植被光合有效辐射吸收比率FPAR(Fraction of absorbed Photosynthetically Active Radiation)反映了植被冠层的光学特性,是表征植被光合作用水平和生长状态的重要参量,因此成为全球变化研究中多种过程模型的重要输入参数。随着定量遥感...植被光合有效辐射吸收比率FPAR(Fraction of absorbed Photosynthetically Active Radiation)反映了植被冠层的光学特性,是表征植被光合作用水平和生长状态的重要参量,因此成为全球变化研究中多种过程模型的重要输入参数。随着定量遥感研究的深入和新型传感器的使用,从区域到全球尺度上的FPAR遥感估算方法不断提出,多样化的遥感FPAR产品越来越多地应用于碳循环、能量循环、生产力估算及作物估产等研究领域。本文梳理了遥感估算的植被光合有效辐射的相关概念和算法,并着重对过去十年间遥感估算FPAR的新进展进行了系统总结和探讨。研究表明,近年来FPAR遥感的研究工作一方面聚焦于对现有算法的改进与各类型产品的验证,更多的研究则侧重于FPAR概念体系的拓展,叶片、叶绿素水平的FPAR估算,直射光、散射光的FPAR建模等新方向逐渐成为研究热点。展开更多
为探索高分一号卫星(GF-1)估算农作物光合有效辐射吸收比率(Fraction of absorbed photosynthetically active radiation,FPAR)的潜力,以田间小区与大田夏玉米为对象,基于GF-1卫星的16 m空间分辨率宽视场(Wide field view,WFV)传感器光...为探索高分一号卫星(GF-1)估算农作物光合有效辐射吸收比率(Fraction of absorbed photosynthetically active radiation,FPAR)的潜力,以田间小区与大田夏玉米为对象,基于GF-1卫星的16 m空间分辨率宽视场(Wide field view,WFV)传感器光谱响应函数对地面实测冠层高光谱反射率进行重采样,获取GF-1 WFV的模拟反射率,构建宽波段植被指数,利用与FPAR极显著相关且具有较高相关系数的植被指数,建立不同生育期夏玉米FPAR的一元与多元逐步回归模型,筛选FPAR估算的最适模型,并在此基础上实现县域尺度不同生育期的FPAR动态估算。结果表明:模拟宽波段光谱反射率与GF-1 WFV光谱反射率间的相关系数|R|为0.967~0.985,决定系数R^(2)为0.935~0.969;基于模拟反射率构建3波段植被指数与FPAR的相关性优于2波段植被指数,增强型植被指数(EVI)、土壤调节植被指数(MTVI2)、可见光大气阻抗植被指数(VARI)、综合植被指数(TCARI/OSAVI)等3波段植被指数与FPAR均呈极显著相关性(P<0.01),且|R|为0.813~0.925;基于优选3波段植被指数估算FPAR的多元逐步回归模型效果优于一元回归模型,估算模型决定系数R^(2)为0.762~0.843,验证模型决定系数R^(2)为0.839~0.880,相对误差RE为7.037%~9.571%,说明多元逐步回归模型能更好地估算FPAR;以优选模型对区域尺度的FPAR进行空间分布及动态估算,并以实测值进行验证,估算值与实测值间决定系数R^(2)为0.819~0.856,相对误差RE为8.41%~13.37%,说明基于GF-1 WFV估算区域夏玉米FPAR与实际空间分布及动态变化规律一致,为基于GF-1 WFV高分辨率遥感数据估算区域玉米FPAR及生产潜力提供了科学依据。展开更多
The effects of varying nitrogen （N）： phosphorus （P） ratios on the growth and N-uptake and assimilation of the harmful dinoflagellates Prorocentrum minimum and Prorocentrum donghaiense were examined in turbidistat...The effects of varying nitrogen （N）： phosphorus （P） ratios on the growth and N-uptake and assimilation of the harmful dinoflagellates Prorocentrum minimum and Prorocentrum donghaiense were examined in turbidistat culture experiments. Algal cultures were supplied with media containing PO4^3- in various concentrations to obtain a wide range of N：P ratios. Experiments to determine rates of N uptake and assimilation of different N sources （NO^3-, NH4^＋, urea and glycine by P. minimum and NO3^-, NH4^＋ by P. donghaiense） were conducted using ^15-N tracer techniques at each N：P ratio. The growth rates suggested nutrient limitation at both high and low N：P ratios relative to the Redfield ratio. On a diel basis, the growth of both species was regulated by the light-dark cycle, which may be a result of regulation of both lightdependent growth and light-independent nutrient uptake. Maximum growth rates of both species always occurred at the beginning of light phase. In P-rich medium （low N：P ratio）, both species had higher N assimilation rates, suggesting N limitation. Low assimilation coefficients at high N：P ratios suggested P limitation of N uptake and assimilation. NO3 ^-and NH4^＋ contributed more than 90% of the total N uptake of P. minimum. Reduced N sources were more quickly assimilated than NO3^-. Highest average daily growth rates were recorded near an N：P ratio of 12 for both species. The N uptake rates of cultures at N：P ratios near Redfield ratio were more balanced with growth rates. The linkage between growth rates and N uptake/assimilation rates were conceptually described by the variation of cell N quota. The N：P ratios affect the N uptake and growth of Prorocentrum spp., and may regulate their bloom progression in eutrophic ecosystems.展开更多
Safflower represents an important oil crop internationally and may have a production potential under low input conditions, but its putatively high phosphorous use efficiency is not sustained. This study aims to direct...Safflower represents an important oil crop internationally and may have a production potential under low input conditions, but its putatively high phosphorous use efficiency is not sustained. This study aims to directly compare safflower with sunflower in terms of phosphorus use efficiency in nutrient solution under controlled conditions. Growth of both species responded strongly to increasing P supply. Safflower recovers less proportion of added P than sunflower. External P requirement （（g P supply （100 g dry matter （DM） produced）~） was higher in safflower than sunflower. The efficiency of the crops for DM production based on accumulated P （mg P potl, efficiency ratio）, and P concentration in DM （（mg P （g DM）＇I）, utilization index） were interpreted using Michaelis-Menten kinetics as growth response curves. Accordingly, Km constant was lower in sunflower compared to safflower in terms of utilization index, but both were similar in terms of efficiency ratio. High Km constant in safflower in terms of utilization index indicates the high P concentration in tissues to produce 50% of potential maximum DM, consequently less efficient crop. Utilization efficiency contributed more than uptake efficiency in overall PUE in the efficient cultivar and could be the cause of its superiority in PUE. It can be concluded that safflower has a high requirement for P with respect to growth, sunflower is more efficient in terms of uptake and utilization of P at optimal and sub-optimal P supplies indicating that safflower can not be considered a low nutrient input crop compared to sunflower with respect to phosphorus.展开更多
The problem of collecting solar energy and increasing its efficiency was studied in this paper. It was discovered that a 3DPV （three-dimensional photovoltaic） structures can generate greater amounts of measured ener...The problem of collecting solar energy and increasing its efficiency was studied in this paper. It was discovered that a 3DPV （three-dimensional photovoltaic） structures can generate greater amounts of measured energy densities than stationary flat PV panels （rate： 2 to 20）. It has been found that the same structures work better not only because they are made in 3D but because PV panels do not have linear dependency on geometry. It seems that the conversion efficiency depends on the process of absorption of the solar energy, too, or in other words on the E. Yablonovich limit. The findings suggest that the quantity of material of solar panels may be reduced to generate the same amount of electricity.展开更多
文摘植被光合有效辐射吸收比率FPAR(Fraction of absorbed Photosynthetically Active Radiation)反映了植被冠层的光学特性,是表征植被光合作用水平和生长状态的重要参量,因此成为全球变化研究中多种过程模型的重要输入参数。随着定量遥感研究的深入和新型传感器的使用,从区域到全球尺度上的FPAR遥感估算方法不断提出,多样化的遥感FPAR产品越来越多地应用于碳循环、能量循环、生产力估算及作物估产等研究领域。本文梳理了遥感估算的植被光合有效辐射的相关概念和算法,并着重对过去十年间遥感估算FPAR的新进展进行了系统总结和探讨。研究表明,近年来FPAR遥感的研究工作一方面聚焦于对现有算法的改进与各类型产品的验证,更多的研究则侧重于FPAR概念体系的拓展,叶片、叶绿素水平的FPAR估算,直射光、散射光的FPAR建模等新方向逐渐成为研究热点。
文摘为探索高分一号卫星(GF-1)估算农作物光合有效辐射吸收比率(Fraction of absorbed photosynthetically active radiation,FPAR)的潜力,以田间小区与大田夏玉米为对象,基于GF-1卫星的16 m空间分辨率宽视场(Wide field view,WFV)传感器光谱响应函数对地面实测冠层高光谱反射率进行重采样,获取GF-1 WFV的模拟反射率,构建宽波段植被指数,利用与FPAR极显著相关且具有较高相关系数的植被指数,建立不同生育期夏玉米FPAR的一元与多元逐步回归模型,筛选FPAR估算的最适模型,并在此基础上实现县域尺度不同生育期的FPAR动态估算。结果表明:模拟宽波段光谱反射率与GF-1 WFV光谱反射率间的相关系数|R|为0.967~0.985,决定系数R^(2)为0.935~0.969;基于模拟反射率构建3波段植被指数与FPAR的相关性优于2波段植被指数,增强型植被指数(EVI)、土壤调节植被指数(MTVI2)、可见光大气阻抗植被指数(VARI)、综合植被指数(TCARI/OSAVI)等3波段植被指数与FPAR均呈极显著相关性(P<0.01),且|R|为0.813~0.925;基于优选3波段植被指数估算FPAR的多元逐步回归模型效果优于一元回归模型,估算模型决定系数R^(2)为0.762~0.843,验证模型决定系数R^(2)为0.839~0.880,相对误差RE为7.037%~9.571%,说明多元逐步回归模型能更好地估算FPAR;以优选模型对区域尺度的FPAR进行空间分布及动态估算,并以实测值进行验证,估算值与实测值间决定系数R^(2)为0.819~0.856,相对误差RE为8.41%~13.37%,说明基于GF-1 WFV估算区域夏玉米FPAR与实际空间分布及动态变化规律一致,为基于GF-1 WFV高分辨率遥感数据估算区域玉米FPAR及生产潜力提供了科学依据。
基金supported by the University of Maryland Center for Environmental Science (UMCES), Horn Point Laboratory. This is UMCES contribution number 4503
文摘The effects of varying nitrogen （N）： phosphorus （P） ratios on the growth and N-uptake and assimilation of the harmful dinoflagellates Prorocentrum minimum and Prorocentrum donghaiense were examined in turbidistat culture experiments. Algal cultures were supplied with media containing PO4^3- in various concentrations to obtain a wide range of N：P ratios. Experiments to determine rates of N uptake and assimilation of different N sources （NO^3-, NH4^＋, urea and glycine by P. minimum and NO3^-, NH4^＋ by P. donghaiense） were conducted using ^15-N tracer techniques at each N：P ratio. The growth rates suggested nutrient limitation at both high and low N：P ratios relative to the Redfield ratio. On a diel basis, the growth of both species was regulated by the light-dark cycle, which may be a result of regulation of both lightdependent growth and light-independent nutrient uptake. Maximum growth rates of both species always occurred at the beginning of light phase. In P-rich medium （low N：P ratio）, both species had higher N assimilation rates, suggesting N limitation. Low assimilation coefficients at high N：P ratios suggested P limitation of N uptake and assimilation. NO3 ^-and NH4^＋ contributed more than 90% of the total N uptake of P. minimum. Reduced N sources were more quickly assimilated than NO3^-. Highest average daily growth rates were recorded near an N：P ratio of 12 for both species. The N uptake rates of cultures at N：P ratios near Redfield ratio were more balanced with growth rates. The linkage between growth rates and N uptake/assimilation rates were conceptually described by the variation of cell N quota. The N：P ratios affect the N uptake and growth of Prorocentrum spp., and may regulate their bloom progression in eutrophic ecosystems.
文摘Safflower represents an important oil crop internationally and may have a production potential under low input conditions, but its putatively high phosphorous use efficiency is not sustained. This study aims to directly compare safflower with sunflower in terms of phosphorus use efficiency in nutrient solution under controlled conditions. Growth of both species responded strongly to increasing P supply. Safflower recovers less proportion of added P than sunflower. External P requirement （（g P supply （100 g dry matter （DM） produced）~） was higher in safflower than sunflower. The efficiency of the crops for DM production based on accumulated P （mg P potl, efficiency ratio）, and P concentration in DM （（mg P （g DM）＇I）, utilization index） were interpreted using Michaelis-Menten kinetics as growth response curves. Accordingly, Km constant was lower in sunflower compared to safflower in terms of utilization index, but both were similar in terms of efficiency ratio. High Km constant in safflower in terms of utilization index indicates the high P concentration in tissues to produce 50% of potential maximum DM, consequently less efficient crop. Utilization efficiency contributed more than uptake efficiency in overall PUE in the efficient cultivar and could be the cause of its superiority in PUE. It can be concluded that safflower has a high requirement for P with respect to growth, sunflower is more efficient in terms of uptake and utilization of P at optimal and sub-optimal P supplies indicating that safflower can not be considered a low nutrient input crop compared to sunflower with respect to phosphorus.
文摘The problem of collecting solar energy and increasing its efficiency was studied in this paper. It was discovered that a 3DPV （three-dimensional photovoltaic） structures can generate greater amounts of measured energy densities than stationary flat PV panels （rate： 2 to 20）. It has been found that the same structures work better not only because they are made in 3D but because PV panels do not have linear dependency on geometry. It seems that the conversion efficiency depends on the process of absorption of the solar energy, too, or in other words on the E. Yablonovich limit. The findings suggest that the quantity of material of solar panels may be reduced to generate the same amount of electricity.
