Solar-induced chlorophyll fluorescence (SIF) is a subtle but informative probe of plant photosynthesis. Quantifying the three-dimensional (3D) distribution of SIF benefits a better understanding of photosynthesis variations over heterogeneous canopies. Although radiative transfer models (RTMs) provide a solid theoretical basis for simulating the 3D SIF distribution, most RTMs use virtual scenes with complex reconstruction processes. This study aims to develop a 3D SIF simulation model (FluorLiDAR) directly driven by terrestrial light detection and ranging (LiDAR) data using leaf and canopy RTMs, including a 3D PAR (photosynthetically active radiation) simulation model, the model, the atmosphere radiative transfer module in , and the multiple scattering coefficients of sunlit and shaded leaves from the model. The results show that (1) the simulated and measured SIF patterns were consistent, with R (RMSE) values of 0.73 (0.17 mW/nm/m/sr) and 0.76 (0.12 mW/nm/m/sr) for 1-min sampling and 10-min averages, respectively. Moreover, the R between FluorLiDAR and the DART simulation reached 0.94. The R of FluorLiDAR and DART were both higher than 1D mSCOPE using every 10-min sampling data. (2) Point density, denoted by average NPD (nearest point distance), influenced the performance of our model mainly when it was smaller than 0.1 m. Chlorophyll content had less influence on the model accuracy (R and rRMSE), and the bias between simulation and measurement decreased as chlorophyll content increased. (3) The simulated 3D SIF distribution pattern closely resembled PAR within the canopy. Besides, FluorLiDAR can simulate the hot spot effect like DART and mSCOPE though the effect was not as obvious as the other two models. This study highlights the potential of a LiDAR-driven SIF model for 3D SIF simulation over a heterogeneous canopy, which may benefit the understanding of the structural impacts on forest photosynthesis in real forest scenes.

中文翻译：

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激光雷达驱动的森林远红太阳诱导叶绿素荧光三维模拟模型


太阳诱导的叶绿素荧光（SIF）是植物光合作用的一种微妙但信息丰富的探针。量化 SIF 的三维 (3D) 分布有助于更好地了解异质冠层的光合作用变化。尽管辐射传输模型 (RTM) 为模拟 3D SIF 分布提供了坚实的理论基础，但大多数 RTM 使用具有复杂重建过程的虚拟场景。本研究旨在开发使用叶子和冠层RTM直接由地面光探测和测距（LiDAR）数据驱动的3D SIF模拟模型（FluorLiDAR），包括3D PAR（光合有效辐射）模拟模型、模型、大气辐射传输中的模块，以及模型中阳光照射和阴影树叶的多重散射系数。结果表明：(1) 模拟和测量的 SIF 图案一致，1 分钟内 R (RMSE) 值为 0.73 (0.17 mW/nm/m/sr) 和 0.76 (0.12 mW/nm/m/sr)分别为采样和 10 分钟平均值。此外，FluorLiDAR与DART模拟之间的R达到0.94。使用每 10 分钟采样数据时，FluorLiDAR 和 DART 的 R 均高于 1D mSCOPE。 (2)点密度，用平均NPD（最近点距离）表示，主要在小于0.1 m时影响我们模型的性能。叶绿素含量对模型精度（R 和 rRMSE）影响较小，并且随着叶绿素含量的增加，模拟与测量之间的偏差减小。 (3) 模拟的 3D SIF 分布模式与冠层内的 PAR 非常相似。此外，FluorLiDAR可以像DART和mSCOPE一样模拟热点效应，尽管效果不如其他两种模型明显。 这项研究强调了激光雷达驱动的 SIF 模型在异质树冠上进行 3D SIF 模拟的潜力，这可能有助于理解真实森林场景中森林光合作用的结构影响。