Knowledge Resource Center for Ecological Environment in Arid Area
| 中国区域植被变化及其区域气候水文效应 | |
| 其他题名 | Vegetation changes and their effects on regional climate and hydrology in China |
| 韩云环 | |
| 出版年 | 2017 |
| 学位类型 | 博士 |
| 导师 | 马柱国 ; 李明星 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 随着大规模退耕还林/还草生态工程的实施，中国区域土地利用/覆盖发生了显著的变化，成为区域天气气候变化的重要驱动力之一，其引起的气候水文效应目前还不甚清楚。基于此，本文首先综合利用MODIS（MODerate-resolution Imaging Spectroradiometer）和中国统计年鉴数据，对中国区域土地利用/覆盖变化（Land Use/Cover Changes，LUCC）的特征进行分析；其次，对比分析不同气候区植被覆盖变化特征及其与气候变化的关系；再次，基于陆面模式CLM（Community Land Model）模拟退耕还林以来2001-2010年中国区域植被变化对能量平衡和水分循环的影响，认识退耕还林对气候水文的影响机理。最后，在此基础上利用数值试验验证土地利用/覆盖变化-陆面能量水分相互作用机制在生态环境建设中的可应用性，为退耕还林工程的进一步实施提供科学依据。本文的主要研究结果如下：（1）MODIS和中国统计年鉴典型土地覆盖类型（森林、城市和农田）的变化特征具有高度一致性，均表明中国大部分区域森林覆盖率呈增加趋势。2004-2011年，年鉴和MODIS森林覆盖率的空间相关系数高达0.9以上，两种数据在中国各省（市、区）的变化一致性较好，均显示全国大部分省份（市、区）的森林覆盖率增加。年鉴中中国东部城市建成区覆盖率及其增长远高于西部地区，黄淮海地区、东南沿海地区城镇用地呈现加速扩张趋势，符合实际情况；但MODIS数据没有表征出中国区域近十年来经历的快速城市化过程，这应该是MODIS数据的主要问题。MODIS农田面积和年鉴农作物播种面积、有效灌溉面积覆盖率的数值和空间分布均有较好的一致性，它们的共同特征是黄淮海地区覆盖率最大。（2）干湿气候分界线与植被变化的强度存在密切的联系，不同气候区的植被覆盖变化与气候要素的相关性存在显著差异。过去对气候区的划分存在多种标准，这里通过与植被变化的对比研究发现，200 mm、500 mm和800 mm年降水量线上植被的变率最大，它们是干旱区与半干旱区、半干旱区与半湿润区、半湿润区与湿润区的理想分界线，这是气候区域划分的一种新思路。除湿润区外，年平均NDVI (Normalized Difference Vegetation Index)和温度在其他气候区都呈显著正相关，而年平均NDVI与降水的相关在各区域差异显著。半干旱区、半湿润区月NDVI随温度增加呈指数增长，湿润区月NDVI随温度增加呈线性增长；四个气候区月NDVI均随降水量增加而线性增加，其中半干旱区NDVI对降水量变化最敏感。（3）中国区域土地利用/覆盖变化对陆面能量平衡和水分循环过程具有显著的影响。相对于2001年，2010年中国整体植被覆盖增加，尤以过渡带最明显；植被变化后，感热通量增加，潜热通量变化不大，叶面蒸发和蒸腾均增加，土壤表面蒸发减小，入渗增加，径流减小；中国西北东部、华北和东北地区土壤湿度减小，其他区域土壤湿度增加，仅干旱半干旱区过渡带的土壤湿度变化显著，且随深度增加变干越明显。2001-2010年连续LUCC使中国区域平均LAI增加，感热通量增加，潜热通量和蒸散在北方增加，南方减少，径流和土壤湿度北方减小，南方增加。在荒漠-草地过渡带，2001-2010年连续LUCC使LAI呈增加趋势，地表反照率呈减小趋势，感热通量和潜热通量没有明显变化趋势；冠层蒸发和冠层蒸腾与LAI密切相关，呈增加趋势，而土壤蒸发、总蒸散、径流和中浅层土壤湿度均和降水的波动一致，没有明显变化趋势；LUCC使土壤湿度尤其深层土壤湿度减小，连续LUCC的深层土壤湿度随时间变化呈减小趋势。黄土高原的变化与上述过渡带的情况大体相似，只是各层土壤湿度尤其深层土壤湿度的变化有差异。（4）土地利用/覆盖变化-陆面能量水分相互作用机制在黄土高原生态环境建设中的应用表明，大规模的植被覆盖增加会导致土壤干化。黄土高原大规模推进退耕还林，适于土地利用/覆盖变化-能量水分相互作用机制在生态环境建设中的应用研究。降水减少和LUCC均影响着土壤湿度的变化，为了分离气候变化背景下退耕还林对土壤湿度的影响，进行了森林持续增加的理想试验。结果表明森林增加使各层土壤湿度不同程度减小，且随深度增加干化加剧，最浅层和最深层分别减小0.02、0.06 m3 m-3。模拟与观测的土壤湿度的变化接近，表明气候变化的影响较小，植被覆盖变化是土壤变干的主要原因。上述研究表明近年来中国区域土地利用/覆盖发生了显著的变化，并引起陆面能量平衡和水循环过程的明显改变，增加了陆面储水的蒸散损失，导致深层土壤干化加剧。土地利用/覆盖变化-陆面能量水分平衡-气候水文效应的作用机制为开展生态环境保护和建设提供了基础性的科学依据。 |
| 英文摘要 | With the implementation of Grain for Green Project (GFGP), great land use/cover changes have occurred in China, which became one of the important driving forces for regional weather and climate change. However, it’s still unclear about the effects of vegetation changes caused by GFGP on climate and hydrology now. Based on these questions, firstly, MODIS (MODerate-resolution Imaging Spectroradiometer) and China Statistical Yearbook data were comprehensively used to analyze the characteristics of LUCC (Land Use/Cover Changes) in China. Then, the vegetation cover changes and their relationship with climate change in various climate zones were compared and analyzed. Next, the effects of vegetation changes during 2001-2010 after GFGP on energy balance and water cycle in China were investigated using CLM (Community Land Model), to better understand the mechanisms of how GFGP influence the climate and hydrology. Finally, based on the above, the usability of interaction mechanism between LUCC and surface energy and hydrology in ecological environment construction was verified using numerical simulation, and it provided scientific basis for the further implementation of GFGP. The main research results were as follows:(1) The change characteristics of typical land cover types (forests, urban, croplands) from MODIS and China Statistical Yearbook were highly consistent. Both data showed forest cover increased in most parts of China. Spatial correlation coefficients of forest cover from MODIS and China Statistical Yearbook were above 0.9 during 2004-2011. The changes of the forest cover in provinces (municipalities、autonomous regions) of China from these two data showed good consistency. Both showed forest cover increased in most provinces (municipalities、autonomous regions) of China. The cover of urban built districts from China Statistical Yearbook and its increment were much higher in Eastern China than in the western region. Huanghuaihai Region and Southeastern coastal regions showed significantly accelerated expansion trend of the urban land, conforming to the actual situation. But MODIS data did not reflect the process that China has experienced rapid urbanization development over the past decade, which was the main problem for MODIS data. Both the values and spatial distribution were in good consistency among MODIS cropland, sown area of farm crops and irrigated area from China Statistical Yearbook, and the common characteristic of these three data was that the region with largest coverage was in Huanghuaihai region.(2) There was close relationship between the boundaries of dry and wet climate zoning and intensity of vegetation changes. And there were big differences among different climate zones about the correlations of vegetation cover changes and climate factors. There were many standards for the climate division in the past. By comparing the vegetation changes, we found there were big vegetation variabilities on the 200 mm, 500 mm and 800 mm annual precipitation contour lines, and they were the ideal boundaries of arid and semi-arid regions, semi-arid and semi-humid regions, and semi-humid and humid regions, respectively. It is a new way to climate zoning. NDVI (Normalized Difference Vegetation Index) had a significantly positive correlation with temperature in the other three climate zones except humid region. While there were big differences in different regions about the correlations between NDVI and precipitation. NDVI increased exponentially with monthly average temperature increasing in semi-arid and semi-humid region, and NDVI increased linearly as monthly average temperature increased in humid region. Monthly NDVI increased linearly with increased monthly cumulative precipitation in the four climate zones, and NDVI in semi-arid region was the most sensitive to the monthly cumulative precipitation.(3) There were significant effects of LUCC in China on the processes of energy balance and water cycle. Compared with 2001, vegetation cover increased in 2010 in China on the whole, especially in the transition zones. After vegetation cover changed, sensible heat flux increased, and latent heat flux had little change. Both canopy evaporation and canopy transpiration increased and ground evaporation decreased. Infiltration increased and surface runoff decreased. Soil moisture in eastern Northwest, North China and Northeast regions decreased, while it increased in other regions. Only in the transition zone of arid and semi-arid regions, the soil moisture changed significantly, and it decreased more with the increased soil depth. Transient LUCC in 2001-2010 made regional LAI increased, sensible heat flux increased, latent heat flux and evaporation increased in the North and decreased in the South, while surface runoff and soil moisture decreased in the North and increased in the South. In the barren-grass transient zone, transient LUCC in 2001-2010 caused increased trend with LAI, decreased trend with albedo, and no obvious trend with sensible heat flux and latent heat flux. Canopy evaporation and canopy transpiration closely related to LAI showed increased trend. While ground evaporation, evapotranspiration, surface runoff and soil moisture in the middle-shallow layers were consistent with precipitation fluctuations, and they had no obvious change trend. LUCC led to the decrease of soil moisture, especially deep soil moisture, and transient LUCC made the deep soil moisture show decreased trend. The changes of the Loess Plateau are similar to the above changes of the transition zone, and their main differences were the changes of soil moisture, especially the deep soil.(4) The application of interaction mechanism between LUCC and surface energy and water in ecological environment construction in the Loess Plateau indicated that increased vegetation cover massively led to soil desiccation. GFGP was promoted on a large scale in the Loess Plateau, and this region is suitable for the applied research of interaction mechanism between LUCC and surface energy and water in ecological environment construction. Both decreased regional precipitation and LUCC influenced the changes of soil moisture. To isolate the effects of GFGP on soil moisture variations from the effects of climate change, this study performed ideal simulation experiment of continuous increased forest. The results showed the soil moisture with increased forest cover decreased in different degrees at each layer, and it decreased more as the soil depth increased, with top and bottom layer decreases of 0.02, 0.06 m3 m-3, respectively. The simulated soil moisture variation was close to the observed changes, which indicated that the effect of climate change was relatively small and vegetation cover change was the main reason for soil desiccation.The above study showed great LUCC have taken place in China in recent years, which caused significant changes in energy balance and water cycle on land surface, increased the evapotranspiration losses of land water storage, and aggravated the desiccation of deep soil. The interaction mechanism of LUCC- land surface energy and water balance-effects of climate and hydrology provided scientific basis for ecological environment protection and construction. |
| 中文关键词 | 退耕还林 ; 土地利用/覆盖变化 ; 气候水文效应 ; 数值模拟 ; 土壤干化 |
| 英文关键词 | Grain for Green Project，Land Use/Cover Changes，Effects on climate and hydrology，Numerical simulation，Soil desiccation |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 气象学 |
| 来源机构 | 中国科学院大气物理研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287852 |
| 推荐引用方式 GB/T 7714 | 韩云环. 中国区域植被变化及其区域气候水文效应[D]. 中国科学院大学,2017. |
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