The retrieval of leaf carbon-based constituents of vegetation species and their separation from the overall leaf mass per area using radiative transfer models was historically challenging, until the recent re-calibration of the PROSPECT-PRO model. Nevertheless, it remains unexplored for temperate tree species. This study evaluated the retrieval of carbon-based constituents of fresh leaf samples from four European temperate tree species using the PROSPECT-PRO model. We collected a comprehensive dataset of 249 fresh leaf samples obtained from the top canopy of temperate forest species in Germany and the Netherlands. Measurements of the carbon-based constituents were conducted in the lab using a novel customisation of the traditional method, and the spectral measurements of leaf samples were obtained with the ASD FieldSpec-3 and integrating sphere. Employing a look-up table approach, the PROSPECT-PRO model was inverted across the 800 to 2400 nm wavelength range, and the model was also applied with optimal bands selected for leaf carbon-based constituents. The retrieval of carbon-based constituents yielded reasonable accuracy for the four species: European beech (R2 = 0.53, NRMSE = 0.36), English oak (R2 = 0.45, NRMSE = 0.34), Scots pine (R2 = 0.63, NRMSE = 0.36) and Norway spruce (R2 = 0.62, NRMSE = 0.26). Slight improvements were observed in the retrieval accuracies with the identified optimal spectral bands. As such, the NRMSE values decreased by 0.03 and 0.05 for European beech and English oak; however, they slightly worsened for Norway spruce and Scots pine by 0.05 and 0.01, respectively. This study highlights the effect of considering individual constituents in laboratory measurements and during the calibration of absorption coefficients within the model. This could have a more substantial influence on the retrieval accuracy of carbon-based constituents than the influence of water interference or solely applying optimal spectral bands.

中文翻译：

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使用 PROSPECT-PRO 检索的温带森林物种的叶碳基成分


使用辐射传输模型检索植被物种的叶碳基成分并将其与单位面积的总叶质量分离在历史上是具有挑战性的，直到最近重新校准 PROSPECT-PRO 模型。尽管如此，温带树种仍未得到探索。本研究使用 PROSPECT-PRO 模型评估了四种欧洲温带树种新鲜叶样品的碳基成分的检索。我们收集了从德国和荷兰温带森林物种的顶部树冠中获得的 249 个新鲜叶样本的综合数据集。碳基成分的测量在实验室中使用传统方法的新颖定制进行，叶子样品的光谱测量是使用 ASD FieldSpec-3 和积分球获得的。采用查找表方法，PROSPECT-PRO 模型在 800 至 2400 nm 波长范围内进行了反转，并且该模型还应用了为叶碳基成分选择的最佳波段。对碳基成分的检索对四个树种产生了合理的准确性：欧洲山毛榉 （R2 = 0.53， NRMSE = 0.36）、英国橡树 （R2 = 0.45， NRMSE = 0.34）、苏格兰松 （R2 = 0.63， NRMSE = 0.36） 和挪威云杉 （R2 = 0.62， NRMSE = 0.26）。在确定的最佳光谱波段下，观察到检索精度略有提高。因此，欧洲山毛榉和英国橡木的 NRMSE 值分别下降了 0.03 和 0.05;然而，挪威云杉和苏格兰松的差异分别略微恶化了 0.05 和 0.01。本研究强调了在实验室测量和模型内吸收系数校准过程中考虑单个成分的影响。 这可能比水干扰或仅应用最佳光谱波段的影响对碳基成分的检索精度产生更大的影响。