Knowledge Resource Center for Ecological Environment in Arid Area
| 中国北方草地退牧还草工程的固碳潜力 | |
| 其他题名 | Carbon Sequestration Potential of National Program of Returning Grazing Land to Grassland in North China |
| 熊定鹏 | |
| 出版年 | 2016 |
| 学位类型 | 博士 |
| 导师 | 石培礼 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 围栏管理、适度放牧、人工草地建设等人工干预可望提高草地植被生产力和土壤有机碳的积累，退化草地生态系统具有巨大的固碳潜力。我国自 2003 年起开始实施退牧还草工程，截至 2012 年底，工程实施总面积超过 7000 万公顷。本研究通过历史资料收集、文献数据挖掘与同化、野外调查等多种方式构建了退牧还草工程的相关固碳计量参数，采用 meta-analysis，时间序列法，清查法，IPCC碳收支清单法等多种方法，在区域尺度评估了我国北方草地退牧还草工程的固碳量和固碳速率，匡算了工程区的固碳增汇潜力，研究影响工程不同草地利用和管理方式的生物环境控制因子，提出退牧还草工程区增强固碳潜力的适应性草地管理模式和工程措施。本研究得出的主要结论如下： （1）整合分析结果表明，在全国尺度上，围栏禁牧工程有效地增加了植被盖度，草地生态系统碳储量和土壤养分含量，但倾向于降低草地群落的物种多样性。研究结果表明，在我国，围栏禁牧是一种有效草地恢复手段。气候因子，特别是年降水量显著地影响了草地碳库对围栏禁牧的响应。湿润地区的草地具有更高的固碳效率。随禁牧措施不断进行，土壤固碳速率逐渐降低。当持续时间小于5 年时，短期内，围栏禁牧对生物多样性表现为正效应，但超过 5 年的禁牧显著降低群落生物多样性。因此，考虑到物种多样性与草地碳固持间的权衡关系，不超过 5 年的围栏禁牧既能有效的恢复草地植被，又能最大化固碳效益。 （2）2003-2010 年北方退牧还草工程区内草地生态系统碳汇总量约为 120.3±16.89 Tg，其中植被碳汇为 64.68±5.83 Tg（地上部分碳汇 7.59±1.24 Tg，地下部分碳汇 57.09±4.59 Tg），土壤碳汇约为 55.61±12.77 Tg。由于工程措施贡献导致的草地生态系统碳累积量约为 116.76±9.95 Tg，其中植被固碳量为 63.23±3.42 Tg（地上部分固碳量 7.75±0.87 Tg，地下部分固碳量 55.48±2.55 Tg），土壤固碳量为 53.53±10.65 Tg。不同省份退牧还草工程固碳量由大至小分别为四川，内蒙古，青海，新疆，甘肃，西藏，宁夏。不同草地类型来看，草甸类具有固碳量较高，荒漠类草地固碳量较低。 （3）2010-2020 年我国北方草地退牧还草工程可实现的固碳潜力约为 184.6±33.4 Tg，其中植被约为 99.5±13.5Tg（地上部分，11.8±1.7 Tg；地下部分，87.7±12.0 Tg），土壤固碳潜力约为 85.1±19.8 Tg。退牧还草工程下草地植被和1m 深度土壤的平均固碳速率分别为 0.13 Mg ha -1 yr -1 和 0.11 Mg ha -1 yr -1 。结构方程模型结果表明，土壤氮储量变化和年降水量是直接影响退牧还草工程区草地的碳固持效应的两大主要因子。 （4）利用修正的 IPCC 第二层级方法估算了我国 2003-2012 年十年间 0-30cm草地土壤碳储量变化，结果表明 0-30cm 土壤有机碳总增量约为 75.5 Tg（59.9 Tg-97.1 Tg），其中围栏建设工程固碳量约为 54.6Tg（40.8-68.7 Tg），补播工程固碳量约为 20.9Tg（14.1-28.1Tg）。我国北方草地土壤年度固碳量约为 7.5 Tg yr -1 ，平均土壤固碳速率约为 0.11 Mg C ha -1 yr -1 。敏感性分析结果表明，四川省和青海省的高寒草甸类土壤碳密度参考值及其管理因子的误差大小是影响估算结果不确定的主要因子。 （5）耕地建植草地，放牧地建植人工草地、沙地建植人工植被以及草原围栏管理均显著地增加了草地土壤碳含量。不同管理措施对土壤碳含量的影响主要发生于 30cm 以上土层。随着管理措施持续年限的增加，土壤固碳速率随时间表现出非线性降低趋势。 |
| 英文摘要 | Degraded grasslands have huge carbon sequestration potential. Improved grassland management such as fencing, improved grazing, grassland reseeding are recommended as possible options to increase plant productivity and enhance soil carbon accumulation. Chinese government launched an national conservation program of Returning Grazing Land to Grassland (RGLG) since 2003, till the end of 2012, the project area achieved ca. 70 million hectares. In this study, data were extracted from large scale field survey, historical material and published references to calculate parameters in relation to regional carbon accounting. We used meta-analysis, time serious method, inventory method and IPCC good practice evaluate the carbon change in northern China’s grasslands induced by RGLG project. We also estimated the carbon sequestration potential of the RGLG project, and analyzed the major environmental and biological factors that modifying the effects of RGLG project. Certain suggestions were raised for improving the management measures in terms of carbon sequestration based on our results. Main results are as fellows: (1)In this meta-analysis, we found that GE had positive effects on plant cover, ecosystem C stocks and soil nutrient content, but tended to decrease biodiversity in China’s natural grasslands. Our results demonstrated that GE is an effective way to restore degraded grasslands in China. Climatic factors, especially precipitation, strongly affected the effects of GE on grassland C stocks. GE was more efficient in areas with favorable precipitation in terms of C sequestration. Annual soil C sequestration rates were greater in the early stage under GE and decayed rapidly over time. Short-term GE had significant positive effect on biodiversity, but this effect shifted to negative in the long run. Therefore, in an integrated approach, we suggest that approximately no more than five years GE was appropriate and effective in recovering vegetation and increasing biodiversity and C stocks in China’s grasslands. (2) Based on our estimation, from 2003 to 2010, the ecosystem level carbon accumulation inside the project region is 120.3±16.89 Tg, partioning to 64.68±5.83 Tg in vegetation (aboveground, 7.59±1.24 Tg; belowground, 57.09±4.59 Tg) and 55.61±12.77 Tg in soils. During this period, carbon the biomass carbon stock increased by 63.23±3.42 Tg (aboveground, 7.75±0.87 Tg; belowground, 55.48±2.55 Tg) and soil carbon stock increased by 53.53±10.65 Tg, owing to the implementation of the RGLG projct. The amount of carbon increment sorted by size was Sichuan, Inner Mongolia, Qinghai, Xinjiang, Gansu, Tibet, Ningxia. In terms of grassland types, the increment was relative higher in meadow but lower in desert.(3) The carbon sequestration potential of RGLG project in northern China’s grasslands were 99.5 ± 13.5 Tg in vegetation (aboveground, 11.8 ± 1.7 Tg; belowground, 87.7±12.0 Tg) and 85.1±19.8 Tg in soil, together nearly 184.6±33.4 Tg in the whole grassland ecosystem. With the implementation of the RGLG project, the average carbon sequestration rate of plant biomass and soil were 0.13 Mg ha -1 yr -1 and 0.11 Mg ha -1 yr -1 , respectively. The results of structural equation model indicated that the change of soil total nitrogen and annual precipitation were the main factors which could facilitate the ecosystem carbon sequestration. (4) IPCC Tier 2 method was used to estimate the soil carbon stock change from 2003 to 2012 induced by the RGLG project. The results showed that the 30 cm layer soil organic carbon stock increased by 75.5 Tg，with a 95% confidence interval ranging from 59.9 Tg to 97.1 Tg. Under the fencing management, soil carbon stock increased by 54.6Tg, with a 95% confidence interval ranging from 40.8 Tg to 68.7 Tg. Under the pasture sawing, soil carbon stock increased by 20.9Tg, with a 95% confidence interval ranging from 14.1 Tg to 28.1 Tg. The annual carbon stock change was 7.5 Tg yr -1 , the average soil carbon sequestration rate was 0.11 Mg C ha -1 yr -1 . Sensitive analysis indicated that the management factor and soil reference carbon density of Qinghai and Sichuan province were the main factors that strongly influence the uncertainty of the final results. (5) Convert cropland to grassland, construct artificial grassland in grazed land, establishing vegetation in sand land and fencing management significantly increased soil carbon content in grassland ecosystem. The effects of management measures on soil carbon were mainly occurred in surface layer (< 30 cm). The temporal pattern of the soil carbon dynamic indicated a nonlinear decreasing trend of soil carbon sequestration rate with the management measures. |
| 中文关键词 | 退牧还草 ; 固碳速率 ; 固碳潜力 ; 碳汇 ; 环境因子 |
| 英文关键词 | Returning Grazing Land to Grassland carbon sequestration rate carbon sequestration potential carbon sink environmental factors |
| 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/2XILL650/287656 |
| 推荐引用方式 GB/T 7714 | 熊定鹏. 中国北方草地退牧还草工程的固碳潜力[D]. 中国科学院大学,2016. |
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