Knowledge Resource Center for Ecological Environment in Arid Area
| 祁连山区土壤有机碳垂直分布特征及其影响因素 | |
| 其他题名 | The vertical distribution of Soil Organic Carbon content and its determining factors in the Qilian mountain |
| 杨敏 | |
| 出版年 | 2016 |
| 学位类型 | 硕士 |
| 导师 | 张甘霖 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 有机质（碳）对改善土壤结构、提高土壤肥力和土壤生产力、缓解温室气体排放等方面具有重要影响。土壤有机碳含量、组成、空间变异、分布及其形成、转化和稳定机制主控因子的研究一直是农业与环境方面的热点。土壤有机碳的剖面分布是有机质长期累积的结果, 与土壤发育以及有机质的更新密切相关。土壤剖面有机碳分布模式及其形成机制, 对理解土壤的形成和演变过程，提高土壤碳库计算精度和预测土壤碳汇潜力具有重要意义，而复杂山地系统中关于土壤有机碳的剖面分布模式报道较少。鉴于此，为了探索高山复杂景观下土壤有机碳的剖面分布及影响因素，在祁连山区，基于典型点的目的性采样原则共采集了97个土壤剖面。本研究分析了土壤有机碳的分异特征、区域尺度下有机碳分异的主控因子、划分了祁连山区土壤有机碳的主要垂直分布模式，并研究了典型土壤有机碳轻组分和重组分的分布特征及其影响因素。主要研究结果如下：1. 祁连山区土壤有机碳含量与全国的平均水平相比整体较高。表层（0-20cm）土壤有机碳平均含量为42.6 g kg-1，随着土壤深度的增加，逐渐降低到底层（80-100cm）的15.33 g kg-1；祁连山区土壤有机碳含量具有较强烈的变异性，属中度或强变异，变异系数随土壤深度而增加。土壤有机碳受植被类型、地形（海拔、坡向）、气候（温度、降水）和土壤属性（颗粒组成、酸碱度）等影响。不同植被类型有机碳含量不同，森林草原>灌丛草甸>高寒草甸>山地草原>荒漠化草原。土壤有机碳含量随着海拔的上升而增加，阴坡各土层及土体有机碳含量均显著高于阳坡。土壤有机碳含量与降水呈显著正相关关系，与温度负相关，但不显著。土壤有机碳含量与粘粒含量呈显著正相关，而与pH呈显著负相关关系。利用随机森林方法对不同深度土层的SOC含量和密度进行预测，并比较了各因子影响土壤有机碳含量和密度分布特征的相对重要性。结果表明，其对表层SOC含量和密度的预测能力最强，R2分别为0.68和0.52，模型的预测能力随土层深度增加呈现下降趋势。其中，环境要素（主要是NDVI和年均降水）是表层SOC含量和密度主要驱动因子，而土壤性质则对下层土体SOC含量和密度影响较大。2. 土壤有机碳在剖面中主要的变化规律是随着剖面深度的增加而递减，但其含量和密度在剖面中的分配比例受到环境要素、土壤属性的综合影响可能出现多种变化。基于土壤有机碳相对含量（Cp），即各土层有机碳含量在剖面中的分配比例，对1m的土壤剖面样点进行分析（63个）得出祁连山区土壤有机碳在剖面中的垂直分布划分为四种模式，分别为：普通递减型，表层聚集型，均一分布型和不规则分布型。其中， 37个剖面属于普通递减型，约占58%；13个剖面属于表层聚集型，约占总体的20%；均一分布型所占比例较少，约为13%；不规则分布型最少（5个）。其中，普通递减型模式中典型剖面的土壤有机碳含量与研究区有机碳含量频度范围分布一致；表层聚集型模式中典型剖面的有机碳含量分布相对比较集中，高于总体平均值；均一分布型模式中典型剖面的土壤有机碳含量主要分布在祁连山区土壤有机碳频度分布区间的高、低两端；不规则分布型模式中典型剖面的有机碳含量差异较大。普通递减型分布于祁连山区各景观单元，其他三种分布模式有其形成的景观环境独特性。 3.土壤有机碳不同组分的含量在剖面之间的差异较大；但其分配比例差异较小， 重组碳占70%以上，轻组碳的平均分配比例仅为4.8%～12.9%。重组碳和轻组碳均随着土壤深度的增加而逐渐减少，重组碳的垂直变化趋势与总有机碳一致，而轻组碳在剖面的垂直变化主要发生在0-60cm的土层中，在60cm以下的土壤深度里趋于稳定，剖面中土壤有机碳的垂直分布模式主要受到重组碳的影响。土壤类型、植被类型是影响土壤有机碳不同组分含量和分布的重要因素。 |
| 英文摘要 | Soil organic carbon (SOC) plays an important role in improving soil structure, enhancing soil fertility and productivity, alleviating greenhouse gas emissions etc. Thus research on the contents, fractions, spatial variation and distribution of SOC remain hotspot of agricultural and environmental research.The SOC distribution along profile is the results of long term accumulation of SOC, which is closely related to the pedogenesis of soil profile and the updating process of SOC. Systematic research on the vertical distribution pattern of SOC and its control factors under complicated surrounding conditions is important for improving the accuracy for soil carbon reserves and future prediction of soil carbon sequestration. However limited research has been reported on the vertical distribution pattern of SOC for complicated mountain landscapes. Thus, the objectives of this research are to explore the differential characteristics of SOC and the main control factors in the Qilian Mountains; to investigate the main SOC distribution patters and corresponding soil-forming conditions; to make a comparison research on the distribution features of soil light fraction carbon (SLFC) and soil heavy fraction carbon (SHFC) and their affecting factors. The main conclusions are as following: 1. SOC contents in the Qilian Mountains were higher than the national average level. SOC decreased with soil depth. There was large variation for SOC in this area and the coefficient of variation increased with soil depth. SOC is affected by a lot of factors, such as vegetation type, terrain (elevation, aspect), climate (temperature, precipitation) and soil properties (particle size, pH). SOC contents varied among different vegetation types, in general, forest steppe> shrub meadow> alpine meadow> mountain grassland>desert steppe. SOC contents increased with elevation, and SOC contents for all horizons of north-faced profiles were significantly higher than those of south-faced profiles. SOC contents were significantly positively correlated with precipitation, and the correlation with temperature was negative but not significant. The correlation between SOC and pH showed negative at significant level,while the correlation with clay contents was significantly positive. Vertical variations of soil organic carbon (SOC) as well as their drivers within different soils depths were analyzed. Results showed that SOC content a had moderate to strong variability, and the coefficient of variation increased with depth. Random forest method was adopted to predict the content of SOC with multiple influencing factors and each factor was ranked according to their relative importance in the model. It turned out that the surface soil layer (0-20 cm) had the best model performance with R2 reaching 0.68 and 0.52 for SOC content respectively and R2 decreased with increasing soil depth. Moreover, the environmental factors (esp. NDVI and MAP) were the main drivers for variations in surface SOC content, while edaphic factors added their weights with increasing soil depth.2. The vertical distribution of SOC along profile varies under different environments. Based on the relative SOC contents, i.e. the proportion of SOC contents at each horizon to those of the whole profile, 63 profiles sampled to the depth of 1m were analyzed. Four vertical distribution patters of SOC in the Qilian Mountains area were summarized:：the uniform vertical distribution style，the first layer gathered distribution style，the common distribution style and the disordered distribution style。37 profiles belong to” the common distribution style，accounting for 58%; followed by the first layer gather distribution style，the uniform vertical distribution style and the disordered distribution style. the common distribution style was mostly common in the research are, while the other three vertical distribution patters were characterized by unique environmental features.3. It was found that different fractions of SOC contents varied dramatically among different profiles, but the differences of proportions were small. SHFC accounted for more than 70% of SOC, while the percentage of SLFC was only 4.8%～12.9% . Thus, more research on SHFC can help improve the understanding of using soil carbon sequestration to reduce gas emission and the satiability of SHFC is the key factor determining the capacity of soil carbon sequestration. For the same profile, as soil depth increased, both SHFC and SLFC decreased gradually. The vertical change of SLFC mainly occurred at depth interval of 0-60 cm, and SLFC contents stabilized beneath 60 cm. The distribution trend of SHFC was the same as total SOC, thus, the vertical distribution pattern of SOC was mainly influenced by SHFC. SLFC and SHFC contents of Histosols were higher than other soil types. In addition, vegetation type was also an important factor affecting the contents and distribution of different SOC fractions. |
| 中文关键词 | 土壤有机碳 ; 垂直分布模式 ; 有机碳组分 ; 影响因子 |
| 英文关键词 | SOC Vertical distribution pattern，SOC fraction，Control factors |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 农业资源利用 |
| 来源机构 | 中国科学院南京土壤研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287735 |
| 推荐引用方式 GB/T 7714 | 杨敏. 祁连山区土壤有机碳垂直分布特征及其影响因素[D]. 中国科学院大学,2016. |
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