The Mediterranean region is experiencing a stronger warming effect than other regions, which has generated a cascade of negative impacts on productivity, biodiversity, and stability of the ecosystem. To monitor ecosystem status and dynamics, aboveground biomass (AGB) is a good indicator, being a surrogate of many ecosystem functions and services and one of the main terrestrial carbon pools. Thus, accurate methodologies for AGB estimation are needed. This has been traditionally done by performing direct field measurements. However, field-based methods, such as biomass harvesting, are destructive, expensive, and time consuming and only provide punctual information, not being appropriate for large scale applications. Here, we propose a new non-destructive methodology for monitoring the spatiotemporal dynamics of AGB and green biomass (GB) of M. tenacissima L. plants by combining structural information obtained from terrestrial laser scanner (TLS) point clouds and spectral information. Our results demonstrate that the three volume measurement methods derived from the TLS point clouds tested (3D convex hull, voxel, and raster surface models) improved the results obtained by traditional field-based measurements. (Adjust-R² = 0.86–0.84 and RMSE = 927.3–960.2 g for AGB in OLS regressions and Adjust-R² = 0.93 and RMSE = 376.6–385.1 g for AGB in gradient boosting regression). Among the approaches, the voxel model at 5 cm of spatial resolution provided the best results; however, differences with the 3D convex hull and raster surface-based models were very small. We also found that by combining TLS AGB estimations with spectral information, green and dry biomass fraction can be accurately measured (Adjust-R² = 0.65–0.56 and RMSE = 149.96–166.87 g in OLS regressions and Adjust-R² = 0.96–0.97 and RMSE = 46.1–49.8 g in gradient boosting regression), which is critical in heterogeneous Mediterranean ecosystems in which AGB largely varies in response to climatic fluctuations. Thus, our results represent important progress for the measurement of M. tenacissima L. biomass and dynamics, providing a promising tool for calibration and validation of further studies aimed at developing new methodologies for AGB estimation at ecosystem regional scales.

中文翻译：

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地中海阿尔法草原的非破坏性生物量估算：通过结合近端遥感工具改进测量干燥和绿色部分的传统方法

地中海地区正在经历比其他地区更强烈的变暖效应，这对生产力、生物多样性和生态系统的稳定性产生了一系列负面影响。为了监测生态系统状态和动态，地上生物量 (AGB) 是一个很好的指标，它是许多生态系统功能和服务的替代品，也是主要的陆地碳库之一。因此，需要准确的 AGB 估计方法。这在传统上是通过执行直接现场测量来完成的。然而，基于现场的方法，如生物质收获，具有破坏性、昂贵和耗时，并且只能提供准时的信息，不适合大规模应用。在这里，我们提出了一种新的非破坏性方法来监测 AGB 和绿色生物量 (GB) 的时空动态。M. tenacissima L. 植物通过结合从地面激光扫描仪 (TLS) 点云和光谱信息获得的结构信息。我们的结果表明，源自所测试的 TLS 点云的三种体积测量方法（3D 凸包、体素和光栅表面模型）改进了传统基于场的测量获得的结果。（对于 OLS 回归中的 AGB，Adjust-R ² = 0.86–0.84 和 RMSE = 927.3–960.2 g 和 Adjust-R ²= 0.93 和 RMSE = 376.6–385.1 g（梯度提升回归中的 AGB）。在这些方法中，空间分辨率为 5 cm 的体素模型提供了最好的结果；然而，与 3D 凸包和基于光栅表面的模型的差异非常小。我们还发现，通过将 TLS AGB 估计与光谱信息相结合，可以准确测量绿色和干生物量分数（OLS 回归中的调整-R ² = 0.65-0.56 和 RMSE = 149.96-166.87 g，调整-R ² = 0.96-0.97 RMSE = 46.1–49.8 g（梯度提升回归），这在异质的地中海生态系统中至关重要，其中 AGB 随气候波动而变化很大。因此，我们的结果代表了测量M. tenacissima 的重要进展 L. 生物量和动力学，为进一步研究的校准和验证提供了一个有前途的工具，旨在开发生态系统区域尺度上 AGB 估计的新方法。