Aims Light-use efficiency(LUE)is an important tool for scaling up local CO_(2)flux(F_(CO_(2)))tower observations to regional and global carbon dynamics.Using a data set including F_(CO_(2))and environmental factors ob...Aims Light-use efficiency(LUE)is an important tool for scaling up local CO_(2)flux(F_(CO_(2)))tower observations to regional and global carbon dynamics.Using a data set including F_(CO_(2))and environmental factors obtained from an alpine meadow on the Tibetan Plateau,we examined both diurnal and seasonal changes in LUE and the environmental factors controlling these changes.Our objectives were to(i)characterize the diurnal and daily variability of LUE in an alpine meadow,(ii)clarify the causes of this variability,and(iii)explore the possibility of applying the LUE approach to this alpine meadow by examining the relationship between daily LUE and hourly LUE at satellite visiting times.Methods First,we obtained the LUE—the ratio of the gross primary production(GPP)to the absorbed photosynthetically active radiation(APAR)—from the flux tower and meteorological observations.We then characterized the patterns of diurnal and seasonal changes in LUE,explored the environmental controls on LUE using univariate regression analyses and evaluated the effects of diffuse radiation on LUE by assigning weights through a linear programming method to beam photosynthetically active radiation(PAR)and diffuse PAR,which were separated from meteorological observations using an existing method.Finally,we examined the relationships between noontime hourly LUE and daily LUE and those between adjusted noontime hourly and daily LUE because satellites visit the site only once or twice a day,near noon.Important Findings The results showed that(i)the LUE of the alpine meadow generally followed the diurnal and seasonal patterns of solar radiation but fluctuated with changes in cloud cover.(ii)The fraction of diffuse light played a dominant role in LUE variation.Daily minimum temperature and vapor pressure deficit also affected LUE variation.(iii)The adjusted APAR,defined as the weighted linear sum of diffuse APAR and beam APAR,was linearly correlated with GPP on different temporal scales.(iv)Midday adjusted LUE was closely related to daily展开更多
The accurate measurement of the dynamics of photosynthesis in China’s subtropical evergreen forest ecosystems is an important contribution to carbon(C) sink estimates in global terrestrial ecosystems and their respon...The accurate measurement of the dynamics of photosynthesis in China’s subtropical evergreen forest ecosystems is an important contribution to carbon(C) sink estimates in global terrestrial ecosystems and their responses to climate change. Eddy covariance has historically been the only direct method to assess C flux of whole ecosystems with high temporal resolution, but it suffers from limited spatial resolution. During the last decade, continuous global monitoring of plant primary productivity from spectroradiometer sensors on flux towers and satellites has extended the temporal and spatial coverage of C flux observations. In this study, we evaluated the performance of two physiological remote sensing indices, fluorescence reflectance index(FRI) and photochemical reflectance index(PRI), to measure the seasonal variations of photosynthesis in a subtropical evergreen forest ecosystem using continuous canopy spectral and flux measurements in the Dinghushan Nature Reserve in southern China.The more commonly used NDVI has been shown to be saturated and mainly affected by illumination(R^2=0.88, p <0.001), but FRI and PRI could better track the seasonal dynamics of plant photosynthetic functioning by comparison and are less affected by illumination(R^2=0.13 and R^2=0.51, respectively) at the seasonal scale. FRI correlated better with daily gross primary production(GPP) in the morning hours than in the afternoon hours, in contrast to PRI which correlated better with light-use efficiency(LUE) in the afternoon hours. Both FRI and PRI could show greater correlations with GPP and LUE respectively in the senescence season than in the recovery-growth season. When incident PAR was taken into account, the relationship between GPP and FRI was improved and the correlation coefficient increased from 0.22 to 0.69(p < 0.001). The strength of the correlation increased significantly in the senescence season(R^2=0.79, p < 0.001). Our results demonstrate the application of FRI and PRI as physiological indices for the accurate measureme展开更多
为了提高育苗质量,降低冬春季低温弱光环境对设施种苗优质生产的制约,该研究利用人工光型植物工厂的LED光照与环控技术研究光质和日累积光照量(Daily Light Integral,DLI)对番茄种苗形态建成和生物量累积的影响,通过对光能利用效率(Ligh...为了提高育苗质量,降低冬春季低温弱光环境对设施种苗优质生产的制约,该研究利用人工光型植物工厂的LED光照与环控技术研究光质和日累积光照量(Daily Light Integral,DLI)对番茄种苗形态建成和生物量累积的影响,通过对光能利用效率(Light Energy Use Efficiency,LUE)和电能利用效率(Electric Energy Use Efficiency,EUE)的实际测试,分析人工光育苗的能耗水平。光质环境以白色荧光灯为对照,选用红蓝比(R∶B)为0.9的白色LED和R∶B为1.2(L1.2)和2.2(L2.2)的白红LED灯具,在DLI为10.1、12.6和15.1 mol/(m^2·d)下培育“丰收”番茄种苗31 d。结果表明:在LED下生长的番茄种苗的壮苗指数、生物量和光合能力均显著优于荧光灯下,增强DLI有利于番茄种苗的形态建成和生物量累积;在L1.2下设置DLI为12.6 mol/(m^2·d)时,番茄种苗的株高、茎粗、叶面积、干质量日均增长量(G值)、壮苗指数、及干/鲜质量都达到最大。番茄种苗在相同光质下的光合能力不受DLI的影响,但在L1.2下的净光合速率最高。利用LED生产番茄种苗的LUE和EUE比在荧光灯下显著提高,当DLI为12.6 mol/(m^2·d)时,L1.2下的该值比荧光灯下分别提高79%和321%。因此,R∶B为1.2的白红LED比其他光质更适合番茄种苗生产,推荐DLI为12.6 mol/(m^2·d)作为番茄设施育苗的光环境调控指标。展开更多
草地是陆地生态系统重要的组分,利用遥感技术在宏观尺度分析天然草原长势变化与其驱动力是了解草地生态状况的重要手段。本研究基于气候模型和光能利用率模型分别模拟2000-2018年锡林郭勒草原植被潜在植被净初级生产力(NPP)和实际NPP,...草地是陆地生态系统重要的组分,利用遥感技术在宏观尺度分析天然草原长势变化与其驱动力是了解草地生态状况的重要手段。本研究基于气候模型和光能利用率模型分别模拟2000-2018年锡林郭勒草原植被潜在植被净初级生产力(NPP)和实际NPP,以它们的差值作为由人类活动导致的NPP残损值,并利用最小二乘法在像元尺度分析锡林郭勒草原NPP时空变化规律以及气候和人类活动对NPP的驱动作用。结果表明:2000-2018年间,锡林郭勒草地NPP在空间上呈由西向东递增分布规律,年均NPP为271.54 g C·m^-2·a^-1,NPP上升(草地恢复)面积为3.65万km^2,NPP下降(草地退化)面积为5.99万km2;潜在NPP在温度和降水的驱动下趋于上升趋势,年均上升6.5 g C·m^-2·a^-1,表明研究期间区域气候(降水和温度)对锡林郭勒草原NPP的提升具有积极作用,草地退化的驱动力主要来自人类活动;人类活动导致的研究区NPP残损值呈由东向西、由南向北递减分布,其中,乌珠穆沁草甸草原及南部典型草原残损值最高;采矿、开垦等人类活动对草地NPP的影响最明显。展开更多
基金Supported by the projects‘Integrated Study for Terrestrial Carbon Management of Asia in the 21st Century Based on Scientific Advancements’and‘Early Detection and Prediction of Climate Warming Based on the Long-Term Monitoring of Alpine Ecosystems on the Tibetan Plateau’funded by the Ministry of the Environment,Japanresearch fund from the Program for New Century Excellent Talents in University,from Ministry of Education,China,to J.C.
文摘Aims Light-use efficiency(LUE)is an important tool for scaling up local CO_(2)flux(F_(CO_(2)))tower observations to regional and global carbon dynamics.Using a data set including F_(CO_(2))and environmental factors obtained from an alpine meadow on the Tibetan Plateau,we examined both diurnal and seasonal changes in LUE and the environmental factors controlling these changes.Our objectives were to(i)characterize the diurnal and daily variability of LUE in an alpine meadow,(ii)clarify the causes of this variability,and(iii)explore the possibility of applying the LUE approach to this alpine meadow by examining the relationship between daily LUE and hourly LUE at satellite visiting times.Methods First,we obtained the LUE—the ratio of the gross primary production(GPP)to the absorbed photosynthetically active radiation(APAR)—from the flux tower and meteorological observations.We then characterized the patterns of diurnal and seasonal changes in LUE,explored the environmental controls on LUE using univariate regression analyses and evaluated the effects of diffuse radiation on LUE by assigning weights through a linear programming method to beam photosynthetically active radiation(PAR)and diffuse PAR,which were separated from meteorological observations using an existing method.Finally,we examined the relationships between noontime hourly LUE and daily LUE and those between adjusted noontime hourly and daily LUE because satellites visit the site only once or twice a day,near noon.Important Findings The results showed that(i)the LUE of the alpine meadow generally followed the diurnal and seasonal patterns of solar radiation but fluctuated with changes in cloud cover.(ii)The fraction of diffuse light played a dominant role in LUE variation.Daily minimum temperature and vapor pressure deficit also affected LUE variation.(iii)The adjusted APAR,defined as the weighted linear sum of diffuse APAR and beam APAR,was linearly correlated with GPP on different temporal scales.(iv)Midday adjusted LUE was closely related to daily
基金National Key Research and Development Program of China(2017YFC0503803)National Natural Science Foundation of China(41571192)+1 种基金Natural Science Foundation of Hebei,China(D2016302002)Science and Technology Planning Project of Hebei,China(17390313D)
文摘The accurate measurement of the dynamics of photosynthesis in China’s subtropical evergreen forest ecosystems is an important contribution to carbon(C) sink estimates in global terrestrial ecosystems and their responses to climate change. Eddy covariance has historically been the only direct method to assess C flux of whole ecosystems with high temporal resolution, but it suffers from limited spatial resolution. During the last decade, continuous global monitoring of plant primary productivity from spectroradiometer sensors on flux towers and satellites has extended the temporal and spatial coverage of C flux observations. In this study, we evaluated the performance of two physiological remote sensing indices, fluorescence reflectance index(FRI) and photochemical reflectance index(PRI), to measure the seasonal variations of photosynthesis in a subtropical evergreen forest ecosystem using continuous canopy spectral and flux measurements in the Dinghushan Nature Reserve in southern China.The more commonly used NDVI has been shown to be saturated and mainly affected by illumination(R^2=0.88, p <0.001), but FRI and PRI could better track the seasonal dynamics of plant photosynthetic functioning by comparison and are less affected by illumination(R^2=0.13 and R^2=0.51, respectively) at the seasonal scale. FRI correlated better with daily gross primary production(GPP) in the morning hours than in the afternoon hours, in contrast to PRI which correlated better with light-use efficiency(LUE) in the afternoon hours. Both FRI and PRI could show greater correlations with GPP and LUE respectively in the senescence season than in the recovery-growth season. When incident PAR was taken into account, the relationship between GPP and FRI was improved and the correlation coefficient increased from 0.22 to 0.69(p < 0.001). The strength of the correlation increased significantly in the senescence season(R^2=0.79, p < 0.001). Our results demonstrate the application of FRI and PRI as physiological indices for the accurate measureme
文摘为了提高育苗质量,降低冬春季低温弱光环境对设施种苗优质生产的制约,该研究利用人工光型植物工厂的LED光照与环控技术研究光质和日累积光照量(Daily Light Integral,DLI)对番茄种苗形态建成和生物量累积的影响,通过对光能利用效率(Light Energy Use Efficiency,LUE)和电能利用效率(Electric Energy Use Efficiency,EUE)的实际测试,分析人工光育苗的能耗水平。光质环境以白色荧光灯为对照,选用红蓝比(R∶B)为0.9的白色LED和R∶B为1.2(L1.2)和2.2(L2.2)的白红LED灯具,在DLI为10.1、12.6和15.1 mol/(m^2·d)下培育“丰收”番茄种苗31 d。结果表明:在LED下生长的番茄种苗的壮苗指数、生物量和光合能力均显著优于荧光灯下,增强DLI有利于番茄种苗的形态建成和生物量累积;在L1.2下设置DLI为12.6 mol/(m^2·d)时,番茄种苗的株高、茎粗、叶面积、干质量日均增长量(G值)、壮苗指数、及干/鲜质量都达到最大。番茄种苗在相同光质下的光合能力不受DLI的影响,但在L1.2下的净光合速率最高。利用LED生产番茄种苗的LUE和EUE比在荧光灯下显著提高,当DLI为12.6 mol/(m^2·d)时,L1.2下的该值比荧光灯下分别提高79%和321%。因此,R∶B为1.2的白红LED比其他光质更适合番茄种苗生产,推荐DLI为12.6 mol/(m^2·d)作为番茄设施育苗的光环境调控指标。
文摘草地是陆地生态系统重要的组分,利用遥感技术在宏观尺度分析天然草原长势变化与其驱动力是了解草地生态状况的重要手段。本研究基于气候模型和光能利用率模型分别模拟2000-2018年锡林郭勒草原植被潜在植被净初级生产力(NPP)和实际NPP,以它们的差值作为由人类活动导致的NPP残损值,并利用最小二乘法在像元尺度分析锡林郭勒草原NPP时空变化规律以及气候和人类活动对NPP的驱动作用。结果表明:2000-2018年间,锡林郭勒草地NPP在空间上呈由西向东递增分布规律,年均NPP为271.54 g C·m^-2·a^-1,NPP上升(草地恢复)面积为3.65万km^2,NPP下降(草地退化)面积为5.99万km2;潜在NPP在温度和降水的驱动下趋于上升趋势,年均上升6.5 g C·m^-2·a^-1,表明研究期间区域气候(降水和温度)对锡林郭勒草原NPP的提升具有积极作用,草地退化的驱动力主要来自人类活动;人类活动导致的研究区NPP残损值呈由东向西、由南向北递减分布,其中,乌珠穆沁草甸草原及南部典型草原残损值最高;采矿、开垦等人类活动对草地NPP的影响最明显。
