Knowledge Resource Center for Ecological Environment in Arid Area
| 气候变化下冻融作用对藏北高寒草地土壤有机碳时空变化的影响 | |
| 其他题名 | Effects of freeze-thaw cycles on spatio-temporal variation of soil organic carbon under climate change in alpine grassland, Northern Tibet |
| 陆晴 | |
| 出版年 | 2017 |
| 学位类型 | 博士 |
| 导师 | 吴绍洪 ; 赵东升 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 藏北地区地处青藏高原腹地，平均海拔超过4500 m，气候寒冷，是西藏高寒草地的集中分布区。藏北地区也是青藏高原多年冻土的重要分布区，受其独特气候影响，土壤有机质分解较慢，土壤中固存了大量的土壤有机碳。研究表明青藏高原增温速率明显高于中国以及全球平均水平，气候变暖将导致多年冻土发生退化，进而通过土壤的水热循环变化改变植被的生存环境，影响高寒生态系统的碳循环过程。藏北地区生态环境脆弱，探讨气候变化下土壤有机碳对冻融作用的响应，可为藏北地区生态系统功能提升和畜牧业可持续发展提供科学依据和数据支撑。本研究基于气候插值数据、未来情景数据以及野外采样数据等，运行空间化后的CENTURY模型，分析藏北地区土壤有机碳密度时空变化特征；对CENTURY模型进行冻融过程的耦合，辨析冻融作用对藏北地区土壤有机碳密度的影响，进一步分析冻融作用下藏北地区土壤有机碳密度发展态势。主要结论如下：（1）全球变化背景下藏北地区气候呈温度上升、降水增加发展趋势，随着时间推移，降水增加速率趋缓，而气温升高速率逐渐加快，多年平均气温由-4.45 °C (1961~2015年) 升高到-2.0 °C (2016~2050年RCP8.5情景下)。（2）藏北地区高寒草甸0~50 cm土层深度的土壤有机碳密度约为高寒草原的3倍，分别为5.10 kg·C·m-2和1.78 kg·C·m-2；随着土层的加深，土壤有机碳密度逐渐减小。与高寒草甸土壤有机碳密度相关性较高的环境因子为土壤养分、容重、含水量和土壤颗粒组成，与高寒草原土壤有机碳密度相关性较高的为全氮、全磷含量；逐步回归结果显示，全氮含量与高寒草地土壤有机碳密度的关系最为密切。（3）冻融过程耦合后CENTURY模型模拟结果表明，近55年来，藏北地区土壤有机碳密度呈减小趋势，减小速率为0.872 g·C·m-2·yr-1，高寒草甸草原减小速率最大，高寒荒漠最小；在1980s到1990s中期整个时段内，土壤有机碳密度波动较小，为其稳定时期。在空间上，土壤有机碳密度从东南到西北为逐渐减小趋势；藏北地区约2/3区域的土壤有机碳密度呈显著减小趋势，呈增加趋势的草地类型为高寒草原。（4）考虑气候变化冻融过程影响下，CENTURY模型模拟结果表明，2016~2050年不同情景下不同植被类型土壤有机碳密度均呈减小趋势，其中RCP8.5情景下减小趋势最大，RCP6.0情景下最小。藏北地区约74%的区域土壤有机碳密度低于2.0 kg·C·m-2，分布在藏北地区北部，主要植被类型为高寒草原、高寒荒漠草原和高寒荒漠；土壤有机碳密度呈减小趋势的区域面积约占藏北地区总面积的78%，RCP8.5情景下面积最大。冻融作用对藏北地区土壤有机碳分解先为缓解作用后逐渐转为增强作用；高寒草甸区冻融作用对土壤有机碳分解的作用呈逐渐增强趋势。 |
| 英文摘要 | The northern Tibet is located in the hinterland of the Qinghai-Tibet Plateau with an average elevation of more than 4500 m and the climate is cold. The northern Tibet is the main distribution area of alpine grassland in Tibet. It is also an important distribution area of permafrost on the Qinghai-Tibet Plateau. The decomposition of soli organic matter is slow due to the unique climatic conditions, and a large number of soil organic carbon is sequestered in soil in northern Tibet. The permafrost on the Qinghai-Tibet Plateau has been degraded with climate warming which was faster than the average value in China and over the world. The environment in which vegetation live would be changed through the impact of soil water and heat cycle, thus affecting the carbon cycle process in alpine ecosystem. With the fragile ecological environment in northern Tibet, evaluating the response of soil organic carbon to freeze-thaw cycles under climate change, it aims to provide scientific basis and data support for the stability of ecosystem and the sustainable development of animal husbandry in northern Tibet. In this study, driving the space CENTURY model based on interpolated climate data, climate data under different climate change scenarios and data from sampling points, analyzing the spatio-temporal variations in soil organic carbon density. The response of soil organic carbon density to freeze-thaw cycles was evaluated by the CENTUR model with the freeze-thaw process was coupled. The changing trend of soil organic carbon density in northern Tibet under the freeze-thaw cycles of frozen soil was analyzed further. The main conclusions are as follows: (1) The climate has become warming and wetting from 1961 to 2050 in northern Tibet under global climate change. Based on climate change during 1961~2015, the increasing trend of annual precipitation would be slow, but of annual mean temperature would be fast. The mean value of annual average temperature would increase from -4.45 °C during 1961~2015 to -2.0 °C during 2016~2050 under RCP8.5 scenario.(2) The soil organic carbon density for alpine meadow at 0~50 cm soil depth in northern Tibet was about three times that for alpine steppe, with the value of 5.10 kg·C·m-2 and 1.78 kg·C·m-2, respectively. The soil organic carbon density in northern Tibet decreased gradually with the deepening of soil layers. The results of correlation analysis showed that the correlation of soil organic carbon density and soil nutrient content, soil bulk density, soil water content and soil texture for alpine meadow were higher, while environmental factors with higher relationship for alpine steppe were soil total nitrogen content and soil phosphorus content. Then stepwise regression analysis was used to analyze the relationship between the soil organic carbon density and the environmental factors with higher correlation coefficients, we found that soil total nitrogen content and soil texture were mostly closedly related to soil organic carbon density for alpine meadow, while that for alpine steppe was soil total nitrogen content.(3) The soil organic carbon density significantly decreased at a rate of 0.872 g·C·m-2·yr-1 from 1961~2015 in northern Tibet. The decreasing rate of soil organic carbon density for alpine meadow steppe was the largest, while for alpine desert was the smallest. From 1980s to the mid of 1990s, the fluctuation of soil organic carbon in northern Tibet was small, thus the soil system was thought to be more stable. The soil organic carbon density of variations in northern Tibet was in spatial heterogeneity, representing high in the southeast and low in the northwest. The soil organic carbon density in most of regions showed decreasing trends, that about 2/3 of area in northern Tibet. While soil organic carbon density showed increasing trends in the regions where were covered by alpine steppe. (4) With the impact of freeze-thaw cycles under climate change taken into account, the soil organic carbon density in different vegetation types would decrease from 2016 to 2050 under different climate change scenarios, with the largest decreasing rate under RCP8.5 and the smallest under RCP6.0. The soil organic carbon density in the area of about 74% in northern Tibet was less than 2.0 kg·C·m-2，which was distributed in the northern regions of northern Tibet and was covered by alpine steppe, alpine desert steppe and alpine desert. The area of decreasing trend of soil organic carbon density accounted for about 78% with the largest area under RCP8.5 scenario. The effect of freeze-thaw cycles on the decomposition of soil organic canbon in northern Tibet was mitigated and then gradually enhanced to increased, but that in alpine meadow was gradually increasing. |
| 中文关键词 | 藏北地区 ; 土壤有机碳密度 ; 冻融作用 ; 气候变化 |
| 英文关键词 | Northern Tibet soil organic carbon density freeze-thaw cycles climate change |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院地理科学与资源研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287864 |
| 推荐引用方式 GB/T 7714 | 陆晴. 气候变化下冻融作用对藏北高寒草地土壤有机碳时空变化的影响[D]. 中国科学院大学,2017. |
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