Knowledge Resource Center for Ecological Environment in Arid Area
| 黄土高原植被覆盖变化的影响因素与生态系统服务效应 | |
| 其他题名 | Vegetation coverage change, driving forces and ecosystem service effects in Chinese Loess Plateau region |
| 张琨 | |
| 出版年 | 2018 |
| 学位类型 | 博士 |
| 导师 | 吴能友 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 植被是陆地生态系统的重要组成部分，对环境变化具有高度的敏感性，被认为是能够有效表征生态系统变化的指标。位于黄河中游的黄土高原是世界上水土流失问题最为严重的地区之一，同时也是中国“两屏三带”生态安全格局构建的关键地区和“退耕还林（草）”工程的试验示范区，该地区的生态环境变化态势得到了学术界和环境管理者的共同关注。经过十余年的发展，黄土高原植被覆盖度提升和生态系统服务改善成效显著。但是，植被恢复可持续性的问题随之成为了新的研究热点。因此，有必要从趋势格局、影响因素以及实施成效等方面对退耕还林（草）工程实施以来黄土高原的植被覆盖变化进行系统性分析。本研究以植被覆盖度（FVC）为主要指标，将黄土高原自南向北划分为林地区、林地-草地区、草地区、草地-沙漠区以及沙漠区五个生物气候区，对2000-2015年黄土高原植被覆盖时空变异进行了定量评估；在此基础上结合气象观测数据和土地利用数据探讨了气象因素和生态恢复活动对植被覆盖变化的影响；最后结合土壤保持服务、产水服务和碳固定服务的模型模拟，分析了植被覆盖变化所带来的生态系统服务效应。本研究的主要结果如下。（1）2000-2015年黄土高原植被覆盖度格局以中低水平为主（FVC≤60%），低覆盖度区域和中覆盖度区域分别占区域总面积的47.7%和42.2%。植被覆盖度在空间上呈自东南向西北逐渐降低的总体趋势。植被覆盖度随时间的变化具有明显的非线性和时间异质性特征。显著恢复植被(p<0.05)在2000-2005年、2000-2010年和2000-2014年的比例分别为2.1%、21%和76.2%，表现出加速扩展的趋势。显著恢复植被主要集中在林地-草地区和草地区。（2）黄土高原植被覆盖受到气象因素和生态恢复活动的影响。在区域气候暖干化的背景下，降水、温度与FVC的相关性分析表明，降水和温度对于植被覆盖度的年内波动具有显著影响。但是就年际变化而言，2000-2015年降水和温度均未发生显著变化，与植被覆盖度的变化过程也无明显关联。因此，黄土高原植被覆盖度显著增加的主要影响因素是生态恢复因素而非气象因素。退耕还林（草）工程的实施引发了研究区土地利用格局的明显转变。工程驱动的耕地-草地转变和耕地-林地转变是对植被覆盖度增加促进作用最显著的土地利用变化过程，分别带来了21105.1 km2和6544.1 km2的植被净增加规模。同时还发现，生态恢复措施的促进效果会随着时间的延长而逐渐增强。（3）研究区土壤保持、产水和碳固定服务总体上呈现自东南向西北逐渐降低的趋势。植被覆盖度与各生态系统服务类型的相关程度有所差异。在植被覆盖度显著变化的前提下，覆盖度与土壤保持服务显著相关的比例为53.1%，与产水服务显著相关的比例为10.7%，与碳固定服务显著相关的比例则达到了87.6%。本研究对各项生态系统服务进行整合获取了生态系统服务综合指数，以表征区域整体的生态系统服务水平。研究发现植被覆盖度的提高会促进该综合指数的上升，但此促进作用在各生物气候区有其对应阈值效应。当植被覆盖度在林地区、林地-草地区和草地区分别超过70%、64%和58%的情况下，该综合指数随植被覆盖度的提升会趋于停滞甚至转为小幅降低。此外，研究发现了植被覆盖度对该综合指数的提升具有边际效应，即覆盖度的提升效率呈先增后减的变化趋势。植被覆盖度在林地区、林地-草地区、草地区和草地-沙漠区分别达到40%、24%、36%以及38%的情况下，其对该综合指数的提升作用效率最高，之后趋于减弱。本研究围绕黄土高原植被覆盖变化开展了系统性定量分析，明确了植被覆盖变化的趋势格局、影响因素及生态系统服务效应。研究在明确植被覆盖变化的非线性与时间异质性特征、探明植被覆盖对提升生态系统服务的阈值和边际效应等方面有所创新。本研究的结果突出了重大生态恢复项目在黄土高原植被恢复进程中的重要性，也揭示了合理设置植被覆盖恢复目标的必要性。本研究可为黄土高原以及其他干旱-半干旱地区大规模生态恢复工程的规划和实施提供科学依据。 |
| 英文摘要 | Vegetation is an important component in the terrestrial ecosystem. Due to its high sensitivity to the external environmental changes, vegetation is regarded as an appropriate indicator for the evolution of ecosystem. Located in the middle reaches of the Yellow River in China, the Loess Plateau is one of the most severely eroded areas in the world. In the meanwhile, this region is also a vital component in the Chinese national ecological security strategic pattern titled "Two Barriers and Three Belts" pattern, and the key area in the implementation of the large scale ecological restoration project called "Grain to Green Program" (GTGP). The researchers and policy makers pay great attention on the ecological environment of the Loess Plateau. After more than one decade, the vegetation coverage and the ecosystem services had got greatly improvement. However, the sustainability of vegetation restoration became the new hotspot of research. Therefore, it is necessary to conduct a systemic study to research the trend and pattern, influence factors as well as implementation effects of the vegetation coverage change of the Loess Plateau since the GTGP. In this study, we chose the fractional vegetation cover (FVC) as the main index, divided the Loess Plateau into five bioclimatic zones (forest zone, forest-grass zone, grass zone, grass-desert zone and desert zone), and quantitatively assessed the spatial and temporal change of the vegetation coverage in the Loess Plateau in 2000-2015. Based on the assessment results, combining the meteorological observation and land use data, we briefly analyzed the influences of the climate factor and ecological restoration activity factor on the vegetation coverage change. Furthermore, we calculated the soil retention service, water yield service and carbon sequestration service, and analyzed the effects of the vegetation coverage improvement on the ecosystem services. The main findings of this study were as follows:(1) In 2000-2015, the distribution pattern of the vegetation coverage was main in low and moderate coverage level (FVC≤60%). The area with low vegetation coverage and moderate vegetation coverage covered 47.7% and 42.2% of the study area, respectively. Spatially, the vegetation coverage decreased from southeast to northwest. The change of the vegetation coverage showed significant temporal heterogeneity. The significantly restored vegetation (p<0.05) was in a accelerating expansion process, with the proportions of 2.1%, 21% and 76.2% in 2000-2005, 2000-2010 and 2000-2015, respectively. The significant vegetation restoration mainly concentrated in the forest-grass zone and grass zone in the middle part of the study area.(2) The vegetation coverage was both impacted by the climate factor and the ecological restoration activity factor. Under the background of climate warming and drying, we found that temperature and precipitation had significant influences on the monthly variation of vegetation coverage. However, the precipitation and temperature did not experienced significant change in 2000-2015, and had little influences on the annual change of vegetation coverage. Therefore, it was the ecological restoration activity rather than the climate factor that played the role of the main influencing factor to the vegetation coverage improvement. The GTGP resulted in obvious land use change in the study area. The GTGP-driven farmland-grass conversion and farmland-forest conversion promoted the increase of vegetation coverage significantly, as resulting in net vegetation restoration with areas of 21105.1 km2and 6544.1 km2, respectively. Besides, we found that the effects of ecological restoration tended to strengthen along with restoration age. (3) The soil retention service, water yield service and carbon sequestration service tended to decrease from southeast to northwest. There were differences existed in the correlation between vegetation coverage and the three ecosystem services. Within the area of significant vegetation restoration, 53.1% of the area showed the significant correlation between vegetation coverage and soil retention service, 10.7% of the area showed the significant correlation between vegetation coverage and water yield service, and 87.6% of the area showed the significant correlation between vegetation coverage and carbon sequestration service. Based on the identification of the relationship between vegetation coverage and each ecosystem service, we intergrated the three ecosystem service and obtained the comprehensive index of ecosystem service (CIES), aiming to indicate the integral level of regional ecosystem service. As indicated by the results, we found that the vegetation coverage could promote the increase of CIES, and further revealed that the promotion had threshold effects in each bioclimatic zone. The thresholds of the promotion effects of vegetation coverage were 70%, 64% and 58% in forest zone, forest-grass zone and grass zone, respectively. The CIES increased along with vegetation coverage before it reaching the corresponding threshold in each bioclimatic zone, and stagnated and even turned to slightly decreasing after vegetation coverage exceeding the threshold. In addition, we further revealed the marginal utility in the promotion of the vegetation coverage. The promotion efficiency tended to firstly increase and then decrease. We quantitatively identified the occurrence condition as 40%, 24%, 36% and 38% in forest zone, forest-grass zone, grass zone and grass-desert zone, respectively. The promotion efficiency achieved maximum when vegetation coverage in the abovementioned values, and decreased gradually as exceeding them.In this study, we launched a systemic quantitative analysis with the core of vegetation coverage change in the Loess Plateau, identified its variation pattern, influencing factors and ecosystem services effects. We got innovation in the identification of the non-linear and temporal heterogeneity of the vegetation coverage change, as well as in the exploration of the threshold and marginal utility in the promotion of vegetation coverage on ecosystem services. The findings of this study highlight the importance of the large scale ecological restoration projects in the vegetation restoration process in the Loess Plateau, and revealed the necessity of appropriate target definition. This study could provide scientific references for planning and implementation of the large scale ecological restoration program in the Loess Plateau and in other arid and semi-arid regions globally. |
| 中文关键词 | 植被覆盖度 ; 生态恢复 ; 退耕还林（草）工程 ; 生态系统服务 ; 黄土高原 |
| 英文关键词 | Vegetation coverage Ecological restoration Grain to Green program Ecosystem service the Loess Plateau |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院生态环境研究中心 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/288114 |
| 推荐引用方式 GB/T 7714 | 张琨. 黄土高原植被覆盖变化的影响因素与生态系统服务效应[D]. 中国科学院大学,2018. |
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