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Interannual Variability of the normalized difference vegetation index on the Tibetan Plateau and Its Relationship with Climate Change

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Advances in Atmospheric Sciences 2007年第3期24卷 474-484页

作者：周定文范广洲黄荣辉方之芳刘雅勤李洪权 Institute of Atmospheric Physics Chinese Academy of Sciences Chengdu University of Information Technology

The Qinghai-Xizang Plateau, or Tibetan Plateau, is a sensitive region for climate change, where the manifestation of global warming is particularly noticeable. The wide climate variability in this region significantly affects the local land ecosystem and could consequently lead to notable vegetation changes. In this paper, the interannual variations of the plateau vegetation are investigated using a 21-year normalized difference vegetation index （NDVI） dataset to quantify the consequences of climate warming for the regional ecosystem and its interactions. The results show that vegetation coverage is best in the eastern and southern plateau regions and deteriorates toward the west and north. On the whole, vegetation activity demonstrates a gradual enhancement in an oscillatory manner during 1982-2002. The temporal variation also exhibits striking regional differences： an increasing trend is most apparent in the west, south, north and southeast, whereas a decreasing trend is present along the southern plateau boundary and in the central-east region. Covariance analysis between the ndvi and surface temperature/precipitation suggests that vegetation change is closely related to climate change. However, the controlling physical processes vary geographically. In the west and east, vegetation variability is found to be driven predominantly by temperature, with the impact of precipitation being of secondary importance. In the central plateau, however, temperature and precipitation factors are equally important in modulating the interannual vegetation variability.

关键词： Tibetan Plateau normalized difference vegetation index （NDVI） ecosystem climate change interannual variability

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Satellite-based Studies on Large-Scale vegetation Changes in China

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Journal of Integrative Plant Biology 2012年第10期54卷 713-728页

作者： Xia Zhao Daojing Zhou Jingyun Fang State Key Laboratory of vegetation and Environmental Change Institute of Botany the Chinese Academy of SciencesBeijing 100093 China Department of Ecology College of Environmental Sciences and Key Laboratory of Earth Surface Processes of the Ministry of EducationPeking University Beijing 100871 China

Remotely-sensed vegetation indices, which indicate the density and photosynthetic capacity of vegetation, have been widely used to monitor vegetation dynamics over broad areas. In this paper, we reviewed satellite-based studies on vegetation cover changes, biomass and productivity variations, phenological dynamics, desertification, and grassland degradation in China that occurred over the past 2-3 decades. Our review shows that the satellite-derived index （normalized difference vegetation index, ndvi） during growing season and the vegetation net primary productivity in major terrestrial ecosystems （for example forests, grasslands, shrubs, and croplands） have significantly increased, while the number of fresh lakes and vegetation coverage in urban regions have experienced a substantial decline. The start of the growing season continually advanced in China＇s temperate regions until the 1990s, with a large spatial heterogeneity. We also found that the coverage of sparsely-vegetated areas declined, and the ndvi per unit in vegetated areas increased in arid and semi-arid regions because of increased vegetation activity in grassland and oasis areas. However, these results depend strongly not only on the periods chosen for investigation, but also on factors such as data sources, changes in detection methods, and geospatial heterogeneity. Therefore, we should be cautious when applying remote sensing techniques to monitor vegetation structures, functions, and changes.

关键词： normalized difference vegetation index （NDVI） phenology remote sensing vegetation coverage vegetation degradation vegetation productivity

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Projections of the Advance in the Start of the Growing Season during the 21st Century Based on CMIP5 Simulations

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Advances in Atmospheric Sciences 2015年第6期32卷 831-838页

作者： XIA Jiangjiang YAN Zhongwei JIA Gensuo ZENG Heqing Philip Douglas JONES ZHOU Wen ZHANG Anzhi Key Laboratory of Regional Climate-Environment for East Asia Institute of Atmospheric PhysicsChinese Academy of Sciences Ministry of Environmental Protection of Jiuzhaigou Country Climatic Research Unit University of East Anglia Center of Excellence for Climate Change Research and Department of Meteorology King Abdulaziz University Guy Carpenter Asia-Pacific Climate Impact Centre School of Energy and EnvironmentCity University of Hong Kong

It is well-known that global warming due to anthropogenic atmospheric greenhouse effects advanced the start of the vegetation growing season （SOS） across the globe during the 20th century. Projections of further changes in the SOS for the 21st century under certain emissions scenarios （Representative Concentration Pathways, RCPs） are useful for improving understanding of the consequences of global warming. In this study, we first evaluate a linear relationship between the SOS （defined using the normalized difference vegetation index） and the April temperature for most land areas of the Northern Hemisphere for 1982-2008. Based on this relationship and the ensemble projection of April temperature under RCPs from the latest state-of-the-art global coupled climate models, we show the possible changes in the SOS for most of the land areas of the Northern Hemisphere during the 21st century. By around 2040-59, the SOS will have advanced by -4.7 days under RCP2.6, -8.4 days under RCP4.5, and -10.1 days under RCPS.5, relative to 1985-2004. By 2080-99, it will have advanced by -4.3 days under RCP2.6, -11.3 days under RCP4.5, and -21.6 days under RCP8.5. The geographic pattern of SOS advance is considerably dependent on that of the temperature sensitivity of the SOS. The larger the temperature sensitivity, the larger the date-shift-rate of the SOS.

关键词： start of growing season （SOS） normalized difference vegetation index （NDVI） temperature sensitivity Repre-sentative Concentration Pathways （RCPs） CMIP5

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vegetation greenness modeling in response to climate change for Northeast Thailand

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Journal of Geographical Sciences 2013年第6期23卷 1052-1068页

作者： Watinee THAVORNTAM Netnapid TANTEMSAPYA Department of Environmental Engineering Khon Kaen University Khon Kaen 40002 Thailand Research Center for Environmental and Hazardous Substance Management Khon Kaen University KhonKaen 40002 Thailand

In Northeast Thailand, the climate change has resulted in erratic rainfall and tem- perature patterns. The region has experienced both periods of drought and seasonal floods with the increasing severity. This study investigated the seasonal variation of vegetation greenness based on the normalized difference vegetation index （NDVI） in major land cover types in the region. An assessment of the relationship between climate patterns and vegeta- tion conditions observed from ndvi was made. ndvi data were collected from year 2001 to 2009 using multi-temporal Terra MODIS vegetation Indices Product （MOD13Q1）. ndvi pro- files were developed to measure vegetation dynamics and variation according to land cover types. Meteorological information, i.e. rainfall and temperature, for a 30 year time span from 1980 to 2009 was analyzed for their patterns. Furthermore, the data taken from the period of 2001-2009, were digitally encoded into GIS database and the spatial patterns of monthly rainfall and temperature maps were generated based on kriging technique. The results showed a decreasing trend in ndvi values for both deciduous and evergreen forests. The highest productivity and biomass were observed in dry evergreen forests and the lowest in paddy fields. Temperature was found to be increasing slightly from 1980 to 2009 while no significant trends in rainfall amounts were observed. In dry evergreen forest, ndvi was not correlated with rainfall but was significant negatively correlated with temperature. These re- sults indicated that the overall productivity in dry evergreen forest was affected by increasing temperatures. A vegetation greenness model was developed from correlations between ndvi and meteorological data using linear regression. The model could be used to observe the change in vegetation greenness and dynamics affected by temperature and rainfall.

关键词： normalized difference vegetation index （NDVI） vegetation greenness climate variability modeling

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Detecting Agro-Droughts in Southwest of China Using MODIS Satellite Data

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Journal of Integrative Agriculture 2013年第1期12卷 159-168页

作者： ZHANG Feng ZHANG Li-wen WANG Xiu-zhen HUNG Jing-feng Institute of Agricultural Remote Sensing & Information Application Zhejiang University Key Laboratory of Environmental Remediation and Ecological Health Ministry of Education/College of Natural Resources and Environmental Science Zhejiang University Institute of Remote Sensing and Earth Sciences Hangzhou Normal University The Provinical Key Laboratories of Agricultural Remote Sensing and Information System Zhejiang Province

The normalized difference vegetation index （NDVI） has proven to be typically employed to assess terrestrial vegetation conditions. However, one limitation of ndvi for drought monitoring is the apparent time lag between rainfall deficit and ndvi response. To better understand this relationship, time series ndvi （2000-2010） during the growing season in Sichuan Province and Chongqing City were analyzed. The vegetation condition index （VCI） was used to construct a new drought index, time-integrated vegetation condition index （TIVCI）, and was then compared with meteorological drought indices-standardized precipitation index （SPI）, a multiple-time scale meteorological-drought index based on precipitation, to examine the sensitivity on droughts. Our research findings indicate the followings：（1） farmland ndvi sensitivity to precipitation in study area has a time lag of 16-24 d, and it maximally responds to the temperature with a lag of about 16 d. （2） We applied the approach to Sichuan Province and Chongqing City for extreme drought monitoring in 2006 and 2003, and the results show that the monitoring results from TIVCI are closer to the published China agricultural statistical data than VCI. Compared to VCI, the best results from TIVCI3 were found with the relative errors of -4.5 and 6.36% in 2006 for drought affected area and drought disaster area respectively, and 5.11 and -5.95% in 2003. （3） Compared to VCI, TIVCI has better correlation with the SPI, which indicates the lag and cumulative effects of precipitation on vegetation. Our finding proved that TIVCI is an effective indicator of drought detection when the time lag effects between ndvi and climate factors are taken into consideration.

关键词： time-integrated vegetation condition index （TIVCI） time lag normalized difference vegetation index （NDVI） drought monitor standardized precipitation index （SPI）

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Spatial pattern of impervious surfaces and their impacts on land surface temperature in Beijing,China

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Journal of Environmental Sciences 2007年第2期19卷 250-256页

作者： XIAO Rong-bo OUYANG Zhi-yun ZHENG Hua LI Wei-feng SCHIENKE Erich W WANG Xiao-ke State Key Lab of Urban and Regional Ecology Environmental Sciences Chinese Academy of Sciences Belting 100085 China Department of Science and Technology Studies Rensselaer Polytechnic Institute Troy NY 12180 USA

Land surface temperature （LST）, which is heavily influenced by urban surface structures, is a significant parameter in urban environmental analysis. This study examined the effect impervious surfaces （IS） spatial patterns have on LST in Beijing, China. A classification and regression tree model （CART） was adopted to estimate IS as a continuous variable using Landsat images from two seasons combined with QuickBird. LST was retrieved from the Landsat Thematic Mapper （TM） image to examine the relationships between IS and LST. The results revealed that CART was capable of consistently predicting LST with acceptable accuracy （correlation coefficient of 0.94 and the average error of 8.59%）. Spatial patterns of IS exhibited changing gradients across the various urban-rural transects, with LST values showing a concentric shape that increased as you moved from the outskirts towards the downtown areas. Transect analysis also indicated that the changes in both IS and LST patterns were similar at various resolution levels, which suggests a distinct linear relationship between them. Results of correlation analysis further showed that IS tended to be positively correlated with LST, and that the correlation coefficients increased from 0.807 to 0.925 with increases in IS pixel size. The findings identified in this study provide a theoretical basis for improving urban planning efforts to lessen urban temperatures and thus dampen urban heat island effects.

关键词： urban heat islands urban land cover normalized difference vegetation index （NDVI） climate mitigation regression tree

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Multi-Temporal Detection of Rice Phenological Stages Using Canopy Spectrum

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Rice science 2014年第2期21卷 108-115页

作者： WANG Lin ZHANG Fu-cun JING Yuan-shu JIANG Xiao-dong YANG Shen-bin HAN Xiao-mei Jiangsu Key Laboratory of Agricultural Meteorology College of Applied MeteorologyNanjing University of Information Science& Technology

Information on rice phenology is essential for yield estimation and crop management. To test the ability of remote sensing in detecting multiple phenological stages, paddy rice canopy spectrum was measured by a hand-held radiometer. normalized difference vegetation index （NDVI） was calculated from spectrum, and the slope of ndvi was obtained as its difference. We evaluated the response of ndvi and its slope to rice growth with a comparison of two late-season rice cultivars. The results showed that ndvi and its slope curves had distinct variation corresponding to rice development and they could be used as cultivar-independent phenological indicators. The dates of flooding and transplanting, tillering, panicle development, heading and flowering, maturity, harvest stages, and even field management practices, could be deduced from these indicators. ‘ndvi ≤ 0’ could be used as a single threshold for the detection of flooding and transplanting. The largest spike in the curve of the ndvi slope indicated the duration of tillering stage. The next spike corresponded to panicle development. The heading and flowering stage was characterized by the maximum ndvi and the change of ndvi slope from positive to negative. At the maturity stage, ndvi decreased continuously, and its slope fluctuated just below zero. When rice grains were completely mature and ready for harvest, ndvi decline was accelerated. At harvest, ndvi slope reached its minimum value. The distinction between heading and maturity stages was obscure, most likely due to ndvi saturation at high biomass. The study might provide references for paddy rice phenology determination through remote sensing images.

关键词： ground remote sensing normalized difference vegetation index （NDVI） ndvi slop ricephenology

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The aboveground biomass of desert steppe and its spatiotemporal variation in western Inner Mongolia

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Research in Cold and Arid Regions 2013年第3期5卷 339-346页

作者： Tian Gao Bin Xu XiuChun Yang YunXiang Jin HaiLong Ma JinYa Li HaiDa Yu Key Laboratory of Agri-informatics Ministry of Agriculture/Institute of Agricultural Resources and Regional Planning Chinese Academy of Agricultural Sciences

A precise understanding of the aboveground biomass of desert steppe and its spatio-temporal variation is important to understand how arid ecosystems respond to climate change and to ensure that scarce grassland resources are used rationally. On the basis of 756 ground survey quadrats sampled in western Inner Mongolia steppe in 2005-2011 and remote sensing data from the Moderate Resolu- tion Imaging Spectroradiometer （MODIS）--the normalized difference vegetation index （NDVI） dataset for the period of 2001-2011--we developed a statistical model to estimate the aboveground biomass of the desert steppe and further explored the rela- tionships between aboveground biomass and climate factors. The conclusions are as follows：（1） the aboveground biomass of the steppe in the research area was 5.27 Tg （1 Tg=1012 g） on average over 11 years; between 2001 and 2011, the aboveground biomass of the western Inner Mongolia steppe exhibited fluctuations, with no significant trend over time; （2） the aboveground biomass of the steppe in the research area exhibits distinct spatial variation and generally decreases gradually from southeast to northwest; and （3） the important factor causing intemnnual variations in aboveground biomass is precipitation during the period from January to July, but we did not find a significant relationship between the aboveground biomass and the corresponding temperature changes. The precipitation in this period is also an important factor influencing the spatial distribution of aboveground biomass （R2=0.39, P〈0.001）, while the temperature might be a minor factor （R2=0.12, P〈0.01 ）. The uncertainties in our estimate are primarily due to uncertainty in converting the fresh grass yield estimates to dry weight, underestimates of the biomass of shrubs, and error in remote sensing dataset.

关键词： Inner Mongolia desert steppe normalized difference vegetation index （NDVI） aboveground biomass climate factors

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