen addition were very sensitive.(5) The correlations of vegetation characteristic and soil properties under different management indicated that soil pH was significantly positive correlated with species richness, perennial plant biomass, root biomass, whereas significantly negative correlated with annual plant biomass. Soil inorganic nitrogen was significantly positive correlated with aboveground biomass, litter mass and annual plant biomass, whereas significantly negative correlated with species richness, perennial plant richness and biomass. There were significantly positive correlations between soil moisture and species richness, annual plant richness, perennial plant biomass, root biomass. Therefore, fencing, water and N addition mediates the community composition and biomass through directly influencing on the soil pH, available nitrogen and moisture. (6) Fencing and nitrogen addition can markedly affect the change of plant-soil carbon and nitrogen content and storage of sandy grassland. Nitrogen addition significantly reduced aboveground plant and litter carbon, but increased their nitrogen content and storage, topsoil carbon and had no effect on soil nitrogen. Fencing significantly increased aboveground plant litter carbon and litter carbon and nitrogen storage. After short-term experiment, topsoil carbon content and storage had a significant accumulation. These results indicated that sandy grassland dominated by annual plant had a short-term rapid soil carbon accumulation and could provide a theoretical basis for the recovery of degraded sandy grassland and carbon management.In conclusion, this study illustrated the response and adaptation of plant-soil system and the allocation of carbon and nitrogen to long-term grazing at Horqin grassland. The results indicate that community compositon and function of sandy grassland and soil properties have sensitively response to change of water and nitrogen condition, confirm that fencing, water and N addition affect the community structure and function through directly influencing on the soil pH, available nitrogen and moisture, reveal that sandy grassland have short-term rapid carbon accumulation and the soil mechanism of the change of vegetation composition and function in sandy grassland. Therefore, the managements of fencing, water addition and nitrogen addition are effective ways to make sandy grassland’s restoration and sustainability development. |
| 中文关键词 | 科尔沁草地 ; 植被结构与功能 ; 土壤特性 ; 植被-土壤系统碳氮储量 ; 管理方式 |
| 英文关键词 | Horqin grassland vegetation structure and function soil properties plant-soil system carbon and nitrogen storage management |
| 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/2XILL650/287962 |
| 推荐引用方式 GB/T 7714 | 张婧. 科尔沁草地生态系统结构和功能对不同管理措施的响应[D]. 中国科学院大学,2017. |
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