【作者】 王红岩；

【导师】 李增元；

【作者基本信息】 中国林业科学研究院 ， 森林经理学， 2013， 博士

【摘要】 土地退化是指在各种自然生态以及人为活动影响下所发生的导致土地的生产能力或土地利用和环境调控潜力等持续下降甚至完全丧失的过程。荒漠化是指包括气候变化和人类活动在内的各种因素作用下，干旱、半干旱和亚湿润干旱区的土地退化，是直接威胁人类赖以生存的自然环境的一种灾难，这种灾难的严重后果是土地的生物或经济生产力和多样性下降或丧失。荒漠化本质即为土地退化，土地退化/荒漠化研究涉及社会经济和自然科学，是当今全球面临的最严重的环境与社会经济问题之一。受气候、自然地理环境以及不合理的人类活动的影响，我国的土地退化问题日益严重，生态环境质量明显下降，严重影响了我国的国际形象，也对我国政治、经济、文化可持续发展造成严重威胁，维护生态安全已成为我国经济社会可持续发展的根本保证。土地退化监测与评价是荒漠化研究的核心内容之一，随着遥感技术的发展，遥感信息成为土地退化评价研究的重要信息来源，同时又为土地退化监测与评价提供了技术和精度保证。基于遥感技术进行高精度、定量化的土地退化信息提取，并以此为基础确定规范化的数量化的土地退化评价指标，对实现土地退化定量评价与监测研究至关重要。本文在总结国内外土地退化研究成果和存在问题的基础上，以时间序列的MODIS数据为基本数据源，尝试通过利用植被降水利用效率（RUE）评价土地生产能力，利用时间序列NPP变化监测植被退化，以此对近10年京津风沙源区土地退化进行遥感综合评价和监测，并结合高空间分辨率的气候变化观测数据，定量分析人为活动和气候变化对区域土地退化的贡献，以期为不同尺度土地退化遥感评价和监测技术的改进以及京津风沙源治理工程效益的评价和后期治理工程合理布局决策提供支撑。主要研究结果如下：（1）研究提出了利用RUE和NPP进行土地退化综合评价的方法。该方法以多年平均相对RUE（rRUE_me）和年极大相对RUE（rRUE_ex）两个指标评价土地的生产能力，以年NPP变化监测植被的退化趋势，以此实现土地退化的遥感综合评价与监测。较之前人方法，该方法更能反映土地退化的客观情况，更有利于大范围土地退化的遥感定量评价与监测。（2）利用京津风沙源区1981-2010年的气象资料，采用多种数理统计方法分析了研究区近30年来年降水量、年平均气温和湿润指数的变化趋势，得出：近30年来京津风沙源区年平均气温呈现增加趋势，年降水量和湿润指数都呈现震荡波动下降变化，但下降趋势并不显著。基于MK检验分析，近30年来，研究区93.12%区域年平均气温都呈显著上升趋势，69.77%的区域年降水量呈下降趋势，在0.1置信水平下显著下降区域占18.76%；研究区84.93%区域湿润指数呈下降趋势，气候变干旱，其中通过0.1置信检验的显著变干旱区域达28.02%。（3）利用2001-2010年时间序列的月度MODIS NDVI数据，基于改进的CASA模型估测获得了研究区长时间序列的年NPP数据，并结合年降水量计算获得了相应的RUE数据。通过趋势检验分析发现，京津风沙源区2001-2010年NPP和RUE都呈现下降趋势，植被活动总体在退化，但变化趋势并不显著。相关分析结果显示，研究区64.24%的NPP呈下降趋势，但仅有14.74%区域下降显著。京津风沙源区的NPP和RUE两个指标变化的空间分布差异较大，NPP显著下降区域主要分布在京津风沙源区的东北部，NPP下降区呈现明显的西南-东北向条带状分布，而RUE显著下降区域的空间分布则比较分散。（4）选择年均相对RUE（rRUE_me）和年极大相对RUE（rRUE_ex）两个指标对研究区像元水平的土地生产能力进行了评价。rRUE_me可反映10年土地生产能力的平均状态，rRUE_ex可反映不同生态系统的抗干扰恢复弹力。研究结果显示，京津风沙源区生产能力极差的土地占总面积的2.45%，生产能力较差的土地占总面积的5.44%，而生产能力好和极好的土地占总面积的92.10%。生产能力极差和较差的土地主要分布在研究区西部气候干旱的荒漠草原、浑沙达克沙地中部、晋北山地丘陵区以及东部的科尔沁沙地。（5）通过时间序列NPP与时间变化的相关分析表明，在气候变化和人为活动的共同影响下，近10年京津风沙源区有6.74万km~2的植被发生退化，占研究区土地总面积的14.74%，同期植被恢复的面积为1.83万km~2，占总面积的3.99%。植被退化区主要分布在京津风沙源区东北部的锡林郭勒草原东部地区，而植被恢复区主要分布在京津风沙源区南部的晋北和冀北山地丘陵区。（6）通过对土地生产能力评价和植被退化监测结果的分析，提出了土地退化综合评价的方法，对研究区近10年的土地退化进行了综合评价。结果表明，京津风沙源区的退化土地总面积为9.10万km~2，占总面积的19.88%，其中，重度退化土地占2.45%，中度退化占5.44%，轻度退化占11.99%。重度和中度退化土地主要分布在研究区西部的内蒙古荒漠草原区、浑善达克沙地以及西南部的晋北山地丘陵区，轻度退化土地主要分布在研究区中部的浑沙达克沙地东部、研究区东部的典型草原和大兴安岭南部地区。（7）京津风沙源区近10年的土地退化，主要由人为活动引起的土地退化占68.05%（占研究区总面积的10.03%），由人为活动和气候变化共同引起的土地退化占31.95%（占研究区总面积的4.71%）。而植被恢复主要是人为因素作用的结果，这可能与近年来该区域生态治理工程的实施有关。更多还原

【Abstract】 Land degradation refers to the land productive capacity or the land use and potentialenvironmental regulation continue to decline or even comletely loss under the influence of avariety of natural ecosystems and human activities. Desertification is defined as the landdegradation in arid and semi-arid and dry-sub-humid areas resulting from various factors,including climatic variations and human activities. Desertification is a disaster directlythreatening human survival of the natural environment. The serious consequences is decreasedor loss of the land biological or economic productivity and diversity. Desertification isessentially land degradation. The land degradation which relates to the social economy andnatural sciences is one of the most serious environmental and socio-economic issues in theworld. Land degradation has become increasingly serious and ecological environmental qualitydecreases significantly in China affected by climate change and unreasonable human activities,which seriously affect China’s international image and pose a serious threat to the sustainabledevelopment of the political, economic, cuitural. The maintenance of the ecological safety hasbecome a fundamental guarantee for the sustainable development of economy and society inChina. Monitoring and assessment of land degradation is the core content of desertificationresearch. With the development of remote sensing technology, remote sensing information hasbecome the important sources for land degradation assessment, while provided the technologyand accuracy guarantee for monitoring and assessment of land degradation reseach. Highprecision and quantitative desertification information extraction based on remote sensingtechnology, which is critical to achieving the quantitative assessment and monitoring of landdegradation.On the basis of summarizing the new research achievements and questions at home andabroad for land degradation, this paper tried to assess the land productivity based on vegetationrain use efficency (RUE) and to monitor the vegetation degradation by annual variation ofvegetation net primary productivity (NPP) for long time series, taking the long time series MODIS data as the main data source. Combining with the high spatial resolutionclimatological data, this paper assessed and monitored the land degradation comprehensivelyusing remote sensing technology in the Beijing-Tianjin dust and sandstorm source region forrecent10years, and analyzed the contribution of human activity and climate change to regionalland degradation quantitatively, in order to improve the land degradation assessment andmonitoring technology based on remote sensing at different scale and to provide the basis forbenefit evaluation of the project in the Beijing-Tianjin dust and sandstorm source region andfor the reasonal layout of the future management.The main research contents are as follows:(1) This paper put forward a new comprehensive method for land degradation assessmentbased on RUE and NPP. The land productivity was assessed quantitatively based on relativeaverage RUE（rRUE_me）and extreme maximum RUE（rRUE_ex）, and the land degradationassessment and monitoring were conducted with remote sensing technology by analyzing thevegetation degradation trend based on the long time series NPP variation. Compared with theother methods, this method can reflect the land degradation more objectively and be benefit toassess and monitor the land degradation quantitatively with remote sensing at a larger range.(2) Based on the meteorological data, the annual precipitation, annual average temperatureand moisture index trends during1981-2010were analyzed using a variety of mathematicalstatistics methods in the Beijing-Tianjin dust and sandstorm source region. The results werethat the annual average temperature showed a significant increasing trend, and the precipitationand moisture index exhibited a downward trend in the past30years in the Beijing-Tianjin dustand sandstorm source region. However the downward trend was not significant. In the last30years, there was a significant increase trend in93.12%of the study area for the averagetemperature based on Mann-Kendall test. And for the precipitation and moisture index, therewas a decreasing trend respectively in69.77%and84.93%of the study area. While thesignificant downward trends at0.1confidence level only accounted for18.76%and28.02%inthe Beijing-Tianjin dust and sandstorm source region. (3) The NPP for long time series in the study region was calculated based on the improvedCASA model using monthly MODIS NDVI data for2001-2010, and the RUE data wasobtained, combining with annual precipitation. It can be seen that the NPP and RUE exhibiteda downward trend and the vegetation activity was being degraded in the Beijing-Tianjin dustand sandstorm source region during2001-2010, but the decreasing trends were not significant.There was a downward trend of the NPP in64.24%of the study area using the correlationanalysis method, while only14.74%of the study area was significant at0.1confidence level.The spatial distributions of trends in NPP and RUE were very different in the Beijing-Tianjindust and sandstorm source region. For the NPP, the significantly decreased areas were mainlylocated in the northeastern part of the study area, these significant decreasing regions weremainly a southwest to northeast band within the area, however the spatial distributions of thesignificant downward trends for RUE were scattered.(4) The land productivity was assessed at the pixel level based on the rRUE_me andrRUE_ex. The rRUE_me can reflect the medial state of land productivity for10years, whilethe rRUE_ex can reflect the jamproof restore elasticity of different ecosystems. The resultsshowed that the lands with the lowest and lower productivity accounted for2.45%and5.44%of the total area of Beijing-Tianjin dust and sandstorm source region, which mainly located inthe western arid regions include desert grassland, the central of Otindag sandy land, andNorthern Shanxi’s mountains. While the land with good productivity accounted for92.1%ofthe whole study area.(5) By analyzing the correlation between NPP and time series, the results showed that thevegetation about67.4thousands km~2had degradated in recent10years under the influence ofclimate change and human activities, it took up about14.74%of the whole study area.Meanwhile, the recovered area of vegetation was18.3thousands km~2, which accounted for3.99%of the total area. The degradated vegetation region mainly distributed in the east ofXilingol grassland, located in the northeast of the Beijing-Tianjin dust and sandstorm sourceregion, while the recovered region mainly located in the south of the study area, such as thehilly and mountainous area in the north of Shanxi and Hebei province. (6) By analyzing the results of land productivity assessment and vegetation degradationmonitoring, the comprehensive method for land degradation assessment was put forward, and ithad been applied to assess the land degradation in the study area for recent10years. As theresults showed that the area of degradated lands in the Beijing-Tianjin dust and sandstormsource region was91thousands km~2, and it took up19.88%of the whole area, among whichthe degradated land at severe degree accounted for2.45%and the moderate degree took up5.44%, they were mainly distributed in the western region, such as Inner Mongolia desertgrassland, Otindag sandy land and the hilly and mountainous area in the north of Shanxiprovince. While the area of slightly degraded land was the largest and accounted for11.99%,which mainly distributed in the east of the Otindag sandy land and the south of Great Khingan.(7) Among the land degradation in the Beijing-Tianjin dust and sandstorm source regionfor recent10years, that mainly caused by human activity was68.05%, while the degradatedland caused by both of them accounted for31.95%. The other degradated land may bedegenerated much earlier, but its reason needs to be verified further. By contrast, the vegetationrecoverage mainly caused by human activity, it may be correlated to the ecologicalengineerings in the study area for recent years.更多还原