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Simple method for extracting the seasonal signals of photochemical reflectance index and normalized difference vegetation index measured using a spectral reflectance sensor

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Journal of Integrative Agriculture 2021年第7期20卷 1969-1986页

作者： Jae-Hyun RYU Dohyeok OH Jaeil CHO Department of Applied Plant Science Chonnam National UniversityGwangju 61186Republic of Korea

A spectral reflectance sensor(SRS)fixed on the near-surface ground was developed to support the continuous monitoring of vegetation indices such as the normalized difference vegetation index(NDVI)and photochemical reflectance index(PRI).NDVI is useful for indicating crop growth/phenology,whereas PRI was developed for observing physiological conditions.Thus,the seasonal change patterns of NDVI and PRI are two valuable pieces of information in a crop-monitoring system.However,capturing the seasonal patterns is considered challenging because the vegetation index values estimated by the reflection from vegetation are often governed by meteorological conditions,such as solar irradiance and precipitation.Further,unlike growth/phenology,the physiological condition has diurnal changes as well as seasonal characteristics.This study proposed a novel filtering method for extracting the seasonal signals of SRS-based NDVI and PRI in paddy rice,barley,and garlic.First,the measurement accuracy of SRSs was compared with handheld spectrometers,and the R^(2)values between the two devices were 0.96 and 0.81 for NDVI and PRI,respectively.Second,the experimental study of threshold criteria with respect to meteorological variables(i.e.,insolation,cloudiness,sunshine duration,and precipitation)was conducted,and sunshine duration was the most useful one for excluding distorted values of the vegetation indices.After data processing based on sunshine duration,the R^(2)values between the measured vegetation indices and the extracted seasonal signals of vegetation indices increased by approximately 0.002–0.004(NDVI)and 0.065–0.298(PRI)on the three crops,and the seasonal signals of vegetation indices became noticeably improved.This method will contribute to an agricultural monitoring system by identifying the seasonal changes in crop growth and physiological conditions.

关键词： photochemical reflectance index normalized difference vegetation index vegetation remote sensing spectral reflectance sensor

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Bi-directional normalized difference vegetation index: concept and application

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Progress in Natural Science:Materials International 2002年第2期 37-41页

作者： LI Xiaowen , GAO Feng , WANG Jindi , YANG Hua, A. STRAHLER and C. SCHAAF( Research Center for Remote Sensing and Department of Geography, Beijing Normal University, Beijing 100875, China Department of Geography and Center for Remote Sensing, Boston University, Boston MA02215, USA) Research Center for Remote Sensing and Department of Geography，Beijing Normal University，Beijing 100875，China Department of Geography and Center for Remote Sensing，Boston University，Boston MA02215，USA Department of Geography and Center for Remote Sensing，Boston University，Boston MA02215，USA Research Center for Remote Sensing and Department of Geography，Beijing Normal University，Beijing 100875，China

The data products of land surface bi-directional reflectance distribution function (BRDF) from the space-borne Polarization and Directionality of the Earth Reflectance (POLDER) of France and the Moderate Resolution Imaging Spectroradiometer (MODIS) of USA are available recently, but the atmospheric correction for meeting the requirement of quantitative remote sensing is still a very difficult problem. This paper presents a concept: bi-directional normalized difference vegetation index (Bi-NDVI), in order to consider simultaneously the effects of both land surface BRDF and atmospheric path scattering. An atmospheric quality index is thus defined for satellite multi-angular observations. The quality of MODIS/BRDF data products can be improved notably through iterative inversion weighed by this index.

关键词： bi-directional reflectance normalized difference vegetation index atmospheric correction.

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Climate-vegetation Coverage Interactions in the Hengduan Mountains Area, Southeastern Tibetan Plateau, and Their Downstream Effects

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Advances in Atmospheric Sciences 2024年第4期41卷 701-716页

作者： Congxi FANG Jinlei CHEN Chaojun OUYANG Lu WANG Changfeng SUN Quan ZHANG Jun WEN Key Laboratory of Mountain Hazards and Earth Surface Processes Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu 610299China State Key Laboratory of Cryospheric Science Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China College of Urban and Environmental Sciences Peking UniversityBeijing 100871China Institute of Global Environmental Change Xi’an Jiaotong UniversityXi’an 710049China The State Key Laboratory of Loess and Quaternary Geology Institute of Earth EnvironmentChinese Academy of SciencesXi’an 710061China College of Atmospheric Sciences Chengdu University of Information TechnologyChengdu 610225China

Little is known about the mechanism of climate-vegetation coverage coupled changes in the Tibetan Plateau(TP)region,which is the most climatically sensitive and ecologically fragile region with the highest terrain in the world.This study,using multisource datasets(including satellite data and meteorological observations and reanalysis data)revealed the mutual feedback mechanisms between changes in climate(temperature and precipitation)and vegetation coverage in recent decades in the Hengduan Mountains Area(HMA)of the southeastern TP and their influences on climate in the downstream region,the Sichuan Basin(SCB).There is mutual facilitation between rising air temperature and increasing vegetation coverage in the HMA,which is most significant during winter,and then during spring,but insignificant during summer and autumn.Rising temperature significantly enhances local vegetation coverage,and vegetation greening in turn heats the atmosphere via enhancing net heat flux from the surface to the atmosphere.The atmospheric heating anomaly over the HMA thickens the atmospheric column and increases upper air pressure.The high pressure anomaly disperses downstream via the westerly flow,expands across the SCB,and eventually increases the SCB temperature.This effect lasts from winter to the following spring,which may cause the maximum increasing trend of the SCB temperature and vegetation coverage in spring.These results are helpful for estimating future trends in climate and eco-environmental variations in the HMA and SCB under warming scenarios,as well as seasonal forecasting based on the connection between the HMA eco-environment and SCB climate.

关键词： Hengduan Mountains Area normalized difference vegetation index climate change net heat flux downstream effects

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Bofedal response to climate variability, local management, and water extraction: A case study of Chucuyo, Northern Chile

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Journal of Mountain Science 2022年第1期19卷 241-252页

作者： URIBE-ÁLVAREZ Monserrat C PRIETO Manuel MESEGUER-RUIZ Oliver Departamento de Ciencias Históricas y Geográficas Universidad de TarapacáArica 1010069Chile Departamento de Ciencias Históricas y Geográficas Universidad de TarapacáIquique 1101783Chile

Andean high-altitude wetlands are important ecosystems that serve a range of socialecological functions. In the Andes, bofedales, a specific type of peat-producing wetland, are essential for the sustainability of mountain ecosystems and indigenous pastoralist communities. The Chucuyo bofedal in northern Chile is affected by climatic variability and water extraction for agricultural uses via the Lauca canal. Herders in the local community also actively manage this wetland according to their traditional ecological knowledge to ensure permanent fodder for their animals. In this article, we analyze the annual behavior of the Chucuyo bofedal after the wet season. Based on precipitation data, extracted water flows, vegetation vigor from satellite images, and an ethnographic approach, we determined that the bofedal’s productivity was negatively correlated with the amount of precipitation and positively correlated with the surface area of the wetland. However, water extraction via the Lauca channel had no significant relationship with either surface area or vegetation vigor. We identify community practices and traditional ecological knowledge as key elements in the maintenance of these ecosystems. This situation is critical in the context of an aging population and the current pattern of migration out of the region to urban areas. The results provide substantial empirical evidence for future decision-making regarding the conservation of these ecosystems.

关键词： Atacama Bofedales Indigenous people Lauca canal normalized difference vegetation index

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Seasonal Responses of Net Primary Productivity of vegetation to Phenological Dynamics in the Loess Plateau, China

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Chinese Geographical Science 2022年第2期32卷 340-357页

作者： HAN Hongzhu BAI Jianjun MA Gao YAN Jianwu WANG Xiaohui TA Zhijie WANG Pengtao School of Tourism&Research Institute of Human Geography Xi'an International Studies UniversityXi'an 710128China School of Geography and Tourism Shaanxi Normal UniversityXi'an 710119China China Academy of Space Technology-Xi'an Xi'an 710000China School of Humanities and Social Sciences Xi'an University of Posts and TelecommunicationsXi'an 710121China

With global warming, the great changes in the patterns of plant growth have occurred. The conditions in early spring and late autumn have changed the process of vegetation photosynthesis, which are expected to have a significant impact on net primary productivity(NPP) and affect the global carbon cycle. Currently, the seasonal response characteristics of NPP to phenological changes in dryland ecosystems are still not well defined. This article calibrated and analyzed the normalized difference vegetation index(NDVI)time series of Advanced Very-High-Resolution Radiometer(AVHRR) data from 1982 to 2015 in the Loess Plateau, China. The spatial and temporal distributions of vegetation phenology and NPP in the Loess Plateau under semihumid and semiarid conditions were investigated. The seasonal variation in the NPP response to vegetation phenology under the climate change was also analyzed. The results showed that, different from the northern forest, there was distinct spatial heterogeneity in the effect of climate change on the dynamic change in vegetation growth in the Loess Plateau: 1) an advance of the start of the growing season(SOS) and a delay of the end of the growing season(EOS) significantly increased the NPP in spring and autumn, respectively, in the humid southeast;2) in the arid northwest, the NPP did not significantly increase in spring and autumn but significantly decreased in summer.

关键词： climate change normalized difference vegetation index phenology net primary productivity Loess Plateau,China

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Monitoring the abundance of saproxylic red-listed species in a managed beech forest by landsat temporal metrics

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Forest Ecosystems 2022年第4期9卷 529-539页

作者： Francesco Parisi Elia Vangi Saverio Francini Gherardo Chirici Davide Travaglini Marco Marchetti Roberto Tognetti GeoLAB-Laboratorio di Geomatica Forestale Dipartimento di Scienze e Tecnologie AgrarieAlimentariAmbientali e ForestaliUniversita degli Studi di FirenzeVia San Bonaventura 1350145FirenzeItaly Dipartimento di Bioscienze e Territorio Universita degli Studi del MoliseContrada Fonte Lappone86090 PescheIserniaItaly Fondazione per il Futuro delle Citta FirenzeItaly Dipartimento Agricoltura Ambiente e AlimentiUniversita degli Studi del MoliseVia De SanctisI-86100CampobassoItaly

Background:Rapid climate changes lead to an increase in forest disturbance,which in turn lead to growing concerns for biodiversity.While saproxylic beetles are relevant indicators for studying different aspects of biodiversity,most are smaller than 2 mm and difficult to sample.This,together with a high number of species and trophic roles,make their study remarkably challenging,time-consuming,and expensive.The Landsat mission provides data since 1984 and represents a powerful tool in this scenario.While we believe that remote sensing data cannot replace on-site sampling and analysis,in this study we aim to prove that the Landsat Time Series(TS)may support the identification of insects’hotspots and consequently guide the selection of areas where to concentrate field analysis.Methods:With this aim,we constructed a Landsat-derived NDVI TS(1984–2020)and we summarised the NDVI trend over time by calculating eight Temporal Metrics(TMs)among which four resulted particularly successful in predicting the amount of saproxylic insects:(i)the slope of the regression line obtained by linear interpolating the NDVI values over time;(ii)the Root Mean Square Error(RMSE)between the regression line and the NDVI TS;(iii)the median,and the(iv)minimum values of the NDVI TS.The study area consists of four monitoring sectors in a Mediterranean-managed beech forest located in the Apennines(Molise,Italy),where 60 window flight traps for flying beetles were installed.First,the saproxylic beetle's biodiversities of monitoring sectors were quantified in terms of species richness and alpha-diversity.Second,the capability of TMs in predicting the richness of saproxylic beetles family and trophic categories was assessed in terms of Pearson's product-moment correlation.Results:The alpha diversity and species richness analysis indicate dissimilarities across the four monitored sectors(Shannon and Simpson's index ranging between 0.67 to 2.31 and 0.69 to 0.88,respectively),with Landsat TS resulting in effective predictors for estimating saproxylic b

关键词： Alpha-diversity Beetle assemblages Biodiversity hotspots normalized difference vegetation index Temporal metrics

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Enhanced soil moisture improves vegetation growth in an arid grassland of Inner Mongolia Autonomous Region, China

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Journal of Arid Land 2023年第7期15卷 871-885页

作者： ZHANG Hui Giri R KATTEL WANG Guojie CHUAI Xiaowei ZHANG Yuyang MIAO Lijuan School of Geographical Sciences Nanjing University of Information Science&TechnologyNanjing 210044China State Key Laboratory of Remote Sensing Science Aerospace Information Research InstituteChinese Academy of SciencesBeijing 100094China Department of Infrastructure Engineering the University of MelbourneMelbourne 3010Australia School of Geography&Ocean Science Nanjing UniversityNanjing 210093China

Climate change impacts on grasslands that cover a quarter of the global land area, have become unprecedented during the 21~(st) century. One of the important ecological realms, arid grasslands of northern China, which occupy more than 70% of the region's land area. However, the impact of climate change on vegetation growth in these arid grasslands is not consistent and lacks corresponding quantitative research. In this study, NDVI(normalized difference vegetation index) and climate factors including temperature, precipitation, solar radiation, soil moisture, and meteorological drought were analyzed to explore the determinants of changes in grassland greenness in Inner Mongolia Autonomous Region(northern China) during 1982–2016. The results showed that grasslands in Inner Mongolia witnessed an obvious trend of seasonal greening during the study period. Two prominent climatic factors,precipitation and soil moisture accounted for approximately 33% and 27% of grassland NDVI trends in the region based on multiple linear regression and boosted regression tree methods. This finding highlights the impact of water constraints to vegetation growth in Inner Mongolia's grasslands. The dominant role of precipitation in regulating grassland NDVI trends in Inner Mongolia significantly weakened from 1982 to 1996, and the role of soil moisture strengthened after 1996. Our findings emphasize the enhanced importance of soil moisture in driving vegetation growth in arid grasslands of Inner Mongolia, which should be thoroughly investigated in the future.

关键词： grassland growth normalized difference vegetation index climate change soil moisture Inner Mongolia

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Identification and spatial pattern analysis of alpine timberline by remote sensing methods in Yarlung Zangpo Grand Canyon

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Journal of Mountain Science 2021年第9期18卷 2304-2314页

作者： ZHU Bei WANG Shi-yan SU Wei CHEN Kai-qi LIU Chang DU Yan-liang WANG Liang HAN Zhen ZOU Jiang-xiang State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin Beijing 100038China China Institute of Water Resources and Hydropower Research Beijing 100038China College of Hebei Agricultural University Huanghua 061100China Appraisal Center for Environment and Engineering Ministry of Environmental ProtectionBeijing 100012China

As an important ecotone,the alpine timberline is the boundary between closed-canopy montane forest and alpine vegetation,and is highly sensitive to global and regional climate changes.We provided a way to identify and extract the alpine timberline in Yarlung Zangpo Grand Canyon Nature Reserve by using remote sensing data and spatial analysis based on land use/land cover classification and NDVI distribution characteristics.Combining DEM data,the influence of slope and aspect on the distribution of alpine timberline was explored.The results showed that the alpine timberline in Yarlung Zangpo Grand Canyon is transitional timberline,with the upper boundary approximately distributed at the elevation of 3422-4373 m,the lower boundary at approximately 3270-4164 m,with a width of about 110-280 m.Alpine timberline was mainly distributed on steep and very steep slopes ranging from 25°to 45°.The maximum elevation of both the upper and lower boundaries occurred on steep slopes.The distribution of alpine timberline varies with aspects,with sunny slopes having a higher boundary than shady slopes.

关键词： Alpine timberline Aspect normalized difference vegetation index Remote sensing classification Slope

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Changing Spring Phenology Dates in the Three-Rivers Headwater Region of the Tibetan Plateau during 1960–2013

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Advances in Atmospheric Sciences 2018年第1期35卷 116-126页

作者： Shuang YU Jiangjiang XIA Zhongwei YAN Kun YANG Key Laboratory.of Regional Climate-Environment for East Asia Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Key Laboratory of Tibetan Environment Changes and Land Surface Processes Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100107China University of Chinese Academy of Sciences Beijing 100049China

The variation of the vegetation growing season in the Three-Rivers Headwater Region of the Tibetan Plateau has recently become a controversial topic. One issue is that the estimated local trend in the start of the vegetation growing season(SOS)based on remote sensing data is easily affected by outliers because this data series is short. In this study, we determine that the spring minimum temperature is the most influential factor for SOS. The significant negative linear relationship between the two variables in the region is evaluated using Moderate Resolution Imaging Spectroradiometer–normalized difference vegetation index data for 2000–13. We then reconstruct the SOS time series based on the temperature data for 1960–2013.The regional mean SOS shows an advancing trend of 1.42 d(10 yr)during 1960–2013, with the SOS occurring on the 160th and 151st days in 1960 and 2013, respectively. The advancing trend enhances to 6.04 d(10 yr)during the past 14 years. The spatiotemporal variations of the reconstructed SOS data are similar to those deduced from remote sensing data during the past 14 years. The latter exhibit an even larger regional mean trend of SOS [7.98 d(10 yr)] during 2000–13. The Arctic Oscillation is found to have significantly influenced the changing SOS, especially for the eastern part of the region,during 2000–13.

关键词： start of growing season normalized difference vegetation index spring minimum temperature Three-Rivers Headwater Region Arctic Oscillation

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Estimation of net primary productivity and its driving factors in the Ili River Valley,China

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Journal of Arid Land 2018年第5期10卷 781-793页

作者： JIAO Wei CHEN Yaning LI Weihong ZHU Chenggang LI Zhi State Key Laboratory of Desert and Oasis Ecology Xinjiang Institute of Ecology and Geography Chinese Academy of Sciences School of Remote Sensing and Information Engineering Wuhan University

Net primary productivity（NPP）, as an important variable and ecological indicator in grassland ecosystems, can reflect environmental change and the carbon budget level. The Ili River Valley is a wetland nestled in the hinterland of the Eurasian continent, which responds sensitively to the global climate change. Understanding carbon budget and their responses to climate change in the ecosystem of Ili River Valley has a significant effect on the adaptability of future climate change and sustainable development. In this study, we calculated the NPP and analyzed its spatio-temporal pattern of the Ili River Valley during the period 2000–2014 using the normalized difference vegetation index（NDVI） and an improved Carnegie-Ames-Stanford（CASA） model. Results indicate that validation showed a good performance of CASA over the study region, with an overall coefficient of determination（R2） of 0.65 and root mean square error（RMSE） of 20.86 g C/（m^2·a）. Temporally, annual NPP of the Ili River Valley was 599.19 g C/（m^2·a） and showed a decreasing trend from 2000 to 2014, with an annual decrease rate of –3.51 g C/（m^2·a）. However, the spatial variation was not consistent, in which 55.69% of the areas showed a decreasing tendency, 12.60% of the areas remained relatively stable and 31.71% appeared an increasing tendency. In addition, the decreasing trends in NPP were not continuous throughout the 15-year period, which was likely being caused by a shift in climate conditions. Precipitation was found to be the dominant climatic factor that controlled the inter-annual variability in NPP. Furthermore, the correlations between NPP and climate factors differed along the vertical zonal. In the medium-high altitudes of the Ili River Valley, the NPP was positively correlated to precipitation and negatively correlated to temperature and net radiation. In the low-altitude valley and high-altitude mountain areas, the NPP showed a negative correlation with precipitation and a weakly positive correlation with temperature and net radiation. The r

关键词： net primary productivity Carnegie-Ames-Stanford model spatio-temporal pattern climatic impacts precipitation normalized difference vegetation index

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