基于多源遥感数据的区域生态系统服务价值年际动态监测 ——以中原城市群为例

通过对多源遥感数据在生态系统服务价值（ESV）遥感模型中的尺度效应分析,选择满足最佳空间分辨率和长时间序列的遥感数据,对中原城市群区域2001~2013年的ESV实现了逐年逐像元水平的动态监测。结果表明：该区应用于遥感模型输入数据的最适空间分辨率为30~1 000 m,相对于30 m尺度,其他尺度估算结果的相对偏差均小于0.4%;结合年际动态监测的需求,选择了MODIS数据产品（空间分辨率500 m,时间尺度1 a）作为遥感模型的最佳数据源;研究区ESV总值在研究期内整体上呈显著增长趋势,增速约为8.6亿元/a,但在持续增长过程中经历了3次波动,且表现得越来越剧烈;在空间上,研究区ESV多年均值呈现出明显的不均衡性,表现为从西南向东部递减的趋势。研究表明此方法简单易行,初步实现了区域ESV年际动态监测遥感模型的准业务化运行。     

中国省域犯罪率影响因素的空间非平稳性分析

收入差距和流动人口是影响犯罪率的两个重要因素, 以往研究基于OLS模型, 在假设地域空间为均质的前提下分析其对犯罪率的影响, 但现实世界的空间单元往往难以满足“均质”的假设, 多数表现为“空间异质”。以OLS计量空间异质会造成计量结果出现偏差, 同时无法了解不同空间单元的不同影响。而地理加权回归模型通过将空间结构嵌入线性回归模型中, 很好的解决了空间异质的计量问题。利用地理加权回归模型研究2008 年中国大陆省域单元犯罪率的影响因素, 结果表明:① 犯罪率的影响因素表现出空间非平稳性, 流动人口与犯罪率显著相关, 但各个省份相关程度并不相同, 影响关系随空间位置变化而变化;② 地理加权回归模型的计量精度和拟合度比OLS模型有大幅提高     

民勤绿洲水资源利用与生态系统退化分析

石羊河流域生态平衡失调,生态系统退化在我国干旱、半干旱地区内陆河流域中具有典型的代表性。通过对石羊河流域近代地表水资源开发及其绿洲变迁,近年来流域用水量分配,降水特征及其对植被的影响,流域下游民勤绿洲地下水位、水质的变化等因素多年来观测研究,认为：降水量对天然植被的生长没有大的作用;由于人口的增加,流域地表水资源分配不均,水资源开发过度,地下水位急剧下降,造成流域生态系统退化。流域经济因素促进社会因素的变化,社会因素的变化导致自然环境的变迁,社会、经济、自然诸因素相互作用,通过水资源的变化驱动石羊河流域生态系统的变化。     

石羊河流域绿洲城市水土资源利用生态风险评价——以武威市为例

石羊河流域是西北内陆典型缺水区,水土资源是相互制约相互影响的有机整体,其供需状况成为决定该流域社会、经济与环境协调发展的生命主线.以武威市为例,基于各区县1987和2010年土地利用数据以及2003 -2009年石羊河水资源公报基础数据,选取水土资源利用效应相关指数,根据各指标所反映的风险内涵,将计算结果加权或分级组合,独立构建水、土资源利用生态风险评估及对策体系,分析研究各区县水土资源生态风险动态及空间变化,最后依据流域位置对评价结果进行综合等级划分.研究结果表明:(1)研究期内武威市各区县土地利用综合风险指数均有所增加,土地利用格局的变化产生了一定的生态风险;(2)2003 -2009年武威市水资源利用生态风险等级明显增加,不同地区需要结合自身条件,采取相应措施,应对水资源生态风险的变化;(3)武威市各区县水土组合生态风险在空间上表现出一定差异性:中下游地区综合生态风险总体大于上游地区.     

干旱生态系统净初级生产力估算及变化探测

针对中国西部干旱区特有的气候-植被特征,利用卫星遥感混合像元分解技术对干旱区植被进行了光合作用植被和非光合作用植被区分和组分解析,尝试通过对干旱覆被植被灌层结构进行解析而解决因植被区系差异和环境背景干扰的问题,并参考国际上遥感-生态模型GLO-PEM和CASA,借助遥感生态反演的物理分析,初步构建起基于遥感与生态过程的干旱区适用的光能利用率模型NPP-PEM,并以中国西部干旱区喀什地区叶尔羌-喀什噶尔河流域山地-绿洲-荒漠生态系统为案例,利用AVHRR/NOAA气象卫星遥感数据和气候资料估算了1992年和1998年中国西部喀什地区叶尔羌-喀什噶尔河流域山地-绿洲-荒漠生态系统1 km分辨率年净第一性生产力,并进行了变化探测分析。模拟检验结果精度较好,生态系统碳吸收的空间异质性特征明显。结果表明,考虑了干旱植被生理特征和灌层结构的光能利用模型,模拟结果较为合理,也为引入其他生态模型应用到干旱区生态系统研究提供了借鉴,从而为干旱区陆地生态系统碳循环研究开辟了途径。     

尺度政治视角下的地缘能源安全评价方法及应用

通过引入政治地理学的尺度政治、国际关系学的安全理论和能源安全理论,考虑到能源争夺中的尺度转换、地缘环境中的地缘关系和地缘结构以及安全的三个属性等因素,重新构建了地缘能源安全评价模型,并基于此模型对1995-2010 年俄罗斯太平洋石油管道建设中的中国地缘石油能源安全进行了定量评价。结果表明：① 从时间上来看,中国在俄罗斯太平洋石油管道建设中的地缘石油安全指数不断攀升,中国在此石油能源尺度政治争夺中越来越处于不利地位,考虑到今后韩国、美国等国家的参与,竞争将更加激烈;② 从地缘关系上看,中日两国能源竞争指数趋于减少,但是两国从俄罗斯进口能源竞争加剧;③ 俄罗斯能源出口战略长期以来一直偏重欧洲,但是已经出现转向的趋势,其能源出口战略指数已显著下降;④ 中国石油消费的比重稳定和中俄之间友好关系在一定程度上缓解了中国地缘石油能源安全;⑤ 从地缘结构上来看,中国经济增长带动下的整体综合国力的增强,将会加剧东北亚地区的地缘石油竞争。     

土体直剪力学特性颗粒尺度效应理论与试验研究

土体是一种颗粒物质,其强度与变形特性具有显著的颗粒尺度效应。根据土体颗粒间的连结性状和微重比,将土颗粒划分为基体颗粒与加强颗粒。构建了反映土体内部材料信息和颗粒特征信息的土体胞元,基于应变梯度理论建立可以描述土体颗粒尺度效应的土体胞元模型。设计一系列饱和重塑土的直接快剪试验以研究土体直剪力学特性的颗粒尺度效应,并定量计算了土体胞元模型的应变梯度和內禀尺度等微细观计算参数。试验结果表明,土体的剪切屈服应力随加强颗粒体积比和平均应变梯度的增加而增加,且与加强颗粒体积比呈近似线性关系,与平均应变梯度呈抛物线关系;加强颗粒粒径对土体的剪切屈服应力影响不明显。土体剪切屈服应力的试验结果与土体胞元模型的预测结果一致。     

East Asia winter monsoon variations on a millennial time‐scale before the last glacial–interglacial cycle

Grain size and magnetic susceptibility measurements on samples from a typical loess–palaeosol sequence on the central Chinese Loess Plateau are used to reconstruct the Pleistocene East Asian monsoon climate. The coarse‐grained fraction, i.e. the weight percentage > 30 μm of the bulk grain‐size distribution, is used as a sensitive proxy index of the East Asia winter monsoon strength. On the basis of an absolute time‐scale, time‐series variations of this proxy show that winter monsoon strengths varied on millennial time‐scales during the periods 145–165, 240–280, 320–350, 390–440, 600–640, 860–890, 900–930 and 1330–1400 kyr BP. The wavelength of these climatic oscillations varied between 1.89 and 4.0 kyr, as is shown by spectral analysis using the multitaper method. Although numerical simulation experiments show that high frequencies also can arise from measurement errors in the grain‐size analysis, the frequencies prove to be sufficiently stable when the spectral analysis is repeated with a different number of tapers. For the time being, we do not correlate these climatic oscillations with palaeoclimatic records in the North Atlantic deep‐sea sediments because both time‐scales need to be further improved. Our data, however, certainly demonstrate that millennial‐scale East Asian winter monsoon variations in the last 1.4 million years can be detected from terrestrial loess records. Copyright © 1999 John Wiley & Sons, Ltd.     

Streamflow scaling properties: investigating characteristic scales from different statistical approaches

This paper studies the links between scaling properties of river flow time series by comparing the results of three techniques applied to an extended data set of 34 French discharge gauging stations. The three approaches used are based on different mathematical tools and hypotheses: (1) shape analysis of flood hydrographs; (2) a multifractal framework through spectral and moment analyses, and (3) flood frequency analysis through the fitting of flood duration frequency curves (QdF). The general aim is to test the hypothesis of scaling invariance of river flow and the shape invariance of the hydrographs, in order to investigate the link between scaling properties and flow dynamics. In particular, the coherence between different approaches widely used in the literature to describe these characteristics is evaluated through the estimation of parameters defining the range of time‐scales on which the scaling properties are valid. The results show that most of these timescale parameters are linked to the flow dynamics and suggest that the approaches applied are interrelated. Copyright © 2008 John Wiley & Sons, Ltd.     

Distorted Froude‐scaled flume analysis of large woody debris

This paper presents the results of a movable‐boundary, distorted, Froude‐scaled hydraulic model based on Abiaca Creek, a sand‐bedded channel in northern Mississippi. The model was used to examine the geomorphic and hydraulic impact of simplified large woody debris (LWD) elements. The theory of physical scale models is discussed and the method used to construct the LWD test channel is developed. The channel model had bed and banks moulded from 0·8 mm sand, and flow conditions were just below the threshold of motion so that any sediment transport and channel adjustment were the result of the debris element. Dimensions and positions of LWD elements were determined using a debris jam classification model. Elements were attached to a dynamometer to measure element drag forces, and channel adjustment was determined through detailed topographic surveys. The fluid drag force on the elements decreased asymptotically over time as the channel boundary eroded around the elements due to locally increased boundary shear stress. Total time for geomorphic adjustment computed for the prototype channel at the Q₂ discharge (discharge occurring once every two years on average) was as short as 45 hours. The size, depth and position of scour holes, bank erosion and bars created by flow acceleration past the elements were found to be related to element length and position within the channel cross‐section. Morphologies created by each debris element in the model channel were comparable with similar jams observed in the prototype channel. Published in 2001 John Wiley & Sons, Ltd.