Improving the potential of red SIF for estimating GPP by downscaling from the canopy level to the photosystem level
Improving the potential of red SIF for estimating GPP by downscaling from the canopy level to the photosystem level
复制标题
通过从冠层水平缩小到光系统水平，提高红色 SIF 估算 GPP 的潜力
DOI：
10.1016/j.agrformet.2019.107846
复制
发表时间：
2020-02-15
影响因子：
6.2
通讯作者：
Du, Shanshan
中科院分区：
文献类型：
--
作者：
Liu, Xinjie;Liu, Liangyun;Du, Shanshan
大量研究表明，太阳能诱导叶绿素荧光（SIF）是一个很好的代理总初级生产力（GPP）。SIF光谱覆盖从约640 nm到850 nm的光谱窗口。由于红波段叶绿素的强烈吸收效应，红波段SIF比近红外（NIR）SIF更容易受到冠层内辐射传输效应的影响。因此，在冠层水平上，近红外SIF显示出更大的潜力，用于估计GPP。然而，红波段的SIF包含更多的信息PS II，这是更敏感的光合作用。因此，在理论上，如果冠层辐射传输效应可以被校正，红色SIF的潜力估计GPP将大大提高。在本文中，我们提出了一个新的简单的基于反射率的方法来估计在近红外波段和红色波段的光系统水平的SIF。利用两个作物点的SIF和GPP的长期观测资料（共4个数据集），研究了SIF与GPP在冠层或光系统水平上的关系。通过简单的基于反射率的方法降尺度的SIF被发现是一致的，发现使用随机森林回归方法以前提出的。对于NIR波段，用于GPP估计的树冠级SIF和PS级SIF的性能是相似的，而对于红色波段，在将树冠级SIF降尺度到PS级之后，SIF和GPP之间的相关性大大提高。对于四个测试数据集，在红带处，SIF-GPP关系的R-2值在降尺度后从0.213-0.599增加到0.398-0.759。在PS级别，红色SIF用于GPP估计的性能与近红外波段SIF的性能一样好甚至更好。研究结果表明，估算SIF光系统水平对冠层逃逸概率的重要性，在GPP监测中应重视红波段SIF。
Numerous studies have proved that solar-induced chlorophyll fluorescence (SIF) is a good proxy of gross primary production (GPP). The SIF spectrum covers the spectral window from about 640 nm to 850 nm. Due to the strong chlorophyll absorption effect at the red band, the red SIF is much more influenced by the radiative transfer effect inside the canopy than the near infrared (NIR) SIF is. Therefore, at the canopy level, the NIR SIF shows more potential for use in estimating GPP. However, the red-band SIF contains more information about PS II, which is more sensitive to photosynthesis. So, in theory, if the canopy radiative transfer effect could be corrected for, the potential of the red SIF for estimating GPP would be greatly improved. In this paper, we propose a new simple reflectance-based method for estimating the photosystem-level SIF at both the NIR band and the red band. Longterm observations of SIF and GPP at two crop sites in two years (four datasets in total) were used to investigate the SIF-GPP relationship at the canopy or photosystem level. The SIF downscaled by the simple reflectance-based approach is found to be consistent with that found using the random forest regression method proposed formerly. For the NIR band, the performance of the canopy-level SIF and PS-level SIF for GPP estimation is similar while, for the red band, the correlation between the SIF and GPP is greatly improved after downscaling the canopy-level SIF to the PS level. For the four test datasets, at the red band, the values of R-2 for the SIF-GPP relationship increase from 0.213-0.599 to 0.398-0.759 after the downscaling. At the PS level, the performance of the red SIF for GPP estimation is as good as or even better than that of the NIR-band SIF. The results of this study indicate that estimation of the SIF photosystem level to canopy level escape probability is important, and that more importance should be paid to the red-band SIF in the monitoring of GPP.