水平和垂直尺度乔、灌、草覆盖度遥感提取研究进展

植被覆盖及其变化是区域生态系统环境变化的重要指示,而植被覆盖度是植物群落覆盖地表状况的一个综合量化指标,是生态模型、碳循环、水循环模型等的重要特征参量。传统的植被覆盖度是指一定尺度下所有植被(乔、灌、草)覆盖的综合反映值,当考虑植被垂直方向的异质性,垂直尺度的乔、灌、草覆盖度提取为定量化准确衡量生态环境、全球气候变化等领域提供更具有生态意义的植被参量。目前,遥感大面积估算水平尺度乔、灌、草覆盖度已有比较成熟和可靠的算法,主要方法有：植被指数法、回归分析法、分类决策树法、神经网络法、像元分解模型法、物理模型反演法等,其估算精度基本能达到应用要求。植被垂直方向的异质性给垂直尺度乔、灌、草覆盖度遥感提取带来较大挑战,垂直尺度上的乔、灌、草覆盖度遥感提取的研究在欧美等国已经有了一定规模的开展,在国内则处于起步阶段。遥感提取垂直尺度乔、灌、草覆盖度的主要手段有：激光雷达（LIDAR）、多角度遥感以及两层结构冠层反射模型反演。综述了水平尺度和垂直尺度上乔、灌、草覆盖度遥感提取的最新进展,比较和分析主要的遥感提取方法、模型和现存的一些问题,并对未来的研究发展趋势进行了展望。     

气候变化对中国北方荒漠草原植被的影响

气候变化对陆地生态系统的影响及其反馈是全球变化研究的焦点之一。利用气候变量实现对遥感植被指数所表示的植被绿度信息的模拟，可以尝试作为表达生物圈过去和未来状态的一种途径。利用1961-2000年的气温、降水和1983-1999年的NOAA/AVHRR资料，分析了中国北方地带性植被类型荒漠草原植被分布区的短尺度气候的年际和季节变化，及其对植被的影响。结果表明，过去40年中该区域年际气候变化表现为增温和降水波动。年NDVI的最大值（NDVI_max）可以较好地反映气候的变化，过去17年中NDVI_max出现的时间略有提前。综合分析NDVI、植被盖度、NPP、区域蒸散量、土壤含水量及其气候的年际变化，表明增温加剧了土壤干旱化，降水和土壤含水量仍是制约本区植被生长的根本原因。     

中国陆地生态系统植被结构和净第一性生产力对未来气候变化响应

本文对现有的区域植被动态模型进行了改进,改进后的模型包含了生态系统中生物量动态、植被结构动态、氮素循环过程三者之间的耦合,以及植被和土壤的相互作用.新模型的状态变量包括植被的绿色和非绿色生物量及其氮素浓度,3层土壤的水分,土壤的全氮和速效氮含量.利用全国范围内在过去数10年中定点观测生物量、生产力、土壤全氮和速效氮的含量、卫星遥感植被指数、全国植被图、地形图、土壤图等多方面的基础数据,我们进行了模型的参数化工作,并对模型做了初步验证.结果说明本模型能够比较准确地模拟当前气候条件下植被的生物量、生产力和氮素吸收等动态过程.在此基础上,我们将改进后的模型用于中国陆地生态系统对全球变化响应的研究.为此我们采用了7个大气环流模型的输出的降水和温度的改变量和大气CO2浓度加倍条件,结合现有气候条件,生成未来气候变化情景(scenarios),并用这些情景来驱动改进后的模型直到模型到达稳定状态.模拟结果说明:在未来气候变化条件下,温带常绿针叶林、亚热带山地常绿针叶林、落叶阔叶林、常绿阔叶林,典型禾草草原的分布将显著增加,而落叶针叶林、亚热带常绿针叶林、常绿灌木、禾草和半灌木草原、高寒禾草草甸的分布将有显著的下降,其他植被类型对全球变化的响应不太敏感.33°N以南,净第一性生产力将有显著增加,而33°N以北,净第一性生产力增加较少,局部地区生产力甚至下降.模拟的中国陆地生态系统的北部生产力比南部具有较大的变化和不确定范围.因此,从最大程度的减少和降低生态系统对气候变化响应的不确定程度出发,未来气候变化的研究的重点应该在北方.     

植被物候观测与指标提取方法研究进展

植被物候直接反映了植被生理生态过程对环境变化的响应,在气候变化研究中受到了越来越多的关注,并形成了不同的物候观测技术和指标提取方法。基于文献调研,首先分类评述了当前常用的植被物候观测技术,其次系统介绍了基于不同类型观测数据的植被物候指标提取方法,最后基于实测数据综合比较了多源数据和多种提取方法获取的植被物候指标之间的差异。分析表明,不同植被物候观测技术具有各自适宜的时间和空间尺度,而各种方法的相互补充将有助于完善植被物候观测体系;同时,利用不同观测技术和提取方法所获取的植被物候指标之间存在明显差异,尤其是对于植被秋季物候指标。因此,合理评估多源数据和多种方法间植被物候的差异,并建立可相互比较与转换的处理方法体系,对于改进和完善植被物候观测具有重要的意义。     

利用“3S”技术检测我国北方气候变化的植被响应

本文利用“3S”技术,结合气象观测资料,发现反映区域植被覆盖特征的遥感植被指数变化基本上与器测温度和降水变化相一致,显示出我国北方植被对气候短尺度变化响应敏感。荒漠化总体加剧深受气候变化的影响,人类活动起着相对加强或削弱的作用。     

青藏高原植被动态与环境因子相互关系的研究现状与展望

青藏高原是中国乃至全球对气候变化最敏感的地区之一,是全球平均海拔最高的地理单元,对周边地区起到重要的生态安全屏障作用。近年来,当地植被受到气候变化和人类活动的双重压力。本文基于文献检索分析青藏高原的植被生理、生态特征对气候变化和人为干扰的响应,并利用荟萃分析定量综述植被覆盖度变化对土壤理化性质的影响。在此基础上分析青藏高原植被与环境因子相互关系的研究尺度与方法。结果表明:(1)气温、降水、辐射等自然因素和放牧、农耕、筑路等人为活动均对青藏高原植被的碳交换、水分利用效率、元素含量与分布格局、物候、多样性等指标产生显著影响,植被的变化也同时影响着土壤的水热交换、水文过程和理化性质等;(2)在植被退化过程中,由高覆盖度向中覆盖度转变时对土壤理化性质产生的不利影响强于由中覆盖度转为低覆盖度时,高覆盖度地区的植被保护需要引起更多关注;(3)现有研究更多关注单一要素、单一尺度,未来应关注多要素间的相互耦合,通过合作与共享获取数据,开展多尺度对比和尺度效应研究,系统梳理和分析植被与环境因子的相互关系可为制定科学合理的生态修复策略提供科学依据。     

城市化对降水影响的研究综述

通过长期研究,关于城市化会对局地降水产生一定影响已成为共识,但由于不同地区降水形成、分布机制的复杂性以及气象观测资料、数值天气模式的局限性,目前国际上对于城市化影响降水的物理机制及驱动因素仍存在不同认识,关于不同条件下城市化对降水影响的具体规律也具有争议。在阐述城市化对降水影响的主要物理机制的基础上,从站点资料解析和综合遥感资料解析两方面归纳和比较了近年城市化对降水影响的主要资料检测事实,总结了关于城市化单一因素和综合因素对降水影响的数值模拟试验的主要结论,最后从城市综合气象观测试验、城市化降水效应的系统检测、城市化降水效应的精细化模拟、城市化降水效应的区域影响、城市化降水效应的适应与调控5个方面,论述了存在的主要问题及发展方向,为深化对城市化降水效应的科学认识以及应对其不利影响提供了参考。     

全球气候变化对湿地生态水文的影响研究综述

近百年来全球气候呈现以变暖为主要特征的显著变化,并且未来气温将继续上升,降水模式也会发生改变。从气候变化对湿地水文水资源的影响、气候变化影响下湿地水文与生态的相互作用过程以及湿地生态水文模型等3个方面,对国内外相关研究动态和发展趋势进行了总结分析。从中发现,当前全球气候背景下的湿地生态水文学正在从单一湿地生态水文过程为主要对象,发展成为以研究气候-水文-生态三者相互作用机制为主要内容的综合性、交叉性学科。现关于气候变化影响下水文-生态之间的关系多集中于单向作用的研究,特别是水文过程对植被的影响研究较多,缺乏对气候变化影响下湿地水文过程与生态过程相互作用机理的全面认识。气候变化对湿地生态水文的影响机制研究已经成为水文学研究亟待解决的科学问题,而基于物理机制的湿地生态水文模型,逐渐成为预测未来气候变化下湿地生态水文响应的重要工具。     

遥感提取植物生理参数LAI/FPAR的研究进展与应用

植物生理参数LAI/FPAR是2个重要的陆地特征参量。利用遥感光谱模型并结合地面验证是提取区域尺度的LAI/FPAR最有效的途径。提取LAI/FPAR的模型主要有光谱指数模型和辐射传输模型两类,经过精确的辐射标定和大气纠正的遥感数据可以得到较高精度的LAI/FPAR数据。影响LAI/FPAR精度的因素很多,其中主要因素是像元的异质性、植被类型和物候期等。LAI/FPAR与作物产量有更直接的关系,也是大量作物生长模型的基础,利用这些参数可以实现真实的作物产量预测,特别是开展全球尺度的单产预测。     

草地植被盖度的多尺度遥感与实地测量方法综述

植被盖度作为一个重要的生态学参数被用在许多气候模型和生态模型中。地表实测和遥感测量是获取植被盖度的两种基本途径。以草地植被盖度的测量为研究对象,综合讨论了目前地表实测和遥感测量常用的方法,分析了它们的优缺点,并对如何提高草地植被盖度的测量精度做出展望。数码相机、高光谱遥感以及多尺度遥感数据的综合使用可能是未来草地植被盖度测量发展的趋势。     

Review on Vegetation Phenology Observation and Phenological Index Extraction

Vegetation phenology directly reflects the response of ecosystem physiological and ecological processes to environmental changes and has received increasing attention in climate change, which leads to the development of various phenology monitoring techniques and methods of extracting the phenological index. Based on relevant literatures, the monitoring techniques of vegetation phenology were reviewed. Second, the methods of extracting phenological index using different techniques were introduced systematically. Thirdly, the differences from multi-source data and from multi-methods were evaluated based on ground phenology record, flux observation and vegetation index. Although various methods have been adopted in current vegetation phenological studies, it should be aware of their appropriately spatiotemporal scales for different methods, and the mutual complementation will help to improve the system for phenology monitoring. Meanwhile, the comparison indicated the obvious differences in derived vegetation phenological index using various observation techniques and extraction methods, especially for the autumn vegetation phenological index. Such results highlight the importance to assess reasonably these differences from multi-source data and from multi-methods, and to establish a rational processing system for the mutual comparison and conversion from different methods.     

近海浮游植物水华动力学和生物气候学研究综述

浮游植物水华作为近海重要的生物过程,其动态变化对生态系统内的能童传递、生产力水平和各生源要素的循环等均有重要影响.随着气候变化对生态系统影响研究的深入,浮游植物水华生物气候学研究已成为当前生物海洋学研究的热点.综述了浮游植物水华的研究历史、研究方法及其发生发展的动力学机制,重点评述了气候变化对浮游植物水华动态的影响及国...     

快速城市化地区多尺度水文观测试验与暴雨洪水响应机理分析

城市下垫面改变引起水文循环过程发生变异, 导致目前已掌握的天然情况下的产汇流规律和机制难以解释城市化等新形势下的水文现象与过程, 而面临需重新再认识的挑战。本文以长三角地区为典型, 建立了不同城市化水平及空间规模的水文试验流域, 探讨了快速城市化地区暴雨洪水响应规律和机制。结果表明: ①不同量级降水事件下城镇用地土壤水响应程度(表层土壤水涨幅基本超过4%)总体高于其他土地利用类型, 城市化地区下垫面的改变通过影响土壤水动态响应模式直接影响了地表产流过程, 植被覆盖率较低的城镇用地和荒地土壤含水率呈现出陡涨陡落现象, 而植被作用下的土地利用类型则表现出缓慢上升和缓慢消退的土壤水响应过程。②流域洪峰滞时和洪峰流量整体表现为随流域面积增加而呈幂律函数关系形式的增加。③总降水量与主要洪水特征(如洪峰流量、单位面积洪峰流量和径流深)基本呈显著相关(相关系数分别达0.49、0.41和0.78以上)。城市下垫面通过改变土壤水动态响应等产汇流特征而直接影响了洪水过程, 未来长三角地区暴雨洪水在城市化和气候因素双重作用下呈现持续加剧的趋势。     

利用MODIS fAPAR傅立叶时间序列分析研究植被光合作用活动对净辐射和降雨的响应：青藏高原个例研究

气候变化对植被动力学有非常大的影响。为了定量描述气候变化对植被的影响，文章利用MODIS fAPAR 数据和NCEP 的净辐射和降雨再分析数据对青藏高原地区气候变化对植被的影响进行了时间序列分析。研究所用的数据时间跨度为2000年至2005年。首先利用NCEP 再分析数据建立了干旱度因子的时间序列，为了与MODIS fAPAR 具有相同的时间采样间隔，由NCEP的日净辐射和日降雨量得到每8天的平均净辐射和8日降雨的和。根据一定时间间隔的净辐射与降雨量的比可以用来衡量相对于可利用水分的剩余能量，因此该比值也是干旱灾害的度量。其次，对MODIS fAPAR 的傅立叶时间序列分析提供了两个植被光合作用对干旱相应的因子，即fAPAR的年平均值及其年振幅值。在时间和空间尺度上对植被光合作用活动与干旱指数之间的关系进行了定量分析。对湿年和干年之间的响应差异进行了比较。研究表明较干地区对气候变化的响应最为显著。分析应该扩展到更长的时间跨度以便更加有效地在时间和空间尺度上评估气候变化对植被动力学的影响。     

Interaction between land-use change,flooding and human health in Metro Vancouver,Canada

Many regions of the world are experiencing an increase in frequency and intensity of floods. There has been increasing understanding among emergency preparedness and natural disaster planners that rapid urbanization is enhancing the risk from river flooding in urban areas. Many regions of Canada have been exposed to particularly severe floods over the course of the last few years, much of this due to land-use change. This study aims at understanding the risk of flooding for the City of Metro Vancouver, British Columbia, Canada, which is located in the Fraser River Delta. The paper presents a fast, efficient and reliable method that can be used to produce vegetation maps from advanced very high resolution radiometer images and SPOT vegetation maps. A 10-day maximum normalized difference vegetation index maps were produced to assess the dynamics of the urbanization process in Vancouver. Remotely sensed data show a significant decrease in vegetation cover in the Metro Vancouver City between 1984 and 2012. The proposed method can be used as an effective tool for raising early land-use change awareness and assist with flood risk management. Flood risk management has a substantial impact on human health and well-being in urban areas, and this flood risk information will be used to assess the impact of flooding and explore the complex relationship between land-use change, urbanization, flooding and impact on urban dwellers.     

气候变化和人类活动对三江源地区植被生产力的影响

利用三江源区1982-2013年18个气象台站地面观测资料、GIMMS和MODIS两个卫星源的遥感监测值,以NDVI值和周广胜模型分别计算植被生产力和气候生产力,将植被生产力与气候生产力的差值定义为人类活动影响。在分析该区域植被生产力和气候生产力变化趋势的基础上,通过分离气候变化和人类活动对植被生产力的影响,从而定量评估两者的影响大小,研究结果表明：（1）在气候变化和人类活动的叠加作用下,三江源地区植被生产力、气候生产力和人类活动影响均趋于好转,平均每10a分别增加179kg·hm^-2、154kg ·hm^-2和24kg·hm^-2;（2）气候变化是影响植被生产力的决定性因素,但人类活动在一定程度上加快了其变化速率,尤其是进入21世纪以来人类活动正面影响较为明显,气候变化和人类活动对植被生产力的贡献率分别为87%和13%。     

Assessing vegetation dynamics impacted by climate change in the southwestern karst region of China with AVHRR NDVI and AVHRR NPP time-series

The relationship between climate change and vegetation dynamics in the southwestern karst region of China has been identified by recent studies. Based on previous researches and AVHRR (Advanced Very High Resolution Radiometer) GIMMS (Global Inventory Monitoring and Modeling Studies) NDVI (Normalized Difference Vegetation Index) (1982–2003) and AVHRR GloPEM (Global Production Efficiency Model) NPP (Net Primary Production) (1981–2000) datasets, vegetation dynamics impacted by climate change in the southwestern karst region of China were assessed. The results show that: (1) since the early 1980s, both vegetation cover density and net primary production have insignificant ascending tendencies. However, the inter-annual variation rates of vegetation indexes have apparent spatial differentiations; (2) the correlation coefficients between the inter-annual variations of vegetation indexes and the inter-annual variations of climate factors vary geographically; (3) as indicated by NDVI and NPP, various vegetation types have different responses to climate change, and the annual mean temperature variation has more significant impact on vegetation dynamics than the annual precipitation variation in the study area; (4) distribution laws of correlation coefficients between the inter-annual variations of vegetation indexes and the inter-annual variations of climate factors in different climate conditions are apparent. All these findings will enrich our knowledge of the natural forces which impact the stability of the karst ecosystems and provide scientific basis for the management of the karst ecosystems.     

Research Progress on the Impact of Urbanization on Climate Change

The world has been undergoing a remarkable process of urbanization, especially in developing countries in recent years. The urbanization process has brought about great urban development and large population agglomeration, changes in production and lifestyle, and man-made disturbances such as greenhouse gas and pollution emissions. As the global urbanization process continues to advance, its impact on climate change continues to strengthen significantly. This paper mainly reviewed and summarized relevant researches from two aspects: the influence of urbanization on climate change and the mechanism of influence of urbanization on climate change. Urbanization causes regional warming and urban heat island effect, extreme events such as high temperature, heat wave and heavy rainfall increase in frequency, and also leads to increased urban flood risk. The increase of pollutant emission in the process of urbanization is the main cause of air quality deterioration. Urbanization also has an indirect impact on air quality by changing urban climate. Urbanization has an important impact on climatic factors such as relative humidity, wind speed, sunshine and cloud cover. The impacts of urbanization on climate change are mainly realized through underlying surface changes, greenhouse gas and pollution emissions, anthropogenic heat emissions and urban high heat capacity. Urbanization not only directly affects the regional/local climate, but also indirectly affects the regional/local climate by promoting global climate change. Therefore, the impact of urbanization on climate change has a global and regional multi-scale superposition effect.     

Simulating climate change impact on soil erosion using RUSLE model <Emphasis Type="BoldItalic">−</Emphasis> A case study in a watershed of mid-Himalayan landscape

Climate change, particularly due to the changed precipitation trend, can have a severe impact on soil erosion. The effect is more pronounced on the higher slopes of the Himalayan region. The goal of this study was to estimate the impact of climate change on soil erosion in a watershed of the Himalayan region using RUSLE model. The GCM (general circulation model) derived emission scenarios (HadCM3 A2a and B2a SRES) were used for climate projection. The statistical downscaling model (SDSM) was used to downscale the precipitation for three future periods, 2011–2040, 2041–2070, and 2071–2099, at large scale. Rainfall erosivity (R) was calculated for future periods using the SDSM downscaled precipitation data. ASTER digital elevation model (DEM) and Indian Remote Sensing data – IRS LISS IV satellite data were used to generate the spatial input parameters required by RUSLE model. A digital soil-landscape map was prepared to generate spatially distributed soil erodibility (K) factor map of the watershed. Topographic factors, slope length (L) and steepness (S) were derived from DEM. Normalised difference vegetation index (NDVI) derived from the satellite data was used to represent spatial variation vegetation density and condition under various land use/land cover. This variation was used to represent spatial vegetation cover factor. Analysis revealed that the average annual soil loss may increase by 28.38, 25.64 and 20.33% in the 2020s, 2050s and 2080s, respectively under A2 scenario, while under B2 scenario, it may increase by 27.06, 25.31 and 23.38% in the 2020s, 2050s and 2080s, respectively, from the base period (1985–2013). The study provides a comprehensive understanding of the possible future scenario of soil erosion in the mid-Himalaya for scientists and policy makers.