【目的】通过日光诱导叶绿素荧光(solar induced fluorescence,SIF)指标,探明植被光合能力与空气负离子(negative air ion,NAI)的关系,揭示森林植被对NAI的作用机制。【方法】以北方典型针叶树种侧柏(Platycladus orientalis)为研究对象...【目的】通过日光诱导叶绿素荧光(solar induced fluorescence,SIF)指标,探明植被光合能力与空气负离子(negative air ion,NAI)的关系,揭示森林植被对NAI的作用机制。【方法】以北方典型针叶树种侧柏(Platycladus orientalis)为研究对象,基于主要生长季节叶面积指数相对稳定时期同步观测得到的冠层NAI、SIF及光合有效辐射(photosynthetically active radiation,PAR)强度等数据,分析不同时间尺度、日内不同时间段及不同强度PAR条件下NAI与SIF的关系。【结果】冠层NAI与SIF的时间变化趋势一致,SIF能够很好地追踪NAI的季节变化;二者之间存在显著的线性正相关关系,日尺度、小时尺度上二者决定系数R2为分别为0.596、0.474;不同光照强度条件下,冠层NAI与SIF的散点出现明显分层现象,冠层NAI和SIF之间相关性强度在高PAR条件下显著高于低PAR条件,二者的决定系数R2分别为0.483、0.456。【结论】当植被光合作用过程完全激活时,冠层SIF能够更准确地表征NAI的变化过程,对进一步精准评估森林植被对NAI的贡献潜力、丰富森林生态服务功能评估内容具有指导意义。展开更多
The first Chinese Carbon Dioxide Observation Satellite Mission(TanSat), which was launched on December 21, 2016, is intended to measure atmospheric CO_2 concentration.The high spectral resolution(0.044 nm) and high SN...The first Chinese Carbon Dioxide Observation Satellite Mission(TanSat), which was launched on December 21, 2016, is intended to measure atmospheric CO_2 concentration.The high spectral resolution(0.044 nm) and high SNR(360 at 15.2 mW m^(-1) sr^(-1) nm^(-1)) measurements in the region of the O_2-A band of the Atmospheric Carbon dioxide Grating Spectroradiometer(AGCS) module onboard TanSat make it possible to retrieve solar-induced chlorophyll fluorescence(SIF) from TanSat observations at the global scale.This paper aims to explore the potential of the TanSat data for global SIF retrieval.A singular vector decomposition(SVD) statistical method was employed to retrieve SIF using radiance over a micro spectral window(～2 nm) around the Fe Fraunhofer lines(centered at 758.8 nm).The global SIF at 758.8 nm was successfully retrieved with a low residual error of 0.03 mW m^(-1) sr^(-1) nm^(-1).The results show that the spatial and temporal patterns of the retrieved SIF agree well with the global terrestrial vegetation pattern.The monthly SIF products retrieved from the TanSat data were compared with other remote sensing datasets, including OCO-2 SIF, MODIS NDVI, EVI and GPP.The overall consistency between TanSat and OCO-2 SIF products(R^2= 0.86) and the consistency of the spatial patterns and temporal variations between the TanSat SIF and MODIS vegetation indices and GPP enhance our confidence in the potential and feasibility of TanSat data for SIF retrieval.TanSat, therefore, provides a new opportunity for global sampling of SIF at fine spatial resolution(2 km × 2 km), thus improving photosynthesis observations from space.展开更多
为实现冬小麦条锈病早期探测、提高冬小麦产量和品质,研究了日光诱导叶绿素荧光(Solar-induced chlorophyll fluorescence,SIF)对冬小麦条锈病早期探测的可行性。基于3波段夫琅和费暗线(3-band Fraunhofer line discrimination,3FLD)和...为实现冬小麦条锈病早期探测、提高冬小麦产量和品质,研究了日光诱导叶绿素荧光(Solar-induced chlorophyll fluorescence,SIF)对冬小麦条锈病早期探测的可行性。基于3波段夫琅和费暗线(3-band Fraunhofer line discrimination,3FLD)和反射率荧光指数2种方法提取了冠层SIF数据,计算了对小麦条锈病敏感的光谱指数(Spectral index,SI),通过相关性分析优选了遥感探测小麦条锈病早期的特征参量,利用偏最小二乘(Partial least squares,PLS)算法构建冬小麦条锈病早期光谱探测模型。研究结果表明:O2-A波段的荧光强度(SIF-A)以及反射率荧光指数ρ440/ρ690、ρ675ρ690/ρ2683、ρ690/ρ655、ρ690/ρ600、DλP/D744、D705/D722均与小麦条锈病早期病情指数(Disease index,DI)达到了极显著相关,相关系数分别为-0.793、-0.523、-0.539、-0.497、0.541、0.446、0.490,可作为冬小麦条锈病早期光谱探测的荧光特征参量;基于3组SIF数据构建的PLS-SIF检验模型的决定系数分别为0.801、0.772、0.807,均方根误差分别为3.3%、3.1%、3.2%,较反射率光谱指数构建的SI-PLS模型决定系数至少提高了27%,均方根误差至少减少了24%。因此,冠层SIF数据更适于冬小麦条锈病的早期探测。本研究结果对及时进行冬小麦条锈病防控具有重要应用价值,可为利用卫星荧光遥感数据对小麦条锈病早期大面积、无损探测提供参考依据。展开更多
Background:Vegetation phenology research has largely focused on temperate deciduous forests,thus limiting our understanding of the response of evergreen vegetation to climate change in tropical and subtropical regions...Background:Vegetation phenology research has largely focused on temperate deciduous forests,thus limiting our understanding of the response of evergreen vegetation to climate change in tropical and subtropical regions.Results:Using satellite solar-induced chlorophyll fluorescence(SIF)and MODIS enhanced vegetation index(EVI)data,we applied two methods to evaluate temporal and spatial patterns of the end of the growing season(EGS)in subtropical vegetation in China,and analyze the dependence of EGS on preseason maximum and minimum temperatures as well as cumulative precipitation.Our results indicated that the averaged EGS derived from the SIF and EVI based on the two methods(dynamic threshold method and derivative method)was later than that derived from gross primary productivity(GPP)based on the eddy covariance technique,and the time-lag for EGSsif and EGSevi was approximately 2 weeks and 4 weeks,respectively.We found that EGS was positively correlated with preseason minimum temperature and cumulative precipitation(accounting for more than 73%and 62%of the study areas,respectively),but negatively correlated with preseason maximum temperature(accounting for more than 59%of the study areas).In addition,EGS was more sensitive to the changes in the preseason minimum temperature than to other climatic factors,and an increase in the preseason minimum temperature significantly delayed the EGS in evergreen forests,shrub and grassland.Conclusions:Our results indicated that the SIF outperformed traditional vegetation indices in capturing the autumn photosynthetic phenology of evergreen forest in the subtropical region of China.We found that minimum temperature plays a significant role in determining autumn photosynthetic phenology in the study region.These findings contribute to improving our understanding of the response of the EGS to climate change in subtropical vegetation of China,and provide a new perspective for accurately evaluating the role played by evergreen vegetation in the regional carbon budget.展开更多
文摘【目的】通过日光诱导叶绿素荧光(solar induced fluorescence,SIF)指标,探明植被光合能力与空气负离子(negative air ion,NAI)的关系,揭示森林植被对NAI的作用机制。【方法】以北方典型针叶树种侧柏(Platycladus orientalis)为研究对象,基于主要生长季节叶面积指数相对稳定时期同步观测得到的冠层NAI、SIF及光合有效辐射(photosynthetically active radiation,PAR)强度等数据,分析不同时间尺度、日内不同时间段及不同强度PAR条件下NAI与SIF的关系。【结果】冠层NAI与SIF的时间变化趋势一致,SIF能够很好地追踪NAI的季节变化;二者之间存在显著的线性正相关关系,日尺度、小时尺度上二者决定系数R2为分别为0.596、0.474;不同光照强度条件下,冠层NAI与SIF的散点出现明显分层现象,冠层NAI和SIF之间相关性强度在高PAR条件下显著高于低PAR条件,二者的决定系数R2分别为0.483、0.456。【结论】当植被光合作用过程完全激活时,冠层SIF能够更准确地表征NAI的变化过程,对进一步精准评估森林植被对NAI的贡献潜力、丰富森林生态服务功能评估内容具有指导意义。
基金supported by the National Key Research and Development Program of China (2017YFA0603001)Scientific Research Satellite Engineering of Civil Space Infrastructure Projectthe National Natural Science Foundation of China (41671349, 41701396)
文摘The first Chinese Carbon Dioxide Observation Satellite Mission(TanSat), which was launched on December 21, 2016, is intended to measure atmospheric CO_2 concentration.The high spectral resolution(0.044 nm) and high SNR(360 at 15.2 mW m^(-1) sr^(-1) nm^(-1)) measurements in the region of the O_2-A band of the Atmospheric Carbon dioxide Grating Spectroradiometer(AGCS) module onboard TanSat make it possible to retrieve solar-induced chlorophyll fluorescence(SIF) from TanSat observations at the global scale.This paper aims to explore the potential of the TanSat data for global SIF retrieval.A singular vector decomposition(SVD) statistical method was employed to retrieve SIF using radiance over a micro spectral window(～2 nm) around the Fe Fraunhofer lines(centered at 758.8 nm).The global SIF at 758.8 nm was successfully retrieved with a low residual error of 0.03 mW m^(-1) sr^(-1) nm^(-1).The results show that the spatial and temporal patterns of the retrieved SIF agree well with the global terrestrial vegetation pattern.The monthly SIF products retrieved from the TanSat data were compared with other remote sensing datasets, including OCO-2 SIF, MODIS NDVI, EVI and GPP.The overall consistency between TanSat and OCO-2 SIF products(R^2= 0.86) and the consistency of the spatial patterns and temporal variations between the TanSat SIF and MODIS vegetation indices and GPP enhance our confidence in the potential and feasibility of TanSat data for SIF retrieval.TanSat, therefore, provides a new opportunity for global sampling of SIF at fine spatial resolution(2 km × 2 km), thus improving photosynthesis observations from space.
文摘为实现冬小麦条锈病早期探测、提高冬小麦产量和品质,研究了日光诱导叶绿素荧光(Solar-induced chlorophyll fluorescence,SIF)对冬小麦条锈病早期探测的可行性。基于3波段夫琅和费暗线(3-band Fraunhofer line discrimination,3FLD)和反射率荧光指数2种方法提取了冠层SIF数据,计算了对小麦条锈病敏感的光谱指数(Spectral index,SI),通过相关性分析优选了遥感探测小麦条锈病早期的特征参量,利用偏最小二乘(Partial least squares,PLS)算法构建冬小麦条锈病早期光谱探测模型。研究结果表明:O2-A波段的荧光强度(SIF-A)以及反射率荧光指数ρ440/ρ690、ρ675ρ690/ρ2683、ρ690/ρ655、ρ690/ρ600、DλP/D744、D705/D722均与小麦条锈病早期病情指数(Disease index,DI)达到了极显著相关,相关系数分别为-0.793、-0.523、-0.539、-0.497、0.541、0.446、0.490,可作为冬小麦条锈病早期光谱探测的荧光特征参量;基于3组SIF数据构建的PLS-SIF检验模型的决定系数分别为0.801、0.772、0.807,均方根误差分别为3.3%、3.1%、3.2%,较反射率光谱指数构建的SI-PLS模型决定系数至少提高了27%,均方根误差至少减少了24%。因此,冠层SIF数据更适于冬小麦条锈病的早期探测。本研究结果对及时进行冬小麦条锈病防控具有重要应用价值,可为利用卫星荧光遥感数据对小麦条锈病早期大面积、无损探测提供参考依据。
基金supported by the National Natural Science Foundation of China(Grant No.41901117)Natural Science Foundation of Hunan Province,China(Grant No.2020JJ5362)+1 种基金the Outstanding Youth Project of Hu’nan Provincial Education Department(No.18B001)the Natural Sciences and Engineering Research Council of Canada(NSERC)Discover Grant.
文摘Background:Vegetation phenology research has largely focused on temperate deciduous forests,thus limiting our understanding of the response of evergreen vegetation to climate change in tropical and subtropical regions.Results:Using satellite solar-induced chlorophyll fluorescence(SIF)and MODIS enhanced vegetation index(EVI)data,we applied two methods to evaluate temporal and spatial patterns of the end of the growing season(EGS)in subtropical vegetation in China,and analyze the dependence of EGS on preseason maximum and minimum temperatures as well as cumulative precipitation.Our results indicated that the averaged EGS derived from the SIF and EVI based on the two methods(dynamic threshold method and derivative method)was later than that derived from gross primary productivity(GPP)based on the eddy covariance technique,and the time-lag for EGSsif and EGSevi was approximately 2 weeks and 4 weeks,respectively.We found that EGS was positively correlated with preseason minimum temperature and cumulative precipitation(accounting for more than 73%and 62%of the study areas,respectively),but negatively correlated with preseason maximum temperature(accounting for more than 59%of the study areas).In addition,EGS was more sensitive to the changes in the preseason minimum temperature than to other climatic factors,and an increase in the preseason minimum temperature significantly delayed the EGS in evergreen forests,shrub and grassland.Conclusions:Our results indicated that the SIF outperformed traditional vegetation indices in capturing the autumn photosynthetic phenology of evergreen forest in the subtropical region of China.We found that minimum temperature plays a significant role in determining autumn photosynthetic phenology in the study region.These findings contribute to improving our understanding of the response of the EGS to climate change in subtropical vegetation of China,and provide a new perspective for accurately evaluating the role played by evergreen vegetation in the regional carbon budget.
