光合有效辐射分量(Fraction of Photosynthetically Active Radiation,FPAR)是进行生态系统功能和全球变化研究的重要参数,准确估算FPAR具有重要意义。通过对野外实测玉米高光谱数据和光合有效辐射数据的分析,探讨了主成分分析方法在高...光合有效辐射分量(Fraction of Photosynthetically Active Radiation,FPAR)是进行生态系统功能和全球变化研究的重要参数,准确估算FPAR具有重要意义。通过对野外实测玉米高光谱数据和光合有效辐射数据的分析,探讨了主成分分析方法在高光谱信息提取及估算玉米冠层FPAR参数方面的可行性,在此基础上,结合植被指数验证FPAR估算效果,分析近红外及短波红外高光谱数据在FPAR估算方面的应用潜力。展开更多
光合有效辐射吸收比率(Fraction of Absorbed Photosynthetically Active Radiation,FPAR)是主要的植物生理参数之一。本研究根据地面实测数据和由HJ-1CCD(Charge-coupled Device,CCD)及Landsat-8OLI(Operational Land Imager,OLI)影像...光合有效辐射吸收比率(Fraction of Absorbed Photosynthetically Active Radiation,FPAR)是主要的植物生理参数之一。本研究根据地面实测数据和由HJ-1CCD(Charge-coupled Device,CCD)及Landsat-8OLI(Operational Land Imager,OLI)影像提取的NDVI,分别建立研究区FPAR估算模型,对比分析和评价了CCD和OLI数据在反演研究区FPAR的精度。结果表明,基于CCD和OLI数据计算的NDVI与实测FPAR之间均呈现良好的正相关关系;针对每个基本采样单元(Elementary Sampling Units,ESU),两种数据反演的FPAR具有显著的一致性,且反演值相差甚少;剔除影像中受到云和云影影响的区域,整个研究区利用CCD与OLI数据反演的FPAR相关性好、分布趋势一致,且反演值均值差很小。本研究结果对该区域FPAR的进一步研究具有借鉴和指导意义,在以后的研究中可以尝试使用HJ-1CCD数据。展开更多
FPAR(fraction of photosynthetically active radiation absorbed by the canopy)是植被冠层阻截太阳光合有效辐射的比例,是遥感估算陆地生态系统植被净第一性生产力(NPP)的重要参数。利用Monte Carlo方法模拟光子在植被冠层中的辐射...FPAR(fraction of photosynthetically active radiation absorbed by the canopy)是植被冠层阻截太阳光合有效辐射的比例,是遥感估算陆地生态系统植被净第一性生产力(NPP)的重要参数。利用Monte Carlo方法模拟光子在植被冠层中的辐射传输过程,以植被冠层二向反射分布函数的模拟来验证模拟的正确性;在此基础上对400—700nm光合作用波段范围内的植被叶片吸收光子辐射比例的FPAR进行模拟。FPAR的Monte Carlo模拟结果,揭示了FPAR与太阳天顶角及植被冠层参数之间的关系。展开更多
In this study, two different methods including Digital Camera and Reference Panel （DCRP） and traditional in situ fPAR observation for measuring the in situ point fPAR of very short alpine grass vegetation were compa...In this study, two different methods including Digital Camera and Reference Panel （DCRP） and traditional in situ fPAR observation for measuring the in situ point fPAR of very short alpine grass vegetation were compared, and the Moderate Resolution Imaging Spectroradiometer （MODIS） fPAR products were evaluated and validated by in situ point data on the alpine grassland over the Northern Tibetan Plateau, which is sensitive to climate change and vulnerable to anthropogenic activities. Results showed that the MODIS alpine grassland fPAR product, examined by using DCRP, and traditional in situ fPAR observation had a significant relationship at the spatial and temporal scales. The decadal MODIS fPAR trend analysis showed that, average growing season fPAR increased by 1.2 × 10^-4 per year and in total increased 0.86% from 2002 to 2011 in alpine grassland, when most of the fPAR increments occurred in southeast and center of the Northern Tibetan Plateau, the alpine grassland tended to recover from degradation slightly. However, climatic factors have influenced the various alpine grassland vegetation fPAR over a period of 10 years; precipitation significantly affected the alpine meadow fPAR in the eastern region, whereas temperature considerably influenced the alpine desert steppe fPAR in the west region. These findings suggest that the regional heterogeneity in alpine grassland fPAR results from various environmental factors, except for vegetation characteristics, such as canopy structure and leaf area.展开更多
文摘光合有效辐射分量(Fraction of Photosynthetically Active Radiation,FPAR)是进行生态系统功能和全球变化研究的重要参数,准确估算FPAR具有重要意义。通过对野外实测玉米高光谱数据和光合有效辐射数据的分析,探讨了主成分分析方法在高光谱信息提取及估算玉米冠层FPAR参数方面的可行性,在此基础上,结合植被指数验证FPAR估算效果,分析近红外及短波红外高光谱数据在FPAR估算方面的应用潜力。
文摘光合有效辐射吸收比率(Fraction of Absorbed Photosynthetically Active Radiation,FPAR)是主要的植物生理参数之一。本研究根据地面实测数据和由HJ-1CCD(Charge-coupled Device,CCD)及Landsat-8OLI(Operational Land Imager,OLI)影像提取的NDVI,分别建立研究区FPAR估算模型,对比分析和评价了CCD和OLI数据在反演研究区FPAR的精度。结果表明,基于CCD和OLI数据计算的NDVI与实测FPAR之间均呈现良好的正相关关系;针对每个基本采样单元(Elementary Sampling Units,ESU),两种数据反演的FPAR具有显著的一致性,且反演值相差甚少;剔除影像中受到云和云影影响的区域,整个研究区利用CCD与OLI数据反演的FPAR相关性好、分布趋势一致,且反演值均值差很小。本研究结果对该区域FPAR的进一步研究具有借鉴和指导意义,在以后的研究中可以尝试使用HJ-1CCD数据。
文摘估算并消除冠层非光合组分(non-photosynthetic vegetation,NPV)吸收的光合有效辐射,对准确估算生态系统总初级生产力(gross primary productivity,GPP)具有重要意义。以落叶阔叶林为例,通过设置不同情景,应用任意倾斜叶片散射(scattering by arbitrary inclined leaves,SAIL)模型进行冠层光合有效辐射吸收分量(fraction of absorbed photosynthetically active radiation,FPAR)的分层模拟,分析冠层NPV的FPAR的变动及其对冠层FPAR的贡献,并初步探讨落叶阔叶林NPV的FPAR的估算方法。结果表明,冠层NPV的FPAR的大小与冠层结构相关,在高覆盖度植被区NPV对冠层FPAR的贡献通常较小,但在低植被覆盖区的贡献会较高;NPV降低了冠层在近红外波段的反射;增强型植被指数(enhanced vegetation index,EVI)与NPV的FPAR存在显著的线性负相关关系,可用来描述NPV的变化。
文摘FPAR(fraction of photosynthetically active radiation absorbed by the canopy)是植被冠层阻截太阳光合有效辐射的比例,是遥感估算陆地生态系统植被净第一性生产力(NPP)的重要参数。利用Monte Carlo方法模拟光子在植被冠层中的辐射传输过程,以植被冠层二向反射分布函数的模拟来验证模拟的正确性;在此基础上对400—700nm光合作用波段范围内的植被叶片吸收光子辐射比例的FPAR进行模拟。FPAR的Monte Carlo模拟结果,揭示了FPAR与太阳天顶角及植被冠层参数之间的关系。
文摘In this study, two different methods including Digital Camera and Reference Panel （DCRP） and traditional in situ fPAR observation for measuring the in situ point fPAR of very short alpine grass vegetation were compared, and the Moderate Resolution Imaging Spectroradiometer （MODIS） fPAR products were evaluated and validated by in situ point data on the alpine grassland over the Northern Tibetan Plateau, which is sensitive to climate change and vulnerable to anthropogenic activities. Results showed that the MODIS alpine grassland fPAR product, examined by using DCRP, and traditional in situ fPAR observation had a significant relationship at the spatial and temporal scales. The decadal MODIS fPAR trend analysis showed that, average growing season fPAR increased by 1.2 × 10^-4 per year and in total increased 0.86% from 2002 to 2011 in alpine grassland, when most of the fPAR increments occurred in southeast and center of the Northern Tibetan Plateau, the alpine grassland tended to recover from degradation slightly. However, climatic factors have influenced the various alpine grassland vegetation fPAR over a period of 10 years; precipitation significantly affected the alpine meadow fPAR in the eastern region, whereas temperature considerably influenced the alpine desert steppe fPAR in the west region. These findings suggest that the regional heterogeneity in alpine grassland fPAR results from various environmental factors, except for vegetation characteristics, such as canopy structure and leaf area.
