Department of Microsystems Engineering-IMTEK, University of Freiburg, 79110 Freiburg, Germany.
Hydrology, Faculty of Environment and Natural Resources, University of Freiburg, Friedrichstraße 39, 79085 Freiburg, Germany.
Sensors (Basel). 2022 Jul 5;22(13):5048. doi: 10.3390/s22135048.
The leaf area index (LAI) is a key parameter in the context of monitoring the development of tree crowns and plants in general. As parameters such as carbon assimilation, environmental stress on carbon, and the water fluxes within tree canopies are correlated to the leaves surface, this parameter is essential for understanding and modeling ecological processes. However, its continuous monitoring using manual state-of-the-art measurement instruments is still challenging. To address this challenge, we present an innovative sensor concept to obtain the LAI based on the cheap and easy to integrate multi-channel spectral sensor AS7341. Additionally, we present a method for processing and filtering the gathered data, which enables very high accuracy measurements with an nRMSE of only 0.098, compared to the manually-operated state-of-the-art instrument LAI-2200C (LiCor). The sensor that is embedded on a sensor node has been tested in long-term experiments, proving its suitability for continuous deployment over an entire season. It permits the estimation of both the plant area index (PAI) and leaf area index (LAI) and provides the first wireless system that obtains the LAI solely powered by solar cells. Its energy autonomy and wireless connectivity make it suitable for a massive deployment over large areas and at different levels of the tree crown. It may be upgraded to allow the parallel measurement of photosynthetic active radiation (PAR) and light quality, relevant parameters for monitoring processes within tree canopies.
叶面积指数（LAI）是监测树冠和一般植物发育的关键参数。由于碳同化、碳环境胁迫以及树冠内的水流等参数与叶片表面相关，因此该参数对于理解和建模生态过程至关重要。然而，使用手动最先进的测量仪器对其进行连续监测仍然具有挑战性。为了解决这个挑战，我们提出了一种基于廉价且易于集成的多通道光谱传感器 AS7341 的创新传感器概念，以获取 LAI。此外，我们还提出了一种处理和过滤所收集数据的方法，与手动操作的最先进仪器 LAI-2200C（LiCor）相比，该方法可以实现非常高的精度测量，nRMSE 仅为 0.098。嵌入在传感器节点上的传感器已在长期实验中进行了测试，证明其适合在整个季节内进行连续部署。它可以估计植物面积指数（PAI）和叶面积指数（LAI），并提供了第一个仅由太阳能电池供电的无线系统来获取 LAI。其能量自给自足和无线连接使其适合在大面积和树冠不同层次上进行大规模部署。它可以升级为允许同时测量光合有效辐射（PAR）和光质，这是监测树冠内过程的相关参数。
