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
光化学植被指数PRI(photochemical reflectance index)为估算植被的光能利用率LUE(light use effi-ciency)提供了一种快速、有效的方法。越来越多的研究关注外界环境对PRI和LUE之间关系的影响,这些因素包括水分含量、CO2浓度等等。文章...光化学植被指数PRI(photochemical reflectance index)为估算植被的光能利用率LUE(light use effi-ciency)提供了一种快速、有效的方法。越来越多的研究关注外界环境对PRI和LUE之间关系的影响,这些因素包括水分含量、CO2浓度等等。文章选择了不同氮、钾施肥量处理的小麦,测量其LUE和PRI,分析不同肥料处理对二者关系的影响。实验表明,氮、钾施肥量的增加将提高冠层光谱的PRI值和叶片内部叶绿素的含量,在此基础上提高小麦的LUE。对于不同氮、钾处理的小麦,PRI和LUE之间都获得了很好的相关关系,总的相关系数R2分别是0.7104和0.8534。随着氮、钾肥量的增加,PRI和LUE之间的相关性也在增加。对1,2,3份的氮施肥量,相关系数R2分别是0.6020,0.6404和0.8014;钾施肥量为1,2,3份时,R2分别为0.3791,0.6404和0.6769。因此,PRI不仅能够获可靠精度的LUE,并且为监测小麦的肥料状况提供了一种间接方法,这将为田间管理和精细农业提供了必要的参考信息。展开更多
光化学植被指数(PRI)被成功的应用于估算不同叶片生化组分的光能利用率(LUE),这些生化组分包括叶片含水量、氮元素浓度等。以往的研究中已经成功建立了叶片、冠层和景观尺度PRI和LUE的相关关系。但是,为了利用PRI更加准确地估算叶片LUE...光化学植被指数(PRI)被成功的应用于估算不同叶片生化组分的光能利用率(LUE),这些生化组分包括叶片含水量、氮元素浓度等。以往的研究中已经成功建立了叶片、冠层和景观尺度PRI和LUE的相关关系。但是,为了利用PRI更加准确地估算叶片LUE,很多问题仍然亟需解决,比如当LUE高于0.03mol CO2 mol-1PPFD(photosynthetic photon flux density),PRI会出现一个明显的饱和区域以及PRI和LUE关系会随季节发生较大变化。文章对PRI进行了修正,并基于PROSPECT模型对这一修正形式进行了4个参数的敏感性分析。分析结果表明,叶片SR-PRI(Simple ratio PRI)对叶肉结构参数(N)、叶绿素浓度(cab)敏感性要高于叶片的等效水厚(cw)和干物质浓度(cm)。因此叶肉结构参数(N)和叶绿素浓度(cab)的微小变化都会造成SR-PRI的较大变化,进而影响到LUE的估算精度。对SR-PRI的实证实验表明,这一指数也能够很好地用来估算叶片的光能利用率并且结果要优于PRI和LUE之间的相关关系。SR-PRI最重要的一方面在于其更清晰的物理意义和对531nm处反射率变化的敏感性,因为这一波段位置的反射率变化是评价光能利用率的核心参数。展开更多
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
文摘光化学植被指数PRI(photochemical reflectance index)为估算植被的光能利用率LUE(light use effi-ciency)提供了一种快速、有效的方法。越来越多的研究关注外界环境对PRI和LUE之间关系的影响,这些因素包括水分含量、CO2浓度等等。文章选择了不同氮、钾施肥量处理的小麦,测量其LUE和PRI,分析不同肥料处理对二者关系的影响。实验表明,氮、钾施肥量的增加将提高冠层光谱的PRI值和叶片内部叶绿素的含量,在此基础上提高小麦的LUE。对于不同氮、钾处理的小麦,PRI和LUE之间都获得了很好的相关关系,总的相关系数R2分别是0.7104和0.8534。随着氮、钾肥量的增加,PRI和LUE之间的相关性也在增加。对1,2,3份的氮施肥量,相关系数R2分别是0.6020,0.6404和0.8014;钾施肥量为1,2,3份时,R2分别为0.3791,0.6404和0.6769。因此,PRI不仅能够获可靠精度的LUE,并且为监测小麦的肥料状况提供了一种间接方法,这将为田间管理和精细农业提供了必要的参考信息。
文摘光化学植被指数(PRI)被成功的应用于估算不同叶片生化组分的光能利用率(LUE),这些生化组分包括叶片含水量、氮元素浓度等。以往的研究中已经成功建立了叶片、冠层和景观尺度PRI和LUE的相关关系。但是,为了利用PRI更加准确地估算叶片LUE,很多问题仍然亟需解决,比如当LUE高于0.03mol CO2 mol-1PPFD(photosynthetic photon flux density),PRI会出现一个明显的饱和区域以及PRI和LUE关系会随季节发生较大变化。文章对PRI进行了修正,并基于PROSPECT模型对这一修正形式进行了4个参数的敏感性分析。分析结果表明,叶片SR-PRI(Simple ratio PRI)对叶肉结构参数(N)、叶绿素浓度(cab)敏感性要高于叶片的等效水厚(cw)和干物质浓度(cm)。因此叶肉结构参数(N)和叶绿素浓度(cab)的微小变化都会造成SR-PRI的较大变化,进而影响到LUE的估算精度。对SR-PRI的实证实验表明,这一指数也能够很好地用来估算叶片的光能利用率并且结果要优于PRI和LUE之间的相关关系。SR-PRI最重要的一方面在于其更清晰的物理意义和对531nm处反射率变化的敏感性,因为这一波段位置的反射率变化是评价光能利用率的核心参数。
